We get outdoor weather more often – and it gets even worse

We get outdoor weather more often - and it gets even worse

Meteorologists and climatologists were speechless three times in quick succession. Between the end of June and the end of July 2021, the weather was very severe. First in Canada, then in Western Europe and then in China. What happened here was disproportionate. Totally unexpected.

In late June, a heat wave swept through western Canada. On June 29, mercury in Lytton reached 49.6 degrees Celsius, at least 5 degrees above the old heat record. Two weeks later, severe flooding ensued in Limburg and parts of Germany and Belgium. More than 90 mm of rain fell in one day. In the German Ahr-Erft basin, no more than 54 mm fell on the wettest summer day of the last century. This was followed by heavy rains in the Chinese province of Henan, and in particular the city of Zhengzhou. On the evening of July 20, 200 mm of rain fell One hour. The previous record was 165 mm.

As the temperature rises faster, there is a greater chance that you will suddenly make a big leap after ten, twenty or thirty years

Eric Fisher Eidgenössische Technische Hochschule

The researchers immediately asked: How did these unusual extreme events happen? Whatever the geographical distance between them, were they possibly related?

Science is busy trying to better understand this extremely violent weather. This is already clear: With global warming continuing right now, heat waves, droughts, torrential rains and severe hurricanes will occur more frequently and become more intense. But how to deal with this external class Events arise exactly? How often can we expect it? and where? This is less clear.

Tens of thousands of dead

Interest in extreme weather has grown strongly since 2010, says Diem Cuomo, professor of extreme weather and social impact at VU University Amsterdam, as well as a researcher at KNMI. In the summer of 2010, there was a severe heat wave in Russia and Ukraine, which killed tens of thousands. The wheat crop collapsed, among other things. Food prices have raised all over the world. At the same time, Pakistan was hit by torrential rains. A fifth of the country was flooded. It killed 1,700 people and caused extensive damage to infrastructure. It is becoming clear, Cuomo says, that climate change Currently Already affects the extremism that occurs. “It was a wake-up call for many, and especially for me,” he said during his inaugural lecture last May. He recalled the extreme weather events of the time black swans. This term dates back to the Roman era. Black swans were seen as an impossible thing. In Europe, only white swans are known. Until the Dutch captain Willem de Fleming sailed to Australia at the end of the 17th century and was the first European to see a black swan.” Como says that in climatology the term is now used to refer to severe weather that was not expected and was more intense than previously observed extremes.

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The growing interest in this matter is reflected in the reports of the United Nations Intergovernmental Panel on Climate. In her report published last August, she devoted an entire chapter (chapter 11, nearly 250 pages) to severe weather. In the previous report, in 2013, the topic expanded to 15 pages and was tucked away in the General Notes section.

An important finding from the latest IPCC report is that temperature extremes on Earth are more or less in line with the increase in the global average. In the summary of this report there are a number of graphs that clearly explain this. A heat wave that occurs on average once every ten years in the period 1850-1900, 2.8 times with a 1°C temperature rise, 2°C 5.6 times the temperature, and a 4°C temperature 9.4 times. The frequency and intensity of heavy rains and droughts are also in line with the global average temperature, albeit to a lesser degree than heat waves.

Drought and dust storms

But these are global averages. It is also clear that things could go very differently at the local level. A group of researchers wrote in May that heat waves have not increased in the Central Plains of the United States Earth’s future. The highest temperatures so far were reached during the Dust Bowl, a period of severe drought and dust storms in the 1930s. They wrote that in India there is hardly a trend in extremely high temperatures. In other regions, such as Western Europe, heat waves are heating up faster than the Earth, on average. The first author of this study is Gert Jan van Oldenburg, a KNMI employee, who passed away last October. It was his last post. Van Oldenburg has been wondering for some time how temperatures in the Netherlands could have increased so rapidly in temperatures. Since 1900, the highest annual maximum temperature in De Bilt has increased by 4 degrees, while the average temperature on Earth has increased by 1.2 degrees.

