Scientists have found out when the warming on the planet actually began

Scientists have found out when the warming on the planet actually began
Scientists have found out when the warming on the planet actually began
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Researchers from the United States and China have found out what is the discrepancy between the results of climate modeling and geological data in the interpretation of global climate trends over the past 12 thousand years. The corrected results showed that ocean temperatures steadily increased throughout the Holocene. The article was published in the journal Nature.

Scientists have long noticed that the results of climate modeling for the Holocene, the modern geological era that began 12 thousand years ago, contradict temperature reconstructions based on indirect geological data - measurements of isotopic ratios in fossilized shells of foraminifera - single-celled marine organisms, and analysis of the presence in marine sediments of alkeones - organic compounds produced by algae and used as biomarkers.

These measurements indicate that the peak of heat, the so-called thermal maximum of the Holocene, fell on the period from 10 to 6 thousand years ago. Geologists believe that at this time the Earth was warmer than it is now. Even warmer, in their opinion, was at the beginning of the last interglacial period, 128-123 thousand years ago, and modern warming began only with the onset of the industrial era.

At the same time, long-term climate modeling assumes continuous warming throughout the Holocene.

After analyzing the results obtained from indirect geological data, the authors of the study came to the conclusion that most of them reflect single - that is, seasonal rather than annual values ​​of paleotemperatures.

Scientists developed a method for estimating seasonal biases and used it to calculate the average annual sea surface temperature. The result showed that over the past 12 thousand years it has been steadily increasing: first due to the active retreat of ice sheets from 12 to 6, 5 thousand years ago, and recently - due to an increase in greenhouse gas emissions.

The current average annual temperatures, according to the authors, are the highest in the last 12 thousand years and are approaching the temperatures in the last interglacial period. Only during the last interglacial period, which lasted from 128 to 12 thousand years ago, temperatures were stable due to practically unchanged concentrations of greenhouse gases, the level of the World Ocean and the area of ​​ice sheets, and now the average annual temperatures and sea level continue to rise steadily. This, according to the researchers, the current climatic situation is fundamentally different from the last interglacial period.

As for the thermal maximum of the Holocene, its authors associate it with the peak of summer insolation in the Northern Hemisphere, which fell on the early Holocene. Scientists have not found any evidence of maximum mean annual temperatures in the early Holocene.

The authors note that establishing long-term trends in climate change is critical to understanding the context of current global warming and predicting its consequences.

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