The Critical Flaw in Single-Event Hurricane Climate Attribution

Robert Vislocky, Ph.D.

Less than a month has passed since the official end of the 2025 hurricane season for the Northern Hemisphere. Interestingly, 2025 statistics show that Accumulated Cyclone Energy (ACE) in the northern hemisphere was roughly 20% below the 1991-2020 mean while the number of major hurricanes and major hurricane days were down about 27% and 36%, respectively, compared to their 30-year averages (shown in parentheses).¹

¹Seasonal hurricane statistics from the Department of Atmospheric Science, Colorado State University
https://tropical.atmos.colostate.edu/Realtime/

Despite the otherwise lackluster hurricane season, the climate activist community had their poster child in hurricane Melissa, one of the most intense tropical cyclones in history. Of course the media had a field day blaming it on climate change. Here are some quotes and headlines …

“Hurricane Melissa Is a Reminder of Our Dangerous New Reality as the Climate Crisis Accelerates”
“Manmade climate change clearly made Hurricane Melissa stronger and more destructive”
https://www.sierraclub.org/sierra/hurricane-melissa-reminder-our-dangerous-new-reality-climate-crisis-accelerates

“How Climate Change Turned Hurricane Melissa into a Monster”
https://www.climaterealityproject.org/blog/how-climate-change-turned-hurricane-melissa-monster

“After Melissa, how much stronger will future hurricanes be?”
“Is it time for a Category 6?”
https://www.theinvadingsea.com/2025/11/10/hurricane-melissa-category-6-rapid-intensification-climate-change-sea-surface-temperatures-volo/

“Was climate change to blame for the strength of Hurricane Melissa?”
https://www.bbc.com/weather/articles/c205zwz4yj9o

The last article begs the question …. Did climate change, or more accurately anthropogenic global warming (AGW), really make Melissa stronger? Enter the world of single-event attribution science, where climate change can be shown to enhance any hurricane, even if it’s the only hurricane of the season! All that’s needed is to show that higher water temperatures will intensify existing hurricanes and that water temperatures have increased due to AGW. Just like that the hurricane is proven to be enhanced by climate change. News organizations feed the frenzy by publishing the results without dispute and lawyers take oil companies to court to pay for their part of the damages.
Now single-event attribution science is significantly more complicated than the above over-simplification, and admittedly their methods are quite intuitive and mathematically rigorous. After all, they are based on “peer-reviewed” science (tongue-in-cheek). There are several organizations that specialize on attribution science and ambulance-chase storms around the globe hoping to find a climate change connection. Several of the more prominent outfits include World Weather Attribution, Climate Central, and ClimaMeter. Although their methods differ significantly, all three of these companies determined that human-driven climate change enhanced Melissa’s wind speeds by about 7-10%, which doesn’t seem quite as dramatic or impactful as the news headlines indicated above.

https://www.worldweatherattribution.org/climate-change-enhanced-intensity-of-hurricane-melissa-testing-limits-of-adaptation-in-jamaica-and-eastern-cuba/
https://www.climatecentral.org/tropical-cyclones/melissa-2025
https://www.climameter.org/20251027-hurricane-melissa

Nonetheless, despite their diverse methodologies, all of their single-event hurricane attribution studies contain the same critical flaw. Specifically, they don’t assess the role of climate change in areas where there are no storms to gauge the total effect of climate change on hurricane activity or to see if climate change might have actually prevented an intense hurricane in another location. This point was alluded to at least a couple times in the past on WUWT, for example see Rotter (2023) and Vislocky (2018) below. However it’s an important point that needs to be exposed and repeated often given the meteoric rise in single-event climate attributions.

https://wattsupwiththat.com/2023/07/11/extreme-weather-attribution-or-just-sharpshooting-in-texas/
https://wattsupwiththat.com/2018/12/07/wildfire-attribution-study-full-of-smoke/

As it is right now, single-event attribution science is the equivalent of a pathologist performing an autopsy on one victim who passed away as a result of an allergic reaction to a vaccine and concluding that the vaccine is causing excess deaths. After all there’s no denying how the person died or the science used in determining the cause of death. But such a superficial analysis is incomplete because the total efficacy of the vaccine hasn’t been taken into account. Was a study performed to see if the vaccine saved thousands or millions of other lives from a deadly pathogen, or whether people who took the vaccine perished at a lower rate than those who did not take the vaccine? Until those additional analyses are completed there would be no way to determine the *overall* role of the vaccine on human health based on just that one autopsy. Similarly, there’s no way single-event attribution science can measure the influence of climate change on the totality of hurricane activity. Sure, there’s probably little doubt that AGW enhanced water temperatures made Melissa up to 10% stronger, but it can’t measure whether climate change is increasing overall hurricane activity unless additional analyses are completed. Even more preposterous is it’s entirely conceivable in a hypothetical season where only one hurricane occurs that single-event attribution science could still ascribe a portion of that hurricane’s strength on climate change!

