-- 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.
"To my knowledge, this is indeed the most exhaustive end-to-end analysis of climate change impacts yet performed," notes Michael Mann, a climatologist at Penn State University and also an IPCC author. "The results of the analysis are sobering, namely that we face a monumental challenge if we are to avoid dangerous interference with the climate system."
Earlier this week, the National Climatic Data Center reported that the Earth's temperature for the first third of this year was the sixth-warmest on record. The global combined land and ocean surface temperture of 55.8 degrees F is tied with 2003 for the sixth-warmest January-April period, since records began in 1880. As for April, the global temperature of 56.7 degrees was the fifth-warmest April on record, and marked the 33rd consecutive April with an average surface temperature above the 20th-century average.
In the USA, April was cooler-than-average, just under 1 degree below the 20th-century average. Precipitation was above normal, with the central and southern USA experiencing the wettest conditions.