Without climate change, Hurricane Milton would have hit as a Cat 2, not a Cat 3  » Yale Climate Connections

Without climate change, Hurricane Milton would have hit Florida as a Cat 2 storm, not a Cat 3, according to the conclusions of a study by World Weather Attribution, an international scientific group. The group issued the study on October 11, just two days after Milton hit. A separate study on Hurricane Milton released the same day by researchers at the Imperial College of London found that this increase in intensity made Milton nearly twice as destructive.

World Weather Attribution’s analysis found that storms with Milton’s wind speeds have become approximately 40% more frequent and the winds associated with storms of similar rarity have become nearly 11 mph (5 m/s) higher (an increase of about 10%) because of the 1.3 degrees Celsius (2.3°F) of global warming since preindustrial times. Thus, without climate change, Milton would have hit Florida as a Cat 2 with 110 mph winds instead of a Cat 3 with 120 mph winds.

Read: Climate change made Hurricane Helene and other 2024 disasters more damaging, scientists find

Milton’s rains made 10-50% greater by human-caused climate change

To produce such a fast attribution study, the group did not perform the traditional modeling done for such studies, instead relying on observed trends over the past 75 years, plus modeling done for Hurricane Helene, a very similar storm in almost the same location that hit just two weeks prior. Looking at the past 75 years of data for central Florida, they found that rainfall extremes have increased significantly with global warming. Their analysis for Milton’s rainfall found that human-caused climate change likely increased the rainfall intensity by 10-50% and made such heavy rains about twice as likely to occur. This is very similar to the results they found for Hurricane Helene.

Influence of record-warm ocean temperatures

Along Milton’s track, ocean temperatures were consistently more than 1 degree Celsius (1.8°F) warmer than they would have been in a world without climate change, the researchers found, and were made between 400 to 800 times more likely during the intensification into a major hurricane (see Climate Central’s Climate Shift Index: Ocean (Ocean CSI), Fig. 1). This affected Milton’s environment and made it more likely for the storm to develop and intensify throughout its lifetime. 

Climate change made Hurricanes Helene and Milton nearly twice as destructive

Although a 10% increase in hurricane winds because of climate change may not seem like a big deal, it is a big deal because hurricane damage increases exponentially with wind speed. For example, according to NOAA, a Category 2 hurricane with 100 mph (161 kph) winds will do 10 times the damage of a Category 1 hurricane with 75 mph (121 kph) winds. This includes damage not only from winds but also from storm surge, inland flooding, and tornadoes. Bottom line: A 10% increase in winds yields about a doubling in hurricane damage (Fig. 2).

Researchers at the Imperial College of London separately determined that climate change increased Helene’s wind speeds at landfall by about 13 mph or 11%, and Milton’s by almost 11 mph or 10%. Using a previously published damage function and data on exposed value of global assets, the researchers determined that 44% of the economic damages caused by Helene and 45% of those caused by Milton could be attributed to climate change. They added that the analysis “likely underestimates the true cost of the hurricanes because it does not capture long-lasting economic impacts such as lost productivity and worsened health outcomes.”

Bob Henson contributed to this post.