Millions of Americans are once again in the grip of dangerous heat. Warmer winds swept across Europe at the end of last week, leaving parts of France and Spain feeling like they usually do in July or August. High temperatures scorched northern and central China, while heavy rains caused flooding in the south of the country. Some places in India started experiencing exceptional heat in March, although the onset of monsoon rains has brought some respite.
It is too early to say whether climate change is directly responsible for causing severe heat waves in these four powerhouse economies – which are also the top emitters of heat-trapping gases – at roughly the same time, just days in the summer. .
While global warming continues to make extreme heat more common around the world, a deeper analysis is needed to tell scientists whether specific weather events were made more likely or more intense due to human-induced warming. (A team of researchers studying this spring’s devastating heat in India found that climate change had made it 30 times more likely to happen.)
Nevertheless, for reasons related to the jet stream and other rivers of air affecting weather systems around the world, concurrent heat waves have been hitting certain groups of remote locations with increasing frequency of late.
Studies have shown that parts of North America, Europe and Asia are connected in this way. Scientists are still trying to determine how these patterns may change as the planet progresses, but for now it means that simultaneous heat extremes will probably continue to affect the places where the world is located. A lot of economic activities are concentrated in
Daniel E., a climate scientist at Northwestern University. “For a heat wave to occur, we need heat, and we need an atmospheric circulation pattern that allows heat to accumulate,” Horton said. With global warming, he said, “we’re definitely getting more heat.” But climate change may also affect the way this heat is distributed across the globe by air currents around the world, he said.
Simultaneous weather extremes at multiple locations are not just meteorological curiosities. Individual heat waves can cause disease and death, wildfires and crop failure. Concurrent foods could jeopardize global food supplies, which are under alarming tension this year due to Russia’s invasion of Ukraine.
While heat waves are shaped by complex local factors such as urbanization and land use, scientists are no longer skeptical about whether climate change is making them worse. Soon, the world’s most devastating heat waves may have no historical analogue from the time humans began pumping greenhouse gases into the atmosphere, some scientists argue, as a main driver of whether climate change Makes this question obsolete.
Andrew Dessler, a climate scientist at Texas A&M University, said the heat of recent decades has made it difficult for scientists to know what to call a heat wave and what to consider a new normal for warmer weather.
For example, if the threshold for a heat wave is just over 100 degrees Fahrenheit, for example, then it’s “not unexpected at all,” Dr. Dassler said, seeing them happen more regularly in multiple areas at once. “As time goes on, more and more planets will experience those temperatures until eventually, with enough global warming, every land area in the mid-latitude northern hemisphere will be above 100 degrees,” he said.
Yet when scientists look at how often the temperature exceeds a certain level relative to the moving average, they still find a large increase in the frequency of simultaneous heat waves.
A recent study that did this found that the average number of days between May and September with at least one major heat wave in the Northern Hemisphere doubled between 1980 and 2010, from 73 to nearly 152. But the number of days with two or more heat waves was seven times higher, rising from 20 to about 143. This is almost every single day from May to September.
The study also found that these concurrent heat waves affected large areas and were more severe by the 2010s, with peak intensities that were about a fifth higher than in the 1980s. The study found that on days when there was at least one major heat wave somewhere in the Northern Hemisphere, an average of 3.6 of them were occurring per day.
Deepti Singh, a Washington State University climate scientist and author of the study, said the “dramatic” increase came as a surprise.
Dr. Singh and his co-authors also looked at where concurrent heat waves occurred most frequently during those four decades. One pattern stood out: simultaneous large heat waves in eastern North America, Europe and parts of central and eastern Asia increased rapidly between 1979 and 2019 – “far more than what we would expect from the effects of warming alone.” ,” Doctor. Singh said.
The study did not seek to predict whether heat waves with this pattern would become more frequent as global warming continues, she said.
Scientists are working to explore how the rotation of the jet stream, which has long-standing weather patterns for billions of people, may change in this warming era. One factor is the rapid warming of the Arctic, which reduces the difference in temperature between the northern and southern bands of the Northern Hemisphere. Exactly how this might affect extreme weather is still a matter of debate.
But those temperature differences are the major force driving the winds that keep weather systems moving around the planet. As the temperature difference decreases, these air currents may slow down, said Kai Kornhuber, a climate scientist at the Lamont-Doherty Earth Observatory at Columbia University. This means that extreme events such as heat waves and heavy rains are likely to last longer.
“The longer a heat wave lasts, the more you shore up natural and social order,” said Dr. Kornhuber.
He said climate change already means that there will be more extreme weather events in the world, and more extreme events will occur simultaneously. “These change the circulation, they will act on top of that,” he said, “and will make the extremities even more severe and more frequent.”