(CNN) – In the same week that Tropical Storm Fred caused catastrophic flooding in North Carolina and Hurricane Grace made landfall for the second time in Mexico, Hurricane Henri was heading toward New England, and would be the first to make landfall there in 30 years.
Hurricanes – also called tropical cyclones or typhoons outside North America – are huge heat engines of wind and rain that feed on warm ocean water and humid air. Now scientists say the climate crisis is making them more powerful.
The proportion of high intensity hurricanes has increased due to warmer global temperatures, according to the UN climate report released earlier this month. Scientists have also found that storms are more likely to park up and cause devastating rains and last longer after they make landfall.
“We are very confident that warming from the greenhouse effect increases the maximum wind intensity that tropical cyclones can reach,” Jim Kossin, senior scientist at the Climate Service, an organization that provides climate risk modeling and analysis to governments, told CNN. and companies. “This, in turn, allows the strongest hurricanes – which create the greatest risk by far – to get even stronger.”
Scientists such as Kossin have observed that, globally, a higher percentage of storms are reaching the higher categories (3, 4 and 5) in recent decades, a trend that is expected to continue as the global average temperature increases. They are also closing in on the poles, moving slowly through the earth, getting wetter and stagnating in one place, Kossin found.
“There is evidence that tropical cyclones are more likely to park,” Kossin said, naming hurricanes Harvey in 2017, Florence in 2018, and Dorian in 2019 as examples. Hurricane Harvey dumped more than 1,524 millimeters of rain in parts of Texas, causing about $ 125 billion in damage, according to the National Hurricane Center, and killing more than 100 people.
“All of these were devastating for the places where they stalled.” “The combination of slower movement and more falling rain greatly increases the risk of coastal and inland flooding.”
A 2020 study published in the journal Nature also found that storms are moving further inland than five decades ago. Hurricanes, which are powered by warm ocean water, generally weaken after passing over land, but in recent years they have lasted longer after making landfall. The study concludes that warmer sea surface temperatures cause “slower decomposition” by increasing the moisture carried by the hurricane.
And as storms like Henri make landfall, torrential rains, damaging winds and storms become the most significant, often pernicious threats. The storm surge, produced by wind blowing ocean water onto the shoreline, is also expected to worsen over time due to stronger hurricane force winds and rising sea levels driven by climate change, according to Kerry Emanuel, professor of atmospheric sciences at the Massachusetts Institute of Technology.
“It is a very dangerous phenomenon,” he said. “And it is responsible for a lot of the loss of life in the storms.”
For every fraction of a degree the planet warms, according to the UN report, rainfall rates from high intensity storms will increase, as warmer air can hold more moisture. Earlier this week, what had been Tropical Storm Fred dumped more than 254 millimeters of rain across western North Carolina, according to the National Metereological Service, causing the Pigeon River near Canton to rise 2.7 meters above the flood level, killing at least four people.
The science behind climate change attribution, which attempts to determine what role it plays in extreme weather conditions, has made significant progress in the last decade, according to the UN climate report. Higher heat waves, floods, droughts and coastal storms emerge that scientists are now more confident to link these events to climate change. But there are still some questions about hurricane development that need to be answered, according to Emanuel.
“Knowing where they develop and where they are moving is critical to understanding the threat,” Emanuel said. “So we have to take into account the change of tracks, the change in intensity, the change in frequency and the change in genesis – and we are sure about some of them and we are not so sure about other elements.”
Although it is difficult for scientists to know if the tracks of strange North Atlantic storms, such as Henri’s, are becoming more frequent due to climate change, lasting changes along the coast in the Northeast will influence the storms. make landfall there.
“One thing we could speculate about is that the unusually warm ocean along the northeast coast of the United States and Canada probably has a human footprint,” Kossin added. “These warm waters should allow Henri to maintain a higher intensity as he moves north.”
Bob, in 1991, was the last hurricane to make landfall in the New England region. However, Irene, in 2011, and Sandy, in 2012, were destructive to the Northeast when they made landfall, even though the hurricanes did not make landfall.
The 2020 hurricane season went through the alphabet so fast that he was forced to use Greek letters as names from September to November. This year’s season is already above average – Atlantic storms that begin with the letter H usually occur towards the end of September, meaning Henri formed more than a month earlier than average.
As the planet warms rapidly, extreme weather events will become more disastrous and possibly more difficult to predict.
Unless climate and emergency management policies are in place, Emanuel says damage to infrastructure and possible loss of life will increase.
“Forecasters’ nightmare is to go to bed with a tropical storm in the Gulf of Mexico, head into the populated area, and wake up to Category 4,” Emanuel said. “And as the weather warms, that becomes more and more likely.”