Climate Denialist Claims - And What the Science Says

"Controversy equalizes fools and wise men -
and the fools know it." -
Oliver Wendell Holmes

The community of climate scientists many years ago started an excellent website - - which organizes links to the peer-reviewed professional journal papers on climate, and distilling the essence for the intelligent layman. It also provides a forum for anyone to ask questions or post objections, with climate scientists' answers. It was felt necessary to create as an antidote to the loud misinformation spread by the denialist blogosphere, junk science promoters, and their political and corporate supporters. It includes a well organized wiki debunking the AGW denialist claims. Here is another good listing of the many sources debunking the claims of those denying human responsibility for global warming. I'm doing my own website here, specifically for the Cabrillo College student, but I'd recommend also that you spend time browsing the site to get better informed. SkepticalScience is an even better place for locating published papers debunking the AGW denialist claims although aimed at perhaps a slightly more scientifically literate audience. AGW Observer links the abstracts of essentially all climate-related journal papers. The late Stanford climate scientist Stephen Schneider has an excellent video on the denialism issue. Here is a list of AGW denialist papers and their debunking. Note how very few slip through the process of review and make it into a genuine scientific journal. Among the few papers that did survive review, more than one has led to scandal and resignations due to failure of the journal's review process, as we'll show later here. Denialists and conspiracy theorists have some similar psychological traits - this examination of the supposed moon landing hoax is entertaining and has some nuggets worth remembering.

Here are some accessible (and entertaining) ~10min YouTube videos - Climate Denial Crock of the Week - which show denialist tactics and myths and how they wither when confronted by the real science. While these videos often have fun at AGW denialists expense, take careful note they explicitly demonstrate a good reading of the scientific literature as well. They also contain valuable visualizations and most are well worth watching.

The "Urban Heat Island" myth and here
The "Temperature Leads CO2" myth (includes good visuals on Milakovitch cycles relation to Ice Ages), and 2012 update
The "Global Warming Stopped in 1998" myth
The "Medieval Warming" Myth (and validity of the "Hocky Stick" temperature graph of Michael Mann), also here
The "Solar Cycles Cause Global Warming" myth
The stolen emails ("Climategate"), what the emails actually say, and AGW Denialist tactics. and Part 2, and the Wrap.
Here's an updated version of "Climategate", which includes a chronicle of how an initially skeptical (although he admitted he had not looked at the science already done) Berkeley professor Richard Muller began a large independent study to look at global warming claims, and is finding (to his surprise, it seems), that the previous science was done carefully and is indeed sound.
The "Greenland and the Arctic are Gaining Ice" myth
"The Great Global Warming Swindle" Swindle (on the notorious junk science film released after Gore's "An Inconvenient Truth"), this new video combines many graphs debunking the cosmic ray and sun myths as well.
"Flogging the Scientists"; pretty sobering.
The American Denial of Climate Change (N. Oreskes, and the Republican directive re-labelling Global Warming as "Climate Change")
What We Know About Climate Science.
A good point-by-point debunking of the claims of Marshall Institute chairman William Happer's criticisms of AGW in 2011 .

Read this article in the journal "Nature - Climate Change", which discusses climate denialism in schools, (including Cabrillo College's Environmental Sciences Program in past years), and quotes from a Cabrillo College student (see halfway through. Note they got the city wrong - not Santa Barbara!)

It's important to note that the basic "fingerprints" of anthropogenic greenhouse warming were understood and being observed as long ago as 1982, as this video shows. While modelling and more detailed work has certainly added much in those 30 years, the understanding that it is humans who are causing global warming, is not new - it is a testament to the effectiveness of the massive disinformation campaign of the fossil fuel industry and right wing political types that any can still believe, here in the 21st century, that there is a "controversy" here.

Climate denialists have put up these these and other claims to convince politicians and the general public that either the science of human-caused global warming is deeply flawed, or that climate scientists who are finding humans are responsible for global warming are part of a global conspiracy of lies and they cannot be trusted. The goal - to stop policy changes that threaten the profit streams of the fossil fuel corporations. Let's see what the actual evidence says.

Claim: There is no consensus among climate scientists that global warming is caused by human activities (Richard Lindzen is notorious for making this claim)
Why this Claim is Wrong: I can't say it any better than this - which summarizes several polls of scientists, climate scientists, and the general public. Scientists are in virtual unanimous agreement - today's global warming is caused by humans. Note below how this support is highly correlated with how deep is the knowledge and familiarity the respondent is with the science. Note how much lower is the agreement among the general public, thanks to the misinformation efforts of the AGW-denialist camp. They may not know their subject, but they know how to fool the people they need to fool (voters, politicians) in order to accomplish their intended goals. That global warming is caused by human activities is also the considered judgment of the National Academies of Science of all the industrialized countries, and dozens of other scientific societies in our own country. This piece by Lindzen on the Cato website, on the supposed lack of consensus, is amazing, and wrong on so many counts. There is not one reference cited to support his opinions. And after reading and re-reading, I can only conclude that Richard Lindzen's claim supporting "lack of consensus" boils down to the fact that Richard Lindzen is not part of the consensus (!). (scroll to the bottom of my webpage here for more insight on Lindzen). This paper too, in the Proceedings of the National Academy of Sciences, (Anderegg, et al. 2010) finds 97-98% of active, publishing climate scientists agree that global warming is caused by humans, and that the anti-AGW camp simply has no evidence to support their credibility in judging such things as climate change. Here is an interview discussing this study on YouTube. Note that, despite empty claims to the contrary, the Anderegg et al. (2010) paper does not claim that consensus=truth. They explicitly say there is an honored place for honest, genuine searches for alternative explanations, ad that ultimately it is evidence that decides, but that the strong correlation between demonstrated climate expertise and agreement with the AGW thesis is a crucial fact not previously given its proper place in the discussion.

Response to the survey question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009) General public data come from a 2008 Gallup poll.

In Short: Numerous studies show strong consensus among active climate scientists (98%) supporting AGW. Those with the greatest experience and expertise in climate science show the strongest conviction.

Claim: "32,000 of the World's Leading Scientists" have signed a petition rejecting the idea of anthropogenic global warming
Why this Claim is Wrong: The quotation marks above go with Bob Lutz, executive VP of General Motors, in a well-remembered episode of "The Colbert Report" (described here). The infamous "Oregon Petition" arrived in the mail of tens of thousands of people including some scientists (circulated in 1999 and again in 2007 and signatures summed). It urged their signature rejecting AGW by using a paper by Robinson, Robinson and Soon (RRS 2007) which is junk science at its most extreme. A primary strategy of junk science promoters is to publish in outlets unable or unwilling to give proper expert review. Note that RRS is published in the Journal of Physicians and Surgeons (that's right - not a typo! To say the least, this medical journal is not known for having competent climate science referees!). The petition is not filled with the signatures of scientists - its definition of a scientist is: anyone who signed the petition (!) This is a petition whose layout only allows check marks for PhD, MS, and BS degrees, and who admits they did not check the authenticity of the signers. It's an oil and tobacco company sponsored petition carefully graphic designed to appear to be a scientific journal article, and whose ultimate signatures include an unknown number of real scientists. See this report by the UK's Guardian. Yet the internet is filled with numerous right wing blogs perpetuating this myth and angrily attacking the notion of human-caused global warming. Here is a site collecting numerous debunkings of this claim. Climate scientists at RealClimate address the fraud. Only 39 of the 32,000 signers claim to be "climatologists", and by far the largest category are holders of only a BS "or equivalent", in some subject or other (the lowest educational check box option provided!). This "Climate Crock of the Week" video presentation covers the background of those behind the signature campaign. It's not pretty. Here's a collection of errors major and minor in the petition. In particular, this rebuttal by climate scientist Michael MacCracken is the most detailed, requiring 23 tightly written pages just to enumerate the distortions and falsehoods. I've got one more falsehood - if you check this link to the Oregon Petition, you'll see that listed as a signer of this bogus petition is yours truely - Richard Nolthenius! My guess is that they simply harvested PhD names from public sources and added their names w/o their knowledge.

What of the 2% of climate scientists who are not convinced global warming is all or nearly all human-caused? Three of the most prominent in denialist writings are Richard Lindzen (more on Lindzen later), John Christy, and Roy Spencer. Christy and Spencer's scientific acumen doesn't appear to be very good, judging by their record. See the bottom of my page here for a recent (2011) bit of incredibly poor science by Spencer. Meanwhile, this general line of attack against science continues... In January 2012 , the Rupert Murdoch-owned Wall Street Journal published an op/ed piece supposedly by climate-credible scientists urging that no serious policy changes be made in light of climate change. The op/ed makes serious distortions of published science - serious distortions as described by the authors of that science. These and other major flaws in the piece are explained here.

On the other side, the National Academy of Science (NAS) is made up of the most accomplished scientists in the nation. Here is a letter signed by 250 NAS members condemning the attacks by political forces on science in general and climate science in particular.

In Short: This is a "Big Oil"-sponsored distortion-ridden creation, with an unknown number of those 32,000 signers being scientists in any field. And clearly names of genuine scientists have been added without their knowledge. Even of the genuine signers, it's the sum of two petitions - one in the '90's, and a second one in '07. Would the '90's signers still agree, given the evidence today?

Claim: Water Vapor is vastly more important than CO2 in the greenhouse effect. CO2 is a tiny component of the atmosphere and contributes only a tiny amount of greenhouse warming. And besides, the absorption lines of CO2 are saturated and so adding more CO2 to the atmosphere won't add more greenhouse warming.

Why this Claim is Wrong:

1. Water vapor IS a bigger source of greenhouse warming than CO2 (although not vastly so). But water vapor is not the initiating cause for the rapid warming seen in the past ~60 years. The reasons are many... First, CO2 absorption lines are saturated only in the central core wavelength, adding more CO2 adds opacity in the wings (wavelengths slightly different than the theoretical wavelength of maximum absorption) of the absorption lines and traps additional heat. Also, because of the saturated line core, detailed calculations show that heat trapped only rises as the logarithm of CO2 rise (not linearly), in agreement with observations. - More important, there is always a height in the atmosphere above which the absolute density of CO2 is low enough that the absorption lines are not saturated. As CO2 levels continue to rise, the mean altitude where the bulk of the re-absorption of outgoing IR radiation happens will slowly rise higher (but still far below the stratosphere) - it certainly does not mean that heat trapped is constant with CO2 concentration. The saturated CO2 lines argument is just naive and false. If you'd like a little more detail, this link describes the situation well, even for the spectroscopically challenged. Here's another explanation of how bogus this argument is. The increased warming due to CO2 is amplified by the resulting higher water vapor in the atmosphere and its greenhouse effect, by roughly an equal amount, so the net effect of CO2 greenhouse warming is doubled by adding in the increased water vapor. In absolute terms, existing water vapor contributes 2.3 times more heating than does existing CO2 (Keihl 1997)

2. The water cycle is rapid. Water is evaporated from the surface, and precipitates back down to the ground with a time scale very short , while CO2 cannot liquify out of the atmosphere and cycles through the Earth system on time scales of millenia to millions of years. This means that water vapor in the atmosphere is very close to equilibrium. We cannot FORCE more water into the atmosphere because, other things being equal, it will just condense and rain right back out of the atmosphere very quickly. However, when we burn coal and oil which has been buried underground and taken millions of years to accumulate, and we do it at a rate which will exhaust it in just a few hundred years, the Earth and oceans cannot absorb the resulting CO2 fast enough to take it back out of the atmosphere. This is why CO2 levels are rising so rapidly while water vapor levels are not - water vapor remains in approximate equilibrium because it can liquify and fall immediately out of the atmosphere as rain - CO2 cannot. Now however, if you warm the air, you raise the ability of air to hold water vapor, and not by just a little - but by a lot. Warm the air by only 1 degree C and you raise the saturation point by fully 7% by mass! This illustrates a dangerous positive feedback - raise temperatures by adding CO2 which can't be diffused into the ocean or ground fast enough, thereby evaporating more water and raising the average absolute humidity, which raises greenhouse warming due to water vapor. As of 2012, the average global humidity has gone up 4% in the past 35 years. And rising CO2 levels are the ultimate culprit, even when some of the additional greenhouse heating of the earth is due to water vapor.

3. This reason is the most important: the basic physics of radiation absorption and transport by molecules described above is well understood. Though the calculations are non-trivial - we do need quantum mechanics and good Monte Carlo codes to calculate absorption coefficients vs wavelength for all the relevant molecules - they are nevertheless straightforward and confirmed to be correct in experiments. We know the density, composition, and temperature profile of the atmosphere and this allows us to take those calculations as confirmed by lab results and extend them to the atmosphere as a whole. There are no significant uncertainties here . Therefore...

I can't emphasize this enough - AGW denialists not only need to come up with another culprit for observed global warming, they also need to come up with some sort of amazing physics which will somehow nullify over a hundred years of solid atomic physics and observations both in and out of the laboratory demonstrating the reality of CO2-induced greenhouse warming, dating back to the discovery of the greenhouse effect by Tyndall in 1861. Denialists have done neither.


CO2 levels have been measured with high precision. Note even the seasonal variance as northern hemisphere spring vegetation pulls CO2 out of the atmosphere, and reverse in fall and winter. Note too how levels are not just rising, they're accelerating as the Third World rapidly industrializes.

