During warm periods of the planet’s history, the Sahara ceased to be a desert and was covered with vegetation. Climatologists have now discovered that such overgrowth strongly affects at least the entire Northern Hemisphere, especially the Arctic, Europe, and Central Asia. These findings are interesting in the context of current warming, where some scientists believe a new greening of the Sahara is impending.

Between 11 and 5 thousand years ago, northern summer coincided with the greatest convergence of the Earth and the Sun, corresponding to today’s summer in the Southern Hemisphere. The period 11,000–5,000 years ago was significantly warmer than the entire Holocene (which began 11,000 years ago and continues), as the Southern Hemisphere reflected and reflected light into space much more strongly than the Northern Hemisphere due to ice in Antarctica. to this day). Average temperatures were around plus 15 degrees Celsius, higher than they were in the 2020s and before the onset of human-caused global warming.

Like other warm periods in Earth history, the Holocene Climate Optimum was a time when the Sahara Desert was overgrown and mostly green. However, how much it affects the entire planet has not been fully understood until now. The authors of a new scientific study published in the journal Climate of the Pastdecided to examine this issue. Scientists simulated the Earth’s climate at that time in two versions: with vegetation in the Sahara and without vegetation.

It turns out that the impact of greening the desert on the rest of the world is very significant. Vegetation is darker than the desert surface (it has a lower albedo, or reflectivity), and it also traps sand, nearly suppressing the sandstorms that are a regular scourge of the Sahara and surrounding regions. Microparticles from these storms create health-threatening values ​​as far as Italy, and even in some years (for example, 2024) as far as Moscow. Dust from storms rises high enough to block some of the solar energy and cool the planet noticeably.

Both factors led to a drastic increase in average temperatures from the northern subtropics to the Arctic, particularly in the Arctic, in Northern Hemisphere simulations with an overgrown Sahara. The same was true for precipitation. At the same time, in Western Europe, winters became slightly cooler and summers warmer than in the version in which the Sahara did not green up. While Central and Eastern Europe experienced hot weather with green Sahara, summers were cooler, winters were hotter and precipitation was more in Central Asia. At the same time, the Mediterranean cooled and received more rainfall.

Note that when researchers compared simulation results with paleoclimatic data obtained from fossils (ancient tree rings based on environmental temperature, isotope ratio, etc.), they obtained a result that was far from the ideal match. It was also higher than in the simulation without the green Sahara.

Although the authors of the scientific study analyzed the climatic past, their conclusions are also valid for the future. Currently the Earth is practically back to its Holocene optimum temperatures. Some Western scientists say the Sahara is starting to green, although modern Russian climatologists do not expect this.

Mykhailo Budyko, the greatest domestic climatologist of the past, who predicted the inevitability and exact quantitative value of global warming in the 1970s, believed that the new greening of the Sahara would be an inevitable consequence of the new warming. If everything happens so, the climate of the high and middle latitudes of the Earth may change in the same direction as 5-11 thousand years ago.