Climate change: Hurricanes get stronger on land as world warms

By Matt McGrath
Environment correspondent

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Image source, Reuters
Image caption,
People being evacuated from Houston, Texas, in the wake of Hurricane Harvey in 2017

North Atlantic hurricanes are retaining far more of their strength when they hit land because of global warming, say scientists.

Previously, experts believed these storms died down quickly once they made landfall.

But over the past 50 years, the time it takes for hurricanes to dissipate on the coast has almost doubled.

Researchers says that climate change gives the storms more energy, which continues to power them over land.

The scientists involved say that this will likely make hurricanes more damaging further inland in years to come.

This year, the North Atlantic has already broken the record for the number of named storms, with Hurricane Theta becoming the 29th storm of the season - beating the 28 that formed in 2005.

Experts have noted that in recent years, tropical storms that make land are persisting far longer and doing more damage than in the past.

In 2017, Houston, Texas, was inundated when Hurricane Harvey settled over the city for several days, dumping 127 billion tonnes of water on the US' fourth largest city.

Now, researchers have shown that climate change is preventing these storms from decaying quickly when they move onto dry land.

Image source, NASA

Hurricanes are powered by moisture from warm, tropical oceans - this is the fuel that drives the intense winds that are typical of this type of storm.

Climate change means the air over the oceans can hold more of this moisture, intensifying the storms at sea.

But when these storms hit land, the fuel from the seas is cut off and the hurricanes should decay, or dissipate, very quickly.

However, this new study indicates that is no longer the case.

"We show that hurricanes decay at a slower rate in a warmer climate," said Prof Pinaki Chakraborty, from the Okinawa Institute for Science and Technology in Japan, who led the study.

"For North Atlantic land-falling hurricanes, the timescale of decay has almost doubled over the past 50 years."

Image source, Reuters
Image caption,
Hurricane Eta brought heavy rain to Florida

"As to the underlying reason, our analysis suggests that the culprit is climate change."

The scientists found that in the late 1960s, hurricanes typically lost 75% of their intensity in the first day after landfall.

Nowadays, the decay is only about 50%.

The researchers believe that the key to the storms retaining their power is the warm moisture they have picked up along the way.

It's working like an extra fuel tank to keep the hurricane active even when it's over dry land. As the world gets warmer, this means that tropical storms will likely stay active for longer and do far more damage inland.

"We also show, using simulations, that the slower decay is fuelled by an increased amount of moisture that is stocked in the hurricane from its passage over ocean prior to landfall," said Prof Chakraborty.

"Unfortunately, our research also suggests that as the climate keeps warming, the decay of hurricanes will keep getting slower, and consequently, regions farther inland will face the wrath of ever stronger storms."

The study has been published in the journal Nature.

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