Note the dominance of CO2 absorption. For clarity, water vapor absorption has been removed from the plot. But note how water vapor (on graph at right) and CO2 have their main absorptions in different places in the spectrum

The infrared absorption spectrum of some greenhouse gases, including water and CO2. Left scale is fraction absorbed by our atmosphere. Note that CO2 has absorption lines in general at bluer wavelengths than the main absorption by water, so that both cause greenhouse warming

In Short: Atmospheric water vapor is rising - but it is because CO2 is raising air temperatures, raising the absolute humidity saturation point, compounding CO2-caused warming further. The absorption line saturation argument shows no understanding of physics.


Claim: Scientific consensus is a sign of dogmatism, "group-think", "unwillingness to consider other views", and is analagous to "religious zealotry. It is anti-scientific".
Why this claim is wrong:
See this Willie Soon and Sallie Baliunas editorial on the website of the Heartland Institute (a pro-tobacco and AGW denialist organization) taking this position with respect to climate science. (Someone put me on the mailing list of the Heartland Institute's monthly writings. From the timing of when it began appearing in my mailbox, I have a strong suspicion of who - but do not actually know for sure). For more recent and even more outrageous anti-scientific ad hominum from Heartland, see this). I've seen this disgraceful slander spread even to students (note quotation marks above). It's an amazing claim, really. It is a slap in the face of science itself and shows their desperation as the science supporting AGW continues to expose "other views" for their utter vacuity. The truth is - when scientists do their job well, THAT is when a consensus emerges. It signals the success of constantly improving physical understanding, computer modelling, sensor technology, and years of effort on the part of thousands of bright and dedicated scientists to bring evidence and logic to bear on the relevant questions until they are solved. Scientists have reached consensus on a vast number of difficult scientific questions - for example, the quantum mechanics of semi-conductors and quantum electrodynamics. Does that mean that scientific conviction of the truth of these complex ideas is also only a symptom of slave-ish group-think? Your iPhone wouldn't be possible without valid understanding of this physics. To argue that scientists who have reached consensus are no better than axe-grinding close-minded religous zealots....what a smear! what an insult to all scientists! The wording of the claim at top is taken directly from the smear-artist of this claim - and this person has NO degree in science. Note what is the hallmark of science history - The ability of the peer-review system to check and verify conclusions and generate genuine new knowledge. - this should be overwhelmingly obvious to all. To constantly refine knowledge and continue to subject new ideas to careful thought is, of course, a good thing. And so obvious as to not need stating. As pointed out by Anderegg et al. (2010), these denialist claims are not only made without any evidence, but directly violate the obvious and valid motivations of good scientists, which is to turn a field which has been going down the wrong direction back onto the right direction, and be justifiably acknowledged and rewarded for that achievement. As a scientist myself, and someone who has worked closely with dozens of fellow professional scientists and has much familiarity with hundreds more, I find this slander deeply offensive.

It is bizarre that the denialists try to posture as the lone defenders of healthy scientific skepticism and hold up the example of Alfred Wegner and Continental Drift as a lonely heroic champion of truth - since denialists' current pronouncements that water vapor absorption blankets CO2 absorption, and land vegetation and the oceans would soak up any anthropogenic CO2 so we have nothing to worry about, date back 60 years to the rather naive status quo of the time, and it was the lone defender of better physics - Callendar (1938) - who, despite getting some physics wrong, showed that anthropogenic CO2 would indeed cause significant global warming. By the mid '90's, the evidence, observations, and physics had created an essentially unanimous scientific consensus that CO2 emissions are raising Earth's ground temperatures at a rapid and dangerous rate. There is no honor in being a scientific maverick, and there is no honor in being a member of the scientific consensus. There is only honor in having the Truth be your highest priority. And if your fellow scientists do the same and you find yourself in consensus, as is true in the climate science community at large, it speaks well of the integrity of those in consensus. But look at why equating consensus with religious zealotry accomplishes a great deal for the AGW denialist camp. It makes off-the-wall ideas now hallmarks of heroic struggle against the stale establishment. It legitimizes banner promotions of ideas even if they have already been debunked. It panders to a regretable but very human tendency - to avoid taking responsibility for messes. It also turns our natural and healthy desire for examples of heroism into a weapon against evidence-based truth. To the extent these motives pay off, it buys time for business-as-usual on the part of the oil and mining industries and those they financially sponsor (like the Exxon-sponsored George C Marshall Institute which funds Sallie Baliunas, and oil and coal giants Exxon, Southern, and Koch Industries, which together have paid Willie Soon over $1 millon ).

In Short: It is the denialists who are guilty of big money conflicts of interest, group-think, zealotry, and refusal to look at the facts and take responsibility, preferring to slander science itself in order to preserve business as usual.


Claim: Fewer cosmic rays reach the lower atmosphere during solar maximum, producing fewer low clouds because they act as nucleation sites for cloud droplets, and fewer low clouds lead to higher average ground temperatures (Svensmark 2007). This is an amplifier for solar-caused warming of the Earth.

Why this Claim is Wrong : Unlike many claims, this one is not absurd on its face. I can imagine having a sense of excitement on first considering this hypothesis and that it might be reasonable. It's worth a careful look. First, let's summarize the supposed mechanism, which is a bit more complex than some other claims: High solar activity means a stronger solar magnetic field permeating the solar system, which tends to deflect galactic cosmic rays (very high speed ionizing atomic nuclei) from hitting the Earth. Galactic cosmic rays (GCRs) create charged particles which are presumed to become cloud condensation nuclei (CCNs) from which water droplets form, especially in the lower atmosphere. Thus, the more GCRs, the more clouds and vice versa. Higher solar activity and hence fewer GCRs mean less clouds, reflecting less of the sunlight, and more is absorbed at the surface. In other words, the hypothesis claims - fewer GCRs -> fewer CCNs -> less low-level cloudiness -> more sunlight absorbed by the Earth's surface -> higher temperatures.

First, it is true that fewer cosmic ray secondaries reach the lower atmosphere during solar maximum. The reason is that the solar magnetic field is stronger near solar maximum, and therefore so is the shielding that it provides against cosmic rays from the Milky Way Galaxy in which we live (magnetic fields, as we learned in Astro 3 and Astro 4, cause a bending in the motion of charged particles).

Neutron arrival rate, generated by cosmic ray showers, for the past 60 years. Plotted with sunspot numbers; a good proxy for solar activity and global solar magnetic field intensity. The correlation is strong and compelling.

Change in cosmic ray intensity between 1700 and the present day from four independent
proxies. Intensities have been scaled to the 13-GeV cosmic ray data from Huancayo, Hawaii, and
then normalized to the 1990–2001 mean.The plot shows deviations from this mean. [from Carslaw et al. 2002]. Note that there is no trend after 1957, when the 20th century solar cycle intensities peaked. The 11-year solar cycle appears evident.

Global troposphere temps vs. cosmic ray flux. Note that before plotting they have taken OUT a rising secular temperature trend of 0.14K per decade - yet this is the very temperature rise that argues FOR AGW! So while there does appear to be a correlation here, it is a red herring as far as being an argument against AGW

What about the correlation of low clouds with cosmic ray flux? It is a complex series of steps needed to go from a cosmic ray hit in the lower atmosphere to a cloud condensation nucleus to a nucleated particle big enough to be called a cloud droplet and scatter sunlight and affect climate. The physics shows that there are already far more than plenty of nuclei available for cloud formation, given the other conditions necessary to make a cloud. While there are still uncertainties in modelling the steps, note that Pierce and Adams (2008) find that the number of cloud condensation nuclei caused by cosmic rays modulated by the solar cycle is only about 0.1% of the total cloud condensation nuclei, which is “far too small to make noticeable changes in cloud properties based on either the decadal (solar cycle) or climatic time-scale changes in cosmic rays.”. A good summary of the state of aerosols and cosmic rays and cloud nucleation as of 2009 is here. Also, note that global night time temperatures are rising even faster than daytime temperatures. This fits well with CO2-induced IR absorption, but conflicts strongly with Svensmark's idea that it is cosmic-ray induced changes in albedo due to clouds.

So the theory of cosmic ray induced significant cloud cover looks - evening being maximally charitable - pretty weak. But what about the observations of clouds? After all, maybe some mechanism other than ones considered may be at work and yet induce a significant effect. A good way to see if GCR's affect cloudiness is to study so-called "Forbush Decreases (FD's) ", which are significant and rapid drops in the GCR intensity over a time scale of a few days. Since the lifetime of clouds is of order hours, studying cloud cover over these time scales will at least test if there is any demonstrable mechanism for GCR's to affect clouds, although not over the decades time scale relevant for climate change. Svensmark (2009), using only 5 FD's, says there is an effect from FD's, but Kristjansson et al. (2008) studied a larger sample of FD's and used MODIS satellite data, finding no correlation by several measures. NOAA (The National Oceanic and Atmospheric Administration) website summarizing global warming science, says "global analyses of cloud cover over land for the 1976-2003 period show little change". This site has a fairly comprehensive list of published papers (over two dozen) finding insignificant or no connection between cosmic rays and cloud cover.

More important, the ISCPP satellite data on global cloud cover (used in Svensmark's work) is known to be flawed (Evan et al. (2007) - authors and abstract given below...
"Arguments against a physical long-term trend in global ISCCP cloud amounts": Evan AT (Evan, Amato T.), Heidinger AK (Heidinger, Andrew K.), Vimont DJ (Vimont, Daniel J.), GEOPHYSICAL RESEARCH LETTERS Volume: 34 Issue: 4 Article Number: L04701 Published: FEB 17 2007
Abstract: The International Satellite Cloud Climatology Project (ISCCP) multi-decadal record of cloudiness exhibits a well-known global decrease in cloud amounts. This downward trend has recently been used to suggest widespread increases in surface solar heating, decreases in planetary albedo, and deficiencies in global climate models. Here we show that trends observed in the ISCCP data are satellite viewing geometry artifacts and are not related to physical changes in the atmosphere. Our results suggest that in its current form, the ISCCP data may not be appropriate for certain long-term global studies, especially those focused on trends.''

A good discussion of this viewing angle problem and how it's been used by the Svensmark camp is here. An article in EOS also shows how the claimed correlations are not actually present in the real data, here. The bottom line - claims of trends in cloud cover using this data set are not supported. So far, it appears ISCCP has not issued corrected data.

And finally, from a discussion on the site..."Svensmark and others pointed to an apparent correlation between low-altitude cloud cover and cosmic rays. But after 1995, the beguiling fit of Svensmark's graph depends on a "correction" of satellite data, that the satellite scientists themselves say this is not justified. Here’s a quote…“I went to discuss this with the ISCCP scientists (downstairs) to get their opinion and this is a rough summary of the issues:
1) ISCCP inter-satellite calibration is done by offsets for individual satellites, not through trends. For instance, calibration is done using the warmest and coldest deciles from the satellite radiances. Whenever a new satellite stream is introduced there will be offsets in various parameters (so far ISCCP merges data from 33 different satellites) since the calibrations are done for a limited selection of targets, the satellites sometimes see different things and there may be subtle diurnal or angle related differences. Any new satellite can cause a jump, but it cannot produce a continuing trend. Calibrations are done directly against NOAA-9 (which was the best calibrated of all the satellites and serves as a gold standard for subsequent instruments). Thus the calibration of NOAA-14 (and NOAA 16 – from 2001) is performed directly against the NOAA-9 values, not with respect to overlapping satellites: ). Thus there is no way the 1994 gap between NOAA-14 and NOAA-11 could have produced an ongoing trend in the ISCCP data.
2) The MS03 trend correction is based on the apparent difference between SSMI and ISCCP. But SSMI only sees water clouds and ISCCP sees both ice and water clouds, thus the trend could be a real effect, or it could be related to drifts in either or both instruments or to drifts in the calibration targets. It certainly can’t be assumed only to be a problem with ISCCP, and cannot have anything to do with the ‘gap’ mentioned above (since that would simply have produced an instantaneous offset)."
Bottom line: there is absolutely no good reason to put in a trend correction because of a gap in the satellites."

Svensmark's published correlation between cosmic ray intensity and low cloud cover, shown here, includes satellite calibrations disavowed by the actual scientists who designed and operate the satellites

From Laut (2003), showing the apparent correlation between cloud cover and cosmic ray flux breaks down after ~1995

Another study, by Bago and Butler (2000) in the journal Astronomy and Geophysics, finds a similar breakdown in correlation. Red is total cloud cover, blue is low clouds, and black line is cosmic ray flux from the Climax experiment

For ~50 years now, surface air temperatures have been climbing rapidly, while cosmic ray flux and any cloud nucleation they might induce, have shown no net trend. Conclusion - cosmic rays are no explanation for global warming

From reading the papers and responses (including Svensmarks' here), my conclusion is that the cloud data itself is unfortunately not good enough to say much of anything about Svensmark's hypothesis, except that there is no support. There appear to be on-going problems with calibrations, with the inability of the ISCCP to differentiate between low, mid, and high clouds, view angle problems, and intra-satellite calibration problems. Since we're concerned with trends on the decadal time scale, it may be some time before this particular data is sorted out. While there probably is some correlation between cosmic rays and global temperatures, the simplest and best supported explanation is the already verified change in solar luminosity with solar cycle. Less radiation causes cooler temps, and this just happens to overlap with Svensmark's unrelated hypothesis, since more cosmic rays arrive when the solar cycle is a minimum. With the cloud observations muddled at this time, in judging Svensmark's idea we therefore put more emphasis on other observational/theoretical work, which shows clearly that cloud formation is far more sensitive to other factors (99.9%) than to ionized particle availability (0.1%) created by cosmic rays. I discussed this with a personal friend who is also a leading professor of atmospheric science and who develops models of cloud formation, and he agrees.

