An attempt at a simple explanation
Let's start at the very beginning to understand climate change and its underlying causes. When we talk about climate change today, we are actually talking about man-made climate change. Climate change has existed without humans. It is human-induced climate change that presents us with the greatest challenges.
The greenhouse effect, caused by the atmosphere, ensures that Earth's surface temperature reaches 16 °C. Without the atmosphere, it would be -18 °C. This, along with other conditions, made it possible for life to emerge on Earth.
The burning of fossil fuels disrupts the carbon cycle. So many greenhouse gases are emitted that more carbon dioxide accumulates in the air than plants and oceans can absorb. The excessive carbon dioxide concentration leads to an increase in the Earth's surface temperature.
Factors for the origin of life on Earth
When the universe was formed, all elements were already present in atomic form. Gravitational and other forces created stars and planets, including our Earth.
What is the life zone?
The habitable zone is the area in which planets are capable of retaining water in liquid form, a prerequisite for life. Earth, along with Venus and Mars, is located in the habitable zone of our solar system. Habitable zone is another term for the zone that is suitable for life. However, only Earth, due to its composition, was capable of retaining water vapor for long periods. On Venus, the volatile components were separated by the sun's UV radiation, causing the water to evaporate. Mars is too low in mass, so gravity wasn't strong enough to bind the water vapor. (Mars: 3.69 m/s², Earth: 9.81 m/s²)
Water - How did it come to Earth?
Collisions with asteroids, which mostly contained frozen water, caused the water to accumulate on Earth as water vapor. At that time, the Earth was still a glowing sphere, and with more water, atmospheric pressure and temperature dropped. As a result, a lot of water fell as rain, forming seas and oceans.
The collision with the protoplanet (the name for a precursor to a planet) Theia not only brought water to Earth.
The formation of the moon
The collision with Theia created the Moon. Theia was a body roughly the size of Mars. The broken pieces of Earth and Theia gathered in Earth's orbit and coalesced to form the Moon.
As a result, the Earth's rotational speed slowed from 3 to 4 hours to 24 hours. Winds, which had previously gusted across the Earth's surface at up to 500 km/h, decreased accordingly. This corresponds to a category F5 tornado.
F5 - Incredible Damage - Wooden houses are torn from their foundations, shifted widely, and disintegrated. An F5 tornado can peel asphalt from the road.
- https://de.wikipedia.org/wiki/Fujita-Skala
In addition, the axis of rotation stabilized at 23.4° to the ecliptic (ecliptic = planetary plane; designation of the plane of the orbits of the planets around the sun).
The atmosphere and greenhouse gases
The Earth's atmosphere consists of five layers, the lowest of which is called the homosphere, or colloquially, air. It is composed of various substances.
| gas | Percentage |
| Nitrogen | 78.08% |
| oxygen | 20.95% |
| argon | 0.93% |
| Carbon dioxide | 0.04% |
Even though carbon occurs only in small quantities, as the most abundant greenhouse gas it has a major effect on the climate.
As early as 1856, Eunice Newton-Foote conducted an experiment in which two glass flasks were placed in the sun. One contained "normal" air and the other carbon dioxide. Both heated up, the one filled with air to 37.8 °C, the one filled with CO₂ to 49 °C.
This is because the CO₂ molecules are set into vibration by solar radiation and the associated energy, and then release this energy in an undirected manner, i.e., back toward the Earth's surface. This also applies to other greenhouse gases.
CO₂ is the most abundant and stable greenhouse gas, which is why the others are usually summarized in CO₂ equivalents (kg CO₂e or kg CO₂eq). CO₂ is produced by the decomposition and combustion of carbon-containing compounds.
| greenhouse gas | Global warming potential (GWP in CO2e) |
| Carbon dioxide (CO₂) | 1 |
| Methane (CH4) | 25 |
| Nitrous oxide (N2O) | 298 |
| Partially halogenated fluorocarbons (HFCs) |
124 to 14,800 |
| Perfluorinated hydrocarbons (PFCs) |
7390 to 12 200 |
| Sulfur hexafluoride (SF6) |
22,800 |
| Nitrogen trifluoride (NF3) |
17,200 |
Explanation using the example: Methane
Two factors determine the influence of a gas on global warming:
- Residence time and
- Radiative forcing of the gas.
This is how the influence is calculated.
For the calculation, the global warming potential (GWP-100) is considered over 100 years. If it were only considered over 20 years, the factor would be much more extreme.
The carbon cycle
Carbon is life - chemistry is divided into two major areas:
- inorganic chemistry with about 200 000 compounds (without carbon) and
- Organic chemistry, with approximately 20,000,000 compounds, all containing carbon. The human body consists of 60% water and 9.5% carbon. Carbon is therefore the main component of the body, along with oxygen and hydrogen.
The carbon cycle describes the exchange of carbon between animals and plants. To illustrate this, we will consider human metabolism (cellular respiration) and plant photosynthesis.
During photosynthesis, plants use solar energy to convert water and carbon dioxide into sugar and oxygen. In human metabolism, sugar and oxygen are converted into carbon dioxide, water, and energy.
In other words, we excrete carbon-containing compounds, which are broken down by fungi and microbes. If this conversion occurs anaerobically, methane is produced, which is converted into CO₂ over time. If it occurs aerobically, CO₂ is produced directly. (This decomposition process takes place inside us and is also the reason why cows have such a high carbon footprint.)
This cycle also occurs in water (lakes and seas), as well as between the spheres (hydrosphere, biosphere, atmosphere).
When plants and animals die, the carbon compounds settle, and over millions of years, under the influence of pressure and heat, fossil fuels are formed. Oil and gas are formed in the ocean; coal is formed on land.
(Anthropogenic) climate change
The Earth is continually subject to climate fluctuations. Since its formation, there have been warmer and colder periods. Since the last ice age around 12,000 years ago, the climate has been relatively stable. Only since 1980 has a sharp rise in the average atmospheric temperature been observed.
Carbon dioxide, in particular, plays a crucial role (see graphic), which is produced by the burning of fossil fuels to generate energy. Combined with humanity's increasing energy demand, CO₂ emissions rose from 2 gigatons in 1900 to 34.8 gigatons in 2021 (up from 37.1 Gt in 2017).
Feedback processes and tipping points
Rising temperatures and climate change can lead to effects that further amplify these changes. This amplification effect is particularly dangerous for humanity, especially when tipping points are exceeded. Tipping points are events that, once exceeded, can no longer be reversed. Environmental responses to climate change are entirely natural, but they are irreversible and can render the planet uninhabitable for humans.
3 Examples of these feedback loops are:
Reduced albedo (= reflectivity of a planet/body)
As the ice melts, the incoming solar energy is no longer directly reflected by the white surface, but is absorbed by the dark surface of the sea.
Desertification of the rainforest
Further driven by deforestation, global warming threatens to dry out the rainforest. The forest relies on a lot of rain, which it needs for photosynthesis. Less water, less photosynthesis, less CO₂ that can be stored. This, in turn, means more CO₂ in the atmosphere.
Thawing permafrost
In the Siberian and Canadian permafrost, several billion tons of carbon from the last ice age are probably bound in organic materials at depths of a few meters. Should this permafrost thaw, thousands of tons will be released.
These feedback loops are tied to specific temperatures and are also called tipping points. If these are exceeded, a domino effect can occur that can no longer be stopped.
With this background knowledge, we'll look at coffee and climate change in the next article. What is the impact of coffee on climate change, and what is the influence of climate change on coffee?
