Climate describes the state of the atmosphere in a place or area over a period of at least 30 years. It is influenced by all subsystems of the Earth system, i.e. the atmosphere, the oceans, sea and land ice, ocean and land habitats, land water, soils and humans.
If the Earth had no atmosphere, its surface would have a temperature of -18 °C on average. It is the atmosphere that creates life-friendly conditions through its natural greenhouse effect. To achieve this, the atmosphere absorbs the radiation of gases such as water vapour, carbon dioxide (CO2), methane (CH4) and nitrous oxide (NO2) emitted from the Earth's surface. These gases in turn radiate back towards the Earth's surface, where they increase the energy input and thus the temperature of the Earth's surface, the oceans and the atmosphere near the ground. This natural greenhouse effect leads to an average earth surface temperature of +15 °C.
Since the beginning of industrialisation, the concentration of greenhouse gases in the atmosphere has been steadily increasing due to human influences. In addition to the above-mentioned greenhouse gases, other highly climate-affecting greenhouse gases such as chlorine- or bromine-containing substances, which are produced exclusively by humans, have since entered the atmosphere. Although greenhouse gases are what make the earth habitable in the first place, there is currently an increase of almost 50 per cent in greenhouse gases in the atmosphere compared to pre-industrialisation levels. The increase has been particularly steep over the past three decades.
Since early industrialisation around 1750, global ground-level air temperature has risen by an average of about 1 °C and is now about 1.5 °C on average over all land areas. The extent of warming is generally much greater over land than over the ocean. In 2015 to 2019 the warming was about 1.7 °C above the values of the pre-industrial years. According to scientists, such a temperature level cannot be explained by natural climate fluctuations. For example, the Intergovernmental Panel on Climate Change (IPCC) proves in its assessment reports that humans are primarily responsible for the current global warming. Without taking into account the increase in greenhouse gases in the atmosphere, the observed warming of the climate system, especially the warming since the 1950s, cannot be explained.
The increase of carbon dioxide in the atmosphere can be explained in particular by the combustion of carbon-containing fossil fuels, such as coal, oil or natural gas. The CO2 concentration in the atmosphere is now higher than at any time in the past 800,000 years. Recent research indicates that the concentration of CO2 in the atmosphere has probably never been higher than it is today, even in the last 3 million years. Of the CO2 emissions released by humans in 2009-2018, 86% came from fossil fuel combustion and 14% from land use change. About a third of these emissions (31%) are absorbed by terrestrial ecosystems, about a quarter (23%) by the ocean, while the majority of CO2 emissions (46%) remain in the atmosphere. These high concentrations of CO2 in the atmosphere can destabilise parts of the climate system in the long term.
The proportion of methane in the atmosphere has also increased by about 2.5 times compared to pre-industrial levels. Since the greenhouse effect of methane per molecule is about 25 times as strong as that of CO2, this increase also has immense effects on the climate. Industrial agriculture, especially intensive livestock farming, is largely responsible for methane emissions. Nitrous oxide is also released primarily in agriculture, for example through the use of artificial fertiliser.
Another cause of climate change is human impact on the land surface: forest areas are cleared and burned; peatlands are drained, which causes a further release of greenhouse gases and at the same time leads to a reduction in carbon uptake.
The good news is that we have the opportunity to counteract all this, for example by promoting more sustainable agriculture, protecting forests or preserving peatlands. If you also want to actively contribute to climate protection, feel free to explore Naturefund's conservation projects, which secure land for nature in the long term and thus prevent the release of further greenhouse gases!
Sources:
Leopoldina; Bundeszentrale für politische Bildung; Klimafakten; UN environment programme