More important - since the cosmic ray induced cloud feedbacks clearly must happen (if they happen at all) on very short time scales (hours and days, not decades), and since there has been no secular trend in cosmic ray or solar activity since the mid 1950's (see the far right graph above), Svensmark's idea is a red herring as far as its relation to global warming. The data provide no support whatsoever for Svensmark's hypothesis as an explanation for global warming. In fact, cloud data show that far from acting to cool climate, clouds are reacting to global warming by amplifying it, i.e. acting with a positive feedback (Dessler et al. 2010, and described here)

Here is an excellent in-depth analysis of the numerous flaws in Svensmark's work. Svensmark's response to the valid scientific criticisms of his work is also revealing - he claims a conspiracy is against him. The truth is, he's made strong claims that his work absolutely does not support. Svensmark teamed with writer Nigel Calder to publish a popular-level book "The Chilling Stars"on his hypothesis. The Institute of Physics has reviewed the Calder and Svensmark book here. From my own reading of interviews with Svensmark, I have to say I am inclined to agree, unfortunately, with the Institute of Physics unfavorable judgments. This 10 minute YouTube video "Climate Change - the Objections" is straight-arrow and shows good grasp on the science and gives a nice summary of the major problems with both Svensmark's hypothesis, and also those of Richard Lindzen.

While the early examinations of the Svensmark idea are negative enough, further work in the last few years has made the idea even less plausible. Here's a list of over a dozen papers published in quality journals which demonstrate the flawed science, flawed judgment, and flawed interpretations of data which mar the cosmic ray hypothesis.

Update Aug 28, 2011.
The first paper showing results from the CLOUD experiment at the CERN particle accelerator, testing some ideas about cosmic rays' ability to generate clouds, has been published in Nature, by Kirkby et al.(2011). Climate denialists are making splashy claims that this work proves cosmic rays are causing global warming. But that's not at all the conclusion if you actually look at the paper and listen to the lead author himself, as you can do in this link and here. Instead, the CLOUD results only show that cosmic rays are a significant influence on the rate at which nanometer sized particles form, given the right chemistry. These are far too small to produce cloud droplets. Do these grow to become cloud condensation nuclei? There is no evidence that they do.

In Short: The currrent evidence show that cosmic rays contribute far, far less than 1% of existing cloud condensation nuclei and no evidence these create new clouds. Far more important and to the point - solar activity and cosmic ray flux show no trend for the past ~60 years - precisely the time when climate has most dramatically warmed. The cosmic ray argument is thus seen to be a red herring as an explanation for global warming, even if the cloud - cosmic ray hypothesis were true.

Claim: It's the sun that is causing global warming.
Why this claim is wrong: A large number of studies all show that the sun, whether by straightforward luminosity, or by UV flux, or by modulating cosmic rays, cannot account for more than a small fraction (if that) of global warming in the past 60 years. The sun's total luminosity does fluctuate slightly with the solar cycle, as magnetic field energy thermalizes and emerges as luminosity. However, it is weak, only 0.1% peak to trough. Since 1957, solar cycle maxima have been slightly decreasing in strength, and the same for solar energy flux. And therefore too, all known variants of solar forcing. Meanwhile, this period of time shows the most rapid and accelerating global temperature rises, in lockstep with the rising and accelerating GHG emissions due to human activities. Here's a good article with graphs and summaries of many published studies on the solar influence on climate. What about the claim that somehow, through unknown physics, solar forcings must be higher than the pure irradiance effect, because look at how severe the "Little Ice Age" was, when the solar cycle virtually disappeared for several cycles? The Little Ice Age appears to have been a coincidence of several verified causes beyond the solar activity effect, including volcanic activity, reforestation pulling CO2 out of the atmosphere after the Black Death. The Columbian Exchange (European diseases introduced to the New World) alone is estimated to have caused global human population to drop 20% during the 1500's and 1600's for example.

The denialists will have you believe that global warming is a scam designed to pump up research dollars to the climate scientists. They provide no evidence, nor even any believable rationale, for this claim, only slander. By there kind of logic, who would have more incentive than the Stanford Solar Center (where I worked for a time as a PhD student) to implicate the sun in global warming? Yet, see what they have to say here.

Denialists also claim that other planets are brightening and therefore global warming must be due to the sun. While Neptune is indeed getting brighter - it's been well shown for nearly 10 years that this is a seasonal effect - from which find "Neptune's nearly constant brightness at low latitudes gives us confidence that what we are seeing is indeed seasonal change, as those changes would be minimal near the equator and most evident at high latitudes where the seasons tend to be more pronounced." (Remember too, that Neptune's seasons last 164 times longer than ours!). The other planets for which global warming is claimed are all outer planets with seasonal cycles that last one to many decades - much longer than the one year for the Earth. The planet data is sparse, and consistent with all being seasonal effects, and not due to secular changes in the sun's energy. In fact, you can see that several measures of solar luminosity, including high precision satellite data, show only the solar cycle effect, and that the secular trend is actually slightly down, if anything (graph at right).

In Short: Solar luminosity (after smoothing out the 11 yr solar cycle) shows no increase (in fact, a slight decrease) for the past ~60 years, precisely when climate heating rates are accelerating dramatically, and solar output due to even dramatic shifts in solar magnetic activity, is small compared to the magnitude of global warming and CO2 forcing. Increasingly reliable data and modelling caused me to stop giving any credibility in my classes to the solar/climate argument as an explanation for global warming in 1991, and satellite luminosity data since then leaves no doubt.

Claim: The costs of halting CO2 rise would be crippling to world economic progress, and we should not commit to drastic action until we can prove with certainty that man and fossil fuel burning is causing global warming.
Why this claim is wrong: This IEA report (2008) estimates it will take only about 1% of world annual GDP from now till 2050 in order to reduce CO2 emission rates to 50% of current levels, which is estimated to confine global warming to an additional 2 degrees C above current levels (however, sadly, this is almost certainly now too optimistic, based on the last few years of data and studies). This is still very serious warming with serious consequences, but there is at least a chance it is not completely catastrophic, like the ~6 degrees C which the "business as usual" scenario calculations indicate. Halting CO2 rises no doubt will have a serious impact on oil and coal company profits unless they change their business models, but these business interests should not define themselves as the world economy. Compare this to the projected costs to the United States of the "business as usual" scenario (2008 scientific study, summarized here) in just four areas: increased damage from hurricanes, from real estate losses, from energy sectors losses, and water resources - at 1.8% of GDP. Including other costs, such as disease, wildlife loss, etc raises this to 3.6% of GDP. Impacts to other poorer nations will be even more severe. Here's a good link to the economics of global warming which itself links articles in peer-reviewed journals on costs vs various mitigation strategies. Finally, and this is most important - the argument from uncertainty is simply, outrageously self-serving for the carbon merchants. Even assuming we know less about the consequences of anthropogenic CO2 than we actually do, that uncertainty includes the possibility that the consequences will be MORE severe than estimated (as indeed, new evidence continues to indicate). An everyday example - you see what looks, by the evidence, to be cancerous melanoma growing on your face. Would you not go to the doctor because it'll be expensive and frightening, arguing to yourself that after all you can't PROVE to yourself that it's cancer? While the IEA study looks solid, it was done based on data from 2007 and before, and that's now beginning to look dated. Every year we wait, the costs escalate.

More recent studies (see here, here, and here) show that cap-and-trade approaches to limiting carbon provide economic benefit, not added cost. See the "Strategies" page for more up to date information.

In Short: Studies show it might still (at least in 2008) be possible to confine global warming to a "serious" +2C but not yet "catastrophic" +6C or more rise, for only ~1/3 the cost of doing little or nothing. The thing is - it's the sellers of oil and coal who will take the first costs to halting CO2 emissions, while it's the rest of us and our children who will pay dearly the costs of doing nothing. However, both the cost of heading off the worst of global warming, and the cost to the future of doing nothing, are accelerating very rapidly. Update 2012: Confining to +2C now looks very difficult or perhaps impossible without massive and immediate action. In the past 5 years, policy foot-dragging, data, and models have all made things significantly more pessimistic. This only adds to the urgency, not rationalizations for do-nothing, because the effects are, for all human time scales, permanent.


Note the striking changes in hardiness zones in just 20 years

Claim: CO2 is Good for Plants, and more CO2 is Good for the Earth.
Why this Claim is Wrong: This is another claim which only sounds plausible to a science-ignorant public (who are the target, of course). While CO2 is used by plants to make their own biomass, it is misleading to then try and sell the notion that human-caused rapid injection of CO2 into the atmosphere will be good for plant life. It is not true that today's rising CO2 levels are helping plants in general. Quite the contrary. CO2-induced climate change is stressing plants more than CO2 is helping them, and agricultural scientists are pointing out that rising night-time temperatures, a signature of greenhouse gas-induced warming, are reducing crop yields in the major breadbaskets of the world, as well as stresses on animals grown for agriculture -see the testimony of Dr. J. Hatfield in front of Congress. Natural plants are nearly always nitrogen-limited in their growth, not CO2-limited. Even more alarming is the global decline in the plants of the ocean - the base of the world's food chain. Global phytoplankton has declined by 40% in just the past 60 years. Ocean phytoplankton, which produces half of the living biomass of our planet, and roughly half of our oxygen - that biomass is declining at a very rapid rate - 1% every year (Nature 2010). A new study, published in Nature - Climate Change and announced by the National Science Foundation, shows that after a short, initial growth spurt when CO2 levels rise, plants then become stunted. Update 2013:Here's a new summary of the published literature on how rising CO2 will devastate existing agriculture. This NASA study shows vast regions of the Eastern U.S. where forest canopy is declining due to global warming's add-on effects. Nevertheless, in mid '13 this false claim is still getting press (May 12, 2013 Wall Street Journal link to article and what the science actually says).

In Short: SOME CO2 in our atmosphere, held constant, is clearly good and necessary for plants, but those repeating this nonsense hope you will stop here and not notice (a) most plants are nitrogen-limited, not CO2 limited, (b) that rapidly rising CO2 makes for climate change far faster than ecosystems can accomodate to, and (c) an initial growth spurt is followed by stunted growth in actual observations. Rapidly rising CO2 is destructive to most plant species (one exception is Poison Oak, which thrives in higher CO2 atmosphere concentrations)

Claim: Global warming has stopped since 1998 (or 1999, or 1995; I've seen them all).

Why this claim is wrong: The notorious Richard Lindzen is the originator of this one, thereafter widely repeated in the denialist blogosphere for years. The response? I can't say it any better than this article - "cherry picking"! The "since 1995" claim is extreme cherry-picking. Chosing 2009 back to 1995 is the longest period you can get away with and still just barely fail the standard measure (95% confidence interval) of statistical significance, due to the shortness of the interval. It also expertly includes the hottest El Nino in decades (1998) and ends on a "La Nina" year (2008). La Nina years are cooler than average, as the equatorial Pacific surface waters go through the opposite end of the ENSO oscillation. The disgraceful disingenuousness of it all is discussed here. Note too that 2010 was the hottest year since climate records began, this despite the fact that the sun, over most of the past decade, has been going through the longest and deepest solar minimum (and therefore solar luminosity is low) in a century. El Nino events, the solar cycle, and finite observational accuracy accounts for most of the year-to-year variance. The fact this lie is so obvious doesn't seem to slow down the denialists like Fred Singer, who continue to use it for any time period that suits their purpose. When volcanic, solar cycle, and ENSO oscillations are removed, the underying anthropogenic warming trend is as strong as ever, as this 2 minute video shows. Note the trend since 1880, not long after the first oil well was drilled in the U.S., and decide for yourself whether global warming has really stopped. Yet there are bizarre denialist blog sites that still claim we're headed into another Ice Age.

(a) Global average ocean temperature vs depth in meters. Note how hotter surface waters associated with cooler deeper waters and vice versa. (b) Sea surface temperatures and 160m deep temperatures. Note how they are inversely correlated as the Pacific goes through El Nino/La Nina cycles. From Roemmich & Gilson (2011)

Update 2013:Update 2013: This bogus claim continues in the right-wing and denialist press. Published research in the past two years adds clarity on why the atmospheric temperature rises do not happen at a perfectly constant rate. Here's the basic explanation - greenhouse heating is to the atmosphere, and the atmosphere communicates heat to the ocean surface. The surface ocean then communicates heat to the deep ocean. The transport of surface ocean heat to deeper layers does not happen at a steady constant rate, and the characteristic time scales for the variations are relatively long, since oceans are large, especially the Pacific.

