Even for a period of extreme weather, this autumn has had more than the usual weather disasters.
The Spanish province Valencia has seen the latest incident of massive and deadly flooding in Europe. Heavy downpours also hit France, Austria and Czechia this fall. Italy has had two major floods, once in September and then again in October.
More than 200 people have been killed in the flooding in Spain. At the same time, over half of the United States experiences an almost rain-free October.
Scientists studying the recent weather say the heavy rains are probably connected to climate change in two ways. They say a warmer atmosphere holds and then releases more moisture. The other connection is possible changes in the jet stream that could cause extreme weather. The jet stream is the river of air above land that moves weather systems around the planet.
Several climate scientists and meteorologists said the immediate cause of the flooding is a cut-off lower pressure storm system that came from an unusually wavy and slowed jet stream.
In the United States, the slow movement caused a sunny, high-pressure system with no moisture to cover the country and keep storms away.
“If we’re getting all the dryness, somebody else is getting all the rain,” said Yale Climate Connection meteorologist Jeff Masters, co-founder of Weather Underground.
“The same extremely wavy jet stream that is causing the U.S. drought is also responsible for the horrific flooding in eastern Spain,” said climate scientist Jennifer Francis. She is with the Woodwell Climate Research Center in Cape Cod, Massachusetts.
Francis is an early developer of the theory that connects a wavier and slower-moving jet stream to climate change. The theory is that the Arctic is warming so much; it is now not much colder than the rest of the planet. That theory is gaining more acceptance, but it is not fully accepted by the climate science community.
Climate scientist Erich Fischer is with the university ETH Zurich in Switzerland. He does not fully accept the wavy jet stream theory. But then he lists the storm systems that have slowed and flooded Europe this fall: one in France and two in Italy in September and October and flooding in Austria and the Czech Republic in September.
And then there were the October floods in the Balkans, although Fischer said he is not sure they are similar enough. The European climate service Copernicus says parts of Poland, Germany and the Czech Republic got three months of rain in just five days in September.
Fischer also spoke of the floods in Europe during the summer. “Starting with Bavaria, southern Germany in June, and then it was something like six events in Austria and Switzerland in the mountains, extreme thunderstorms, and now this autumn.”
He said it was an unusual period in which the systems, especially in Spain, France and Austria, stopped in one place and “the rain did not move” from the same valleys for hours.
Even without the changes to the jet stream, several scientists said they are sure that basic physics are making storms like this wetter.
It holds that every degree Celsius the air warms, it can hold seven percent more moisture. The world has warmed 1.3 degrees Celsius because of greenhouse gases, so it has about nine to 10 percent heavier rain, at the least, said Imperial College London climate scientist Friederike Otto. She helps run an organization called World Weather Attribution. It checks for human causes of extreme weather, sometimes finding them, sometimes not.
She said it is very clear that climate change is linked to the rain event in Valencia.
The Mediterranean Sea had its warmest surface temperature on record in mid-August, with a mean temperature of 28.47 Celsius, said Carola Koenig of the Centre for Flood Risk and Resilience at Brunel University of London.
She said that means more moisture is in the air, “resulting in more rain when the atmosphere starts to cool in the autumn.” She warned there may be more heavy rain after this week’s storm.
There may be different ways of counting and attributing climate change and the problems it causes, Otto said, but one thing is for certain: “Burning fossil fuels causes climate change and climate change causes death and destruction.”
I’m Mario Ritter. And I’m Jill Robbins.
Seth Borenstein reported this story for the Associated Press. Jill Robbins adapted it for Learning English.
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Words in This Story
jet stream – n. a strong current of fast winds high above the Earth’s surface
moisture – n. a small amount of a liquid (such as water) that makes something wet or moist
meteorologist – n. a science that deals with the atmosphere and with weather
drought – n. a period with no rain
physics – n. a science that deals with matter and energy and the way they act on each other in heat, light, electricity, and sound
attribute – v. to say that (something) is because of (someone or something)