Mysterious episodes of warming during the glacial period, when temperatures in the north of the Earth rose sharply by 15 degrees, are associated with fluctuations in the concentration of carbon dioxide in the atmosphere and in the restructuring of the currents in the Atlantic. The scientists described this in an article published by the journal Nature Geoscience.
“This discovery does not mean that something similar will happen in the future as a result of rising CO2 levels, because now the boundaries between different climatic regimes look completely different than during the glacial period, but our work shows that sharp climate changes can occur Under the influence of very smooth changes, “says Gerrit Lohmann of the Alfred Wegener Institute in Bremerhaven, Germany.
The last glacial period in the history of the Earth, as geologists now believe, began about 2.6 million years ago and continues to this day. Its main feature is that the area of glaciation and the temperature of the Earth’s surface throughout its entire length were not constant – the glaciers attacked and retreated every 40 and 100 thousand years, and these episodes were accompanied by sharp cooling and warming.
The cycles of glaciations and thaws, as many scientists today believe, are primarily associated with the so-called cycles of Milankovitch – the wobble of the Earth’s orbit, on which it depends how much heat poles and temperate latitudes receive. Other geologists and climatologists believe that in fact these abrupt climate changes are not related to space, but to completely terrestrial factors, such as rearrangements of the “pipeline” of currents in the World Ocean or an increase or decrease in the proportion of carbon dioxide in the atmosphere.
Lohmann and his colleagues found new arguments in favor of the second group of theories. They created a computer model of the Earth from the glacial period and traced how the work of its climatic systems changed with the rise or fall of the CO2 level.
As these calculations have shown, even relatively small and very smooth changes in the concentration of carbon dioxide in the air can lead to sharp, almost instantaneous climate reorganizations.
For example, an increase in the CO2 content in the atmosphere from a level of 180 ppm, a minimum carbon dioxide concentration during the glacial period to 220 ppm, equivalent to about half of the current carbon dioxide content in the air, led to two very serious consequences .
As a result, the phenomenon of El Niño, transporting heat and water from the tropics of the Pacific to temperate latitudes, arose, and the Gulf Stream and associated currents in the North Atlantic increased. Temperatures in the subpolar latitudes increased sharply (in some regions by 15 degrees Celsius), because of which the ice cap disappeared sharply in the seas and significantly decreased on land.
If the concentration of CO2 fell, the climate quickly returned to the previous regime: the currents slowed down, the transfer of heat ceased, and the glaciers retreated to their old boundaries. Why this happened and how such “swing” climates have arisen, scientists do not yet know, but plan to find out by comparing the results of their calculations and the data on actual climate fluctuations in the last million years.