Do we know what we are getting into? (pub. December 14, 2024)
In this wandering, I am going to comment on the variations of 2 gases in the composition of the atmosphere, carbon dioxide (CO₂) and methane (CH4).
And what do these gases matter?
These gases are responsible for the greenhouse effect, playing a predominant role in the climate, and have been responsible for changes in life on earth.
For example, about 800 million years ago the concentration of CO₂ was between 1,000-10,000 ppm and that of CH4 was 10-100 ppm. With that concentration, the greenhouse effect was very high, and the earth was very warm. But then oxygen (O2), produced by the first phototrophic organisms, began to accumulate in the atmosphere and oxidize CH4, transforming it into CO₂, the problem is that CH4 has a greenhouse effect of more than 30 times that of CO₂, so That 700 million years ago the greenhouse effect decreased drastically, so much so that the earth completely froze.
Fortunately, volcanic activity caused CO₂ to increase, causing the temperature to rise, the ice began to melt, releasing methane trapped in them, and conditions improved.
Autotrophs continued to produce O2, which continued to accumulate, allowing the development of more complex organisms, both plants and animals. Thus, about 500 million years ago, CO₂ had a concentration between 10 to 20 times that of today, CH4 would have a presence very similar to today. With this atmospheric composition, one of the greatest changes in the history of the earth occurred, the Cambrian, suddenly virtually all current animal groups appeared.
Just as animals diversified, so did plants, populating the land above sea level. Increasing photosynthesis, decreasing the concentration of CO₂ and the greenhouse effect. Again, the Earth's temperature decreased, forming large glaciers and lowering sea level. This is one of the probable causes of the mass extinction of 444 million years ago.
The earth is very dynamic and geological processes, such as volcanism, allowed CO₂ to increase again and with it the greenhouse effect, making the earth suitable for the development of life.
Things that can be good, if they go beyond any level, can be harmful. Thus, on the one hand, the development of terrestrial vegetation caused many nutrients to reach the sea, and on the other, volcanism caused CO₂ to accumulate a lot in the atmosphere. In this way, eutrophication processes occurred in the sea, causing the O2 in the sea to decrease, and when CO₂ dissolved it formed carbonic acid, so the sea became anoxic and acidic, giving rise to a new mass extinction about 360 million ago. of years.
The earth is very resilient, it recovered, once again suitable conditions for the development of life and about 300 million years ago the CO₂ in the atmosphere would have been around 2,000 ppm and that of CH4 about 10 ppm. Reptiles appear populating the earth, including synapsids, ancestors of mammals.
Very intense geological processes took place, with great volcanic activity, excess CO₂ began to accumulate again, raising the temperature. The terrestrial ecosystems began to decertify and in the sea there was once again great acidification. About 252 million years ago, not only did a new mass extinction occur, it was the largest in the history of the earth; some estimates go as far as 95% of existing living beings perished.
Once again, conditions improved and life recovered, not without shocks. A few millon years later, volcanism again caused the increase in CO₂, repeating the situation of the last extinction, but this one was not as great. This allowed the arrival of the era of dinosaurs, the Jurassic. The atmospheric composition was very similar based on the two main gases, 78% N2 and 21% O2, but CO₂ was above 1,000 ppm and CH4 above 10 ppm, higher than current concentrations.
But again another mass extinction, but this one was caused by something different, a giant aerolite, more than 10 km in diameter, at a speed of more than 36,000 km/hour. This stone affected the entire Earth system, including the atmosphere, large quantities of particles were released that blocked sunlight, causing a sudden global cooling and preventing photosynthesis from taking place. This was 66 million years ago, and 75% of species disappeared, including dinosaurs and, my favorites, pterosaurs.
The Earth recovered and approximate concentrations of CO₂ were 280 ppm and CH4 720 ppb. This allowed the development of the greatest biodiversity in the history of the earth.
But then humans came along, and our activity is causing changes in the composition of the atmosphere. Currently, concentrations are 420 ppm for CO₂ and 1,900 ppb for CH4. That is, in less than 300 years, the concentration of CO₂ has increased by 50% and that of CH4 by 164%.
The increase in CO₂ comes from the burning of fossil fuels and deforestation and that of CH4 from activities such as agriculture (rice cultivation), and livestock (bovines), waste treatment, and the extraction of fuels, natural gas through fracking.
It seems we don't realize what we're getting into.
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