Climate Could Get as Much as 15 Degrees Warmer

University of Washington (UW) researchers have designed a new equation for climate scientists to calculate the global impact of climate change over time by taking account of statistical uncertainties in both climate changing factors, like greenhouse gases, and climate response to these factors, and the picture is surprisingly gloomy.

Until now, climate scientists have had to run climate predicting computer models thousands of time to get one reliable result. The reason for this is that uncertainties become more dependable only after large inputs of data. For instance, in taking an opinion poll, as more and more people are interviewed, the margin of error, or uncertainty, is reduced and a more clearly representative poll emerges.

The mounting accumulation of data on climate change has shown that the global climate system does not respond to increasing research in the same way as is illustrated by polls. On the contrary, greater accumulation of research does not contribute to reducing the uncertainties relevant to the climate system.

Gerard Roe and Marcia Baker, UW associate professor of Earth and space sciences and professor emeritus of Earth and space sciences and of atmospheric sciences respectively, believe that the probabilistic uncertainty in climate change remains so high--without being reduced by additional research--because the global climate system is complex and sensitive to numerous factors, or variables. Some of these factors are the accumulation of CO2, water moisture in the air, amount of reflected versus absorbed sunlight and overall concentration of atmospheric particles.

In opposition to customary model systems where the uncertainty in the physics reduces at about the same proportion as the reduction in the uncertainty of the response, Roe and Baker have found that in the global climate system uncertainty and the sensitivity of variable factors are inextricably bound together. Roe and Baker found that the greater the chance that various factors will cause climate warming, then the greater the uncertainty about how much climate warming will ultimately occur: greater effect of variables produces greater uncertainty of response in the climate system.

The equation and system that Roe and Baker have devised provides a way for climate researchers to take account of all the built-in uncertainties in climate warming so that they can obtain results from their climate models that are reliable and delivered after the models are run a few times rather than a few thousand times: it all depends on taking account of the uncertainties built into the climate system. These built-in uncertainties are due in part to the climate-external variables like CO2 and due in part to climate system specific factors like feedback effects: feedback is the process of one effect amplifying another and causing both to accelerate, e. g., ice melts and allows more solar radiation to be absorbed warming the surroundings and causing even more ice to melt which allows even more radiation....

When the variable of feedback is introduced through the new equation, together with all other variables, the projection for the climate heating up as a result of climate change predicts between 5 degrees and 15 degrees higher than the current projection of 2.2 degrees above present temperatures. "

"The kicker is that small uncertainties in the physical processes are amplified into large uncertainties in the climate response, and there is nothing we can do about that," Roe said.

"Like it or not, uncertainty and climate change go hand-in-hand," University of Washington.