Fewer low clouds in the tropics

With the help of satellite data, ETH scientists have shown that low-level cloud cover in the tropics thins out as the earth warms. Since this cloud cover has a cooling effect on the climate, the two-degree warming target may therefore be reached earlier than many models have predicted. It is indisputable that greenhouse gases emitted into the atmosphere heat up our planet. But it is harder to determine the exact dependence of the temperature rise on greenhouse gas concentrations. Scientists refer to this dependence as climate sensitivity. If we assume that human activity leads to a sustained doubling of the CO₂ concentration in the atmosphere, how much will the earth warm on average? "Probably between 1.5 and 4.5 degrees Celsius" was the vague answer of the Intergovernmental Panel on Climate Change (IPCC) in its most recent Assessment Report from 2013. Climate sensitivity is a key parameter affecting climate projections and climate targets.