Hurricanes, powerful tropical storms, are becoming increasingly intense as global temperatures rise. According to the US National Hurricane Center, Hurricane Melissa has created “extremely dangerous and life-threatening” conditions in Jamaica, exemplifying the threats posed by these storms.
While climate change is not believed to increase the overall number of hurricanes, typhoons, and cyclones worldwide, it is making those that do form more intense. Warmer ocean temperatures and a heated atmosphere contribute to higher wind speeds, increased rainfall, and an elevated risk of coastal flooding.
These storms, referred to collectively as “tropical cyclones,” typically develop in warm tropical ocean waters. They can be classified by their peak sustained wind speed, with major hurricanes categorized as category three and above, reaching at least 111 mph (178 km/h).
The formation of hurricanes begins with atmospheric disturbances, such as tropical waves or areas of low pressure where thunderstorms develop. As warm, moist air rises from the ocean, it creates spinning winds due to the Earth”s rotation near the equator. For a hurricane to develop, sea surface temperatures usually need to be at least 27°C, and wind patterns must remain consistent at different heights.
Despite the lack of increase in the frequency of tropical cyclones over the past century, a higher proportion of these storms are likely reaching category three or higher now compared to forty years ago, as noted by the IPCC. The organization expresses “medium confidence” that average and peak rainfall rates associated with tropical cyclones have risen, along with an increase in rapid intensification events, where wind speeds rise sharply, posing significant dangers.
Additionally, studies indicate a slowdown in the movement of tropical cyclones across the Earth”s surface, leading to increased rainfall in specific areas. For instance, Hurricane Harvey in 2017 stalled over Houston, resulting in significant rainfall accumulation. Certain regions have also seen a shift in the average location where tropical cyclones reach peak intensity, exposing new communities to potential hazards.
Although assessing the precise impact of climate change on individual storms is complex, rising temperatures significantly influence hurricane dynamics. Warmer oceans enable storms to harness more energy, resulting in increased wind speeds. A recent study estimates that between 2019 and 2023, human-driven ocean warming raised maximum wind speeds of hurricanes by an average of 19 mph (30 km/h).
A warmer atmosphere can retain more moisture, leading to heavier rainfall during storms. For example, climate change is thought to have made the extreme rainfall from Hurricane Harvey approximately three times more likely. Rising sea levels, driven by melting glaciers and thermal expansion of seawater, exacerbate storm surges, increasing coastal flooding risks.
The IPCC has stated that there is “high confidence” that human activity has contributed to the increased precipitation associated with tropical cyclones and “medium confidence” that it has raised the likelihood of these storms becoming more intense. While the total number of tropical cyclones is unlikely to rise, the IPCC warns that as global temperatures increase, the intensity and rainfall rates of these storms are expected to rise significantly.
According to projections, the proportion of tropical cyclones reaching categories four and five may increase by about 10% if global warming is limited to 1.5°C, with higher increases anticipated at greater temperature rises.
