Unsupported claims – watts with that?

From the Cliff Mass Weather Blog

It didn’t take long for the media to “tie the dots” and claim with full throats that Hurricane Ida was the stepchild of global warming.

Even the well-known TV weather personality Al Roker (whom I admire very much) intervened: “We’re looking at the consequences of climate change … that created this monster storm”

But that is easy to prove real data shows that these claims are unfounded and that National Public Radio, the Seattle Times, and others publish stories that are contrary to the best of scientific evidence and observation.

The hypothesis in all of these stories is that man-made climate change increased sea surface temperatures (e.g. Gulf of Mexico, tropical Atlantic) and thus “charged” Hurricane Ida.
Now, with regard to Ida, the first thing a responsible journalist would determine would be if the Gulf of Mexico, where Ida was formed, had temperatures well above average last week.
If that is true, a sane journalist would examine whether warming is the result of a long-term trend – something that is required when man-made global warming is significant.
Apparently (as shown below) most journalists didn’t take these basic steps before writing the stories. But i will do it here!
Temperatures in the Gulf of Mexico
Think of the trail of Hurricane Ida as shown in the official NOAA track information below. The shading shows you the locations of tropical storms and gale force winds. The storm turned to hurricane strength south of Cuba and began to turn properly north of 25N.

In order to get a hurricane formation, one needs sea surface temperatures of at least approx. 27 ° C, and practically the entire Gulf of Mexico was at this level, which is typical for this time of year.
Below are the sea surface temperatures for the seven days immediately before Ida came up and reached the mainland. The temperatures of the entire storm route were well above the necessary threshold. Warm water wasn’t a problem for Ida’s development (29 ° C and up pretty much all the way).

Now the million dollar question:

How unusual were sea surface temperatures in the Gulf during the intensification of Hurricane Ida? The figure below shows you the anomaly (or difference) from climatology (normal) in sea surface temperatures before Ida was amplified (Courtesy of Ryan Maue, previously NOAA Chief Scientist).
Impressive. The water temperatures were actually COOLER than normal where Ida started to intensify (south of Cuba). Interestingly, this is due to the vertical mixing from previous Hurricane Grace. And for much of the route north of Cuba, where Ida solidified quickly, temperatures were normal or slightly above normal (less than 1 ° C above normal). Only near the coast, for the shallow waters of the Gulf Shelf, did the temperatures climb by more than 1 ° C above normal.

Conclusion: Warmer than normal water was not the key to the development and intensification of Hurricane Ida. The Gulf of Mexico is almost always warm enough to support the rapid intensification of tropical disturbances.
There were some very favorable elements for Ida: little vertical wind shear (which tears the storms apart) and a cloud of very humid air that was absorbed into the storm (see a map of integrated water vapor transport, IVT, below).

Sea surface temperature trends
While sea surface temperatures were not significantly warmer than normal for Ida, one might ask whether there has been a significant upward trend in sea surface temperatures in the Gulf that could indicate a major global warming trend?
To give you some insight on the subject, here is a graph of August sea surface temperatures over the Gulf from 1983 through this year (click to enlarge). Yes, there has been some warming in almost 40 years … and yes, man-made global warming could have been the cause … but the warming is quite small – less than 1 ° C.

I have independently backed up some NOAA data on sea surface temperature over the Gulf of Mexico for an extended period (1948 to present) for the month of July and plotted it below. Not a big trend as July 2021 is RELATIVELY COOL.

A responsible journalist researching the potential impact of global warming on Hurricane Ida SHOULD investigate the above information and would have found the link to be very weak: sea surface temperatures were not very abnormal (warmer than normal) along the course of the hurricane . and that there has been very little upward trend in sea surface temperatures in the Gulf of Mexico.
And a competent journalist should also have asked: Are there many indications that hurricanes are increasingly reaching the US coasts? Something that should have happened if global warming had been significant.
Below is a plot of the number of landfill hurricanes that have struck the continental US (Courtesy Roger Pielke Jr). The trend line is down.

Severe hurricanes (Category 4 and 5) … the same. No increase.

What a responsible journalist would conclude
A competent journalist writing on the link between global warming and Hurricane Ida would have quickly learned:

  • Hurricane Ida did not develop over unusually warm water.
  • That the Gulf of Mexico is always warm enough to support large hurricanes in late summer.
  • There has been very little warming trend in the Gulf of Mexico over the past half century
  • There is no upward trend in the number of hurricanes in the US
  • There is no upward trend in the number of major hurricanes in the US

And the clear conclusion that would have been drawn from it: There is little reason to believe that global warming has much to do with the rapid increase in the hurricane over the Gulf of Mexico.
Unfortunately, major media journalists from the NY Times to the Washington Post to the Seattle Times did not take the time to research to find out the truth. And they published stories that seriously misinformed their readership.
Global warming is used today by curious, politically minded media to explain almost everything. Do not believe me? Check out this recent Seattle Times headline based on an article in the NY Times. Deeply disappointing.

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