A Climate Change Index (CCI) is developed that is composed of annual and seasonal temperature and precipitation indicators. These indicators are aggregated to a single index that is a measure for the strength of future climate change relative to today's natural variability. The CCI does not represent climate impacts. Its aim is to comply with the increasing need of policy makers to gain a quick overview of complex scientific findings by means of summarized information. The index is calculated on the basis of three GCM simulations of the 21st century under the IPCC emission scenarios A2 and B2. The results indicate that the strongest climate changes by the end of the 21st century, relative to today's natural variability, will occur in the tropics and in high latitudes (especially in the northern hemisphere). The CCI is also calculated on a country basis, allowing for comparison with social and economic country indicators.