Projections of global warming by 2100 doubled to 5.1C.
For the no policy scenario, the researchers concluded that there is now a nine percent chance (about one in 11 odds) that the global average surface temperature would increase by more than 7°C (12.6°F) by the end of this century, compared with only a less than one percent chance (one in 100 odds) that warming would be limited to below 3°C (5.4°F).
On our current emissions path, we have a 9% chance of an incomprehensibly catastrophic warming of 7°C by century’s end, but less than a 1% chance of under 3°C warming.
“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,” said Ronald G. Prinn, professor of atmospheric chemistry at MIT. “It is making the impetus for serious policy much more urgent than we previously thought.”
The Massachusetts Institute of Technology Joint Program on the Science and Policy of Climate Change has joined the climate realists. The realists are the growing group of scientists who understand that the business as usual emissions path leads to unmitigated catastrophe (see, for instance, “Hadley Center: “Catastrophic” 5-7°C warming by 2100 on current emissions path” and below).
The Program issued a remarkable, though little-remarked-on, report in January, “Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters,” by over a dozen leading experts.
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