An Australian-led team of researchers reports that we've underestimated the heating effect of carbon dioxide emissions which suggests we're heading for a 4C future.
Report authors Steven Sherwood, Sandrine Bony and Jean-Louis Dufresne found climate models which show a low global temperature response to CO2 emissions do not factor in all the water vapour released into the atmosphere.
Models typically simulate water vapour as rising to 15km and forming clouds, rather than updraughts of water vapour that rise only a few kilometres and pull away the cloud-forming vapour.
This prediction of cloud cover is important because clouds reflect sunlight, lessening the impact of global warming.
The report, conducted between the University of New South Wales and the Université Pierre et Marie Curie in Paris, finds “real world observations” show the accepted models are wrong.
In reality, the study found, water vapour is distributed to different heights in the atmosphere, causing fewer clouds to form as the climate warms.
In turn, this increases the amount of sunlight entering the atmosphere, making the level of warming far more sensitive to heat-trapping gases such as CO2.
As a result, the world can expect a temperature increase of “at least” 4C by 2100 if, as predicted, there is a doubling of CO2 in the atmosphere. This could then rise by more than 8C by 2200.
Well we can't say we weren't warned. Whether future generations will have to endure climate catastrophe is a choice being made for them by you and by me today. Meanwhile, The Guardian's Myles Allen argues that our only way out of this carbon mess is to bury it.