Key Ideas in Astro 7: Planetary Climate Science

Especially for the non-text material, be sure to also see the red slides at the end of each of the PowerPoint presentations for the summary of key ideas

Chap 0: Scientific Thinking, Nature of Bias

Our Place in the Universe

Light, Matter, Heat

Formation of the Solar System

  The Jovian Planets

Asteroids, Comets, Meteoroids

The Sun
       * The structure of the sun; layers
       * Sunspots and the sunspot cycle, luminosity changes with solar cycle. More sunspots - more luminosity
       * Stars - balancing gravity, energy production, pressure. How changing one affects structure of the sun.
       * Long term evolution of the sun's luminosity - higher!
       * Aurorae; relation to the solar corona, magnetic fields

K20: Heat Transfer Mechanisms
       * Know the 3 modes: conduction, convection, radiation
       * Convection, requires temperatures drop with increasing altitude, and gravity.
       * Radiation, goes as temperature to the 4th power, very steep
       * Conduction: faster in dense media, and media with easily removed electrons (like conventional metals)

Chap 10: The Atmospheres of Terrestrial Worlds (Mercury, Venus, Earth, Mars, the Moon)

K31: Paleo Climate of the Earth
       * History of oxygen in our atmosphere; almost none till cyanobacteria made most of it
       * CO2 and probably methane much richer in early atmosphere, counteracting lower solar luminosity with greenhouse warming
       * mostly indirect evidence for paleo atmosphere. Trapped samples of atmosphere only in the past few hundred million years
       * "Snowball Earth" - brief episodes of frozen planet. Know the evidence and strength of the evidence
       * Know the history of CO2 content of our atmosphere, over 4.5 Byrs, and over last 50 million years
       * Recent Ice Ages: know the cause, critical areas of Earth which are involved in the cause
       * Earth distance from sun has not changed significantly over Earth's history, so early oceans require strong greenhouse warming to account for.


K32: Structure of the Earth's Atmosphere
       * Four separate zones: Troposphere, Stratosphere, Mesosphere, Thermosphere
       * Troposphere heated from sunlight-warmed ground
       * Heating from below allows possible convection, if heating is strong enough and temperature gradient is strong enough
       * Stratosphere heated from the top by ozone absorption of solar UV. Heated from above so no convection, no weather
       * Rising CO2 in the stratosphere cools the stratosphere by providing an avenue for molecular collisional energy into IR radiation to space

K33: Carbon Cycles

       * "Fast cycle" moves carbon from atmosphere to plants via photosynthesis, and into surface ocean and soil, over seasons to decades
       * "Slow cycle" moves CO2 into the ocean's deeper layers with the slow currents, turnover time ~1,000 years.
       * Slower still is the conversion of CO2 into CaCO3 by organisms, removing it from the atmosphere.
       * Volcanoes return some geologic strata limestone CO2 back to the atmosphere, but only at a rate ~1% of human fossil fuel burning today


K34: Climate Modelling

       * A climate model is a computer program which solves simultaneously all the physics equations which govern the atmosphere: heat transfer, radiation transport, gravity, vorticity transport, sunlight, greenhouse effect, volcanoes, human influences, and the interaction with the land and oceans, and the chemistry of the changes.
       * Climate models checked for accuracy: post-dictions of past weather and climate, alter initial conditions to check for stability, quantify uncertainties in physical parameters.
       * Climate models today work very well and need to be taken seriously
       * Greatest uncertainties are: including cloud production and changes, and aerosol effects on clouds
       * Radiation properties of clouds well understood.
       * Global cloud changes when climate changes by large amounts are not well determined.
       * The differential and integral equations governing the physics are turned into difference equations for computer solution.
       * Typical cell in a global climate model today is about 10km on a side, and ~50 vertical cells to model the atmosphere, similar number for the vertical ocean.


K35: Clouds and Aerosols
     * Most important to know - low clouds (e.g. fog, stratus) generally cool climate. High ice clouds warm the climate by trapping outgoing IR
     * Most important property of a cloud as far as climate - how warm is the top surface. If cloud is high and therefore cold, it radiates less to space
     * Clouds are created by rising convection of moist air
     * Plenty of aerosols in the lower troposphere to nucleate clouds. Way more than enough to accomplish that job.
     * To model individual clouds requires much smaller size scales than can be done in a global climate model... like inches or feet!
     * Very non-linear process, the cloud affects its environment greatly, affecting how the cloud itself can grow or not
     * Volcanic aerosols blast into the stratosphere, heating stratosphere but blocking sunlight to the troposphere and cooling it
     * Sulfate aerosols from human air pollution, and volcanics, make tiny droplets which are very reflective.
     * Yellowish bright haze in cities acts to reflect incoming sunlight, cooling the surface
     * Human CO2 heats climate, human air pollution cools it. CO2 has been far dominant, especially as we clean up our smoke-stacks.
     * Raising air temperature 1 degree Celsius allows it to hold fully 7% more water vapor - which is itself a powerful greenhouse gas

K36: Ocean/Atmosphere Connection
     * Rate of heat transfer from atmosphere to ocean is uneven over time scales of a few years.

     * Varying heat transfer produces Pacific Decadal Oscillation, El Nino/La Nina
     * El Nino years leave more heat in the atmosphere, hotter climate
     * Ocean currents driven by solar heating near equator, moving north and south, densifying with cooling until sinking near the poles

     * Thermocline - a layer of sharply dropping temperature and salinity dividing the surface waters with the colder deep ocean
     * CO2 in the atmosphere is absorbed by the ocean.
     * CO2 saturation pressure in ocean is lower at higher water temperature
     * Pacific Decadal Oscillation index has, over the past century, shown no net warming or cooling trend.


