However, the rapid warming during the last 20 years is dominated by other factors.
The variability of the solar radiation is an important factor affecting the climate on Earth. Even though its magnitude merely varies by about a permille over the solar activity cycle, it causes direct variations of the global temperature by about half a degree. But the solar influence is not the only important factor affecting the climate. The rapid temperature increase during the last 20 years is probably not due to a changing Sun, but is most likely caused by man-made greenhouse gases (such as carbon dioxide), the concentration of which was never as high during the last 15'000 years as it is today in the atmosphere. These conclusions were drawn by scientists from around the world this week in Bern. Swiss research groups are among the leading ones studying solar variability.