The Pacific Decadal Oscillation for the past century, black line is smoothed. Early data reconstructed from proxies, based on PDO effects on North American climate

This is the Pacific Decadal Oscillation (PDO). Heat transport to the deep ocean is easier when the thermohaline gradient is weaker, and relevant physical and thermal scales mean this is variable on time scales of a decade or so on average (there is an interdecadal variation of longer duration as well, both are visible in the data at right). When the gradient is less, surface waters are cooler, and heat transport from the atmosphere to the ocean is easier, which lessens the temperature rise remaining in the atmosphere. In the other half of the cycle warm lower density waters sit on the surface, unable to convect lower, the atmosphere warms more rapidly. The PDO was in the 'warming' cycle (when El Nino events predominate) in the late '80's to '90's, and transitioned to the 'cooling' part of the cycle (when La Nina's are more common) after the large 1998 El Nino and continues today in this state. If there were no dominant greenhouse warming, one would've expected global climate to cool. It has not. This recent 'cooling' phase of the PDO has only succeeded in reducing the rate of global warming. 2012 was by far the hottest year on record in the U.S., and 10th highest globally. Climate denialists would have you believe that "global warming has ended". Absolutely false when you look at the data, models, and logic. We can expect when the PDO switches back to the 'heating' part of the cycle, global temperature will rise more rapidly once again. (longer explanation with links). The cherry-picking aspect is well shown through 2012 in this lecture (skip forward to 9:00 to 11:40, but the entire lecture is well worth your listen.)

In Short: This argument against climate change would never have gotten past a scientific journal referee - it has life only in the popular media. The cherry-picked time interval make this a disgrace to honorable scientific debate - far beneath the level one would have expected of an MIT faculty member. Those who blindly give credibility to Lindzen's every opinion deserve a big share of blame as well. The association of "hiatus decades" with ocean heat transport to deeper layers is well known and well established.

Claim: Cloud feedbacks from enhanced warming are negative (i.e. cause a net cooling), so that climate is essentially stable.
Why this claim is wrong:
This is Richard Lindzen's "Iris Effect" hypothesis, proposed in 1990. His claimed is that higher water vapor in the warmed atmosphere rains out lower in the atmosphere, leading to fewer cirrus clouds (stratospheric cirrus clouds have a net heating effect by blocking outgoing IR radiation). The evidence and theory both point to cloud feedbacks actually trending towards increased warming, i.e. a positive feedback (Fasulo and Trenberth 2012 and earlier reference therein). Observations show that increasing sea surface temperatures correlate with a decrease in "anvil" clouds and deep convective clouds. The question is, do these clouds heat, or cool the atmosphere? Brian Soden, a Princeton climate scientist, examined the tropical greenhouse effect in and out of El Nino conditions and finds that clouds behavior is opposite to that hypothesized by Lindzen (Soden 1997). And Lin (2002) finds "The observations show that the clouds have much higher albedos and moderately larger longwave fluxes than those assumed by Lindzen et al. As a result, decreases in these clouds would cause a significant but weak positive feedback to the climate system, instead of providing a strong negative feedback, opposite to Lindzen's hypothesis." This recent study again shows cloud feedback is positive (more CO2 warming leads to more cloud-cover induced warming), not negative. See more studies backing up this conclusion here and here, and Dessler (2011). The next incarnation of Lindzen's idea is in Lindzen and Choi (2009), claiming that the ERBE satellite data show increased outgoing radiation from Earth to space when sea surface temperatures rise. But this work has a number of major flaws which are fatal to the hypothesis, pointed out by Trenberth et al. here. (The journal paper is here). Lindzen is reportedly reworking his claims yet again. Given his original incarnation was published now over 20 years ago, it seems like variants are going to be keep coming, regardless of how embarrassingly wrong they continue to be. The specific problems are not easily put into bullet points for the non-science major, so I would recommend the serious student follow the links to fully digest this. Climate models clearly agree well with the rising global temperatures and Lindzen's ideas are quite outside what both theory and observations demonstrate. More disturbing, these studies above show Lindzen cherry-picking his time interval, cherry-picking his model heat flow parameters, and a deeply flawed portrayal of the relation of the tropical system to global climate (see in particular the Dessler (2011) study of tropical air/ocean/clouds study). On a larger time frame, this "Iris" hypothesis is obviously wrong, as relatively small changes in insolation at the Arctic Circle (Milankovitch cycles) are amplified by feedback via CO2 release to/from the ocean to produce the great Ice Ages. We see the opposite happening today, as the Arctic is melting rapidly, at roughly twice the rate of the globe as a whole.

Update: A 2012 New York Times newspaper article on Lindzen and clouds is a good read for the layman (refreshingly so! Imagine - a newspaper!). In it, Lindzen finally acknowledges "embarassing" and "stupid mistakes" he made in Lindzen and Choi 2009. But the bad science continues - Lindzen's re-worked Lindzen and Choi (2011), is just as deeply flawed as the earlier incarnations. Submitted to an obscure Korean journal after being rejected by the Proceedings of the National Academy of Sciences, reviewers noted that the paper is based on "fundamentally flawed assumptions about global climate sensitivity". A detailing of the flaws is here. This link is a good place to keep up to date on the latest research on cloud feedbacks. Bottom line as of '13 - clouds provide weak but positive feedback on greenhouse warming.

In Short: Despite the fact that cloud modelling is still far from perfect today, observations and theory show cloud changes caused by greenhouse warming are likely making the heating worse, not less: The atmosphere does NOT tend towards stability on the scale of ~10C, as the paleo record shows. The wide changes in Earth's paleo climate accompanied by changing CO2 levels also show that climate is clearly NOT stable at the level cavalierly claimed by Lindzen. Lindzen, now in his 70's, continues to produce poor science in trying to support his claim that human-caused climate change is nothing to worry about.

Claim: Climate models are untrustworthy, they kluge parameters to fit the data.
Why this claim is wrong:
Here's a recent study of climate model accuracies. In 2007 a study by Douglass et al. was claimed to show that models were overpredicting the recent past warming when fed with past data, apparently casting doubt on climate models. But it has been shown that the Douglass paper did a poor job of accounting for systematic errors in the observations and an extremely poor job of calculating error estimates on their conclusions (which is key if statistical significance is to be claimed). The full discussion is a bit technical, but the adventurous can dive in. A more careful analysis was done by Thorne et al. (2007) at the same time and finds no statistical significance to differences between model trends vs observational trends in tropical temperatures. As for "kluge's", this word is designed to make you think climate scientists are simply assuming what they are already convinced is true. No. All computer models of some phenomena must include simplified formulae for certain physics in order to be run in a finite amount of time on real computers. Modellers verify that the simplified formulae give reliable results by a variety of tests before doing "production runs" for their research. Tests such as using past data to generate forward predictions which in fact are already in the past, and verifying that the "post-dictions" are good. Even simplified formulae for physical effects need to be justified in a paper by appeal to real physics. One simply can't make up a bogus equation which violates physical principles and expect the journal referees to accept it. Another standard test is to change the resolution of the modelling grid, both spatial resolution and time resolution, and see if the results are robust (i.e. they don't significantly change). This gives confidence that your predictions are not far off due to finite numerical resolution. It's obviously never going to be possible to calculate the future behavior of a system of a quintillion quintillion quintillion atoms using only Four Fundamental Forces of Nature. It doesn't have to be. Critics will try and claim that the "butterfly effect" in chaos means that even a tiny imperfection will completely destroy your prediction. Such critics are naive, and don't understand the difference between weather and climate. We may never be able to predict whether it will rain in Moscow exactly 2 years from today, but we can make statistically averaged predictions, which are strikingly accurate. Here's an analogy - imagine getting your nose right up to the water of a rushing mountain stream and try and predict exactly what bubbles and eddies will be in front of your nose in 1 minute. It's impossible. That's weather. But get 100 yards away and ask what the stream will look like in 1 minute and you'll be able to get a pretty accurate picture. Models have improved significantly since the 1990's, and continue to give strong support to the conclusion that global warming is primarily due to CO2 from fossil fuels, with secondary add-on damage from human-induced methane, deforestation, and certain types of air pollution. Here is a FAQ on climate models. While this 9 minute YouTube has no details, it does show good visuals on how climate models compare to observations over the years, with a bit of history. This video shows how numerical resolution has improved dramatically over the years, while the fundamental conclusions remain the same. Global warming is real, it is caused by humans, and only humans can take action to solve it.

In Short: Checks and balances on the realism of the modelling come in at all stages, and a thorough error analysis must be done before any paper gets past a peer-review and makes it into a genuine scientific journal. Other researchers using other modelling codes and assumptions do the same, and differences are either resolved, and/or become a measure of quantified remaining uncertainties in predictions. The climate models of today have gone through these evolutions, and show good agreement with observations when using past data.


Claim: Climate scientist Michael Mann (of Penn State University) is guilty of misusing confidential data, engaged in a conspiracy to withhold information, and manipulated or destroyed data to strengthen his case that human activity was changing the global climate.
Why this claim is wrong: Michael Mann is principal author of the famous 1998 paper which first showed the "hockey stick" graph of global temperature for the past one thousand years, ending in the upward "hockey blade" spike during the fossil fuel age. This was a centerpiece in Al Gore's "An Inconvenient Truth" and if a picture is worth a thousand words, this certainly qualifies. It is natural that AGW denialists would go after the author of this work. These charges against Michael Mann are serious, enough to terminate a career if found true. One would hope the AGW denialists had evidence before making and distributing to the press such charges. In fact, the slander revolves around the meaning of the word "trick", found in emails stolen by the AGW denialists ("Climategate"). Scientists and mathematicians often use the word "trick" to refer to a clever insight used to solve a difficult problem. Having hung around other scientists such as myself for 35 odd years, I can tell you this is absolutely true. Anyone who would base such serious slander on their own ignorance of the meaning of the word "trick" clearly has no experience in science or mathematics (or perhaps they knew exactly what it meant, but yet found this a great opportunity to advance their agenda by making such slanderous charges in front of policitians and science-ignorant students, media, and the public). Having on your faculty a prominent scientist guilty of fraud and other misconduct would be a huge liability, and so even if the charges had no basis or evidence, Penn State University conducted an inquiry - and Mann was cleared of any wrong doing or bias. Here's the NY Times article on the inquiry and Mann's vindication, with embedded links. Note also that AGW denialist blogs charged him with witholding data and hiding or destroying data. This inquiry and a dozen others found NO BASIS for this charge. All data and codes legally able to be released were released at the time of his original paper. All data and codes subsequently were cleared by foreign countries to release, and have been released. It was those other countries whose data partially comprised the dataset analyzed. See this recent interview in "Discover" magazine. All relevant climate forcing data is available to anyone, here. Here is Mann's response to the political witch hunt against climate scientists, including himself. And a more recent response (Dec 2011) by Mann is here, and a more recent summary of these political attacks in a talk at the Chapman conference of the AGU in summer 2013, here. I have personally heard these baseless charges against an honorable scientist made by someone quite close. Anyone who would repeat such slanderous charges - worst of all, to students - as if they were fact, as late as 2009, when they in fact have no basis, let alone provide proof they are true... what can you say about their own bias, their own objectivity, their own committment to telling the Truth? Such people deserve our contempt.

Outrageous slanders against Michael Mann aside, how do the data-based criticisms of the "Hockey Stick" temperature plot stand up? Here's an excellent study showing re-analyses even assuming the (mostly invalid) criticisms of the 1999 analysis. Bottom line: no significant change - it's still a temperature "Hockey Stick".


Original temperature reconstruction from Mann & Bradley 1998, as published in the IPCC 2001 document

Reconstructions of Northern Hemisphere temperatures for the 2nd millennium according to various older articles (bluish lines), newer articles (reddish lines), and instrumental record (black line)

IPCC temperature reconstructions using proxy measures of various kinds, for the Northern Hemisphere only. The "medievel warm period" is only seen in the Northern Hemisphere data, not globally. The instrumental record goes back to the 1800's and is shown in black.

Jones and Mann (2004) temperature reconstructions using proxies, with global temperatures at the bottom pane. Actual instrumental temperatures shown in red. Proxies and instruments both agree - still a Hockey Stick

"Climategate" was a fabricated smear campaign against climate scientists, based on stolen emails from the private correspondence between climate scientists and timed to be released to the media shortly before the 2009 UN Copenhagen Climate Summit, no doubt to insure that no significant carbon taxes or other other carbon-limiting agreements would result. Denialists took naive or distorted meanings from out-of-context passages to appear to justify their charges to a gullible, scandal-hungry media that global warming was a scientific fraud. Numerous investigations showed there was no fraud, no bad science, and no lies. The real fraud is the behavior of AGW denialists who so easily slander the work and character of good scientists in the name of preserving "business as usual" corporate profits. The status of this attack on climate scientists is well linked and summarized (as of 2011) here. All this, as if the "Hockey Stick" was the principle reason for the IPCC conclusion that global warming was human-caused - which it is not. Stanford climatologist Stephen Schneider points out (32 minutes into this lecture) that he repeatedly told the media that the IPCC's 2007 conclusion that global warming was human-caused was not at all based on the "hockey stick", but instead on the many "fingerprints" (observational patterns in global warming which can only be produced by greenhouse gases), and not once would the media actually print this fact.

