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 careful 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 One aspect of this in fact points to the inherent honorability of the scientific enterprise (vs the political agenda of the denialists) - IPCC Stephen Schneider relates in 2009 how his initial estimate of the effect of human-generated pollution in the 1970's was that it may be even a stronger coolant to climate than is CO2 as a warming force. Then, it quickly became clear, still in the 1970's, when the data came in about the extent of aerosol pollutions over land area was much more limited than at first guessed, it was clear that aersol cooling was significantly less than the CO2 warming, and that Schneider himself was first to make this announcement. In other words, evidence and truth-seeking over rigid unwillingness to admit mistakes.

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 imminent 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 and reflecting 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.


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