Roy Spencer on feedback

““The climate modelers see from satellite data that warm years have fewer clouds, then assume that the warmth caused the clouds to dissipate. If this is true, it would be positive feedback and could lead to strong global warming. This is the way their models are programmed to behave.

“My question to them was, ‘How do you know it wasn’t fewer clouds that caused the warm years, rather than the other way around?’ It turns out they didn’t know. They couldn’t answer that question.”

One problem is the simplicity of the climate models. Because cloud systems are so complex and so poorly understood, all of the climate models used by the United Nations’ Intergovernmental Panel on Climate Change use greatly simplified cloud parameters to represent clouds. But the calculations that set those parameters are based on assumed cause-and-effect relationships.

Those assumptions might be working in the wrong direction, Spencer said. “What we have found is that cloud cover variations causing temperature changes dominate the satellite record, and give the illusion of positive feedback.”

Using satellite observations interpreted with a simple model, Spencer’s data support negative feedback (or cooling) …” “Cloud Feedback Presentation for Fall 2009 AGU Meeting” Prior posts here, here, here, here, and here.

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