From ClimateRealism
EDITORS NOTE:
On October 9th, as Hurricane Isaias closed in on the coast, Climate Central put out a rapid attribution analysis saying human-caused warming had heated the water under the storm and added about 7 mph to its winds.
Climate Central’s claim was carried by WSMV-TV and many other media outlets.
That same day, a reader asked Chris Martz about a claim attributed to Al Roker, that Isaias was fueled by a Gulf running 5 to 6 degrees above normal. Climate Realism was unable to find the claim online. It probably occurred during a TV segment.
Chris, a friend of Climate Realism, answered with data. His post follows, with a few notes added by Charles Rotter from WUWT. Chris Martz says:
Al Roker is not an actual meteorologist.
But I am.
You ask a really good question. And while Roker has opinions, I have data.
Yes, it is true that tropical cyclones (TCs) operate as thermodynamic heat engines sustained by ocean-to-atmosphere enthalpy fluxes, including sensible and latent heat transfer, with latent heat released during condensation, which maintain the deep convection. The higher the sea surface temperatures (SSTs) are, the higher the likelihood for TC intensification.
However, SST anomalies represent departures from climatological averages rather than absolute SSTs. That means below-average SSTs can still support an intense hurricane. In fact, the Gulf of Mexico (or Gulf of America; call it whatever you want) is warm enough during late August, September, and early October every year to support a hurricane of category four or five strength. That has always been the case and it always will be.
That’s the whole argument in one paragraph. An anomaly is a departure from average. It isn’t the temperature, and the Gulf in September is never short of fuel.
I hypothesized that Gulf SSTAs don’t really affect TC strength as commonly claimed because of this fact. So, I decided to investigate this question to provide a numerical answer. All science is numbers.
For this analysis, I decided to use the NOAA National Hurricane Center’s (NHC) HURDAT2 database, which contains historical TC tracks (coordinates), maximum sustained wind speeds (Vmax), and pressures, which contains data spanning 1851 to 2025. I then employed the Extended Reconstructed Sea Surface Temperature (ERSSTv5) dataset from NOAA, which contains monthly SST estimates on a 2° × 2° grid since January 1854. So, my analysis must be restricted from 1854 to 2025.
I identified 269 TCs that attained hurricane strength (≥64 kt / ≥74 mph) within the Gulf during the study period. Of this subset, 70 originated within the Gulf itself, while the remaining 199 developed elsewhere, primarily in the Atlantic or the Caribbean Sea, before entering the Gulf. For each hurricane, I determined its highest Vmax while inside the Gulf specifically. I then compared that intensity against the mean SSTA (calculated by evaluating SST departures from the 1991–2020 baseline) sampled along its Gulf track, using the monthly ERSSTv5 data.
Monthly SST data is not perfect, but it provides us a fairly good estimate because water has a high heat capacity, meaning it takes a lot of energy gain in order to warm a body of water and a lot of energy loss to cool it. In layman terms, SSTs are usually rather slow to change from week-to-week.
Both datasets are NOAA’s and both are public. Available to everyone.
The results show essentially no linear relationship between Gulf SST anomalies and the maximum sustained wind speeds attained by hurricanes within the basin.
Across all 269 Gulf hurricanes, the Pearson correlation coefficient was just r = +0.036, which indicates an extremely weak positive correlation. The coefficient of determination (R²) was 0.001, meaning that variations in SST anomalies explained approximately 0.1% of the observed variation in peak hurricane intensity under a simple linear regression model. The Spearman rank correlation coefficient was similarly negligible at ρ = +0.012. Furthermore, the Pearson correlation yielded a p-value of 0.555, well above the conventional statistical significance threshold of 0.05.
Therefore, the observed relationship is not statistically significant.
An R² of 0.001. Departures from normal account for about a tenth of one percent of how strong Gulf hurricanes get.
The scatterplot below illustrates this quite clearly. Hurricanes attaining relatively modest maximum intensities of 65–85 kt occurred across a broad range of SSTAs, as did much stronger hurricanes exceeding 100–120 kt. Some of the most intense hurricanes in the dataset occurred during periods when SSTs along their Gulf tracks were below the 1991–2020 average. Conversely, some hurricanes traversing anomalously warm waters never intensified beyond minimal hurricane strength.
In layman terms? An anomalously warm Gulf has no meaningful correlation to Gulf hurricane intensity.
The story you just read is true. Only the name of the Gulf has been changed.
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