How does climate change come about

Climate change

The natural greenhouse effect

The sun sends short-wave radiation to the earth. There it is converted into long-wave radiation on the earth's surface and reflected back again. If these long-wave rays hit a barrier - like the glass roof in a greenhouse - they are reflected back. A completely natural process in which a certain percentage of the radiation gets back into space, while the other part is reflected and thrown back to earth.

This takes place through a natural protective layer: the gas layer of the atmosphere, which also contains natural carbon dioxide (CO₂), does not let the long-wave radiation through and sends it back to earth. Without this natural greenhouse effect, the average temperature on earth would be minus 18 degrees Celsius - life would be impossible.

The right amount of CO₂ and other greenhouse gases determines our climate. If the content of these gases increases, the atmosphere heats up too much - as if the glass in a greenhouse were too thick. Since the beginning of industrialization, greenhouse gases have risen sharply, and since then we have spoken of the anthropogenic greenhouse effect.

What does man do?

Different gases are relevant for the climate and the greenhouse effect. More than half of the human-made effect is due to carbon dioxide (CO₂) and carbon monoxide (CO), both of which are produced when fossil fuels such as oil, coal and gas are burned.

Methane (CH₄) is also relevant for the greenhouse effect, especially in high concentrations. It arises in agriculture and factory farming, in sewage treatment plants and on landfills. Methane is also preserved in permafrost soils. So when the global temperature rises and the permafrost thaws, the atmosphere is further heated.

Much of the methane concentration comes from the stomach of ruminants, and it is also produced when rice is grown. Laughing gas, which is also produced in agriculture, for example when nitrogen compounds are broken down in the soil, has a similar effect on the climate. Most common fertilizers contain nitrogen.

According to the Intergovernmental Panel on Climate Change (IPCC), the strongest greenhouse gas is sulfur hexafluoride, which is used in high-voltage switchgear. This gas comes from industrial processes and does not occur in nature. Although the potential to contribute to the greenhouse effect is great, it is only contained in the atmosphere to a very small extent, so the impact on global warming is rather small.

Global climate change is man-made

For a long time, experts argued about the existence and extent of climate change. In the meantime, there is broad consensus that the earth is heating up and that humans make a decisive contribution to this by emitting carbon dioxide in particular. However, it is difficult to predict exactly how the global climate will change. It is clear that there are and will be major regional differences.

The global climate is getting warmer. The second half of the 20th century was very likely the warmest 50-year period in 500 years. This can be seen from the rising mean temperatures worldwide, the temperatures of the oceans and the melting of ice and snow, which is visible in the rising sea level. Satellite images show that the extent of sea ice in the Arctic decreased by around 40 percent between 1980 and 2015.

Scientists put the loss of glacier areas in the Alps between the years 1850 and 2000 at around 50 percent. According to the 5th assessment report of the Intergovernmental Panel on Climate Change (IPCC) of 2014, the sea level between 1901 and 2010 rose by 19 centimeters, whereby the measurement uncertainty is plus minus 2 centimeters.

This not only threatens the existence of some island states and low-lying coastal regions. Worldwide, people have to reckon with extreme weather phenomena such as cyclones, floods and periods of drought more frequently.

The sea level continues to rise

Heat waves are likely to increase and last longer. The number of frost days is decreasing and periods of drought are threatening, especially in continental areas. So far, it has become apparent that precipitation is increasing, especially in the high latitudes, and is most likely decreasing over the continents in the subtropics. The sea level will continue to rise.

For Germany, climate researchers assume that severe winters and cool summers will become rarer extreme events. In the west and south of the country in particular, the risk of heavy rain falls in winter, which can trigger floods, increases. The trends are therefore different from region to region. While heat waves are likely to increase in the southwest, periods of drought are to be expected in the east in particular.