In Short: No raw data was ever hidden. Some data based outside the U.S. was kept proprietary at the insistence of the other governments, until formal publication, a fact never hidden. All raw data is public and available to anyone. Several independent investigations, after these baseless false claims, showed there was no data tampering, no fraud, no bad science, and the results stand. These intimidations are, unfortunately, a standard in the denialist tactics.

Claim: It can take centuries or thousands of years for temperatures to fully rebound out of an ice age. Global warming may be nothing more than a rebound from the last ice age, or the Little Ice Age.

Why this claim is wrong: The time scale for warming depends in large part, of course, on the magnitude and cause of the forcing. If climates are "relaxing" from the last Ice Age, such that each incremental change in Milankovich insolation forcing means a bit warmer planet, leading to a bit less ice, etc, and if the ice is miles thick and covering vast areas of the northern hemisphere, then yes - it can take many hundreds or even a few thousand years for quasi equilibrium to migrate temperatures slowly upward. That has nothing whatsoever to do with the current situation. The forcing is not the slow migration through equilibriums described above, but a rapid external forcing through strong injection of greenhouse atmospheric gases directly into the fastest responding, lowest thermal mass, lowest thermal capacitance element in the system - the atmosphere. The thermal and CO2 capacitance of the ocean is vastly bigger than that of the atmosphere, due to its mass. But it is into the Earth's thin, low-mass atmosphere that we are directly forcing CO2, with no regard to its equilibrium level. Next, the evidence is strong from both theory and observed correlation that the Ice Ages are primarily controlled by the Milankovitch cycles.

Milankovich cycles: changes in the orientation, tilt and eccentricity of the Earth and its orbit combine to change the amount of sunlight hitting the Arctic lands, leading to increasing or decreasing glaciation - the Ice Ages

The great Ice Ages of the past 600,000 years, and CO2 levels. CO2 was sequestered by the ocean and by permafrost during Milankovitch-driven cooling periods, and liberated and therefore added positive feedback heating during the Milankovitch-driven interglacial periods. With the well-known ~1000 year time scale for complete ocean turnover and contact with the atmosphere, the ~800 year lag in CO2 vs. temperature makes perfect sense - perfect sense, that is, during Milkankovich-driven Ice Ages.

Green: temperatures coming out of the depths of the last great Ice Age. Blue: Holocene temperatures, with gradual decline due to Milankovic cycle effects, ending in the sharp spike upward due to man-made greenhouse gas emissions. Does that spike look like a rebound from either the Little Ice Age or the last great Ice Age? No.

Compare to today, and new anthropogenic greenhouse gas forcings (green curve), and look at the rapidity of the change in forcings, and the change in CO2 levels (to make the changes on the graph of comparable horizontal scale required magnifying the time axis by a factor of 500(!) to show the past century). Said another way, changes are happening of order 500 times faster than during the Ice Age cycles....clearly NOT a mere rebound temperature rise


These Milankovich changes in the Earth's orbit and spin axis are straightforward to calculate by the laws of physics for both the past and future. Currently we are finishing a period of decreasing insolation at the Arctic Circle, and global temperatures for the past many centuries have shown a small, slow, net, cooling - until the rapid CO2-induced warming beginning about a hundred years ago. If we've been rebounding from the last Ice Age, why has there been centuries of slow cooling - until now? Makes no sense. Global temperatures rise at a rate depending on the magnitude and direction of the forcing mechanism. A study using a suite of climate models all show that the temperature rise in the early 20th century is mosly due to rising solar activity, while anthropogenic CO2 is responsible for warming since then (Meehl 2004). We're currently adding a strong forcing upward by CO2 and methane emissions, and temperatures are responding rapidly, as calculations show they should - not the glacially slow progression out of an ice age that ended ~19,000 years ago. The atmosphere's response to thermal forcing in general can be much faster than this ad hoc claimed millenial time scale, most obviously by the response to volcanic eruptions, as graphs on this page show - changes to the atmosphere will change global temperatures in months and years, not millenia. We humans are changing the atmosphere directly, not indirectly as during the Ice Ages. Coming out of true Ice Ages can take many hundreds to thousands of years, due to the feedback of melting ice and resulting lowered albedo and release of ocean and permafrost trapped CO2. Anyone with any familiarity with oceanography ought to know that the turnover time scale for the ocean to release millenia-long sequestered CO2 is about 1,000 years. When air temperatures rise due to Milankovich forcing, it can take therefore ~800 years for significant CO2 to be released to the atmosphere - so the paleo record makes perfect sense. What does that have to do with today? Nothing! Forcings directly applied to the atmosphere will be short, of order years, not centuries or millenia. And that's exactly what we're seeing with current GHG-induced global warming.

Showing science-ignorant people changing temperatures or CO2 levels from the past, spanning hundreds of thousands or millions of years, and claiming (or more outrageous still, simply planting the implicit claim - thus allowing plausible deniability) that it's like today, when today we are seeing comparable or larger changes in only 60-100 years, and doing so without emphasizing the time scale issue, is deeply, unconscionably misleading. See the CO2 graphs below, and the temperature "Hockey Stick" for a better appreciation.

1.2 trillion tons of fossil fuel CO2 has been released into the atmosphere in the past 250 years. Fully half of that has happened just since 1975

From the NASA website. This graph is meant to show just how rapid is the current rise in CO2 compared to the geologic time scale. The cycles of Ice Ages show CO2 levels peaking reasonably consistently at 300 parts per million. From today's rapid fossil fuel burning we've now crossed 400 parts per million.

CO2 levels for the past 150 years. Note the levelling off from the mid '30's to 1950, as World War II served as a distraction from fossil fuel burning by the great majority of people. This, and the reflective tropospheric sulfate air pollution which came with post-WWII industrialization, counterbalanced greenhouse warming till ~1970, in agreement with observed temperatures and climate models.

Note that Earth had been slowly cooling, not "rebound heating" after the last great Ice Age ended over 10,000 years ago. And even after the so-called "Little Ice Age" (a term most climatologists hate as it invites over-exagerated images of temperature), we had a resumption of slow cooling throughout the 19th century, until the rapid heating we are seeing in the 20th and 21st century. Does this look like a rebound from either Ice Age? No.


Regarding the Little Ice Age - there is little doubt temperatures were lower for a few hundred years centered around the year 1600. ~30 years ago it had been widely assumed, due to the popularizing of this idea by the late John Eddy, that the Maunder Minimum in solar activity may have caused the Little Ice Age. However that was only a tentative assumpition as we had no precision satellite data on solar output vs solar activity until recently. We now have good satellite data on insolation over the last several solar cycles, and the insolation only varies by less than 0.1% maximum to minimum in the solar cycle, so that a prolonged period of low solar activity such as the Maunder Minimum would not correspond to low enough solar heating to account for the Little Ice Age. This is confirmed by a recent paper by Feulner and Rahmstorf (2010) , (GRL paper here). Instead, the real causes of the Little Ice Age which best fit the data are (1) there were stronger and more frequent volcanic eruptions, which put sulfate aerosols into the atmosphere and cooled the Earth by reflecting sunlight (Robock 1979), and (2) that the Black Plague and Columbian disease epidemics spread to the New World caused a significant (20%) drop in human population during the late middle ages, leading to cleared land undergoing reforestation which took up enough carbon to account for the 10 ppm drop in observed CO2 levels at the time of the Little Ice Age. This brief reference is interesting, though not a peer-reviewed paper.

In Short: Such Ice Age "rebound"'s happen through a series of semi-equilbrium states, and therefore slowly, run by orbital changes. Today we are FORCING CO2 into our atmosphere and doing it extremely rapidly, not coaxing it slowly out of the ocean as in the distant past. The argument is either a deliberate red herring, or extremely naive. Today's rate of rise of temperature bears no resemblence to that associated before, during, or after the Little Ice Age.

Claim: Why should we believe climate scientists now? In the '70's they were predicting we were headed for an Ice Age!
Why this claim is wrong: In fact, a study of the scientific literature from 1965 to 1979 finds only 7 papers warning of imminent cooling, compared to 44 warning of global warming (Peterson et al. 2008). Media hype of the few "ice age" papers back in the 1970's, and most especially by political and fossil fuel corporate interests today, account for this myth, conclude Peterson Here's an entertaining and informative YouTube video summarizing the history of our understanding about climate change over the past 120 years, including just how many climate science journal articles supported the idea of an immenent cooling in the '70s (very few). Also, the original CAUSE of the concern for cooling was the levelling off of 20th century global warming during the 1940-'70 period, which we know was due to the cooling effect of rapidly rising air pollution caused by the industrialization of the post-WWII world, an unusually active period of significant volcanism, (and to some extent a levelling off in the rise of CO2 during WWII itself). Recall too that in the late '60's and early '70's computers were very primitive and climate modelling was similarly primitive. The effect of aerosols was poorly understood, in part because of a lack of data of planet-wide aerosol events since the era of 20th century instrumentation. This changed in the later 20th century with a number of significant volcanic eruptions, beginning with 1963's Mt. Agung. It was Hansen's analysis of the aerosols from Mt. Agung (Hansen et al. 1978) that showed that CO2-induced warming would overrule aerosol-induced cooling. Even before Hansen's work, most climate scientists were predicting that CO2 greenhouse effect warming would soon overwhelm pollution effects and take over with a vengence (see here). Also, American Institute of Physics: publication on the history of the science of CO2 and climate.

In Short: It's a fabrication. The large majority of climate scientists even in the '70's, were predicting global warming from anthropogenic CO2. The slow-down in warming observed in the post WWII period had mostly to do with rapidly increasing man-made air pollution dimming sunlight reaching the ground, and an unusually active period of volcanic activity adding stratopheric aerosols, especially Mt. Agung in 1963. The few "cooling" papers relied on assumptions about increasing aerosol pollution which we - fortunately, in part through the Clean Air Act - took legal environnmental action to help mitigate.


Claim: Greenland is actually gaining ice, not losing it, as global warming alarmists would have you believe ``The evidence so far suggests that the Greenland ice sheet is actually growing on average" - Richard Lindzen, quoted here

Why this claim is wrong: Cherry-picking, basically is the answer. The cold high altitude interior of Greenland did have a net gain of snow during the '90's, but this was found to be consistent with global warming models, which include higher evaporation of warmer ocean water and deposition as snow at the very high elevations of the top of the Greenland ice cap, which was then still cold enough to have the net snow balance be positive. However, the ERS-1 and ERS-2 satellite data used was not able to say much about the behavior of ice near the coastal areas, where in fact ice has been melting and sliding into the ocean at an accelerating rate. And, since the most often used study which AGW-denialists use to champion this myth was published almost 10 years ago, newer and better satellite data using gravity measurements show that the entire continent is net losing ice (this YouTube shows how GRACE works). A recent paper by Wu et al. (2010) using a different calibration of GRACE data, still finds Greenland is losing its icecap. The graph at left shows the change in the total ice mass of Greenland, interior+coasts. The regular up/down oscillations are due to seasonal summer melting vs winter ice accumulation, not observational error. Note that the rate at which the ice is disappearing has doubled in just this last decade - a decade during which the solar heating contribution has actually been dropping as we've gone from a solar maximum in 2001 to an unusually deep solar minimum in 2008/9. Ice loss is also happening in Antarctica (and here). A major factor is that the speed of Greenland glaciers is rising rapidly. Meltwater on the surface is observed to follow channels down to the base of the glacier, lubricating its gravity-induced motion towards the ocean. Without detailed images of the base of glaciers, it was difficult to model this with any confidence and so to be conservative, the IPCC decided to not include this aspect in their AR4 report. Unfortunately, the result is a significant under-appreciation of the loss of continental ice at the poles due to global warming. To address this, Vermeer and Rahmstorff (2009) have devised a semi-analytic method which captures 98% of the variance in ice volume vs global temperatures, and use it to predict sea-level rises for the coming century using current and historical data. It shows sea-level rise of 3-6 feet by 2100 (depending on anthropogenic emission scenario), which is 3 times the IPCC AR4's conservative calculation (see 3rd panel graph below). Baffin Island, also in the Arctic and the 5th largest island on Earth, has lost 50% of its ice cap in the last 50 years. Globally, glaciers worldwide are in rapid retreat (see graph below right - sorry for the poor reproduction!). See this video of congressional testimony which contains a nice animation of the GRACE data on where and when ice is being gained and lost on Greenland. This 2011 paper in GRL shows excellent agreement between two ice volume measures: GRACE, and ice accumulation vs perimeter loss. They both show accelerating ice loss and strong rising sea level predictions for this century. However, a new paper published in Nature (Sundal et al. 2011) uses satellite measurements to show that once a critical level of melting is exceeded, the drainage under glaciers transitions to a more efficient mode and glacier speed slows. It will be interesting to see this new work included in future modelling of Greenland ice loss, as it is the major determiner of sealevel rise as global warming accelerates. Also contributing to Greenland and other polar ice loss is the darkening of surface ice. The darkening can be caused by partial melting of snow flakes, changing their geometry and reflectivity, and/or to the accumulation of dark pollutants and soot from the growing number of wildfires as climate warms. A short video on the albedo issue here.