K37 - Climate forcing and Climate Time Scales
     * "Time scale" - a wonky term meaning: the approximate time it takes for "significant" change, in our case; for climate
     * Time scales for physical climate processes are longer for higher thermal mass, and shorter for stronger forcing
     * Climate time scale for Earth with current human forcings, is ~50-80 years

K38 - Current Global Warming
     * 100% of global warming can be accounted for by rising human-generated CO2.
     * Other human influences on climate roughly equally produce cooling and warming
     * Know the 4 climate change periods of the past 150 years, and their causes
     * Stratosphere cooling continues even after ozone levels rise after CFC's banned in 1989
     * Satellite data confirms solar luminosity increases by only 0.1% from min to max of sunspot cycle
     * Rising aerosol pollution causes global cooling. Early in 20th century due to Europe, U.S. Now it's Asia.
     * Solar activity contributed some to global warming in first half of 20th century, none since.
     * CO2 emissions retained in Atmosphere, land, and ocean - trends with time for past 50 years (PowerPt graph)
     * Most of 20th century sealevel rise due to thermal expansion as ocean warms
     * Most of 21st century sea level rise predicted to be due to melting continental ice
     * GRACE satellites show rapid ice loss in Greenland and Antarctica
     * Arctic Ocean permanent ice is mostly gone, ~90 years ahead of predictions by IPCC in AR4.
     * Global deforestation adds about 1/4 of the rising CO2 to the atmosphere


K39 - Key Evidence Showing Global Warming is Human-Caused
     * Warming troposphere and cooling stratosphere is observed, and is unique to greenhouse effect

     * Climate models accurately reproduce global temperatures only if humans included. Natural causes produce NO global warming
     * Solar luminosity has been decreasing slightly while global warming accelerating - It's NOT the sun
     * Known anthropogenic CO2 emission rates twice as large as atmospheric CO2 rise rate
     * C13/C12 ratio proves the rising CO2 is due to fossil fuels
     * Volcanoes produce only 1% of human-caused CO2 rates
     * Strongest global ocean oscillation is PDO, and it has been in a cooling trend for ~20 years while global warming continues


K40 - Climate Denialism; Characteristics and Causes
     * Tactics: slander against scientists
     * Tactics: fake experts, cherry picking short-term data, picking fossil fuel trade journals for publications, then citing as if "science"
     * Same people who defended Big Tobacco in cancer battles years ago, now doing climate denialism
     * Right-wing ideologues and those in the pay of fossil fuel corporations are main sources of climate denialism
     * Academic scientists have far better record of integrity in published science than do those employed by corporations
     * Conviction of truth of human-caused global warming rises with education level, but only among democrats, not republicans
     * Conviction of truth of human-caused global warming correlates strongly with demonstrated expertise in climatology

K41 - Debunking Climate Denialist Myths

     * No "urban heat island" effect even if data is left uncorrected for this effect
     * ~dozen observed changes to Earth due to rising temperatures which have nothing to do with our temperature guages
     * Greenland, Antarctica losing ice, not gaining it - proof from GRACE
     * Conspiracy theories against scientists are ridiculously contradicted by obvious scientific career motivations
     * Cosmic rays cannot cause global warming because cosmic ray/solar connection and solar has not trend for 60 yrs
     * Know why cloud nucleation by cosmic rays makes little sense and cannot cause global warming
     * Temperature trends in strong disagreement with claim GW is just rebound from last Ice Age
     * Data shows earlier IPCC claims not "alarmist" - instead they're not nearly alarmist enough.


K42 - Climate: 21st Century and Beyond
      * IPCC AR4 projections left out some important physics and is proving to be far too optimistic. Climate is worsening much faster than expected.
      * 93% of greenhouse heating has moved into the oceans, making for a vast store of heat that will prevent us from cooling down
      * Even if all CO2 emissions are ended, temperatures will not go back down.
      * "Business as Usual" for a few more decades, as the oil companies continue to invest for, means permanent and crippling climate change which will last for tens to hundreds of thousands of years

K43 - Strategies for Dealing with Climate Change
      * Solar, Wind, and Nuclear are the largest sources of low-carbon energy
      * The single most powerful action required, is passing a severe carbon tax-and-dividend law. Motivates EVERYone to reduce carbon
      * Even reducing global CO2 emissions to zero still results in temperatures not going back down, so we need active atmospheric CO2 removal beyond that provided passively by the ocean and land plants
      * Solar PV farms covering about the size of Spain would power entire estimated Earth of 2030
      * Reforestation would only provide a minor amount of carbon sequestration
      * Renewable non-carbon energy currently supplies only a few percent of the Earth's energy
      * Renewable sustainable present technologies can support world’s current population only at a standard of living equivalent to that of Ethiopia. Or, at current income distribution, can support about 2 billion people.
      * Sunshade strategies for reducing solar heating do nothing to lower CO2 and ocean acidification
      * Reducing CO2 from 400ppm to 280ppm by sequestering at CaCO3 would require a Mt Everest sized cube
      * Game theory experiments with real participants show climate negotiations will fail, in a competitive world, due to selfish perceived interests
      * Tragedy of the Commons, plus the Culture of Economic Growth as the top societal value, insures environmental degradation for all.
      * Jevon's Paradox - basically, savings in any resources are simply spent elsewhere, so that ecological footprint reduction requires revolution in culture, not techno-fixes
      * Granting legal rights to the Earth, and/or to future generations, may be required (if it can be agreeed to!). Pachamama strategy
      * Artificial trees might some day pull CO2 from the atmosphere, but sequestring it is problematic.
      * Prof. Greg Rau's calcium bicarbonate solution is promising
      * corn ethanol makes no sense. Cellulosic ethanol better. Algae-based biofuels promising for carbon-neutral fuel.