How climate change affects hurricanes, typhoons and cyclones

Hurricane Melissa, one of the most powerful Atlantic storms ever recorded, created “extremely hazardous and life-threatening” conditions in Jamaica, according to the US National Hurricane Center.

It is believed that climate change will not lead to an increase in the number of hurricanes, typhoons and cyclones around the world.

But warmer oceans, combined with a warmer atmosphere caused by climate change, could make those processes that do form even more intense.

This could potentially lead to increased wind speeds, heavy rainfall and increased risk of coastal flooding.

Hurricanes are powerful storms that develop in warm tropical ocean waters.

In other parts of the world they are known as cyclones or typhoons. Collectively, these storms are called “tropical cyclones.”

Tropical cyclones are characterized by very high wind speeds, heavy rainfall and storm surges – short-term rise in sea level. This often results in widespread damage and flooding.

Hurricanes can be classified by their maximum sustained wind speed.

Severe hurricanes are classified as Category 3 or higher, which means they reach speeds of at least 111 mph (178 km/h).

Hurricanes, typhoons and cyclones begin in the atmosphere. disorder – such as a tropical wave, an area of ​​low pressure where thunderstorms and clouds develop.

When warm, moist air rises from the surface of the ocean, winds begin to blow. This process is related to how the Earth's rotation affects winds in tropical regions near the equator.

For a hurricane to develop and continue to rotate, the sea surface temperature generally must be at least 27°C to provide sufficient energy, and the winds must not vary much with altitude.

If all of these factors come together, a major hurricane can form, although the exact causes of individual hurricanes are complex.

Globally, the frequency of tropical cyclones has not increased over the last century. maybe the number has dropped – although in some regions long-term data are limited.

But it is “likely” that over the past four decades, a large proportion of tropical cyclones around the world have reached category three or higher, meaning they reach the highest wind speeds, according to the UN climate body. IPCC.

Assessing the precise impact of climate change on individual tropical cyclones can be challenging due to the complexity of these storm systems.

But rising temperatures could affect these storms in several ways.

First, warmer ocean waters mean storms can absorb more energy, resulting in higher wind speeds.

Maximum wind speeds for hurricanes increased by an average of about 19 mph (30 km/h) between 2019 and 2023 as a result of human-caused ocean warming. according to a recent study.

Second, a warmer atmosphere can hold more moisture, leading to more intense rainfall.

Climate change made the likelihood of extreme precipitation from Hurricane Harvey in 2017 about three times greater. according to one of the estimates.

Finally, sea levels are rising, mainly due to a combination melting glaciers And ice sheetsand the fact that warmer water takes up more space. Local factors may also play a role. This means that storm surges occur on top of already elevated sea levels. increased coastal flooding.

For example, the estimated flood height for Hurricane Katrina in 2005, one of America's deadliest storms, was 15-60% higher than they would have been under the climatic conditions of 1900.

General, The IPCC concludes there is “high confidence” that humans contributed to the increased rainfall associated with tropical cyclones, and “moderate confidence” that humans contributed to the higher likelihood of a more intense tropical cyclone.

According to experts, the number of tropical cyclones in the world is unlikely to increase. IPCC.

But as the world warms, they say it is “very likely” they will experience higher levels of precipitation and peak wind speeds. This means that a higher proportion will reach the most intense categories, fourth and fifth.

The higher the global temperature, the more drastic these changes will be.

According to the IPCC, the proportion of tropical cyclones reaching category four and five could increase by about 10% if global temperature rise is limited to 1.5°C, rising to 13% at 2°C and 20% at 4°C, although exact figures are unclear.