The research, by scientists at Imperial College London and the University of East Anglia, is the strongest evidence yet that clouds will amplify global heating over the long term, further exacerbating climate change.
The results, published today in Proceedings of the National Academy of Sciences, also suggest that at double atmospheric carbon dioxide (CO2) concentrations above pre-industrial levels, the climate is unlikely to warm below 2°C, and is more likely on average to warm more than 3°C.
Pre-industrial CO2 levels were around 280 ppm (parts per million), but current levels are approaching 420 ppm, and could approach double the pre-industrial amount by mid-century if significant emissions cuts are not made.
The amount of climate warming predicted from a doubling of pre-industrial CO2 levels is known as the ‘climate sensitivity’ – a measure of how strongly our climate will react to such a change.
The largest uncertainty in climate sensitivity predictions is the influence of clouds, and how they may change in the future. This is because clouds, depending on properties such as their density and height in the atmosphere, can either enhance or dampen warming.
