Explainer: How climate change is fueling hurricanes

A man on a motorcycle rides past downed power lines after Hurricane Fiona in Higuey, Dominican Republic September 19, 2022. REUTERS/Ricardo Rojas

September 20 (Reuters) – After a quiet start to the season, Hurricane Fiona swept across Puerto Rico and then devastated the Dominican Republic, leaving more than 1 million people without running water or electricity. Continue reading

While scientists have yet to determine whether climate change has affected Fiona’s strength or behavior, there is strong evidence these devastating storms are getting worse.

Here’s why.

DOES CLIMATE CHANGE AFFECT HURRICANES?

Yes, climate change is making hurricanes wetter, windier, and more intense overall. There is also evidence that it causes storms to travel more slowly, meaning they can dump more water in one place.

Without the oceans, the planet would be much hotter due to climate change. But over the past 40 years, the ocean has absorbed about 90% of the warming caused by heat-trapping greenhouse gas emissions. Much of this ocean heat is contained near the surface of the water. This extra heat can increase the intensity of a storm and drive stronger winds.

Climate change can also increase the amount of precipitation from a storm. Because a warmer atmosphere can also hold more moisture, water vapor builds up until the clouds break up and send down heavy rain.

During the 2020 Atlantic hurricane season — one of the most active on record — climate change increased hourly precipitation rates in hurricane-force storms by 8% to 11%, according to an April 2022 study in the journal Nature Communications.

The world has already warmed by 1.1 degrees Celsius above the pre-industrial average. Scientists from the US National Oceanic and Atmospheric Administration (NOAA) expect that with a warming of 2°C, the wind speed of hurricanes could increase by up to 10%.

NOAA also predicts that the proportion of hurricanes reaching the strongest levels — Category 4 or 5 — could increase by about 10% this century. To date, less than a fifth of the storms since 1851 have reached this intensity.

HOW ELSE WILL THE CLIMATE CHANGE STORM AFFECT?

The typical “season” for hurricanes is shifting as global warming creates conditions conducive to storms in more months of the year. And hurricanes also make landfall in regions well outside of historical norms.

In the United States, Florida has the highest number of hurricanes making landfall, with more than 120 direct hits since 1851, according to NOAA. But in recent years, some storms have reached their peak intensity and are making landfall farther north than in the past — a pole shift could increase with rising global air and sea temperatures are related, scientists say.

This trend is of concern for mid-latitude cities like New York, Boston, Beijing and Tokyo, where “the infrastructure is not prepared for such storms,” ​​said Florida State University atmospheric scientist Allison Wing.

Hurricane Sandy, although only a Category 1 storm, was the fourth costliest U.S. hurricane of all time, causing $81 billion in damage when it struck the Northeast Coast in 2012.

In terms of timing, hurricane activity in North America is common from June through November, peaking in September after a summer buildup of warm water conditions.

The first named storms to make landfall in the U.S. are now hitting more than three weeks earlier than in 1900, pushing the start of the season into May, according to a study published in August in Nature Communications.

The same trend appears to be playing out globally in the Asian Bay of Bengal, where since 2013, cyclones have formed earlier than usual – in April and May – before the summer monsoon, according to a November 2021 study by Scientific Reports.

However, it’s unclear whether climate change is affecting the number of hurricanes that form each year. According to their study published in Nature Communications in December, a team of scientists recently reported that they had noticed an increase in the frequency of North Atlantic hurricanes over the past 150 years. But the research is not yet complete.

HOW DO HURRICANES FORM?

Hurricanes need two main ingredients – warm seawater and moist, humid air. When warm seawater evaporates, its thermal energy is released into the atmosphere. This drives the storm’s winds to intensify. Without them, hurricanes cannot intensify and fizzle out.

CYCLONE, TYPOON, HURRICANE – WHAT’S THE DIFFERENCE?

Although these large storms are technically the same phenomenon, they are given different names based on where and how they originated.

Storms that form over the Atlantic Ocean or the central and eastern North Pacific are called “hurricanes” when their wind speeds reach at least 74 miles per hour (119 kilometers per hour). Until then, they are known as “tropical storms.”

In East Asia, violent, swirling storms that form over the Northwest Pacific are called “typhoons,” while “cyclones” form over the Indian Ocean and South Pacific.

Reporting by Gloria Dickie; Edited by Katy Daigle and Lisa Shumaker

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