A new landmark study using “the most comprehensive modeling yet” on potential climate change scenarios this century shows that the effects of global warming underestimated by half. A temperature increase of up to 10 degrees Fahrenheit possible by century’s end – unless action is taken now to stop it.
Scientists from the Massachusetts Institute of Technology (MIT) released a report saying that global warming this century could be twice as extreme as assumed. They say that temperature rises of 9.3 degrees Fahrenheit (5.2 degrees Celsius) can be achieved by 2100. They had predicted in 2003 that temperature rises of 4.3 degrees Fahrenheit (2.4 degrees Celsius) would occur.
The scientists reported that the differential in the expected future median surface temperature rises had been due to improved economic modeling and newer economic data inputs. They used the MIT’s Global Systems Model (pdf), a detailed computer simulation of global economic activity and climate processes. They ran the model 400 times, with each run using slight variations in input parameters, selected so that each run has about an equal probability of being correct, based on present day observations and knowledge.
The 2003 scenarios based on older models relied on less new economic facts and figures. The older study also masked climate warming by incorporating the cooling effects of volcanic activity, according to the scientists, who also pointed out that the release of soot from volcanoes added to global warming.
The MIT team released a statement accompanying the research, saying that their findings show that “without rapid and massive action,” an almost 10 degree rise in temperatures will take place this century. What’s worse, the outcome of their calculations shows that the end result will be a lot more extreme if our actions to combat climate change are not proficient or adequate. “But there is less change if strong policies are put in place now to cut greenhouse gas emissions”, according to a Reuters report on the study.
[Without action], there is significantly more risk than we previously estimated. This increases the urgency for significant policy action,” commented Ronald Prinn, one of the study’s authors.
“There’s no way the world can or should take these risks,” Prinn said. And the odds indicated by this modeling may actually understate the problem, because the model does not fully incorporate other positive feedbacks that can occur, for example, if increased temperatures caused a large-scale melting of permafrost in arctic regions and subsequent release of large quantities of methane, a very potent greenhouse gas. Including that feedback “is just going to make it worse,” Prinn says.
“The take home message from the new greenhouse gamble wheels is that if we do little or nothing about lowering greenhouse gas emissions that the dangers are much greater than we thought three or four years ago. It is making the impetus for serious policy much more urgent than we previously thought.”
The scientists published their study in the American Meteorological Society’s Journal of Climate.
Image credit: MIT Joint Program on the Science and Policy of Global Change