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En quoi l'érosion des sols est-elle un régulateur du climat ? © Manoj Badola, Pixabay

How did the Earth recover from the latest global warming?

The temperature maximum transition between the Paleocene and Eocene, 55.9 million years ago, represents one of the most important climatic crises the Earth has known. A new study was published in science progress It shows that this extreme global warming has been associated with increased erosion and weathering of continental rocks. These processes would have made it possible in particular to capture a large part of the carbon dioxide2 atmosphere, and thus climate stability.

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The Earth system has several mechanisms that influence, in one direction or another, weather changes. Surface processes, such as mechanical erosion and chemical weathering of rocks, are mechanisms now known to have the ability to reduce the amount of carbon dioxide.2 inAtmosphere.

Silicate rock weathering: a carbon dioxide pump2

Among these surface processes, weathering reactions that attack metal Silicates, turning them into clays, consume carbon dioxide2. The rivers then become responsible for transporting the carbon residues to the oceans, where they will be used by marine organisms for development and production Calcite shaping their shells.

When these animals die and settle to the bottom, the Carbon stored in their own biomass and in their shells then buried in sediment. Over very long periods of time – from tens to hundreds of thousands of years – this chain reaction allows for efficient extraction of carbon dioxide.2 from the atmosphere and store it at the bottom of the oceans, thus regulating the climate.

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What is still poorly understood, however, is Speed which carbon change, erosion and burial can respond to major environmental changes, such as we are seeing. One way to look at this question is to look into the Earth’s past to find it A natural analogy to what is happening today.

Extreme global warming 56 million years ago

In fact, the geological history of the Earth has recorded many events associated with major disturbances in the carbon cycle. These crises are characterized by periods Global Warming Intense. This is the case with the Paleocene-Eocene transition temperature maximum (PETM), which occurred 55.9 million years ago. The origins of this crisis are still debated but we know that at that time, a large amount of carbon was released very quickly into the Earth’s atmosphere (in less than 5,000 years), causing the globe to warm rapidly, in particular, 8°C Celsius increase in water temperature.

One way to look at this question is to look back at Earth’s past for a natural counterpart to what is happening today.

These brutal environmental changes had multiple consequences. In particular, it has led to ocean acidification and disturbances in the hydrological cycle that have caused mass extinction In the deep oceanic domains and major bio-changes at the surface.

This climate crisis lasted about 100,000 years, then it will take another 50,000 to 100,000 years to subside. This stage of steadfastness Of particular interest to scientists trying to figure out whether erosion rates are large enough to help the climate recover in a relatively short period of time.

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2 to 3 times higher wear rates

To study the importance of surface processes at this time, researchers used isotopes The lithium To determine the rates of erosion and chemical weathering of rocks. Lithium has two isotopes: 6Read et al 7Li, the interesting point is that the ratio between these two isotopes (δ7Li) depending on chimical interaction. In seawater, this ratio is strongly influenced by clay composition, making δ7I have a good tracker of erosion rates and weathering.

Samples dating back to the PETM period were analyzed. δ . measurements7they suggest that Water Cycle It was greatly amplified during this climate crisis. The precipitation were larger, which increased the rate of mechanical wear and chemical change of continental rocks. The design conducted by the study authors indicate that erosion rates were two to three times higher during the PETM period compared to rates before the crisis.

The tremendous contribution of Nutrients In the oceans would prefer produce Thing Organic, parallel to carbonate precipitation. Rapid burial of carbon trapped in marine organisms and in carbonate rocks It was certainly the main influencing parameter that facilitated the rebalancing of the climate and the end of this extreme weather event.

These results have been published in science progress, could make it possible to understand how the Earth system as a whole could and might be able to respond to future climate change. From this point of view, it is possible to think of solutions to aid this natural process of carbon capture in order to combat ongoing climate change.