Last changed: 08/10/2010
Global mean surface air temperature has risen gradually since the age of industrialisation. It is now accepted as scientifically proven that we humans are responsible for a significant part of this increase. Hence one speaks of anthropogenic, or man-made, climate change.
Fig.: Deviations of global mean surface air temperature from the average 1961-1990
Source: Climatic Research Unit - University of East Anglia
Carbon dioxide (CO2) accumulates in the atmosphere as a result of combustion of fossil fuels (e.g. coal and petroleum) as well as large-scale deforestation. Agriculture and animal husbandry produce gases such as methane (CH4) and nitrous oxide (laughing gas, N2O). Carbon dioxide, methane and laughing gas are among the gases with high global warming potential. An accumulation of these gases in the atmosphere tends to bring about a warming of the lower atmosphere.
Information about the causes of climate change, the increase of greenhouse gases in the atmosphere, the greenhouse effect (natural and anthropogenic), and the Intergovernmental Panel on Climate Change (IPCC) is here: Background.
Although there is broad scientific consensus about the occurrence of anthropogenic climate change, many doubts continue to be cast upon this in the public debate. Information is spread through books, magazines, TV broadcasts, and the Internet which is either outdated, incomplete, taken out of context, or simply false. At the FAQ in German site we address a number of issues which are meant to raise doubts about the status of scientific knowledge on the subject, and also provide answers to questions of general interest pertaining to anthropogenic climate change.
The climate has been warming over the past century, according to observational data. The global mean surface air temperature has risen, mountain glaciers and snow cover have on average retreated, and extreme weather incidents such as heavy precipitation and heat waves are occurring more frequently. For more on the risks of observed climate change see „Klimawirkungen und Risiken“ (Climate Impact and Risks) in German.
Most people associate a gradual warming of the climate when they hear the term “anthropogenic climate change”. However, it is quite possible that very severe or even abrupt changes will take place. Such processes are associated with critical turning points in the climate system known as ‘tipping points’. Even slight changes in the climate system can achieve a ‘tipping point’ which then brings about an extreme change in the climate. Our „Kipp-Punkte im Klimasystem“ background paper (‘Tipping points in the climate system’: in German) provides comprehensive information on the subject.