From flooding in Germany to fires in the Russian far East to high temperatures and droughts in North America, extreme weather has recently occurred frequently around the world, which has shocked the scientific community.

The Financial Times quoted climatologists as saying that even with full consideration of global warming, the severity of these events had "exceeded the limit". Chris Rapley, a professor of climatology at University College London, said he was "surprised by all this" and that "the frequency of extreme weather has changed dramatically".

Talking about the culprit behind it, scientists set their sights on the high-speed airstream (Jet Stream).

The so-called high-speed airstream is a continuous airstream that flows around the earth and has a great impact on the weather in the northern hemisphere. Tim Woollings, a lecturer in physical climate science at the University of Oxford, said earlier, "if you have to choose only one piece of information to judge the weather in the northern hemisphere, it depends on the high-speed air flow and its direction."

Especially in summer, when the high-speed airflow slows down, the volatility is greater, resulting in heat waves in many places.Michael Mann, director of the Earth system Science Center at Pennsylvania State University, explains that this is because when high-speed airflow slows down and becomes unstable, the number of high-pressure and low-pressure systems increases and gets stuck. This will cause both high temperatures and droughts (related to high pressure systems) and floods (related to low pressure systems) to become more lasting.

Under the background of global warming, the uneven distribution of global warming aggravates this situation. At present, the Arctic is heating up about three times as fast as the rest of the world, and less sea ice means the oceans are absorbing more heat from the sun. On the other hand, the narrowing of the temperature gradient between the poles and the tropics may weaken the high-speed air flow, making its velocity slower and swinging more violently.

The recent extreme heat in North America and northern Russia is due to this phenomenon. Temperatures in western Canada reached as high as 49 degrees Celsius. Yakutsk, the capital of Russia's Sakha Republic, is known as the "ice city" with frequent wildfires, causing one of the world's most serious air pollution incidents, with harmful smog exceeding the alert level.

In Germany and Belgium, high-speed airflow slows to exacerbate flooding this month, killing more than 120 people and destroying towns and villages. Fred Hattermann, a researcher at the Potsdam Climate impact Institute, said there was a low pressure field over central Europe that was supposed to move from west to east, but it did not move and stayed there continuously and permanently.

Mann said that current climatological models can no longer accurately reproduce changes in high-speed airflow. "they underestimate the impact of climate change on extreme weather events," Mann said.

Although global warming is basically in line with climate models predicted decades ago, the increase in extreme weather events has exceeded forecasts.

Image source: Financial Times