Now this notion (that climate change can occasionally prevent extreme storms from forming) may seem preposterous to those who think that climate change can only create more “storm energy” and make everything worse. However, there are some known mechanisms as a result of climate change that can actually stabilize the atmosphere and potentially offset some of enhanced storminess that’s found through the single-event attribution studies. For one such example, it’s well known that arctic amplification is reducing the north-south temperature gradient which, in turn, could reduce the strength of cold fronts in mid-latitudes. Perhaps this is a reason why powerful tornadoes (EF3+) have decreased substantially since the 1950s. In terms of hurricanes, it’s pretty clear that the vertical lapse rate is also lessening with climate change as there appears to be more warming aloft in the 850-700 mb layer than at the surface across tropical latitudes (see graph below).² This could cause an increase in ambient stability making it more difficult for hurricanes to form in the first place. Perhaps this could explain why overall hurricane frequencies are slightly down but the proportion of major to total hurricanes is up (i.e., the more stable air decreases the odds of initial hurricane formation but the warmer sea surface temperature increases its intensity once one forms). The point is there are a myriad of physical mechanisms in which climate change could impact hurricanes, some factors can make them worse, and perhaps some could make them less impactful. Without a deeper analysis we just won’t know the total impact of climate change on hurricane activity, and we certainly can’t assess that through a forensic analysis of one storm. Climate models are of little help as they can’t resolve hurricanes or reproduce our atmosphere accurately (otherwise seasonal hurricane forecasting would be easy), and single-event attribution models don’t provide an answer either as already pointed out.

² Temperature data from NCEP/NCAR Reanalysis Project and NOAA Physical Sciences Laboratory
https://psl.noaa.gov/data/timeseries/

This is why I feel that trend analysis right now is the best way to determine the broader impact of AGW on hurricane activity. However which trends should be computed? One trend would be to estimate the cyclonic energy of each hurricane in the US Landfalling Hurricane database.³ This calculation is simply the annual sum of the squared sustained wind speeds for each hurricane at landfall. The cyclonic energy estimate is similar to the ACE index except in this case it’s just computed at landfall, not over the life of the storm, and I didn’t divide by 10,000 like the ACE. The advantage in using the landfalling hurricane database is its long history back into the 1800s so hurricane activity can be viewed through a wide lens as it impacted the United States. Certainly by the late 1800s most coastlines were populated enough that it would be unlikely to miss a big tropical cyclone, so this would be a fair starting point.

The chart below shows the running 5-year cyclonic energy totals ending at the year shown. Although there’s been a lot of choppiness the most recent couple of decades, the overall trend (dashed line) actually shows a slight but probably statistically insignificant decline. Most importantly there’s no strong evidence that climate change is making US landfalling hurricanes worse. Even the more active periods after 2000 were on par with some of the active periods in the late 19^th century through the middle of the 20^th century.

³ Hurricane landfall data from NOAA’s Atlantic Oceanographic & Meteorological Laboratory
https://www.aoml.noaa.gov/hrd/hurdat/All_U.S._Hurricanes.html

Unfortunately, the use of the US landfalling hurricane dataset to uncover a trend is not without criticism as it only looks at only a small subset of the total hurricane picture. Specifically, the dataset leaves out non-landfalling hurricanes and storms in basins outside the Atlantic. The US landfalling dataset also does not include measurements of hurricanes over their entire life cycle but rather only a snapshot at landfall. Those are all fair criticisms but sadly the ability to detect a trend using all the available hurricane data becomes a challenge as the ability to remote-sense and detect hurricanes over the open oceans has increased greatly over time. As a result historical hurricane data over the open oceans are subject to potential observational biases, more specifically under-sampling biases going back in time, which can significantly distort the real trend. Many hurricanes were missed prior to 1970 due to the lack of 24/7 global satellite coverage. During the 1970s and 1980s satellite technology evolved considerably, and it wasn’t until the 1990s that aircraft reconnaissance could measure surface wind speeds with high accuracy. Despite increased coverage over the last quarter of the 20^th century, a number of very short-lived tropical cyclones over the open waters were still likely missed or their intensity underestimated prior to 2000 as remote-sensing and detection technology gradually improved. Since 2000, there have been a plethora of new tools available to observe hurricanes including scatterometers, GPS dropsondes, stepped frequency microwave radiometers, etc., that weren’t available earlier. Landsea and Blake (2021) discuss on the National Hurricane Center’s blog site, Inside the Eye, the evolution of technology for monitoring tropical cyclones and its impact on counting storm totals (see first link below). Below that are links which further describe the evolution of weather satellite and aircraft recon technology. 

https://noaanhc.wordpress.com/2021/06/30/was-2020-a-record-breaking-hurricane-season-yes-but/
https://www.nesdis.noaa.gov/our-satellites/related-information/history-of-noaa-satellites
https://www.hurricanescience.org/science/observation/aircraftrecon/index.html

With that preface in mind, shown below are plots of annual ACE values for all tropical cyclones in the northern hemisphere and the globe during the post-satellite era.⁴ However, as mentioned above, since detection technology improved significantly over time, and because it’s a relatively short time period overall, the trend in the ACE may be sensitive to the year the graph is started. Therefore, several graphs are provided with different starting dates: 1971, 1980, 1990, and 2000. Note that hurricane data was available for the northern hemisphere and the globe beginning in 1971 and 1980, respectively.

Results show an upward trend in accumulated cyclonic energy for the northern hemisphere in the chart starting in 1971. However every chart with a starting point from 1980 onward shows a slight decline in ACE for both the northern hemisphere and the globe. In light of all of these graphs it’s certainly difficult to make a case that AGW is making hurricanes more powerful and destructive, at least on large time and/or space scales, especially considering the fact that it seems like every successive year in the past couple decades a new record is set for the “hottest year ever recorded”. One would think that if hurricanes were becoming significantly worse from global warming that solid confirmation signals would show up in these charts. Of course this is contrary to the news media articles and the attribution reports from the climate cabal. However, it is consistent with IPCC reports which expressed low confidence in long-term trends in tropical cyclone intensity, frequency, and duration. In the least, it is hoped that these analyses will at least draw doubt and speculation to the efficacy of single-event attribution science which has serious flaws. It is further hoped that word will spread of this speculative science to lawyers and judges so that unnecessary and costly lawsuits can hopefully be avoided.

⁴ Data from the Department of Atmospheric Science, Colorado State University