This is truly alarming news from a new study in the journal Nature. This will be the result of the disruption of low cloud formation as water vapor will rise much higher before forming clouds. That will lead to a drastic reduction of cloud cover, and since cloud cover reflects sunlight, warming will be closer to TWICE previous estimates.
Climate change models underestimate likely temperature rise, report shows
By Oliver Milman
The study, published in Nature, provides new understanding on the role of cloud formation in climate sensitivity – one of the key uncertainties in predictions of climate change.
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.
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.
This is beyond the lower range of predictions and double the 2C limit, compared with pre-industrial times, agreed by countries to prevent the impact of runaway climate change. By comparison, average temperatures have risen 0.8C over the past 100 years.
The implications of a 4C temperature rise by 2100 would be absolutely catastrophic.