CO2 is insufficient to explain warming

Dr. Roy Spencer

Dr. Roy Spencer

On the morning of Saturday May 16, 2009, Dr. Roy Spencer, a principal research scientist at the University of Alabama in Huntsville and a collaborator with CFACT Europe, presented a talk on global warming in the main building of the University of Helsinki. His was the first talk given at a yearly meeting of climate ‘realists’ in Finland, and it was coordinated by Dr. Boris Winterhalter. 

Dr. Spencer’s presentation focused on recent satellite evidence that computerized climate models project far too much warming for the future. Those models mistakenly respond to the small amount of direct warming from extra carbon dioxide in the atmosphere by reducing cloud cover on the Earth. That, in turn, amplifies the warming…an example of “positive feedback”. Out of the 21 climate models tracked by the Intergovernmental Panel on Climate Change (IPCC), the differences in warming exhibited by those models is mostly the result of different strengths of positive cloud feedback. 

In contrast, data from the NASA Terra and Aqua satellites over the period 2000 – 2007 suggests strong negative cloud feedback. The discrepancy between the models and the observations was explained to be the result of the climate model developers not accounting for natural cloud variations causing temperature change in previous satellite studies. In simple terms, previous researchers have confused cause and effect when interpreting the co-variations between temperature and cloud cover. 

These new results, which have been submitted to the Journal of Geophysical Research for publication, also suggest that increasing CO2 is insufficient to explain global-average warming in the last 50 to 100 years. An alternative explanation was presented, wherein the Pacific Decadal Oscillation modulates global cloudiness by a small amount which changes every 30 years or so. Satellite evidence for such a relationship was also presented. 

During the resulting discussion period, most of the participants’ comments focused on the possible role of solar variations in global warming. Spencer admitted that those might also be involved, and that it is obvious that there are many unanswered questions about what really causes climate change on decadal to centennial time scales. After the talk, Dr. Spencer conducted and interview who filmed portions of the presentation to be aired on Finland’s National TV.

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