Global warming estimates double in severity according to new MIT modeling

Jeremy Hance
May 20, 2009

Employing the MIT Integrated Global System Model, scientists have found that global warming could be more than twice as severe as previous estimates six years ago. The MIT Integrated Global Systems Model, which uses computer simulations to analyze the relationship between climatic changes and the global economy, found during 400 runs of the model that there is a 90 percent probability that temperatures will have risen 3.5 to 7.4 degrees Celsius by the end of the century.

The results "unfortunately largely summed up all in the same direction," says Ronald Prinn, the co-director of the Joint Program and director of MIT's Center for Global Change Science. "Overall, they stacked up so they caused more projected global warming."

Each of the 400 runs of the computer simulations incorporated slight variations that scientists selected as having an equal probability of turning out correct based on current data. The Integrated Global Systems Model differs from many other modeling systems since it incorporates data on human-activity—such as economic growth and energy use—as well as analyzing atmospheric, oceanic, and biological systems.

The model estimated that the median rate of surface warming by 2100 is 5.2 degrees, more than doubling the median rate of 2.4 degrees estimated six years ago. This difference is based on a variety of factors, including current economic data which shows a lower probability of society significantly decreasing greenhouse gas emissions than the more optimistic model six years ago.

In addition, the new modeling incorporated new data about cooling in the 20th century due to volcanic activity, occurrences which masked overall warming. The model also takes into account carbon emissions from soot, and, finally, the rate at which oceans are able to remove carbon dioxide from the atmosphere and transfer it to the ocean’s depths has been lowered due to new studies.

Despite the scientists’ gloomy findings, they found that strong policies to cut greenhouse gases proved as effective in curbing global warming as they did in past models.

Without action "there is significantly more risk than we previously estimated," Prinn says. "This increases the urgency for significant policy action. There's no way the world can or should take these risks.”

Prinn notes that computer modeling is always based on current knowledge and so the accuracy of any modeling is dependent on the soundness of the researcher’s available information.

“We do the research, and let the results fall where they may," Prinn explains, "we don't pretend we can do it accurately. Instead, we do these 400 runs and look at the spread of the odds."

According to Prinn, the odds look grim unless societies “start now and steadily transform the global energy system over the coming decades to low or zero greenhouse gas-emitting technologies."

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Jeremy Hance
mongabay.com (May 20, 2009).

Global warming estimates double in severity according to new MIT modeling .