Climate change

Whether man-made or not, global warming is definitely not an "invention of the Chinese," as former U.S. President Donald Trump tweeted in November 2012 (1). The increase in the global average temperature, which largely determines the climate on Earth, is a real and measurable event.

But what actually is this climate that is changing? "Climate, that", is described in the Duden dictionary (2) as the typical annual course of weather in a particular geographical area. The weather in our atmosphere is a complex interaction of meterological elements, as an article (3) of the German Weather Service describes it. The change in global temperature, as one of these elements, affects every other weather element, changing the earth's climate.

Since the global average temperature has changed at a similar rate and time as the atmospheric CO2 concentration, it is suspected that human activities have triggered the current climate change. The basis for this conjecture is the greenhouse effect model (4), which describes how the increased accumulation of gases in the atmosphere, results in a warming of the earth.  These so-called greenhouse gases are primarily composed of carbon monoxide (CO2), which is the main greenhouse gas emitted, methane (CH4) and nitrous oxide (N2O).

Carbon monoxide enters the atmosphere through the combustion of fossil fuels for energy and as fuel for machinery and transportation.   In addition, CO2 is removed from the atmosphere "when it is absorbed by plants as part of the biological carbon cycle," according to an article (5) published by the United States Environmental Protection Agency, or EPA. Conversely, this means that through land use change and deforestation, a large amount of CO2 is released into the atmosphere.

"Methane is always produced where organic material is decomposed in the absence of air," as it is written in an article (6) of the Federal Environmental Agency about greenhouse gases. So methane is emitted, by agricultural activities, by factory farming, in sewage treatment plants, and by decomposition of organic waste in landfills.

Nitrous oxide commonly known primarily as "laughing gas" "enters the atmosphere primarily through nitrogenous fertilizers and factory farming , because it is produced whenever microorganisms break down nitrogen-containing compounds in the soil."(6).

Whereas carbon monoxide is the largest contributor of greenhouse gases to the atmosphere, methane and nitrous oxide are proportionally of similar importance, being quite a bit more effective in terms of the greenhouse effect.

"Compared to methane and nitrous oxide," hydrofluorocarbons are "extremely potent in terms of greenhouse effect."(6) Fluorocarbons do not occur naturally and are contained in refrigerants and extinguishing agents and are a component of soundproofing screens. In summary, these are the most important gases responsible for the greenhouse effect and most likely for the associated increase in global average temperature.

But why does a global temperature increase of a few degrees actually pose a systemic risk, when a little more heat in the summer, and especially in the winter, is something everyone can tolerate? There are far more changes due to global warming than a mere global temperature increase. How exactly these changes will ultimately turn out and what consequences they will have on our lives cannot be predicted with certainty. However, we humans have gained a not inconsiderable understanding of the complex interplay of meterological elements and how they are influenced from the outside. In addition to the direct consequences for the weather in the form of heat and drought periods, which in turn make forest fires more likely, as well as the increase in extreme weather events such as droughts, heavy rain, flooding and storms, the melting of the ice caps, rising sea levels, warming and acidification of the sea and the loss of biodiversity are also logically conceivable consequences of an increase in the global average temperature. These events, which have been observed for decades, each pose a significant risk to life on Earth and to human infrastructures.