Fires, floods, heat waves and droughts. The deadly weather that has developed in recent weeks has left climate scientists “shocked” and concerned that extreme events are coming even faster than models predicted.
In southern Oregon, a fire in an area 25 times the size of Manhattan It has lasted for weeks, helped by a record-breaking heat wave. In China, floods killed 51 after a year of rain fell in a single day in the central city of Zhengzhou, causing more than $ 10 billion in damage.
And in Russia, a state of emergency has been declared in Yakutia, in the Far East, where the authorities are creating artificial rain seeding clouds with silver iodine in an attempt to put out more than 200 fires.
Climate scientists say the severity of these events is simply “out of scale” compared to what atmospheric models predict, even when global warming is taken into account.
“I think I would be speaking on behalf of many climate scientists to say that we are a bit shocked by what we are seeing,” said Chris Rapley, professor of climate science at University College London. “There is a dramatic change in the frequency with which [weather] events happen. ”
From the deadly floods in Germany last week to the scorching heat in Canada and a deluge in the Black Sea region, the pace and scale of the catastrophic damage has been almost unimaginable, even to experts who have spent their lives studying it.
One factor behind many of these events is the changing pattern of the jet stream, a fast-flowing band of air that governs the climate in the Northern Hemisphere. It becomes slower and wavy, especially in the summer months.
When the jet stream becomes slow and wobbly, high-pressure systems and low-pressure systems increase in magnitude and get stuck in place, explains Michael Mann, director of the Center for Earth System Sciences at Pennsylvania State University. .
This means that heat waves and drought (linked to high pressure systems) and floods (linked to low pressure systems) become more persistent.
The phenomenon, known as “planetary wave resonance,” is behind the recent heat wave in North America, for example, where temperatures in western Canada reached 49 ° C.
It also contributed to extreme heat in the Russian Arctic region, where extensive wildfires are producing toxic smoke that has covered the city of Yakutsk, a port city in Siberia, better known as one of the coldest winter cities on the planet. The fires have caused one of the worst air pollution events in the world, generating dangerous levels of particulate matter.
Mann is concerned that current models do not accurately reproduce the behavior of the jet stream. “This means that they are underestimating the magnitude of the impact of climate change on extreme weather events,” he says.
“While the global warming is pretty much in line with climate model predictions from decades ago, the increase in extreme weather events outpaces predictions,” says Mann.
The world has warmed about 1.2 ° C on average since pre-industrial times, but that warming is unevenly distributed, with the Arctic region heating up about three times faster than the rest of the world, largely due to loss of reflective snow and ice.
This Arctic warming has a major impact on the jet stream, which is governed in part by the difference in temperature between cold polar air and warm tropical air.
In Germany and Belgium, the slower jet stream is a contributing factor to this month’s floods that killed more than 120 people and destroyed cities and towns.
“We had a low pressure field over central Europe that was not moving, it was persistent and durable. Normally our weather patterns moved from west to east, ”said Fred Hattermann, a researcher at the Potsdam Institute for Climate Impact Research.
“The driving force behind our west wind is the temperature gradient from the equator to the Arctic,” he explains. Warming in the Arctic means that “this engine that we have is weakened.
Not all extreme weather events are related solely to the jet stream.
Global warming also has a direct impact on precipitation and rain, because warmer air can hold more moisture, roughly 7 percent more water for every 1C of heating.
This is part of the reason why the recent floods in India and China were so devastating, involving monsoon cycles rather than jet stream behavior.
In torrential rain that soaked central China’s Henan province last week, its capital Zhengzhou saw 20 centimeters of water fall in a single hour. The widespread flooding that flooded its subways drowned 12 passengers.
By Friday, the floods had caused 51 deaths and direct damage worth 65.5 billion rupees ($ 10 billion) in Zhengzhou alone. Unusually large volumes of water vapor were pushed inland by typhoons off the southern coasts of China and turned into rain after being washed away by the Henan mountain ranges, according to the China Meteorological Administration.
Constant high pressure over the Sea of Japan and Northwest China meant that the rain clouds stalled in a low pressure vortex over Henan, turning into a slow series of intense and successive storms known as the “train effect.” the administration said. he told Chinese state media.
Chinese authorities said volumes had exceeded anything recorded for the past 5,000 years, extending up to the official start date of Chinese civilization.
Meanwhile, in northeastern Russia, firefighting teams continue to fight more than 200 fires. The Yakutia region has regularly experienced lows of minus 50 ° C in some places, but has recently set several new records for the highest temperatures within the Arctic Circle.
Governor Aysen Nikolayev, 49, has long raised the alarm about the impact of global warming in his region.
“Without a doubt, there is only one reason: global climate change,” he told local television. “It is happening, we see Yakutia heating up every year.”
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