Examining the most newsworthy climate papers in the last decade (Part 6)...

In 2020 the most newsworthy climate paper stated that the probability of major hurricanes is increasing due to climate change. What they didn't tell you, is why.

This is part of a multiple-part, subscriber-only series in which I investigate the most newsworthy climate papers each year and discuss if the predictions made by these papers, which gained so much media attention, have been observed.

The most newsworthy climate paper of 2020…

The most newsworthy climate paper of 2020, as evidenced by the graphic below, was published in the journal Proceedings of the National Academy of Sciences titled "Global increase in major tropical cyclone exceedance probability over the past four decades" which examined trends in the frequency and intensity of tropical cyclones over four decades.

Source: https://www.carbonbrief.org/analysis-the-climate-papers-most-featured-in-the-media-in-2020/

Its primary finding is that there has been a notable global uptick in the proportion of these cyclones that reach major hurricane strength, classified as Categories 3-5 on the Saffir-Simpson scale. This increase in intense cyclones aligns with predictions from climate models. The authors claim that as global sea surface temperatures rise due to climate change, more energy becomes available to fuel these storms, potentially leading to stronger cyclones. But we now know that is untrue…

Although the authors were very careful in their confidence of attributing their results to anthropogenic forcings, stating:

Ultimately, there are many factors that contribute to the characteristics and observed changes in TC intensity, and this work makes no attempt to formally disentangle all of these factors. In particular, the significant trends identified in this empirical study do not constitute a traditional formal detection, and cannot precisely quantify the contribution from anthropogenic factors.

The headlines that followed clearly suggested that hurricanes were getting stronger due to anthropogenic global warming (AGW).

Let’s take a look at the Saffir-Simpson scale and how the actual numbers of hurricanes, including major hurricanes, are changing. After all, we should be concerned with the total number of major hurricanes occurring not their probability.

The Saffir-Simpson Hurricane Wind Scale and ‘major’ hurricanes…

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating system that measures a hurricane's sustained wind speed and estimates the potential property damage and flooding that can be expected upon landfall. This scale is used primarily for hurricanes that form in the Atlantic Basin and the Northern Pacific Ocean.

The scale's genesis began with Herbert Saffir, a structural engineer, in the 1960s. Saffir was working on a United Nations project to study low-cost housing in hurricane-prone regions. While undertaking this project, he realized there was a need for a simple, systematic method to describe the potential damage of a hurricane. Saffir developed a five-category scale that described the potential damage to structures based on wind speeds.

Separately, Dr. Robert Simpson, who was the Director of the U.S. National Hurricane Center (NHC) at the time, recognized that wind speed alone was not an adequate predictor of the danger posed by hurricanes, especially concerning storm surge—the rise in sea level that results from a storm's winds. Simpson collaborated with Saffir to integrate potential storm surge and flooding impacts into the scale.

Together, they introduced the Saffir-Simpson Hurricane Wind Scale to the public in the early 1970s. The scale originally estimated storm surge, wind speeds, and potential damage. However, in recent years, the storm surge estimates were removed from the scale's official definitions because storm surge predictions are highly dependent on a myriad of factors, including the storm's size, speed, and the coastal geography it interacts with.

Today, the Saffir-Simpson scale remains an integral tool for meteorologists, emergency management officials, and the public to understand the intensity of an incoming hurricane and prepare accordingly. While it only measures wind speed, it serves as a rough approximation of the damage potential, with Categories 3, 4, and 5 designated as ‘major’ hurricanes.

Source: https://www.nhc.noaa.gov/prepare/hazards.php#wind

How has the number of ‘major’ hurricanes changed over the last four decades?

Much of the results of the paper discussed above stem from large increases in the probability of major hurricanes in the North Atlantic. In fact, the authors claim that the proportion of ‘major’ hurricanes in the North Atlantic increased from <0.2 to .0.4.

However, a study published the following year in the journal Nature titled, “Changes in Atlantic major hurricane frequency since the late-19th century” concludes: