The most alarming projections for global warming this century also seem to be the most reliable, according to a December study in Nature that compared climate models against what’s already happening in the atmosphere.
The paper concluded that worldwide temperatures could rise nearly 5 °C by the end of the century, 15 percent higher than the previous central estimate under the “business as usual” emissions scenario outlined by the U.N. Intergovernmental Panel on Climate Change.
The authors collected more than a decade’s worth of "top of atmosphere" satellite observations, measuring factors such as how much infrared radiation is escaping from Earth and how much sunlight clouds and snow reflect away. In turn, they compared that data with the results of earlier climate models to determine which ones most closely forecast what the satellites actually saw. It turned out to be the ones that predicted the most warming.
That suggests the risks of climate change are greater than feared, and that we’ll have to cut emissions even deeper to prevent dangerous levels of warming.