An Attempt at a Simple Explanation
Let's start at the very beginning to understand climate change and its origins. When we talk about climate change today, we are actually talking about human-made climate change. Climate change has existed even without humans. It is human-amplified climate change that presents us with the greatest challenges.
The greenhouse effect, caused by the atmosphere, ensures that the Earth has a surface temperature of 16 °C. Without an atmosphere, it would be -18 °C. This and other conditions made it possible for life to originate on Earth.
The burning of fossil fuels throws the carbon cycle out of balance. 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 Origin of Life on Earth
At the time of the universe's origin, all elements were already present in atomic form. Through gravity and other forces, stars and planets formed, including our Earth.
What is the habitable zone?
The habitable zone is the area where planets are able to retain water in liquid form, which is a prerequisite for life. Earth, along with Venus and Mars, is in the habitable zone of our solar system. "Habitable zone" is another term for the life-friendly zone. However, only Earth, due to its composition, was able to bind water vapor long-term. On Venus, the volatile components were split off by the sun's UV radiation, and thus the water evaporated. Mars has too little mass, so gravity was not strong enough to bind the water vapor. (Mars: 3.69 m/s², Earth: 9.81 m/s²)
Water - How did it get to Earth?
Through collisions with asteroids, which mostly contained water in frozen form, water accumulated as water vapor on Earth. At that time, Earth was still a glowing sphere, and with more water, the atmospheric pressure and temperature dropped. This caused a lot of water to fall to Earth as rain, and seas and oceans formed.
The collision with the protoplanet (term 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 fragments of Earth and Theia collected in Earth's orbit and coalesced into the moon.
This slowed Earth's rotational speed from 3 to 4 hours to 24 hours. To the same extent, the winds, which previously blew 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 tornado can peel asphalt from the road.
- https://de.wikipedia.org/wiki/Fujita-Skala
Furthermore, the axis of rotation stabilized at 23.4° to the ecliptic (ecliptic = planetary plane; 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 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 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 flasks were placed in the sun. One contained "normal" air and the second carbon dioxide. Both heated up, the one 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 accompanying energy, and later release this energy undirected, i.e., also back towards the Earth's surface. This also applies to other greenhouse gases.
CO₂ is the most abundant and stable greenhouse gas, which is why others are usually grouped into 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 |
| Partially Halogenated Fluorocarbons (HFC) |
124 to 14,800 |
| Perfluorocarbons (PFC) |
7,390 to 12,200 |
| Sulfur Hexafluoride (SF6) |
22,800 |
| Nitrogen Trifluoride (NF3) |
17,200 |
Explanation using methane as an example
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 over 100 years is considered (GWP-100). 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 approx. 200,000 compounds (without carbon) and
- organic chemistry with approx. 20,000,000 compounds, all with carbon. The human body consists of 60% water and 9.5% carbon. Carbon is therefore, besides oxygen and hydrogen, the main component of the body.
The carbon cycle describes the exchange of carbon between animals and plants. For a simple illustration, we consider human metabolism (cellular respiration) and plant photosynthesis.
In photosynthesis, plants convert water and carbon dioxide into sugar and oxygen with the help of solar energy. In human metabolism, sugar and oxygen produce carbon dioxide, water, and energy.
More broadly, we excrete carbon-containing compounds that are decomposed by fungi and microbes. If this conversion occurs anaerobically, methane is produced, which is converted to CO₂ over time. If it occurs aerobically, CO₂ is produced directly (This decomposition process occurs in us and is also 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, their carbon compounds settle and over millions of years, under the influence of pressure and heat, fossil fuels are formed. In the sea, oil and gas are formed; on land, coal is formed.
(Anthropogenic) Climate Change
The Earth is constantly exposed to climate fluctuations. Since its formation, 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.
Carbon dioxide plays a crucial role in this (cf. graphic), which is produced by burning fossil fuels for energy generation. Combined with the increasing energy demand of humanity, CO₂ emissions rose from 2 gigatons in 1900 to 34.8 gigatons in 2021 (max. 2017 37.1 Gt).
Feedback Loops and Tipping Points
The increase in temperature and the change in climate can lead to effects that further intensify these changes. This amplification effect is particularly dangerous for humanity, especially when tipping points are crossed. Tipping points are events that cannot be reversed once they are crossed. The reactions of the environment to climate changes are completely natural, but they cannot be reversed and can make the planet uninhabitable for humans.
Three examples of these feedback loops are:
Reduced Albedo (= Reflectivity of a planet/body)
As ice sheets melt, incoming solar energy is no longer directly reflected by the white surface but absorbed by the dark ocean surface.
Steppification of the Rainforest
Additionally driven by deforestation, the warming climate threatens to dry out the rainforest. The forest depends 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 presumably bound in organic materials at depths of a few meters. Should this thaw, thousands of tons will be released.
These feedback loops are linked to certain temperatures and are also called tipping points. If these are exceeded, it can lead to a domino effect that can no longer be stopped.
With this background knowledge, in the next article, we will look at coffee and climate change. What is the impact of coffee on climate change, and what is the impact of climate change on coffee?
