An attempt at a simple explanation
Let's start from the very beginning to understand climate change and its background. When we talk about climate change today, we are actually talking about man-made climate change. Climate change existed even without humans. It is the climate change exacerbated by humans that poses the greatest challenges to us.
The greenhouse effect, created by the atmosphere, ensures that the Earth has a surface temperature of 16 °C. Without an atmosphere, it would be -18 °C. This, along with other conditions, was what first made it possible for life to emerge on Earth.
Burning fossil fuels upsets the carbon cycle. So many greenhouse gases are emitted that more carbon dioxide accumulates in the air than plants and oceans can absorb. The excessively high carbon dioxide concentration leads to an increase in the Earth's surface temperature.
Factors for the emergence of life on Earth
When the universe was created, all elements were already present in atomic form. Through gravity and other forces, stars and planets were formed, including our Earth.
What is the habitable zone?
The habitable zone is the area in which planets are able to maintain water in liquid form, which is a prerequisite for life. Along with Venus and Mars, Earth is located in the habitable zone of our solar system. "Habitable zone" is another term for the life-friendly zone. But only Earth was able to bind water vapor long-term due to its nature. On Venus, the volatile parts were split off by the sun's UV radiation, and thus the water evaporated. Mars has too little mass, so its gravity was not strong enough to bind the water vapor. (Mars: 3.69 m/s², Earth: 9.81 m/s²)
Water - How did it come to Earth?
Through collisions with asteroids, which mostly contained water in frozen form, water accumulated as water vapor on Earth. At that time, the Earth was still a glowing sphere, and with more water, the atmospheric pressure and temperature dropped. As a result, a lot of water fell to Earth in the form of rain, and seas and oceans were formed.
The collision with the protoplanet (a term for a precursor to a planet) Theia did not only bring water to Earth.
The formation of the Moon
The Moon was formed by the collision with Theia. Theia was a body roughly the size of Mars. The knocked-off pieces of the Earth and Theia gathered in the Earth's orbit and coalesced into the Moon.
This slowed the Earth's rotation speed from 3 to 4 hours to 24 hours. To the same extent, the winds, which had previously blown over the Earth's surface at up to 500 km/h, decreased. This corresponds to an F5 tornado.
F5 - Incredible Damage - Wooden houses are ripped from their foundations, moved far, and dismantled. An F5-strength tornado can peel asphalt off 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; the term for the plane of the planets' orbits around the sun).
The atmosphere and greenhouse gases
The Earth's atmosphere consists of five layers, with the lowest being referred to as the homosphere or colloquially as 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 only occurs in small amounts, as the most common greenhouse gas, it has a major effect on the climate.
As early as 1856, Eunice Newton-Foote conducted an experiment in which two glass bulbs were placed in the sun. One contained "normal" air and the second contained carbon dioxide. Both heated up; the one with air to 37.8 °C, and the one filled with CO₂ to 49 °C.
This is because CO₂ molecules start vibrating due to solar radiation and the associated energy, later releasing this energy again in an undirected manner, i.e., also back towards the Earth's surface. This also applies to the other greenhouse gases.
CO₂ is the most frequently occurring and stable greenhouse gas, which is why the others are usually summarized in CO₂ equivalents (kg CO₂e or kg CO₂eq). CO₂ is produced during 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 |
| Hydrofluorocarbons (HFC) |
124 to 14,800 |
| Perfluorocarbons (PFC) |
7,390 to 12,200 |
| Sulfur hexafluoride (SF6) |
22,800 |
| Nitrogen trifluoride (NF3) |
17,200 |
Explanation using the example: Methane
Two factors determine a gas's influence on global warming:
- Residence time and
- Radiative forcing of the gas.
The impact is calculated based on this.
For the calculation, the global warming potential is considered over 100 years (GWP-100). If it were only considered over 20 years, the factor would be even more extreme.
The carbon cycle
Carbon is life - chemistry is divided into two major areas:
- inorganic chemistry with approx. 200,000 compounds (without carbon) and
- organic chemistry with approx. 20,000,000 compounds, all of which contain carbon. The human body is 60% water and 9.5% carbon. Thus, next to oxygen and hydrogen, carbon is the main component in the body.
The carbon cycle describes the exchange of carbon between animals and plants. For a simple illustration, let's look at human metabolism (cellular respiration) and plant photosynthesis.
During photosynthesis, the plant uses solar energy to convert water and carbon dioxide into sugar and oxygen. Meanwhile, in human metabolism, sugar and oxygen are converted into carbon dioxide, water, and energy.
Expanded further, we excrete carbon-containing compounds, which are decomposed by fungi and microbes. If this conversion takes place anaerobically, methane is produced, which is converted into CO₂ over time. If it takes place aerobically, CO₂ is produced directly. (This decomposition process takes place inside us and is also the reason why cows have such a high CO₂ footprint.)
This cycle also occurs in water (lakes and oceans), as well as between the spheres (hydrosphere, biosphere, atmosphere).
When plants and animals die, the carbon compounds are deposited, and over millions of years, under the influence of pressure and heat, fossil energy sources are formed. Oil and gas are formed in the sea; coal is formed on land.
(Anthropogenic) climate change
The Earth is constantly exposed to climate fluctuations. Since its inception, there have been warmer and colder periods. Since the last ice age about 12,000 years ago, the climate has been relatively stable. Only since 1980 has there been a sharp increase in the average atmospheric temperature.
In particular, carbon dioxide plays a decisive role (see chart), which is produced by burning 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 (max. 37.1 Gt in 2017).
Feedback processes and tipping points
The increase in temperature and the change in climate can lead to effects that additionally reinforce these changes. This reinforcing effect is particularly dangerous for humanity, especially when tipping points are crossed. Tipping points are events that cannot be reversed once they have been crossed. The environment's reactions to climate changes are completely natural, but they cannot be reversed and can make the planet uninhabitable for humans.
3 examples of these feedbacks are:
Reduced albedo (= reflectivity of a planet/body)
Due to the melting of ice sheets, incoming solar energy is no longer directly reflected by the white surface but is absorbed by the dark surface of the sea.
Steppification of the rainforest
Driven additionally by deforestation, the warming climate threatens to dry out the rainforest. The forest relies on plenty of rain, which it needs for photosynthesis. Less water means less photosynthesis and less CO₂ that can be stored. This, in turn, means more CO₂ in the atmosphere.
Thawing permafrost
In the Siberian and Canadian permafrost soil, presumably several billion tons of carbon from the last ice age are bound in organic materials at depths of a few meters. If this were to thaw, thousands of tons would be released.
These feedbacks are bound to certain temperatures and are also called tipping points. If these are crossed, it can lead to a domino effect that cannot be stopped.
With this background knowledge, we will 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?
