Warm Planet Could Get Warmer Than Thought

May 21, 2006 – Vol.11 No.9

WARM PLANET COULD GET WARMER THAN THOUGHT.

With each subsequent study the outlook for global warming gets grimmer. The latest study says that current climate models showing an average global rise in temperature of as much as 10 degrees F (5.8 degrees C) by the end of this century might be off as much as 3.6 degrees F (2 degrees C). World average temperatures could rise higher than recently thought. The reason, researchers say, is that climate change models don’t adequately account for positive feedback loops in nature which will increase the amount of carbon dioxide and methane in the atmosphere.

(One example of a positive feedback loop is when warming temperatures cause usually frozen arctic tundra to melt and release stored CO2 and methane. As the greenhouse gases rise as the tundra melts, the atmosphere gets even warmer causing even more tundra to melt thus releasing even more greenhouse gases for more warming. The feedback loop is an upwards - positive - spiral of greenhouse gas releases and temperature.)

Authors of the study, scientists Margaret Torn with the Lawrence Berkeley National Laboratory and John Harte of the University of California at Berkeley, agree that if atmospheric concentrations of greenhouse gases actually come down, and global temperatures start to decrease, then feedback loops will kick in to help out and speed the recovery to more normal temperatures.

(The tundra will start to freeze again and trap carbon dioxide and methane.)

But, if we only reduce the rate of increase in greenhouse gases, and don’t actually reduce the levels of greenhouse gases, then the positive feedback loops continue to operate using greenhouse gas concentrations already in place and global average temperatures will continue to rise.

(In other words, not only do we have to cap greenhouse gases we have to reduce them - pull them out of the atmosphere - to get global warming under control.)

The research paper “Missing feedbacks, asymmetric uncertainties and the underestimation of warming” was published in the journal Geophysical Research Letters.

For the full story regarding the Torn/Harte paper visit http://www.lbl.gov/Science-Articles/Archive/ESD-feedback-loops.html .