Global warming may be twice as bad as previously expected

— -- Global warming will be twice as severe as previous estimates indicate, according to a new study published this month in the Journal of Climate, a publication of the American Meteorological Society.

The research, conducted by the Massachusetts Institute of Technology (MIT), predicts a 90% probability that worldwide surface temperatures will rise more than 9 degrees (F) by 2100, compared to a previous 2003 MIT study that forecast a rise of just over 4 degrees.

The Intergovernmental Panel on Climate Change in 2007 forecast a temperature rise of anywhere from 2 to 11 degrees by 2100 based on a variety of different greenhouse-gas-emissions scenarios.

The projections in the MIT study were done using 400 applications of a computer model, which MIT says is the most comprehensive and sophisticated climate model to date. The model looks at the effects of economic activity as well as the effects of atmospheric, oceanic and biological systems.

The improved economic modeling and newer economic data (which gives a lower chance of reduced emissions) are among the major changes from the 2003 model application.

Unless greenhouse gas emissions are reduced, "there is significantly more risk than we previously estimated," says study co-author Ronald Prinn of MIT. "There's no way the world can or should take these risks."

"The results appear to be credible and quantify a certain unease many scientists have on the real magnitude of the climate problem ahead of us, one that is not adequately appreciated by most politicians," writes Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research and an IPCC lead author, in an e-mail.

"The difficulty of dealing with inertia in human systems and infrastructure, and the lack of current incentives and a global approach to the problem means that reducing emissions will be a major challenge for humanity," he added.

Funding for the study came in part in grants from the U.S. Department of Energy and by sponsors of MIT's Joint Program on the Science and Policy of Global Change.