In a new study it was discovered that the reason for the occurrence of the "Little Ice Age" was actually overheating in the period that preceded it. Could the extreme cold return a second time nowadays due to the increase in global temperature and how is this related to the weakening of the Gulf Stream?
Yonatan Sher, Angle - news agency for science and the environment
You may not be one of those who enjoy the season of scarves, hats, socks and gloves, and while you are close to the radiator global warming starts to sound like a not bad deal at all (spoiler: it is a deal terrible). However, it turns out that too much heat can actually cause the opposite phenomenon: extreme cold. BA new American study The surprising answer to a big question that many have tried to answer over the years has been found: What caused the "Little Ice Age", which froze Europe and other parts of the world for hundreds of years in modern times? It turns out that the answer lies in the relatively warm period that preceded it - which raises the fear that similar phenomena will occur even today.
The Little Ice Age There was a period that lasted from the 15th century to the 19th century, during which different regions of the world experienced significant cooling one after the other. The first to experience the cooling were the European countries, which had to deal with crop destruction, famine and epidemics - which led toDeath of millions and to great suffering. "At that time, almost all of Europe froze for several months of the year, and according to the evidence that remains, the ice lasted even in the summer," says Dr. Baruch Ziv, a climate researcher from the Open University. "Usually, the next winter does not 'remember' the previous winter, but then It was a matter of climate change that lasted for a large number of consecutive years - and on the scale of an entire continent."
Until now no satisfactory explanation has been offered as to why the Little Ice Age occurred. According to the researchers who conducted the new study, which comes from the University of Massachusetts at Amherst (UMass) and was published in the scientific journal Science Advances, the answer to the question came to them during a previous study they conducted, in which they examined The historical temperatures of the sea level in the North Atlantic Ocean: they were surprised to find that there was a sudden change in the water temperatures in the area, which were relatively very warm at the end of the 14th century - and became unprecedented at the beginning of the 15th century, only 20 years later.
When the golf course collapses
The effect of sea surface temperatures on the climate of Europe and the world is due to the importance of ocean currents. What most of us know as "The golf stream" is the northern part of the AMOC (Atlantic Meridional Overturning Circulation) - a system of currents in the Atlantic Ocean that causes the dispersion of heat on the Earth's surface, and has a significant effect on the climate. In the AMOC system, warm non-dense water from the tropics and the southern hemisphere flows on the surface of the ocean to the north, where they transfer heat to the colder ocean and atmosphere and cool, and also become saltier due to Evaporation. Both of these processes make the water denser, so it sinks in the deep ocean back to the south, cooling the tropical and southern regions of the Atlantic Ocean. Europe," Ziv explains.
According to the researchers, the AMOC actually strengthened at the end of the 14th century, which led to a larger-than-normal flow of particularly warm water to the north. However, the strengthening of the currents eventually caused their collapse: the unusual warmth of the water caused huge amounts of ice to melt around the North Pole, which cooled the surface water of the Atlantic Ocean and diluted its salinity. "When ice melts, it turns into distilled liquid water," explains Ziv. "Salt water is heavier than fresh water, so it makes sense that the cold, sweet water floated over the warm water that came from the south and covered it. As soon as the warm water did not moderate the winter, Europe froze deeply, and the summer was unable to melt the ice."
Little Ice Age 2.0?
The bad news is that there is a risk that the phenomenon found in the study will happen again - nowadays. The findings of several studies from recent years point to Weakening, on a loss of stability and even on the risk of a complete collapse of the AMOC. The reasons for this Reminiscent of those described in the study on the Little Ice Age – the rise in global temperatures that is currently occurring as part of the Climate crisis is leading to the release of freshwater from melting glaciers in Greenland and the Arctic, disrupting the natural circulation cycle in the ocean. It should be noted that, according to the researchers who conducted the new study, the rise in global temperatures, which has already caused the melting of many glaciers, has resulted in much less ice in the Arctic Ocean that can melt, and therefore an extremely extreme cooling event like that of the early 15th century is unlikely – but they do not rule out the possibility of another collapse of the AMOC, which would have devastating consequences. According to experts, such a collapse could lead to the cooling of large areas in the Northern Hemisphere and the worsening of the heat in the Southern Hemisphere.
In fact, the great complexity of the AMOC system, and the inability of current climate prediction models to deal with it, makes the answer to the question of whether the current system will collapse difficult to predict. In the latest IPCC report, for example, reads: "There is a high probability that the AMOC will weaken under any climate scenario. Also, although there is a moderate degree of confidence that the expected decline of the AMOC will not include a sudden collapse before 2100, such a collapse could occur."
"However, even if the AMOC stops, due to the fact that Europe has warmed by several good degrees in the last decades, even if in a certain winter it freezes - in the summer it will thaw," says Ziv.
Beyond that, the current rise in temperatures is global, and not local like the one that led to the Little Ice Age. The amount of heat that the Earth contains today is much higher than before the Little Ice Age, and the oceans also contain a much larger amount of heat today. All these facts reduce the likelihood that we are in for another little ice age - but they are far from encouraging for the planet and for us.
Either way, Ziv warns against complacency. "Although the models cannot be accurate in long-term predictions regarding the AMOC, no matter how you look at them - they do know how to say that the global temperature will rise," he concludes. "By exactly how much? We don't know that, so we have to prepare for the worst forecast."
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