There have always been temperature changes between warm and cold periods.  Glaciations and temperature increases have alternated over millions of years. Even in the course of the current geological era, the Holocene, there have been repeated climate fluctuations. These have had clear consequences for vegetation and thus also for fauna and humans. Not only temperatures but also rainfall has changed.

That said, since the beginning of industrialization humans have exerted an ever increasing influence on the climate. Since 1850 each of the last three decades has been warmer than the previous one.[1] Through the use of fossil fuels like coal and oil, and changes in land use - e.g. the drainage of bogs or the conversion of forests into agricultural land - human beings have been responsible for an increasing concentration of the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), in the atmosphere. These gases exacerbate the natural greenhouse effect with a huge number of different effects.

There is a total of around 75 billion tons of carbon on earth. 99.95% of it is stored in rock. The remaining 0.05% is found in the oceans, air, soil and living organisms. A continuous cycle is created through photosynthesis (in which carbon is bound), and respiration, (in which carbon is again released).

Plants absorb carbon dioxide from the air and convert it into biomass, such as wood. When the wood decays, the carbon dioxide is released again. This cycle has a natural balance.

But humans intervene in the cycle at many points. When they clear forests this destroys soils and the latter can no longer absorb carbon dioxide from the air. The consumption of fossil fuels also releases carbon dioxide into the atmosphere. Oceans and forests cannot fully compensate for this.

The carbon in the atmosphere is only a small part of the total carbon on Earth. Nevertheless, it has a great influence on the climate. The reason for this is the greenhouse effect:

In a greenhouse the sun's rays pass through glass panes and heat the air and soil. The glass panes retain the heat in the house. This is exactly how it works on Earth. But there is no glass here. Heat radiation is retained in the air by water vapour, carbon dioxide and other gases. Only a part is returned to space.

The natural greenhouse effect ensures that the average temperature on Earth is 15°C. This means that the temperature of the earth's atmosphere is no higher than 15°C. The greenhouse effect is also a factor in the climate. Without it, it would be much colder at minus 18°C. Humans intensify the effect by emitting carbon dioxide and other so-called greenhouse gases. This mainly occurs through our consumption of fossil fuels and the destruction of forests and soils. Then the atmosphere becomes warmer and the climate changes.

Every person in Germany causes an average emission of 10.2 tonnes of carbon dioxide (CO2) per year. This is our so-called carbon footprint: because every product we consume and every action we take causes a CO² emission.

In this sense, people living in Germany have a foot that is much too large. Every single individual can consciously reduce their CO² footprint and conserve resources by, for example, riding a bicycle more often, eating less meat or buying second-hand clothing.