Weather Blockades New evidence of massive climate change

Studies provide new evidence about human involvement in climate change

Heat, drought, flood, forest fires - weather extremes are likely to occur more frequently in the coming years. Two recent studies show major changes in the large air currents, which repeatedly lead to so-called weather blockages. Rain weather is more likely to cause flooding and sunshine, more like drought and forest fires, weather forecasters say. In addition, the evidence that human beings are significantly involved in this development is increasing.

Researchers at the Potsdam Institute for Climate Impact Research (PIK) report on two recent studies that examine the influence of excessive warming of the Arctic on the circulation patterns of air currents. The results of the study suggest that burning fossil fuels has changed the circulation of high airflows, often resulting in weather blockages that leave a certain amount of weather in one place for an unusually long time. The studies have recently been published in the renowned journals "Nature Communications" and "Scientific Reports".

Storms, storms and floods could occur much more frequently in the future. Weather researchers blame the altered circulation patterns of the air masses for increasing weather extremes. (Image: trendobjects / fotolia.com)

Weather extremes will pile up

Rain or shine - in North America, Europe and parts of Asia, the weather is likely to stay the same for the coming summers. This is shown by a team of scientists in the first comprehensive overview of the research on summery blockade weather and jetstream. The inflexible weather conditions would also increase the risk of weather extremes and disasters. Rain increasingly causes floods and hot spells droughts and forest fires.

A manmade problem?

"Huge air flows orbiting our earth in the upper troposphere - we are talking about planetary waves," explains Hans Joachim Schellnhuber, director of PIK in a press release on the study results. Now the evidence would gather that mankind is messing up these huge wind currents. It is likely that man-made greenhouse gas emissions distort natural circulation patterns, according to the climate expert.

The warming of the Arctic is the focus

Normally, the huge air currents oscillate between the equator and the North Pole, transporting high and low pressure areas. "But if they are held in place by a subtle resonance mechanism, they slow down so that the weather gets stuck in a certain region," explains Schellnhuber.

This summer is an impressive example

"Having more sunny weather in the summer does not sound bad at first," commented Dim Coumou from PIK. In fact, there is a considerable risk behind it. Global warming would already cause rising temperatures anyway. If these weather conditions are even more localized, it would be more often catastrophic weather extremes. "That's pretty worrying," says Coumou. The current summer is an impressive example of such a weather blockade.

A comprehensive overview

As the PIK experts report, there are tons of studies on the subject, some of which yielded contradictory results. Now, an international team of scientists has reviewed and evaluated the existing results and combined various research approaches.

Complex interrelationships

"All the mechanisms so far recognized do not work in isolation but interact with each other," explains Simon Wang of Utah State University. In the course of global warming, the Arctic heats up faster than the rest of the northern hemisphere. This reduces the temperature difference between the North Pole and the equator. This temperature difference is a significant driving force for the large air currents in the atmosphere.

The Canadian forest fire disaster as a case study

The forest fire in the Canadian region of Alberta in 2016 was a frightening demonstration of the impact of the slower summer winds. Researchers were able to prove in a study that the fire was actually preceded by a stalling of air currents in the region.

Wave patterns can be predicted

"In fact, our analysis shows that even beyond this single event, planetary waves have been a relevant factor in the forest fire hazard in the region since the 1980s," says Vladimir Petoukhov of PIK, the lead author of the case study. Since it is possible to predict the wave patterns with a relatively long lead time of ten days, this could be used in the future as a warning for forest fires. (Vb)