A key point to make is that simplistic arguments I've heard from denialists about Greenland taking millenia to melt make the assumption that the ice stays in place. High altitude ice is certainly colder and more stable than low elevation ice, yet what we see is meltwater de-stabilizing the deep ice/continental interface and speeding the breakup and transport of ice to the oceans. This has been seen for many years now, described by polar scientists in this 2013 video (5 min). This study, published in Nature: Climate Change in 2012, shows indeed that Greenland is more sensitive to losing it's entire ice cap than previously thought. We are already close to the temperature levels which, if sustained, will completely melt Greenland over the next centuries, even if CO2 levels are brought back down. Hansen and Sato (2012) provide a good update on Greenland and Antarctic ice loss in a "business as usual" scenario into the future, and review the recent papers, arguing that a simple linear extrapolation of past ice loss is a very likely underestimate of this very non-linear process. While sea level rise by 2100 is still highly uncertain, the "scientific reticence" approach (Hansen and Sato 2012) of the IPCC 2007 AR4 should not be relied on for comfort, and sea level rise of over a meter or two are quite possible or even likely.

Change in total Greenland ice mass as determined from the GRACE data

Not only the total ice mass loss is increasing so is the size of the summer area that is experiencing that melt.

Updated graph of melt area. On July 12, 2012, for the first time on record, Greenland experienced melting over 100% of its surface, even at the highest elevations

Global Glacier Thickness Change: This shows average annual and cumulative glacier thickness change, measured in vertical meters, for the period 1961 to 2005. Explosive volcanic eruptions, which contribute aerosols to the stratosphere and cool the Earth's climate, can temporarily raise glacier mass balance. Four significant eruptions with worldwide impacts are shown on this graph and are generally associated with periods of increased mass balance due to lowered temperatures. Image courtesy of Mark Dyurgerov, Institute of Arctic and Alpine Research, University of Colorado, Boulder.

Global sea level rise over the coming century, from Vermeer and Rahmstorff (2009) is much higher vs the IPCC AR4 estimate which neglects the acceleration of ice sheets sliding into the ocean due to meltwater lubrication.




In Short: It's false. Greenland is losing ice, currently at an accelerating rate, as shown by the most reliable of data - the gravity-based GRACE satellite measurements. While there is more snow happening at the top of the Greenland high elevation plateau, due to increased water vapor in the warmer atmosphere, this increasing snowfall is dwarfed by rapidly melting and accelerating glaciers calving into the ocean around the coastlines, and being heated from the inside by meltwaters even deep in the interior, melting cracks and holes and reaching the glacier/baserock interface.

Claim: Antarctica is GAINING ice, so even if there's ice loss in the Arctic, it's just a natural variation as ice gains and losses come and go around the poles.
Why this Claim is Wrong. It's cherry picking again. The Southern Ocean consists of a layer of cold water near the surface and a layer of warmer water below. Water from the warmer layer rises up to the surface, melting sea ice. However, as air temperatures warm, the amount of rain and snowfall also increases. This freshens the surface waters, leading to a surface layer less dense than the saltier, warmer water below. The layers become more thermally stratified and mix less. Therefore less heat is transported upwards from the deeper, warmer waters. Hence less sea ice is melted (Zhang 2007). Meanwhile, the gold standard for total ice mass changes is the gravity measurements of the GRACE satellite system, which measures the total gravity of what is below it. As these satellites have criss-crossed the poles for fully a decade now, they tell an unambiguous story - ice is being lost at an accelerating rate from both the Arctic and the Antarctic continental masses. Will Antarctic ice loss continue at this rate? This is not obvious - Antarctica is a very high continent centered on the south pole and therefore surrounded by a powerful polar atmospheric cell which communicates little with the warmer air to the north (this is not true of Greenland, which is farther from the pole and has a different climate and communication outside the north atmospheric Polar Cell). As of the 2012 AGU meeting results (Rignot) , the glaciers are speeding up along the Antarctic coast, but the snowfall on the top of the continent is increasing, as warmer air can hold more water vapor. Year-to-year snowfall can change significantly over longer time scales than GRACE data exists. It is expected that Antarctica will show a secular, consistent net continental ice loss later in the 21st century, when global and regional temperatures rise further. Or, it's possible this has already begun, as shown by the GRACE data in hand, below.

Sea ice extent, observed by satellite (bottom). (Zhang 2007) It's the bottom graph that the denialists are trying to fool you with. Yes, Antarctic SEA ice extent has been increasing. But air temps are rising too. Note how the rising air temperature is still (so far) below freezing.

Estimates of total Antarctic land ice changes and approximate sea level contributions using many different measurement techniques. Adapted from The Copenhagen Diagnosis. (CH= Chen et al. 2006, WH= Wingham et al. 2006, R= Rignot et al. 2008b, CZ= Cazenave et al. 2009 and V=Velicogna 2009)  (Source here)

Ice mass changes for the Antarctic ice sheet from April 2002 to February 2009. Unfiltered data are blue crosses. Data filtered for the seasonal dependence are red crosses. The best-fitting quadratic trend is shown as the green line (Velicogna 2009).

Monthly changes in Antarctic ice mass, in gigatons, as measured by NASA’s GRACE satellites from 2003 to 2011. Results from five different IMBIE team members using different methods. The data have been adjusted to reflect new models of post-glacial rebound.
(Shepherd 2012).


In Short: It's another lie. Antarctica is currently net losing continental ice at an accelerating rate, as shown by the most reliable of data - the gravity-based GRACE satellite measurements. More warmth, more rain and snow, more stratified fresh water - is preventing warmer deeper ocean layers from melting sea ice so sea ice extent has so far been growing. Sea ice, of course, has NO effect on sea levels, and when air temps rise further and get close to crossing the freezing point in the future, sea ice will be lost as well. We are already seeing accelerating breakup of ice shelfs in Antarctica.


Claim: The domestication of rice and clearing of forests beginning near the dawn of civilization likely saved us from an Ice Age.
What the Science Says: This claim is due to paleoclimatologist William Ruddiman, whose book "Plows, Plagues, and Petroleum: How Humans Took Control of Climate", a popular level book on this idea. Past ice ages are fairly strongly supported to be due to small changes in the obliquity and tilt of the Earth's axis, and the changing ellipticity of the Earth's orbit - the Milankovitch cycles. These are calculatable with modern computers now with high accuracy. The theory in original form is due to Milankovitch. The strongest correlation with the timing of ice ages comes from the amount of incoming solar energy at the 65N latitude, roughly the Arctic circle. The reason is that this latitude is most sensitive to the gain or loss of ice and because of ice's ability to self-refrigerate by reflecting sunlight. Ruddiman's idea is significantly flawed, as we see below...

In past Milankovitch cycles, warming induced the release from the oceans and permafrost of CO2, which then added to further warming. Notice that we currently are in an unusually long period when the Milankovich cycles conspire to prevent an Ice Age from happening again. If one assumes the insolation must drop to levels consistent with previous Ice Ages, it may be another 50,000 years and perhaps 130,000 years from now before the next Ice Age.

Support for the Milankovitch theory of Ice Ages comes well-supported reasoning together with the significant correlation between global temperatures and the insolation at the Arctic Circle. However, it is not perfect. Note the lack of interglacials during two insolation cycles ~160,000 years ago. During the last 8,000 years we have not seen the (moderate) cooling that Milankovitch theory predicted. Human causes certainly dominate lately, and perhaps had some influence as early as a few thousand years ago as well.


During the past 10,000 years insolation has been dropping to current (moderate) levels, where it will remain roughly constant for the next 10,000 years before rising again.

The periodic Ice Ages of the past half million years resulting from the Milankovic cycles. Note too that based on past interglacial time periods, we have many thousands of years to wait for another Ice Age.

Milankovitch cycles show no new Ice Age for another ~50,000 years (NOAA source) . (NOAA = National Oceanic and Atmospheric Administration. The principle federal science agency on ocean and atmospheric science)

Here is a discussion with Ruddiman on his idea, and Ruddiman's eventual concession that early man's agricultural influence can only account for about 1/3 of claimed Ice-Age avoiding warming. In this post by Ruddiman, you'll see that his hypothesis was refuted by Siegenthaler et al. 2005 and by Spahni et al. 2005. Ruddiman disputes these papers because they aligned data to a past interglaciation when insolation values were at a local maximum, and he says it should instead be aligned with a local minimum since we are at a local minimum in insolation today. This complaint by Ruddiman makes no sense, since it is from 8,000 years ago going forward that he claims early humans prevented an ice age by the development of agriculture, and 8,000 years ago did indeed correspond to a time of local insolation maximum, as the Milankovitch cycle insolation graph above shows. Also, in searching this and other discussions, I am surprised to see no one pointing out that the absolute level of insolation in his favored analog period of 400,000 years ago is only 460 watts/square meter, a very large 20 watts/square meter less than current values, and much lower still than the ~520 watts/square meter which prevailed 8,000 years ago. The paleoclimate record indicates it would seem extremely unlikely than an ice age could be triggered at a time of such high insolation. His idea seems to assume that only the direction of changing insolation matters in inducing an Ice Age, not the absolute amount of heating. Ruddiman's hypothesis was tested recently using one of the many sophisticated climate computer models we have designed - the GENESIS climate model, and found that dropping CO2 and CH4 levels to Ruddiman's estimated non-human-caused levels, and see a 2 deg C temperature drop, which is only 1/3 of the temperature drops associated with ice ages, and Ruddiman concedes this. So what was Ruddiman's basis for the dramatic "Ice Age" claim? I have to admit it certainly did make the hypothesis a lurid attention-getter for his popular-level book "Plows, Plagues, and Petroleum: How Humans Took Control of Climate". Note also that we are now no longer in a realm of rapidly dropping Milankovich-induced cooling, and too that CO2 levels now are far higher, due to fossil fuel burning in the last 60 years, than at any time in the past ~800,000 years.

The rapid rise in global temperatures in the last century is the AGW issue, and therefore Ruddiman's hypothesis is also seen to be a red herring in this regard. What's really interesting is how AGW denialists have latched onto Ruddiman's hypothesis as somehow helping their cause. They couldn't be more wrong. A great article with links on this bizarre logic is here.

The Little Ice Age has several contributing causes, not just solar. Robock (1979) finds that enhanced volcanism during this period provides the best fit to the data, while fitting to solar acitivity gives a very poor correlation. Also, the Black Plague de-populated and re-forested Europe and the Columbian Exchange (disease from European colonization of the New World) together caused significant de-populating of the Earth, and the resultant re-forestation of the landscape acted as an efficient remover of CO2 (by 10ppm = 3% by observations) from the atmosphere. In any case, we have accurate satellite measurements of insolation for several complete solar cycles now and therefore have a good idea of how to translate observed sunspot numbers and cosmic ray evidence into insolation estimates for past centuries. The result: even another dramatic Maunder Minimum would not induce another ice age, even a Little one (Fuelner and Rahmstorf 2010).

We clearly can't run an experiment on the entire Earth itself from 8000 years ago to today in order to rule out Ruddiman's hypothesis that man-made activity prevented a new Ice Age completely - but the weight of evidence is clear: it doesn't stand up..

In Short: Human activities almost certainly did keep temperatures a bit higher than they would have been, given the dropping insolation over the past 8000 years, but even without human activities, the evidence does not at all indicate we would have entered a new Ice Age. Regardless, it's amazing that denialists would try and use this issue to argue against doing something about human-caused global warming today. I can only guess that it's another attempt to link "human actions = good for climate" in the public mind, however poorly reasoned.


Claim: There can't be Global Warming. We had record low temperatures here in 2009
Why this Claim is Wrong: Basically, it's the difference between weather (short term variances due to moving cold and warm fronts), and climate (the average of weather over time scales of decades, so that daily and seasonal effects average away, revealing slower secular changes. Imagine getting down on your belly and examing a mountain stream from 2 inches away, and trying to predict what it would look like 2 seconds later. You'd find the task of making the prediction very tough at these tiny scales where mathematical chaos is important. But now stand on the high cliff over that same stream and try and predict what it'll look like in 2 hours. Much easier; it'll be nearly the same. And in 5 weeks? Maybe a little less water flow as summer continues. It's pretty obvious, really. So when you hear AGW denialists claiming the cold winter of '09 disproves Global Warming, it's nonsense . Note also that as of 2011, 2010 was the hottest year on record.

In Short: It's myopic cherry picking. 2008 was a La Nina year, with cool surface waters on the equatorial Pacific. Global warming can only be assessed with a time base that averages over the short-term weather year-to-year. It must span at least a couple of solar cycles and El Nino cycles. Arguing from a single year is naive.


