Global Warming 101

BUT…everything this else in the climate system probably WON’T stay the same! For instance, clouds, water vapor, and precipition systems can all be expected to respond to the warming tendency in some way, which could either amplify or reduce the manmade warming. These other changes are called “feedbacks,” and the sum of all the feedbacks in the climate system determines what is called ‘climate sensitivity’. Negative feedbacks (low climate sensitivity) would mean that manmade global warming might not even be measurable, lost in the noise of natural climate variability. But if feedbacks are sufficiently positive (high climate sensitivity), then manmade global warming could be catastrophic.

Obviously, knowing the strength of feedbacks in the climate system is critical; this is the subject of most of my research. Here you can read about my latest work on the subject, in which I show that feedbacks previously estimated from satellite observations of natural climate variability have potentially large errors. A confusion between forcing and feedback (loosely speaking, cause and effect) when observing cloud behavior has led to the illusion of a sensitive climate system, when in fact our best satellite observations (when carefully and properly interpreted) suggest an IN-sensitive climate system.

Finally, if the climate system is insensitive, this means that the extra carbon dioxide we pump into the atmosphere is not enough to cause the observed warming over the last 100 years — some natural mechanism must be involved. Here you can read about my favorite candidate: the Pacific Decadal Oscillation.

Reproduced with permission

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