September 21, 2023

This summer, a “perfect storm” is unfolding that is “driving up the weather,” says one scientist

A “perfect storm” is unfolding this summer, a climate scientist told CNN, as atmospheric ingredients combine to cause deadly flooding in the Northeast and record-breaking heat in the Southwest and around the world.

Deadly flash floods inundated parts of the northeast, trapping people in their homes and killing at least one woman who was swept away by the rushing water. Rivers in Vermont rose rapidly in Monday’s torrential rain to levels not seen since Hurricane Irene in 2011.

On Sunday, more than 7.5 inches of rain fell in West Point, New York, in just six hours — a 1,000-year rainfall record for the area, according to a CNN analysis of data from the National Oceanic and Atmospheric Administration. A rainfall of 1000 years is so intense that it only happens once every 1000 years on average.

The climate crisis is piling on deck in favor of more intense weather events such as the heavy rainfall and flooding in the Northeast, said Michael E. Mann, a climate scientist and distinguished professor at the University of Pennsylvania.

“Sure, weather is weather. It’s going to happen — rainfall, floods will happen,” Mann told CNN. “What climate change does is it boosts them, so if you get one of those weather systems that produces large amounts of rain, you get more rain.”

There’s another, more surprising way the climate crisis could be driving these extreme rainfall events, Mann said, and it’s something at the forefront of climate research: The jet stream could be “stuck” in positions that prolong these types of extreme events.

The jet stream is the fast-moving river of air high in the atmosphere that heralds weather systems around the world. Importantly, it is fueled by the extreme temperature difference between the equator and the poles.

But the planet is not warming equally in all locations, Mann explained. The Arctic is warming much faster than, say, the Lower 48, “reducing the temperature difference between the equator and the pole.”

Scientists suspect that this decrease in temperature difference changes the behavior of the jet stream.

“The jet stream basically stops and those weather patterns stay in place — those high and low pressure centers stay in place,” Mann said. “And we’re seeing more of this kind of stuck, rippling jet stream pattern associated with these very persistent weather extremes, whether it’s heat, drought, wildfires or flooding.”

A person walks along Roosevelt Row in Phoenix on July 5.  High temperatures may remain above 110 degrees this week.  - Joel Angel Juarez/The Republic/USA Today Network

A person walks along Roosevelt Row in Phoenix on July 5. High temperatures may remain above 110 degrees this week. – Joel Angel Juarez/The Republic/USA Today Network

As the northeast is flooded with torrential rain, dangerous heat threatens other parts of the world. Temperatures are rising this week in the Southwest, where Phoenix could break its record for a consecutive number of days above 110 degrees.

Last week, the planet’s average daily temperature rose to record levels according to data tracked by two climate agencies in the US and Europe. Climate scientists told CNN that global temperatures were likely the highest in at least 100,000 years.

Meanwhile, the EU’s Copernicus Climate Change Service found that last month was the warmest June by a “substantial margin” over the previous record, set in 2019.

Given the exceptional heat, scientists are concerned that 2023 could be the hottest year on record.

Mann said El Niño “adds extra heat, extra fuel to the fire.” El Niño, a warm phenomenon in the Pacific Ocean, combines with the climate crisis “and what you get are new record levels of heat on a planetary scale.”

But Mann said that without the climate crisis caused by burning fossil fuels, “we just wouldn’t be seeing these extreme events.”

“Those are conspiracies. They combine,” Mann said. “The steady warming coupled with an El Niño; extreme weather events related to those changing jet stream conditions – it all comes together, if you will, in a perfect storm of consequences, which translates into really devastating and deadly extreme weather events that we’re dealing with here right now.

CNN’s Rachel Ramirez, Laura Paddison and Jennifer Gray contributed to this story.

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