Global warming contributes to the recent extreme weather

Abnormally atmospheric circulation against the backdrop of global warming played a major role behind the recent extreme weather in the northern hemisphere, said Sun Chenghu, a researcher with Beijing Climate Center (BCC).

During later June and early July, extreme weather has occurred in America and European countries. In the U.S., rarely persistent heat wave with nearly 40 degree Celsius temperature  has influenced many places, killing at least 30 people. And on June 29, a rare stormy weather hit eastern America, causing wide power off and killing 26 people.

Since this July, U.K., Russia, Germany, and other countries in Europe have been struggling against severe flooding which has claimed at least 140 people.

According to the monitor of BCC, since this July, the temperature in northern hemisphere has been generally higher than normal, especially in North America. There is 2 degrees higher-than-normal temperature observed in eastern North America. And in part of southeastern America, rarely 6 degrees above-than-normal temperature has been witnessed.

As for rainfall, it is unevenly distributed. The rainfall in North America has been obviously less than normal while one third more rain has been poured out to Europe. Especially in Russia, the rainfall has doubled than normal since July 7, according to the BCC.

The hot weather and rainstorm is a reflection of abnormally atmospheric circulation, which is happened against the backdrop of global warming, said Sun Chenghu.

The researchers find that as one of the characteristics of global warming, the warming rates are different in high latitudes and mid-and-low latitudes, which lead to different depth of atmosphere over high and mid-and-low latitudes. This slows the west wind and weather system in North America and mid-and-low latitudes, providing conditions for extreme weather.

For the case in America, when high pressure ridge dominates weather system over America, it will be hot and this will last one week usually. However, in this time, it is rarely seen that the high pressure ridge controls weather system in such a long time and large regions, said Sun Chenghu.

At the same time, the low pressure system has controlled the weather system over Europe, leading to severe rainstorm. This comes as a result of abnormal distribution of surface temperature in north Atlantic Ocean.

(Source: www.cma.gov.cn/en)