You Ought to Have a Look is a feature from the Center for the Study of Science posted by Patrick J. Michaels and Paul C. (“Chip”) Knappenberger. While this section will feature all of the areas of interest that we are emphasizing, the prominence of the climate issue is driving a tremendous amount of web traffic. Here we post a few of the best in recent days, along with our color commentary.
More evidence this week that high-end forecasts of coming climate change are unsupportable and Americans’ worry about environmental threats, including global warming, is declining. Maybe the general public isn’t as out of touch with the science as has been advertised?
First up is a new paper by Bjorn Stevens from Germany’s Max Plank Institute for Meteorology that finds the magnitude of the cooling effect from anthropogenic aerosol emissions during the late 19th and 20th century was less than currently believed, which eliminates the support for the high-end negative estimates (such as those included in the latest assessment of the U.N.’s Intergovernmental Panel on Climate Change, IPCC). Or, as Stevens puts it “that aerosol radiative forcing is less negative and more certain than is commonly believed.”
This is important, because climate models rely on the cooling effects from aerosol emissions to offset a large part of the warming effect from greenhouse gas emissions. If you think climate models produce too much warming now, you ought to see how hot they become when they don’t include aerosol emissions. The IPCC sums up the role of aerosols this way:
Despite the large uncertainty range, there is a high confidence that aerosols have offset a substantial portion of [greenhouse gas] global mean forcing.
The new Stevens’ result—that the magnitude of the aerosol forcing is less—means the amount of greenhouse gas-induced warming must also be less; which means that going forward we should expect less warming from future greenhouse gas emissions than climate models are projecting.
Researcher Nic Lewis, who has done a lot of good recent work on climate sensitivity, was quick to realize the implications of the Stevens’ results. In a blog post over at Climate Audit, Lewis takes us through his calculations as to what the new aerosols cooling estimates mean for observational determinations of the earth’s climate sensitivity.
What he finds is simply astounding.