Claim: "How can you trust climate models, they don't even include clouds!"
Why this Claim is Wrong: This was a stunner when I first saw it in Fall 2009 (I'm forbidden to quote the source, but note the direct quotation marks). Climate models have included clouds for decades. It's a gross misrepresentation. As just one example from several years ago, see Hansen et al. 2005, which includes both low and high level clouds in its climate modelling, see also earlier references therein. That said, cloud modelling remains very difficult and until recently, progress in improving the models was slow. Cloud behavior in most models in the past has been done by parameterizations based on observations. This is a good approach when the complex physics doesn't have sufficiently known boundary conditions or numerical resolution to model directly from first principles. It does not mean that the models are nonsense in what they produce. The evidence shows otherwise. Clouds are important to get right since about half of all insolation reflected back out to space is reflected by clouds. The IPCC AR4 identifies cloud modelling as one of the main contributers to the remaining spread in confidence about future temperature trends. But that spread is minor compared to the absolute predictions, which are - severe warming. The radiation physics of clouds is very well known. The absorption and emission of radiation from their bottoms and their tops is well determined, given the actual cloud. What is not yet possible is to generate realistic clouds in global climate models. The problem is that clouds are small, about ~1km in typical size. Grid sizes in global climate models are of order 100 times larger. Modelling clouds on small scales is much easier, but still has a significant uncertainty in the amount of entrainment of dryer surrounding air as convection raises an airmass through an ambient airmass to create the cloud. The solutions so far have been to embed 1- and 2-dimensional cloud model results as parameterized solutions within larger GCM's, and include observed changes in clouds from data.

Since 2006 the situation has improved substantially, with the advent of the "A-Train" satellites observing coherently the same wide regions from space across a wide range of wavelengths in order to measure simultaneously aerosol content, spectroscopic identification of components, albedo, and droplet sizes from reflection properties. Published results show the pollution aerosols make for smaller water droplets and ice crystals and less rainfall from those clouds (Jiang GRL 35, L14804 (2008)). We've confirmed also what we've known since 1989; that large concentrations of sulfate aerosols (e.g. from fossil fuel burning) lead to smaller water droplets and brighter clouds (given the same water content), and that the smaller droplets inhibit precipitation and lead to longer lived clouds. So pollution adds a net cooling, on average. Since the industrialization of Asia has significantly net added to aerosols world wide, we expect a net cooling from this effect, yet clearly global temperature continue to rise despite this. We also see that cloud feedbacks are a positive feedback, meaning that CO2-induced warming alters cloud properties so that they accentuate the warming further. Cloud models have not all been equally good in getting clouds right. According to a study by Clement (2009) studying 55 years of COADS cloud data in the southeast Pacific, rising sea surface temperatures cause a decrease in low clouds and a further increase in low level temperatures. This positive feedback, if correct, accentuates global warming beyond that forecast by the IPCC's 2007 report. The UK Met office's HADGem1 climate model closely matched the behavior of low clouds very well, and also is showing positive feedback. And finally, this paper (Dessler 2011) appeared recently, showing fatal flaws in the claims of Spencer and Lindzen that cloud cover changes are causing global warming, and that models, observations and theory all agree well when done self-consistently. The cloud modelling uncertainties are nowhere near large enough to change the important conclusion - that man-made GHG's are causing the observed global warming.

The two most important ideas to understand - First: if clouds are changing because of the strong global warming we are seeing, then it is a "feedback". Averaged over the globe, that feedback will be either positive (amplify global warming), negative (reduce the rate of global warming) or be zero (have no effect on the global warming determined by the other forcings). Even if, optimistically and against the data so far, one wanted to assume cloud changes were providing a negative feedback, then the magnitude of the effect would diminish as the warming were reduced. There is no way for the cloud feedbacks to REVERSE the warming and bring us back cooler, as we need to be. At best, they only make things less bad than otherwise. Second, it is clear that past climate changes over thousands of year time scales show that clouds are clearly NOT providing a stabilizer to global warming. The Earth's climate has oscillated up and down by about 5C going into and out of Ice Ages, due to the Milankovich cycles, and the relative forcings from current CO2 injection by mankind vs those in the Ice Ages (which were the amplifier for the small orbital forcings) can be seen for comparison here. The conclusion is clear; cloud feedbacks show no evidence of moderating or halting global warming. In fact, the Ice Age forcing vs today show we can expect climate to get much hotter from here. Review the "Cloud feedbacks from warming are negative so climate is essentially stable" claim and why it's wrong, above on this page, for more.

In Short: It's false. Climate models have, of course, included clouds, and continue to. Current studies agree that cloud feedbacks from human-caused warming are making global warming worse, and simple logic tells you that even if cloud feedbacks were negative, they clearly are ineffectual at changing the rapid global warming we are seeing now, as they were coming out of the great Ice Ages as well.


Claim: "Aerosols Are Not Even Considered in Climate Models"
Why this Claim is Wrong: This was another stunner when I first saw it in Fall '09. Of course aerosols are considered in

climate models, and have been for many, many years. This graph at left is from Hansen (2007), which shows climate forcings due to the sun, snow coverage, land use, water vapor, ozone, well-mixed GHG's (methane, CO2, NO2...) and several different aerosol types, all using the Goddard Institute for Space Science's Climate Model E. Note that most aerosols act to cool climate by reflecting some sunlight back out into space before it can reach the ground. Only greenhouse gases have a strong upward and accelerating positive temperature forcing, and for fully 70 years now greenhouse gases have dominated all other effects except temporarily during volcanic eruptions, in line with observed temperatures. We certainly want to understand the detailed physics of aerosols better than we now do, as currently we need a mixture of basic physics and fitting to observed data to parameterize the behaviors under different relevant conditions. But note that even with the unusually frequent volcanic stratospheric aerosol injections since 1960 (including Mt. Agung, Mt. St. Helens, and Mt. Pinatubo) - volcanic eruptions being most powerful net cooling forcings - yet this is precisely the time when global temperatures have actually accelerated upward. While the aerosol forcing curves are likely to move a bit as we gain better understanding and ability to model, even if we're off by 100% on each aerosol curve, it won't come close to changing the net result and net conclusion - aerosols are not the reason for global warming. Man-made greenhouse gases are. The contribution of aerosols to climate is net cooling, and while the uncertainty bars are indeed large, but they do not change the conclusion that anthropogenic GHG's dominate climate change, and this is expected to become more so as cleaner technologies reduce man-made aerosol pollution.

In Short: It's a fabrication. Aerosols are of course included in climate modelling. Remaining aerosol modelling uncertainties are relatively minor compared to the strong and well-understood forcing due to human-caused greenhouse gases. Most natural and man-made aerosols actually cause cooling (via reflection), not warming, so that there is almost no chance that natural aerosols could be responsible for a significant amount of global warming.


Claim: "CO2 Follows Temperature, Not the Other Way Around"
Why this Claim is Shamefully Misleading: Look at the logic this claim attempts to persuade with: Because many past instances in the paleoclimate record show temperatures rising from low levels, followed decades or perhaps a century or two later with rising CO2 levels, that therefore current CO2 rise cannot be causing global warming today. If your response is puzzlement and a struggle to grasp the logic, be reassured - there is no logic to grasp. Human forcings of climate have no precedent in the Ice Age paleo record. Before mankind was pumping huge amounts of carbon into the atmosphere in a geological instant, the large slow temperature changes of the past few million years were primarily caused by the Milankovitch cycles in the Earth's orbit. When temperature rises due to orbital change, the rising ocean temperature brings more CO2 out of solution and into the atmosphere (Callion et al. 2003). The increased CO2 in the atmosphere then causes further temperature rise by the greenhouse effect, which induces more CO2 out of the ocean, etc. This positive feedback, together with the ice albedo positive feedback effect, is sufficient to bring Earth out of an Ice Age into an interglacial. It takes centuries for this process to happen as the CO2 transfers into and out of the ocean are quite slow because global deep ocean currents are very slow, and because the process proceeds through stages of quasi-equilibrium. A good discusion with figures is here, and another is here. The Callion et al. 2003 paper found a lag of ~800 years, but newer research which better understands the movement of air bubbles in paleo ice cores finds that lag is more like 200 years or less, with far smaller error bars (Parrenin et al. 2013 and digested in Scientific American here). Today's global warming is happening not on the thousands of years time scales of the "CO2 Follows Temperature, Not the Other Way Around" cannard, but a few decades. And the record clearly shows CO2 rise is happening at the same time as temperatures rise in the atmosphere and ocean - not ~200 years later. The reason is simple - we're adding CO2 directly to the atmosphere, at a pace far in excess of what the ocean or land can absorb. Not even remotely in equilibrium. It's not at all like "CO2 follows temperature" examples in the paleo record. Ten thousand years ago, humans and their livestock comprised about 0.1% of the land vertebrate biomass. Today, we comprise almost 99%, and strongly altering the atmosphere as we dominate the planet.

In Short: It's deliberate mislead. It's wanting you to believe that the evidence in front of us - that rising CO2 is leading rising temperature today - must be wrong because that's not exactly what happened during past Ice Ages. There is NO logic to such a contention. Today, our CO2 is causing warming directly to the atmosphere so it heats first, not Milankovic cycles which solar heated the ground and oceans first as in past Ice Ages.

Claim: Late 20th Century cycles in temperature, CO2, and sea surface temperatures (SSTs) show that CO2 still lags, and therefore cannot be the cause of modern global warming.
Why This Claim is Wrong: Humlum et al. (2013) and earlier versions are the source of this claim. Their analysis is simplistic and deeply flawed, attempting to take very short term rates of change of these data and because they do not see a simple pattern of CO2 peaking earlier than short-term peaks in SST's and global atmospheric temperatures, conclude there's no cause/effect. This is thoroughly debunked in here. By choosing an analysis method which ignores trends caused by human activities, they seem to find it profound that they do not see obvious anthropogenic effects. They also ignore that rising SST's have a feedback on CO2 in the atmosphere in that hotter SST's will inhibit CO2 uptake by the ocean, leading to higher CO2 left in the atmosphere especially during El Nino's. They also ignore the seasonal biological CO2 cycle. Adding very short term noise from the effects listed above and others will destroy that obvious correlation with anthropogenic causes, as explicitly demonstrated here.

In Short: It's junk science, using completely unsuitable statistics and math which are controlled by noise to then make unjustified claims about CO2 causation of climate change. One wonders why the paper's referee did not call attention to the blatant flaws. The referee process is usually good, but not always. It's also concerning that the authors have collaborations with the Heartland Institute.


Claim: Cities have grown during the 20th century and their asphalt, concrete and buildings absorb much more heat than vegetated countryside. This biases temperature measurements - this "Urban Heat Island Effect" accounts for much or all of global warming, not CO2.
Why This Claim is Wrong: This effect is and has long been very well understood and continues to be factored into studies of global temperatures. The denialist claim is disingenuous in the extreme and aims itself at the naive, who don't realize how obvious and for how long this effect has been understood by climate scientists. For example, the latest IPCC report in 2007 finds that urban heat island effects have been determined to have negligible influence (less than 0.0006 °C per decade over land and zero over oceans) on these measurements. Here's an easily digested summary of the story. There isn't, and never was, a "urban heat island" issue with the data. Here's the latest graph showing global temperatures using all data, and also using only rural weather stations. For the entire 160 year period, there is no difference (with the exception of the Civil War time - questionable data-taking in the heat of battle?) .

Update 2012: This is a good place to mention the work of Professor Richard Muller at UC Berkeley. Muller is an astronomer, but is also interested in science and society, and in science communication. He clearly enjoys being a contrarian in general (I've heard him speak at UCSC). He had been a critic of the AGW climate science community, although he admits he had not actually studied climate science. This shoot-from-the-hip approach can make you endearing ... or it can make you look like a fool. To his credit, he decided to pull together some bright people and re-analyze all available historical temperature data and assess the case for biases, including the urban heat island effect - the BEST project, and read it here as well. His results on the global temperature trend is closely confirming the work of climate scientists, to his surprise, and to the outrage of high profile blogger denialist and Fox News TV weatherman Anthony Watts (wikipedia's entry).Peter Sinclair put together this video on the Richard Muller story. I'm glad to see Muller finally siding with the long standing evidence, as he's had a checkered past (see here) in regards to climate science.

Update 2013: New temperature data over the past century which does not use thermometers but natural systems, re-confirms the steep (in geologic time scale terms) rise in temperature seen in weather station data (Anderson 2013 in Geophysical Research Letters).

In Short: This is and was a well-understood issue which was properly calibrated in the original work. Even if one does not calibrate out the suspect weather stations, numerous studies verify that there is and was no significant "urban heat island" effect in the global temperature data. Remember, even if a weather station is in a hotter urban setting, it is the TREND in temperatures over time which is the signature of global warming.


Sea level since 1993, seasonals removed

Claim: Sea Levels dropped significantly in 2010 and 2011, showing climate scientists' claims of higher CO2 means rising sea levels is seriously flawed.
Why This Claim is Wrong: This got a lot of play, in particular at the climate denialist blog "Watts Up With That", a blog by Fox News TV weatherman Anthony Watts. Hundreds of denialists piled on, loudly claiming climate science was completely wrong about CO2 and human-caused global warming. The truth is that sea levels did indeed fall during those two years, but it was entirely understandable with basic science. The Earth had an unusually strong La Nina phase of the El Nino/Southern Oscillation in 2010-11, and this phase is normally associated with globally greater than normal rainfall and snowfall over land and cooler temperatures. This causes a transfer of water from the ocean to the continents and when it is this strong, this can actually more than compensate for the secular rise in sea level. Since 2011, we have had the ENSO phase shift to mildly into the El Nino phase in 2013, and the resultant loss of continental ice and return of water off the continents to the ocean has more than compensated for the dip in sea level in 2010/11. Even without taking out the ENSO oscillation, it is clear from the sea level graph of the past 20 years (see at right) that the rise in sea levels continue. This graph plots mean sea level from satellite altimetry. Seasonal annual signals removed to reveal secular trend. the glacial isostatic adjustment of 0.3mm/yr is added to account for the slumping of ocean basins. Image from the AVISO website. I'd like you to note the 200 comments entered after the posting in WUWT linked above, and the smug, self-satisfied put-downs of the work of good climate scientists by the denialists who know nothing about science, or honest scientific work. For more detail, see the well-linked coverage of the issue in Skeptical Science. Don't expect to see an apology from WUWT upon seeing the accelerated return and overshoot to the mean sea level rise curve. Apologies are not part of climate denialist's modes of operation.

