That basic physical understanding, confirmed in computer simulations of these storms in current and future climates, as well as recent events, leads to high confidence that rainfall rates in hurricanes increase by at least 7% per degree of warming.

Scientists also have high confidence that wind speeds will increase in a warming climate and that the proportion of storms that intensify into powerful Category 4 or 5 storms will increase. Similar to rainfall rates, increases in intensity are based on the physics of extreme rainfall events.

Damage is exponentially related to wind speed, so more intense storms can have a bigger impact on lives and economies. The damage potential from a Category 4 storm with 150 mph winds, like Ian at landfall, is roughly 256 times that of a category 1 storm with 75 mph winds.

Whether warming causes storms to intensify more rapidly is an active area of research, with some models offering evidence that this will probably happen. One of the challenges is that the world has limited reliable historical data for detecting long-term trends. Atlantic hurricane observations go back to the 1800s, but they’re only considered reliable globally since the 1980s, with satellite coverage.

That said, there is already some evidence that an increase in rapid intensification is distinguishable in the Atlantic.

Within the last two weeks of September 2022, both Noru and Ian exhibited rapid intensification. In the case of Ian, successful forecasts of rapid intensification were issued several days in advance, when the storm was still a tropical depression. They exemplify the significant progress in intensity forecasts in the past few years, although improvements are not uniform.

There is some indication that, on average, the location where storms reach their maximum intensity is moving poleward. This would have important implications for the location of the storms’ main impacts. However, it is still not clear that this trend will continue in the future.

Storm surge – the rise in water at a coast caused by a storm – is related to a number of factors including storm speed, storm size, wind direction and coastal sea bottom topography. Climate change could have at least two important influences.

Stronger storms increase the potential for higher surge, and rising temperatures are causing sea level to rise, which increases the water height, so the storm surge is now higher than before in relation to the land. As a result, there is high confidence for an increase in the potential for higher storm surges.

The speed of the storm can be an important factor in total rainfall amounts at a given location: A slower-moving storm, like Hurricane Harvey in 2017, provides a longer period of time for rain to accumulate.

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