Global warming has increased threat of hurricanes becoming stronger by 8% a decade, study shows

An analysis of satellite imagery from the past four decades suggests that the probability of storms reaching Category 3 or higher has increased by 8% a decade

                            Global warming has increased threat of hurricanes becoming stronger by 8% a decade, study shows
(Getty Images)

As the hurricane season officially starts in the US from June 1, an analysis shows that they have become stronger worldwide during the past four decades. Global warming has increased the likelihood of a hurricane developing into a major one -- of Category 3 or higher with sustained winds greater than 110 miles an hour -- by about 8% a decade. A hurricane is a type of storm called a tropical cyclone, which forms over tropical or subtropical waters. Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage. In the study, scientists from the National Oceanic and Atmospheric Administration or NOAA’s National Center for Environmental Information and University of Wisconsin-Madison Cooperative Institute for Meteorological Satellite Studies analyzed nearly 40 years of hurricane satellite imagery.

The researchers found that in almost every region of the world where hurricanes form, their maximum sustained winds are getting stronger and that a warming planet may be fueling the increase. The analysis shows that the probability of a hurricane having wind speeds of at least 100 knots increased by approximately 15% between the early and latter halves of the 39-year record. This finding corresponded to a statistically significant rate of increase of approximately 8% per decade. “A time series of the proportion of all hurricanes exceeding 100 knots exhibited a similar increasing trend of approximately 6% per decade. The results are consistent with the predictions of physical theory and numerical simulations and increase confidence in the view that tropical cyclones have become stronger under global warming,” says the study published in Proceedings of the National Academy of Sciences (PNAS).

“Our results show that these storms have become stronger on global and regional levels, which is consistent with expectations of how hurricanes respond to a warming world. It's a good step forward and increases our confidence that global warming has made hurricanes stronger, but our results don't tell us precisely how much of the trends are caused by human activities and how much maybe just natural variability,” says lead author James Kossin, an NOAA scientist based at UW-Madison, in the analysis. The National Weather Service describes a Category 3 hurricane as one with winds 111-129 miles per hour. “Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. Unnamed hurricanes of 1909, 1910, 1929, 1933, 1945, and 1949 were all Category 3 storms when they struck South Florida, as were King of 1950, Betsy of 1965, Jeanne of 2004, and Irma of 2017,” say experts. 

Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage (Getty Images)

The current research builds on the previous work, published in 2013, which identified trends in hurricane intensification across a 28-year data set. However, that timespan was less conclusive and required more hurricane case studies to demonstrate statistically significant results, says the team. To increase confidence in the results, the researchers extended the study to include global hurricane data from 1979-2017. “Tropical cyclones, and particularly major tropical cyclones, pose a substantial risk to many regions around the globe. Identifying changes in this risk and determining causal factors for the changes is a critical element for taking steps toward adaptation,” say researchers. They add, “Over the past 40 years (and longer), anthropogenic warming has increased sea surface temperature in tropical cyclone-prone regions, and, in combination with changes in atmospheric conditions, this has increased tropical cyclone potential intensity in these regions.”

The Atlantic hurricane season runs from June 1 through November 30. A fierce 2020 Atlantic hurricane season is expected, according to forecasters with NOAA’s Climate Prediction Center. The outlook predicts a 60% chance of an above-normal season, a 30% chance of a near-normal season, and only a 10% chance of a below-normal season. The NOAA is forecasting a likely range of 13 to 19 named storms (winds of 39 miles per hour or higher), of which 6 to 10 could become hurricanes (winds of 74 miles per hour or higher), including 3 to 6 major hurricanes (category 3, 4 or 5, with winds of 111 miles per hour or higher) this year. The above-normal 2020 Atlantic hurricane season is expected because of several climate factors and warmer-than-average sea surface temperatures, explain scientists. 

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