Three to four billion years ago, the Sun was only 70 to 80 percent bright at its current intensity. The Land It should be a block of ice. In fact, there have been oceans even then. The climate on Earth was very warm for the prevailing conditions. A team of scientists is now providing an explanation for this paradox Fachblatt “Proceedings of the National Academy of Sciences”.
The Earth’s atmosphere in the Archean, part of the earliest times spanning from four billion to about 2.5 billion years before our era, is assumed to have a very high content of carbon dioxide2The content, which is heating the surface of our planet, reports by Daniel Herwartz of the University of Cologne, Andreas Buck of the University of Göttingen and Thorsten Nagel of the Danish University of Aarhus.
The “weak paradox of the sun”
The professional community is aware of the geological mystery surrounding Young Earth, and is very warm to external conditions, as the “weak young sun paradox”. It was first described by astronomers Carl Sagan and George Mullen in 1972. It has been the subject of controversy ever since.
Among other things, researchers have explained the phenomenon in the meantime With clear skiesWhich would have warmed our planet a lot. Experts have now used some kind of climate model to determine the conditions that explain the discrepancy.
A second puzzle solving has also emerged: measurements of oxygen isotopes in very ancient limestone or gravel rocks, known as geothermal thermometers, have thus far suggested that the Earth was not only surprisingly warm in Earth’s beginnings, but also sea temperatures. Although the solar irradiance has decreased, the temperature has exceeded 70 ° C.
According to the researchers’ new modeling, these temperature specifications must now be modified. High carbon dioxide2Experts argue that the contents in the atmosphere may also change the chemical composition of the oceans – so that they do not warm up as easily as previously thought.
As if the entire atmosphere was made of carbon dioxide2
“The high levels of carbon dioxide explain two phenomena at the same time: on the one hand, the warm climate on the Earth, and on the other hand, why the Earth thermometers that often use seem to show hot sea water,” Hurwartz explained. If you take into account the percentage of other oxygen in the seawater, the result is a temperature of 40 degrees Celsius.
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However, it is also conceivable that the high methane content in the atmosphere is warming the Earth – this would not have any effect on the formation of the ocean, and thus it would not explain why the Earth’s thermometer delivers oxygen so high temperatures.
The total amount of carbon dioxide2 The study authors estimate that it’s about one strip of carbon dioxide2. This is very similar to what if our entire atmosphere today was made of carbon dioxide. “Today it is carbon monoxide2 Just a trace of gaseous in the atmosphere. Compared to this, the CO₂ tape seemed to be a ridiculous amount. But if we had our sister’s planet Venus Looking at the CO₂ at about 90 bars puts that into perspective, ”explains co-author Pack.
Large blocks of Earth have pulled carbon dioxide out of the Earth2
Tremendous carbon dioxide2The content is also explained by the appearance of the Earth at that time. This was mostly covered by oceans rather than large land masses that could store carbon. “Nearly three billion years ago, the movement of tectonic plates and the evolution of land masses, in which carbon can be stored for a long time, were only increasing in speed,” Nagle says.
The onset of plate tectonics fundamentally altered the carbon cycle. Large masses of land form with the emergence of mountains in geophysical processes during which carbon dioxide is sequentially drawn from the atmosphere and oceans and stored in the form of coal, oil, gas, black schist and limestone. As a result, it became significantly cooler on Earth, and it also showed an increased incidence of ice ages.
“Previous studies had already indicated that the limestone content in ancient basalt was due to the sharp drop in carbon dioxide in the atmosphere.2– Select the content. This goes well with an increase in oxygen isotopes at the same time, “Hurwartz explains.” Everything indicates that CO2– Atmospheric content decreased rapidly after the movement of tectonic plates.
But in earth sciences, “velocity” is relative: a period spanning hundreds of millions of years.
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