Climate science is in its infancy, and just about every proposition is controversial. The idea that climate science is in any non-trivial sense settled is ridiculous.
One area where this is obvious is clouds. Clouds play a huge role in the Earth’s climate, but the dynamics surrounding the various types of clouds are simply not understood. When climate scientists developed the models on which all global warming alarmism is based, they knew that the role they assigned to CO2 as the principal driver of the Earth’s temperature could not be sustained by a review of the Earth’s climate history. Therefore, they used clouds as a plug factor, programming their models to believe that the human influence on clouds significantly moderates the otherwise extreme influence of added CO2 on the climate. This is one of many ways in which climate “science” is not scientific.
Unfortunately for the alarmists, modern scholarship undermines the role assigned to clouds in the models. At Watts Up With That?, Paul Knappenberger and Patrick Michaels explain:
Currently, details are few, but apparently the results of a major scientific study on the effects of anthropogenic aerosols on clouds are going to have large implications for climate change projections—substantially lowering future temperature rise expectations.
In a blog post from the Department of Meteorology of the University of Reading, Dr. Nicolas Bellouin describes some preliminary results from a research study he leads investigating the influence of aerosols on cloud properties. The behavior of clouds, including how they are formed, how long they last, how bright they are, etc., plays a very large role in the earth’s climate system, and is considered the weakest part of global climate models. …
When it comes to the influence of human aerosol emissions on cloud properties, the scientific mainstream view is that aerosols modify clouds in such a way as to result in an enhanced cooling of the earth’s surface—a cooling influence which has acted to offset some portion of the warming influence resulting from human emissions of greenhouse gases (primarily from the burning of fossil fuels, like coal, oil, and natural gas to produce energy). In the absence of this presumed aerosol cooling effect, climate models predict that the earth should warm at a much faster rate than has been observed. A large cooling effect from aerosols was thus introduced in the early 1990s as a way to “fix” the climate models and bring them closer in line with the modest pace of observed warming. Despite that “fix,”climate models continue to overpredict the observed warming rate—which is bad enough news for climate models already.
As we have said many times, a model that generates false predictions is no good. It is simply wrong, and it can’t be fixed by scrambling around after the fact to add hypothetical influences to “explain” the model’s failure.
But the new results, reported by Bellouin, make things much worse for them. His team’s investigations show that the anthropogenic cooling impact from clouds is much less than “assessed” by the U.N.’s Intergovernmental Panel on Climate Change (IPCC) and also much less than employed by climate models. Less enhanced cloud cooling means that greenhouse gases have produced less warming than the climate models have determined. Another way to put it is that this new finding implies that the earth’s climate sensitivity—how much the earth’s surface will warm from a doubling of the pre-industrial atmospheric carbon dioxide concentration—is much below that of the average climate model (3.2°C) and near the low end of the IPCC’s 1.5°C to 4.5°C assessed range.
If anthropogenic influences on cloud’s can’t explain a lack of significant warming, the inference is that the models greatly overestimate the effect of increased CO2 on the Earth’s climate. There is much more at the link.