Modelling suggests climate is considerably more sensitive to carbon emissions than thought
Worst-case global heating scenarios may need to be revised upwards in light of a better understanding of the role of clouds, scientists have said.
Recent modelling data suggests the climate is considerably more sensitive to carbon emissions than previously believed, and experts said the projections had the potential to be “incredibly alarming”, though they stressed further research would be needed to validate the new numbers.
Modelling results from more than 20 institutions are being compiled for the sixth assessment by the United Nations Intergovernmental Panel on Climate Change, which is due to be released next year.Football pitch-sized area of tropical rainforest lost every six secondsRead more
Compared with the last assessment in 2014, 25% of them show a sharp upward shift from 3C to 5C in climate sensitivity – the amount of warming projected from a doubling of atmospheric carbon dioxide from the preindustrial level of 280 parts per million. This has shocked many veteran observers, because assumptions about climate sensitivity have been relatively unchanged since the 1980s.Advertisement
“That is a very deep concern,” Johan Rockström, the director of the Potsdam Institute for Climate Impact Research, said. “Climate sensitivity is the holy grail of climate science. It is the prime indicator of climate risk. For 40 years, it has been around 3C. Now, we are suddenly starting to see big climate models on the best supercomputers showing things could be worse than we thought.”
Worst-case projections in excess of 5C have been generated by several of the world’s leading climate research bodies, including the UK Met Office’s Hadley Centre and the EU’s Community Earth System Model.
Timothy Palmer, a professor in climate physics at Oxford University and a member of the Met Office’s advisory board, said the high figure initially made scientists nervous. “It was way outside previous estimates. People asked whether there was a bug in the code,” he said. “But it boiled down to relatively small changes in the way clouds are represented in the models.”
But but but…uncertainty?
The IPCC is expected to include the 5+C climate sensitivity figure in its next report on the range of possible outcomes. Scientists caution that this is a work in progress and that doubts remain because such a high figure does not fit with historical records.