Climate change

Is the Atlantic hurricane season getting worse (and is climate change to blame)?

With Cuba and Florida reeling after Hurricane Ian, which made landfall in September 2022 and was one of the region’s strongest and most destructive storms in decades, it’s tempting to blame the carnage of another deadly hurricane season on climate change. . But is climate change the culprit? Recent studies have linked climate change to the environmental conditions that fuel hurricane season, but the link between global warming and individual hurricanes is far from settled science.

Although there is overwhelming evidence that human activities have directly caused sea level rise and global warming – two factors that make hurricanes deadlier – it is not clear whether climate change fuels a significant increase in the number of hurricanes or an intensification of tropical storms that make landfall.

“Hurricane activity is occurring against a backdrop of rising sea levels, which increases the risk of coastal flooding – that’s clear,” said Thomas Knutson, who studies climate change and hurricanes in the United States. National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory. GFDL).

“The global risk – how the frequency and intensity of storms are affected by global warming – is much more complicated,” Knutson told Live Science.

Related: Hurricane season 2022: how long it lasts and what to expect

A warming planet, as a rule, will give us more intense hurricane seasons, researchers have found. Sea level rise, driven by climate change, means more coastal flooding from storm surges when hurricanes make landfall. And global warming is also affecting rainfall, with an estimated 7% increase in precipitation for every 1 degree Celsius (1.8 degrees Fahrenheit) increase in sea surface temperature, scientists reported April 12 in the newspaper. Nature Communication (opens in a new tab). As human activities raise sea levels and surface temperatures, hurricanes are becoming more severe, in the form of floods and heavy rainfallLive Science previously reported.

Along these lines, some climate models have predicted that a 2 degree Celsius (3.6 F) increase in global temperatures will result in a higher percentage of hurricanes reaching Category 5 (sustained wind speeds of 157 mph or 252 km/ h), would increase hurricane wind speeds by about 5% on average and lead to more storms making landfall in the United States, researchers reported in 2013 in the Climate Diary. In an earlier study, published in 2005 in the journal Nature (opens in a new tab)scientists have discovered such a strong correlation between Atlantic hurricanes and sea surface temperatures that they have warned we could see a 300% increase in hurricane activity by 2100.

But despite these grim predictions, we have yet to see a significant increase in global hurricane activity. A confounding factor is that while warmer sea surfaces are ideal breeding grounds for hurricanes, storms that collide with a warm atmosphere tend to die down before doing much damage, have reported researchers in a Nature (opens in a new tab) study published on June 27. This may explain why, even though human activities have caused the planet to warm by 1C since the late 1800s, we have not observed an upward trend in the number or intensity of hurricanes over the past last century – and why Nature study (opens in a new tab)found that climate change may be linked to an overall decrease in the number of hurricanes.

“Increase greenhouse gas can cause sea surface warming, which increases hurricane intensity,” Knutson said. “But there’s even more warming in the upper troposphere, and that’s dampening hurricane intensity.” Knutson nevertheless expects to eventually see a slight increase.”We believe that global warming will still cause a net increase in hurricane intensity, but not as much as if we only had sea surface warming.” , did he declare.

The NOAA GOES-16 satellite captured this geocolored image of three hurricanes – Hurricane Katia, Hurricane Irma and Hurricane José – in the tropical Atlantic on the afternoon of September 8, 2017. (Image credit: NOAA/CIRA)

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Although we haven’t necessarily seen more hurricanes around the world in the past century, there has been an increase in the frequency and intensity of hurricanes in the Atlantic Basin over the past 40 years. But even this increase is not necessarily due to climate change. According to a 2022 study published in Scientists progress. While greenhouse gases cause global warming, aerosols block sunlight and cool the planet. When the United States began to reduce aerosols, this dramatic reduction may have caused a temporary increase in temperature that increased the frequency and intensity of Atlantic hurricanes, the researchers reported.

However, it is possible that factors other than aerosols alone are responsible for this change.

“There has been a sharp increase in hurricanes in the Atlantic Basin since 1980, but we don’t know if this is a greenhouse gas signal, due to changes in aerosol use. or just natural variability,” Knutson said.

Given the number of variables that can affect the formation and strength of hurricanes, it is therefore “premature to conclude with high confidence that the increase in anthropogenic greenhouse gases has had a detectable impact on the activity history of hurricanes in the Atlantic Basin,” according to an Oct. 3 report. written by Knutson for NOAA Geophysical Fluid Dynamics Laboratory. The report cites ongoing concerns that the increase in storm activity in the Atlantic Ocean since 1980 may be attributable to a combination of factors, including a decline in the manufacture and use of aerosol products, volcanic activity, even natural variability.

Still, Knutson added, climate change will almost certainly make future hurricane seasons more dangerous, with more frequent coastal flooding, increased rainfall and warmer seas promoting the formation of more intense storms.

Indeed, the shift is already well underway. In 2020, researchers analyzed data from 4,000 tropical cyclones spanning 39 years, from 1979 to 2017, and concluded that the hurricanes are getting stronger and major tropical cyclones are becoming more frequent, as models predicted, Live Science reported.

“On average, we expect hurricanes to become more intense and have higher precipitation rates due to climate change,” Knutson said. As for Hurricane Ian, which claimed hundreds of lives and was Florida’s deadliest hurricane since 1935, according to the The Washington Post“Instead of saying Ian is the result of climate change, we prefer to say that storms like Ian are likely more intense than they would have been had they occurred in pre-industrial times,” Knutson said. .