In Short: Sea level rise is not perfectly correlated with CO2 levels on a one or two year time scale because ENSO-associated oscillations in total rain and snow over the continents can temporarily move water from the oceans to land, and this was particularly dramatic in 2010-11, and has since reversed.


Claim: "Climate models get energy balance wrong, make too hot forecasts of global warming."
Why This Claim is Wrong: This quote is from a press release issued by the authors of a July, 2011 paper by Roy Spencer and Don Brasswell "On the Misdiagnosis of Surface Temperature Feedbacks from Variations in Earth’s Radiant Energy Balance". The paper claims that climate models overestimate the sensitivity of surface temperatures to CO2 forcing. It does so with a vastly oversimplified one-dimensional model, using naive statistics, and too many unconstrained fitting parameters. The same model can be made to fit either a high sensitivity (of temperature to CO2) or low sensitivity conclusion, but Spencer latches onto the low sensitivity conclusion using very poor decision-making. He was unable to get his paper published in a reputable climate journal and so went straight to publishing his own book via vanity press "The Great Global Warming Blunder". In summer '11 Spencer got it published in an open access journal called "Remote Sensing", which is not a climate journal and it clearly did not get reviewed by climate-competent referees. A good criticism of the work is here, here, and also in Why comment on this? Only because it's getting a fair amount of splash in the denialist blogosphere and Fox news outlets, none of whom have made a good reading of the paper, it would appear.

Update on Sept 4, 2011: The editor of the journal "Remote Sensing" has now resigned, over the inept refereeing and publication which he supposedly oversaw, of the Spencer & Brasswell paper. He agrees with the post-publication severe criticisms of the paper and that his journal did not exercise proper judgment of the paper's deep flaws. Worst, the editor allowed the authors to choose their own referees(!), rather than find independent referees. Will the many biased media outlets, such as the 700 Club, the Christian Post, Fox, and others, issue apologies for hyping this paper? That would be the honorable thing to do, but based on past history, I would not expect it. More analysis of this affair and Spencer's surprising and unfortunate behavior afterward is here.

In Short: It's in the worst traditions of junk science.

Claim: Climate scientists who claim global warming will be a disaster are just alarmists trying to scare you, trying to insure more grant funding for their projects.
Why This Claim is Wrong : Richard Lindzen is fond of repeating this theme (while supplying no evidence) - that climate scientists are just trying to scare you, for their own nefarious purposes. The vast scientific literature supporting the reality of anthropogenic global warming speaks for itself, as I reference throughout this website. But let's consider whether the predictions from the IPCC consensus documents are "alarmist" or not. This link concisely compares the IPCC AR3 (2001) and AR4 (2007) predictions with actual observations since publication. It shows CO2 emissions accelerating upward even faster than the most "alarmist" IPCC scenario, it shows sea level rising at a rate at the extreme upper end of the range of IPCC scenarios since 1990, and it shows Arctic ice loss accelerating faster than even the most alarming IPCC AR4 models. Even the more recent IPCC AR4 issued in 2007 is actually too conservative and not "alarmist" enough in its predictions. The AR4 predicted that the Arctic would not become ice free in summer until near the end of the 21st century, but it did not include modelling the effects of breakage and movement of broken ice. Moving ice finds its way into the ocean currents that carry it south where it melts rapidly (Rampal et al. 2011). It is not only that the area of ice loss that is growing, but the thickness of the ice that does remain is thinning rapidly, so the ice volume is shrinking even more rapidly. The pace of Arctic ice melting is indeed alarming, and this MIT University study (2011) shows far more rapid ice loss predicted for the Arctic Ocean, and an ice-free Arctic is likely to happen many decades earlier. Elsewhere here, I reference observations of ice loss due to glacier movement in Greenland, significantly worse than IPCC predictions because they were unable to model the glacier base/ground interface and so did not include it, yet observations clearly show that glacier movement is accelerating as the Earth warms, faster than the IPCC (AR4 and earlier) predictions.

Observed Arctic Ocean ice area (in red) vs. climate models. The conservative IPCC AR4 modelling is clearly not alarmist enough.

A new low in Arctic Ocean ice area in 2011

The trend is clearly down

Arctic ice area is dropping in all seasons, not just summer.


In Short: It's a slanderous ad hominum against good scientists, without a shred of evidence presented to back it up. The evidence has shown that reality is actually worse than the IPCC AR3 (2001) and AR4 (2007) predictions. The rapidly rising CO2 levels, global temperatures, plummeting polar ice coverage, rising sea levels, and rising extinctions rates, all speak for themselves. The IPCC has clearly not been "alarmist" enough.

Claim: Long term oscillations in the ocean/atmosphere - the Pacific Decadal Oscillation (PDO), and the Atlantic Multi-Decadal Oscillation (AMO), account for ~half of Global Warming; so the climate sensitivity of CO2 must be lower than thought.
Why this claim is wrong: The latest incarnation of this is due to Tung and Zhou (2013). Tung and Zhou ignore that their AMO data is strictly in sea surface temperatures, which are or can be strongly affected by a greenhouse warming atmosphere. Their reasoning is circular. They assume the AMO is unaffected by GHG warming, then notice SST's are rising and assume it's the AMO driving global atmospheric temperatures. In fact, Timino (2013 here) has shown that no matter how the AMO and atmospheric temperature correlations are analyzed (trended or de-trended, linear or not), that atmospheric temperatures lead the AMO SST's by some months, suggesting the causation direction is atmospheric greenhouse warming leading to AMO ocean warming, as basic theory also supports. Here's a link to clarify.

In Short: The reasoning is at least partly circular. AMO and global temperatures are clearly correlated and cause-effect might be in either direction before analysis is done. They ASSUME that AMO and PDO are not caused by global air temperatures, and therefore, unsurprisingly, find the causation goes the other way, having assumed away the reverse (and proper) direction. More careful analysis shows air temperatures lead the ocean AMO temperatures by months, suggesting cause and effect is opposite to that claimed by Tung and Zhou.

More Claims: There are other climate denialist claims, all of which have been thoroughly debunked. A good and very condensed summary statement of each myth and with links for expanded discussion can be found here.

On Richard Lindzen
Richard Lindzen is the highest profile and considered the most prestigious (Sloan fellow at MIT) of the AGW denialists. So it's disturbing that he uses his MIT position (earned by reputable work that was not AGW-denialist oriented way back when he was a young man (in 2012 he was 70 years old)) while making misrepresentations in the Wall Street Journal and other non-science journal outlets about climate science and the scientific evidence for global warming, without references, without support. Here is an account of his testimony in front of the UK's House of Lords and the outright falsehoods about the scientific consensus. A quote from this article: "when a panelist specifically asks ‘how far your view of the role of water vapour is shared by other scientists?’ (Q144), one cannot honestly answer ‘That is shared universally’ when no other scientist in the field has made a case for a negative water vapour feedback. This is probably the most egregious mis-statement in the whole testimony and is deeply misleading."

Here are links to his conflicts of interest in taking money from Big Oil, and to his own grad students' testifying that Lindzen feels a strong emotional need to prove his status at the expense of others, bringing into further question his ability to be objective and truth-oriented above all else: “If you want to prove yourself a brilliant scientist, you don’t always agree with the consensus,” said Daniel Kirk-Davidoff, a former student of Lindzen’s at MIT. “You show you’re right and everyone else is wrong. He certainly enjoys showing he’s right and everyone else is wrong,” Kirk-Davidoff continued. “If you have a ten minute conversation with him, you can tell that.”.

Collection of links on Lindzen's strikingly poor record on climate change ideas, his past funding by oil money

Climate scientists respond to Lindzen's Newsweek interview (2006)

Here's another good video on the junk science objections to AGW, the final few minutes of which does a good summary of the poor science in Lindzen's continually discredited "Iris" hypothesis. Lindzen's continued output of opinion clearly at variance with the evidence, is impressive. A long and growing list of Lindzen quotes and comparisons with reality, is here. No responsible person sincerely desiring to know the truth can afford to simply take his unsupported pronoucements and poor science on faith, just because he's an MIT professor. That is the classic logical fallacy of "the argument from authority". Instead, one gives credibility to a scientist's claims because he's supported his case well, in solid peer-reviewed scientific journals which have stood the test of critical examination.

Update 2012: Despite having been called on his outrageously wrong statements repeatedly, he continues to make them. The latest is described here, and here. Lindzen has another (Aug 22, 2012) op/ed piece in the Wall Street Journal which continues to spread his opinions which are at odds with the evidence, as critically examined here.

Politics and Psychology, and a Prediction
The seemlingly endless Sisyphian task of talking sense into climate denialists has many pondering why they cannot be reasoned with. I myself wonder - Isn't there a point where the need (whatever its motive) to deny human responsibility for climate change is overwhelmed by another very human desire - the desire not to look like a complete idiot, or worse? I don't believe simple greed is the whole story (although it may be that simple for the largest funders of denialism and their paid politicians). There are many motivations that may help explain this. But some new thoughts include these - this interesting article on the correlation between low IQ and political conservatism, and this one from author Chris Mooney and his book "The Republican Brain: The Science Behind Why They Deny Science - and Reality" describing the interesting finding that high education levels correlate with higher conviction on the reality of human-caused global warming among Democrats, but this correlation does NOT exist for Republicans. In a 2012 poll, Republicans are found to be far more likely to believe in Demonic possession (68%) than in climate change (42%) . A new study to be published in the journal Psychological Science finds a strong correlation - people in denial of human-caused global warming also tend towards a belief in a wide variety of conspiracy "theories", and also with free-market orientation. Denialist blog sites responded to this study with (unsurprisingly) - it's a conspiracy! (see journal study here, and also LiveScience). Is this meant to describe every individual conservative? No. But in a political system where it is not intelligence, but sheer vote count is all that matters, these correlations are vitally important.

Update 2011: As the frequency of climate-related disasters increase, certainly the desire to not be on record as a complete idiot will gain traction and the marginal utility of continued denialism will diminish. So how will the rhetoric evolve? As I've been telling my students in '10 and '11, my prediction is that we'll hear more of something like this - Well that's a darn shame. It's a shame the science wasn't settled sooner. Nothing we can do now except adapt to the new climate. Americans are a resilient people, and capable of tackling tough challenges, and we have every confidence in their ability to find a way to adapt to this new world we're heading into. And by the way, we'll need plenty of energy to accomplish the mission, and we - the energy services industry - we'll be here for you, and for all of us! You won't hear apologies, you won't hear admissions of gross lying, admissions of slander against climate scientists, confessions of policy foot-dragging, nor will you hear any willingness by the fossil fuel industry to pay the full costs for what will happen to future generations. If they continue to hold sway, it'll be not the fossil fuel corporations, but the all of us, and our children and grandchildren and great grandchildren who will be expected to adapt, with whatever they can muster.

2012 Updates:
Today (July 12, '12), I got a news item - pollsters are now telling Republicans that they must quietly backpeddle or face their own wrathful voters: This source says "Note: a well informed source tells me that republican pollsters are quietly warning their clients, congresspeople and senators – that unless they walk back their stands on two key issues: climate change and gay marriage, '...nobody under 30 is going to vote for them in 2016.' " If heeded, it's a hopeful comment (but if heeded, would it just be word play, until they win the elections?). Now look at the policy statements on climate from Republican vice-presidential candidate Paul Ryan.

A recent climate denial (presented without evidence, as is typical), appeared in the Wall Street Journal in late January 2012, and simply repeats the claims already shown to be false here and elsewhere. They distort and misrepresent the position of Yale economist William D. Norhaus, who has written a good refutation here. More on this, and excellent links to the catastrophic externalized costs of carbon which the fossil fuel industry is working so hard to convince you it should not pay, is here.

2013 Updates:
Feb 3, 2013: "...Ultimately we have a moral responsibility to the most innocent victims of adverse climate change. Those who will suffer the most are the people who are the most innocent: the world’s poorest citizens and those yet to be born. There is an ancient Native American saying: “We do not inherit the land from our ancestors, we borrow it from our children.” A few short decades later, we don’t want our children to ask, 'What were our parents thinking? Didn’t they care about us?'" From Dr. Steven Chu - letter to his employees after announcing his resignation from his cabinet position as U.S. Secretary of the Department of Energy.

May 2: A new poll finds that 29% of Americans and 44% of Republicans think that armed rebellion may be necessary in the U.S. in the coming years. Is this how Republicans and other denialists will respond - with armed rebellion - if tax-and-dividend or other major policy changes are instituted in order to try and reduce the odds for the most dire of climate science forecasts?


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