Hopes that the rise in average global temperatures by 2100 might be capped below 2.5C can be all but ruled out if greenhouse gas emissions continue at the current rate, new research reassessing the atmosphere’s sensitivity to CO2 suggests. 

New research from the World Climate Research Program has found that hopes that the rise in average global temperatures by 2100 might be capped below 2.5C can be all but ruled out if greenhouse gas emissions continue at the current rate. The study offers the first clear progress in decades toward narrowing the range of temperature rise caused by doubling of carbon dioxide levels since pre-industrial times.

Its findings show that doubling would trigger 2.6 to 4.1 degrees Celsius in average warming above pre-industrial levels, putting the lowest rise more than one degree above scientists’ previous estimated range of 1.5-4.5C.

”The bad news is that if you are hoping that warming just wouldn’t end up being much of a problem, that you’d only get a degree or two of warming, If we double our mission or double our concentrations in the atmosphere, then you should be disappointed because we found that’s not very likely. But at the same time, we found this some truly catastrophic outcomes where we get like five degrees or more warming are also a lot less likely. And so we really found that you know, climate change is about as bad as we thought it was, that the long term best estimate of the amount of warming you get in the sort of doubling of atmospheric CO2 is is pretty close to accurate.”

The scientific consensus that the goal of capping the rise in average global temperatures at 1.5C, as laid out in the 2015 Paris climate accords, is almost certainly out of reach unless greenhouse gas emissions rates fall.

The study, which was published in the journal Reviews of Geophysics on Wednesday, relied on computer simulations using satellite observations, historic temperature records, and evidence of prehistoric temperatures.

It confirmed that the world is on course for extreme sea level rise and other severe climate impacts. These effects are expected from a rise beyond 2C. Already, the average global temperature has warmed by about 1.2C.