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‘Compound Extremes’: Why A Cocktail Of Natural Disasters Is Battering The US

Summer in the American west is off to an explosive start, with extreme weather events ravaging multiple states in recent weeks. In Montana, historic flooding devastated communities and infrastructure in and around Yellowstone national park and forced a rare closure. Further south, reservoirs sank to new lows, triple-digit heatwaves left millions sweltering, and wildfires ripped through Arizona, New Mexico, Alaska and California.

These layered disasters offer a glimpse of what’s to come. As temperatures continue to climb, extreme events will not just increase – they’re more likely to overlap, causing more calamity and testing the limits of the nation’s resilience and recovery.

“The US has a certain amount of capacity to cope with extreme events,” said Dr Andrew Hoell, a meteorologist for the National Oceanic and Atmospheric Administration’s (Noaa) physical sciences laboratory, adding that capacity is stretched when these events build on one another, either regionally or sequentially.

Natural disasters, from floods to droughts to wildfires, have always occurred in areas across the west, and it will take time for scientists to study the precise connections between events like the destruction in Yellowstone and the climate crisis. But it is clear that, in a warming world, combinations of factors are increasingly likely to align and turn routine events into a catastrophe. So-called “compound extremes,” where a combination of contributing factors come together, are on the rise, Hoell said.

A layering of dangerous realitiesThe flood in Yellowstone was one such “compound extreme”.

Warming weather flushed melting snow into the waterways as a deluge pelted the region, dropping up to 3 months-worth of summer rain over the span of just a few days, according to an accounting done by CNN. Researchers with the US Geological Survey (USGS) and two universities had already sounded the alarm that an event like this was increasingly likely, publishing a report last year on how the climate crisis could threaten the park. Noting that average temperatures could increase by up to 10 degrees in the coming decades, they concluded that the region should expect intense dry conditions peppered with dangerous downpours.

“With increasing global surface temperatures the possibility of more droughts and increased intensity of storms will likely occur,” USGS scientists wrote. “As more water vapor is evaporated into the atmosphere it becomes fuel for more powerful storms to develop.”

The moment a house collapses into a river as major floods close Yellowstone national park – videoThe unprecedented and sudden flooding earlier this week toppled telephone poles, knocked over fences, wiped out roads and bridges, and threatened to cut off fresh drinking water supplies to the state’s largest city, after officials in Billings, Montana, were forced to shut down its water treatment plant.

“None of us planned a 500-year flood event on the Yellowstone when we designed these facilities,” said Debi Meling, the city’s public works director. Remarkably no one was reported hurt or killed, but the damage has been possibly permanent and recovery could take years.

“We certainly know that climate change is causing more natural disasters, more fires, bigger fires and more floods and bigger floods,” said Robert Manning, a retired University of Vermont professor of environment and natural resources. “These things are going to happen, and they’re going to happen probably a lot more intensely.”

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