Heatwave in Russia and floods in Pakistan in 2010 have been linked

Eric Fisher Eidgenössische Technische Hochschule

It can have many causes, KNMI authors wrote in an accompanying press release. The IPCC report also addresses it. Changes in buildings, vegetation cover, amount of water in the ground, clouds, prevailing wind directions. All of them affect temperature extremes. Climate models do not adequately take this into account. In order to improve it, they will have to take these kinds of factors into better consideration. For example, deforestation causes extreme temperatures to rise. But irrigation has a cooling effect, as well as increased air pollution. The opposite is also possible. The decline in air pollution in Western Europe, including the Netherlands, may have contributed to the rapid increase in temperature extremes. Remarkably, the impact of this clean air in Western Europe is not limited to this region, the researchers wrote. It even reaches Northeast Asia.

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This touches on another drawback, says Eric Fischer of the Eidgenössische Technische Hochschule in Zurich. “We have been studying extreme weather events mainly in isolation.” But it is becoming increasingly clear that events in different parts of the world can have a common cause. “The heat wave in Russia and the floods in Pakistan in 2010 have been linked,” Fisher says. Cuomo agrees. Posted about it last year. In both cases the cause was the jet stream, strong westerly winds at a height of about 9 to 10 kilometers. It marks the boundary between the cold northern air and the warm southern air. As the Arctic is warming faster than the global average, the contrast between cool northern air and warm southern air has decreased. As a result, the strength of the jet stream decreased in summer. Sometimes it swings all the way around an area of ​​high or low pressure, so that it becomes attached and can stay in the same place for weeks. It happened in the summer of 2010, with a high pressure zone over Russia and a low pressure zone over Pakistan. According to Cuomo, the three extreme events in summer 2021 were also linked “by the dynamics of the jet stream”.

impossible to live

Fisher says the limited view of science is not just geographical. “In extreme weather, we have long been restricted to only temperature or only precipitation.” While extremes also happen together. The Intergovernmental Panel on Climate Change is addressing this issue for the first time in its latest report composite events. Heat often goes hand in hand with dehydration. “For the Netherlands, the combination of heavy precipitation and storm surge can also pose additional risks,” Fischer says. One worrying combination is heat with high humidity. Global warming is causing the atmosphere to become so warm in some places in the world that it becomes physiologically impossible for humans and animals to live there – along with the high humidity – without aid. At higher temperatures, the body has to dissipate more heat, but high humidity hinders sweating.

As the temperature rises faster, there is a greater chance that you will suddenly make a big leap after ten, twenty or thirty years

Eric Fisher Eidgenössische Technische Hochschule

Fisher says he wants to do more research on these combined events. He says knowledge of severe weather is increasing rapidly. He published a study last year about the future potential of unexpectedly severe weather, such as a heat wave in western Canada. events that, he said, broke world records to be. The probability appears to be related to the degree of warming. “With the temperature rising faster, there’s a greater chance ten, twenty, thirty years later that you’ll suddenly make a big jump in maximum temperature, or the amount of precipitation.” Precisely since the 1980s, he says, warming has accelerated, mainly because the amount of greenhouse gases humans are releasing into the atmosphere has increased from year to year. That’s why a lot of extreme weather has been seen disproportionately in recent decades. “So it’s important to slow down global warming as quickly as possible.”

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Cuomo also says that knowledge is increasing rapidly. He himself is trying to improve the ability to predict European summer weather, among other things, through artificial intelligence.

Cuomo wonders how quickly humans will be able to turn the current rapid warming trajectory. And this will certainly continue into the next decade. And so we can expect extreme weather events unexpectedly. “Frankly, I’m not very optimistic,” he said during his opening lecture. “But I am not pessimistic either. Renewable energy is rapidly becoming cheaper, and governments have set ambitious targets. This gives some hope.”

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