6 December 2011

Three Quarters of Climate Change are Man-Made

At least 74% of the climate warming observed since the mid-twentieth century is caused by human activities. This is the headline-making result of a study by NCCR Climate researcher Reto Knutti and Markus Huber at ETH Zurich. According to their paper published in Nature Geoscience, Natural climate variability is extremely unlikely to have contributed more than about one quarter of the temperature rise. The results confirm earlier findings using independent and complementary methodology. The researchers estimated the human contribution to the observed warming, based on an assessment of the Earth's energy balance. They find that since 1950, greenhouse gas emissions have led to a temperature increase of about 0.85°C. Over the same period, aerosols cooled the Earth by about half that amount. Earlier attributions of temperature increases to human action relied on the ability of climate models to accurately simulate spatial and temporal warming patterns from different causes. The new results are not based on this assumption, and therefore substantially raise confidence in the importance of human-induced causes of the recent temperature rise.

> Read the paper (pdf, 470 kB)

11th International NCCR Climate Summer School
"The Water Cycle in a Changing Climate: Observations, Scenarios, Impacts"

9 – 14 September 2012, Centro Stefano Franscini, Monte Verità, Ticino, Switzerland

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