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What is climate change?

Over the course of millions of years, the global climate has experienced fluctuations. Since the beginning of industrialisation, however, the composition of the atmosphere has changed as a result of greenhouse gas emissions. This global warming caused by human beings intensifies the natural greenhouse effect and is leading to detectable changes to the climate. This global warming also has a significant effect on people and nature.

The average global surface temperature has already increased by more than 1°C in the last 140 years. In particular, according to the scientific reports of the Intergovernmental Panel on Climate Change (IPCC), the sharp increase in global warming since 1950 can no longer be explained by natural climate fluctuations. According to the sixth IPCC report from 2021, the “extent of the most recent changes in the entire climate system […] are unprecedented in many hundreds to thousands of years".

Greenhouse gases such as carbon dioxide (CO2) are responsible for this, which enter the atmosphere through the burning of fossil fuels such as coal, crude oil and natural gas and through large-scale land use, for example, the deforestation of tropical rainforests, and increase the greenhouse effect. 



Global warming - a chain reaction 

Rising greenhouse gas concentrations in the atmosphere not only increase air and sea temperatures, but also reduce the total global snow and ice mass. As a result of this, but also due to the increase in the volume of water with rising temperatures, the sea level rises. 



Natural cycles in the global climate 

Apart from the anthropogenic greenhouse effect, i.e. resulting from human activity, the global climate shows more or less strong fluctuations, caused by various natural processes. In general, four different parameters can be named that cause the global climate to fluctuate: 

  • Changes in incident solar radiation 
  • Changes in reflected solar radiation 
  • Changes in thermal radiation emitted into space 
  • Internal fluctuations of the climate system 

Recurrent changes in the earth's orbit can occur in regular, very large intervals of several tens of thousands of years, and high correlations with the climatic changes on earth have been documented here. The activity and thus the radiation of the sun arriving on earth also vary. The conditions on the continents has a direct impact on air and sea circulation and thus on the global climate. Volcanic eruptions emit large amounts of CO2, probably the best-​known greenhouse gas, but also aerosols, volcanic ash and airborne particles, resulting in a temporary cooling of the climate over one to two years. 


Sources: Federal Office of the Environment (UBA) 2017; IPCC 2021, Special Report Global Warming of 1.5º C; FAU Florida Atlantic University 2018; NASA Earth Observatory, 2021 (


You can find further exciting information on the subject of climate change and climate protection in our climate booklet

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