How climate change supercharged Hurricanes Helene, Milton
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A car is stuck in beach sand in Manasota Key, Fla. Photo: Joe Raedle/Getty Images
Multiple studies are clearly showing how human-caused climate change made Hurricanes Helene and Milton more potent and destructive.
Why it matters: These storms combined caused up to $55 billion in insured losses. They portend an era of increasingly human-influenced storms that are wetter and stronger as the climate continues to warm.
The intrigue: Helene and Milton are a painful reminder that climate change is clearly affecting Earth's most powerful storms, primarily by amplifying their rainfall and helping them to intensify at dizzying speeds and reach greater peaks.
- The physics behind this is relatively straightforward: A warmer ocean provides more energy for hurricanes to tap into, and warmer air temperatures allow the atmosphere to hold more moisture.
- This enables such storms to deliver more rainfall and grow more intense.
- Hurricanes are particularly efficient at concentrating large quantities of water vapor and wringing it out at nearly unheard-of rates, as seen in the deluges in the Tampa-St. Petersburg area during Milton and in western North Carolina during Helene.
- These each qualified in some places as 1-in-1,000-year rainfall events, which means the rainfall totals within a particular period of time had just a 0.1% chance of occurring in any given year.
Zoom in: Hurricane Milton also put on a display of rapid intensification that was more akin to warp speed than "rapid," as its maximum sustained winds increased by about 90 mph in 24 hours.
- To achieve rapid intensification, a tropical cyclone needs to increase its winds by a comparably paltry 35 mph.
- Hurricane Helene also went through a period of rapid intensification but did not get anywhere near the upper echelon of fastest intensifying storms on record, as Milton did.
Rapid attribution analyses of Hurricane Helene have focused most closely on the destructive rainfall associated with it.
- For example, a study published by World Weather Attribution, an international and loose-knit group of researchers, found that the rainfall was about 10% heavier in the hardest-hit areas of the Carolinas and Gulf Coast due to climate change.
- Climate change also made the rainfall totals between 40% and 70% more likely than they would have been during the preindustrial era, the group found.
Between the lines: Their study also looked at shifts in the storm's environment, particularly the record-hot ocean temperatures that Helene encountered (Hurricane Milton also went over record-warm waters in a different part of the Gulf of Mexico).
- Researchers found that climate change has increased hurricanes' potential intensity, a speed limit for storms, for storms that take Helene's path in the Gulf during the month of September.
- This is especially significant since the month is host to the peak of the Atlantic hurricane season, with a history of many intense storms.
- "Together, these findings show that climate change is enhancing conditions conducive to the most powerful hurricanes like Helene," the study found.
What they found: The same group conducted a limited, lightning-fast analysis of Hurricane Milton that was released in the immediate aftermath of the storm on Oct. 11.
- It found that climate change is leading to a 40% increase in the number of storms of its intensity and that such storms' maximum wind speeds are stronger now than in a world without climate change.
- "In other words, without climate change Milton would have made landfall as a Category 2 instead of a Category 3 storm," the study stated.
- A separate rapid attribution analysis from the nonprofit research organization Climate Central found that human-driven climate change made the record-warm ocean temperatures that Milton drew its energy between 400 to 800 times more likely.
Yes, but: These studies, while based on peer-reviewed methods and taking into account climate models as well as observational data, aren't the final word on how climate change affected these two devastating storms.
- Additional studies are likely to be published on climate change trends and their influence on each storm, and they may find a more or less significant signal.
Even so, other research — conducted largely on the fly during or immediately after Helene and Milton — has so far come to similar conclusions as the WWA study.
- That evidence, plus physical science research, lends credence to the WWA findings and that of other groups, though this is very early in the storms' wake.
The bottom line: Climate change is skewing the odds toward wetter, stronger and therefore more costly hurricanes, both in dollars and lives. The main questions are by how much, and how damaging will this become in the future?
