Sunday, May 24, 2009

MIT model predicts accelerating warming trends

Hotter and Hotter

If an unusually detailed computer simulation at the Massachusetts Institute of Technology has it right, global warming in this century is on track to be about twice as bad as predicted six years ago.

The MIT model is said to be the only one that incorporates among its variables possible changes in economic growth and other human activities and draws on peer-reviewed science on the climatic effects of atmospheric, oceanic and biological systems.

After running the model 400 times with slight variations in the inputs, the new predictions are for surface temperatures to warm by 6.3 to 13.3 degrees Fahrenheit. The prediction is for a 9.4-degree increase in the median temperature, more than double the 4.3 degrees predicted in a 2003 simulation.

Ronald Prinn, co-author of a paper in the Journal of Climate describing the results, said the higher numbers are due to several factors, including better economic modeling, new data showing a lower probability of low-emission scenarios in the future, and better accounting for the effects of past volcanoes and soot emissions.

The simulations also examined what is likely to happen under various policy scenarios. Without strong policies to curb greenhouse gas emissions, the changes in the computer model "stacked up so they caused more projected global warming," Prinn said in a statement. With drastic steps to curb emissions buildup, however, there was less change from the earlier projections.

-- Nils J. Bruzelius

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