Climate change is making hurricanes more dangerous and three times as frequent in America now than 100 years ago

The findings are consistent with expectations that climate change will increase storm intensity, and major hurricanes will become even stronger in a warming world, says the research team


                            Climate change is making hurricanes more dangerous and three times as frequent in America now than 100 years ago

Hurricanes in the US have become more destructive, and the most damaging ones are over three times as frequent now than 100 years ago, as a result of climate change, says a new research.

In their analysis - conducted by researchers from the Niels Bohr Institute, University of Copenhagen - the rsearch team found that the weather has become more dangerous on the south and east coast of the US. According to them, the findings reveal that global warming is associated with an increase in the force released in the most extreme hurricanes. They are consistent with expectations that major hurricanes will become even stronger in a warming climate, says the team.

“Hurricane destruction has been increasing. The frequency of the most damaging storms is now three times more frequent than a century ago. This, of course, poses an additional challenge for adaptation. Our results are consistent with our expectations from climate modeling. The more lines of evidence that point in the same direction, the more confident we can be in the projections for the future," Aslak Grinsted from the Niels Bohr Institute told MEA WorldWide (MEAWW).  

The study, published in Proceedings of the National Academy of Sciences (PNAS), explores hurricane damage in the US from 1900 to 2018. 

Tropical storm destruction from 1900-2018  on the North American south- and east coast.
(Aslak Grinsted, Niels Bohr Institute)

Hurricanes are the costliest natural disasters in the US. According to the scientists, the damage costs from Hurricane Katrina have been estimated to be $125 billion, which was 1% of gross domestic product (GDP) for the entire US in 2005. Accordingly, says the team, a better understanding of hurricane-related damage and its costs over time, is of immense societal importance.

The destruction caused by Hurricane Katrina - a collapsed house, downed trees, and downed powerlines - Mississippi. September 2005. (Barbara Ambrose NOAA/NODC/NCDDC)

The researchers explain that comparing the damage from recent and historical storms is challenging because of changing factors, such as the value of vulnerable property over time. To address this issue, they developed a method to compare the impact of hurricanes across centuries and report that storms have become more damaging over time. This method accounts for, or normalizes, changes in exposed wealth. Instead of framing storms in terms of economic damage, the technique frames losses in terms of a more easily quantified factor: land area. 

"The traditional way of calculating hurricane damage, to be able to compare hurricanes and follow their development over time, was to survey the subsequent cost of the damage done by each hurricane. In other words, what would a hurricane from the 1950s cost if it made landfall today? Using this method, a typical find is that the majority of the rising tendency in damage can be attributed to the fact that there are more of us, and we are more wealthy, and there is quite simply more costly infrastructure to suffer damage. But evidence of a climatic change in destructive force by hurricanes has been obscured by statistical uncertainty," says the study.

The experts calculated the historical figures in a new way. Using an insurance industry database, they calculated the amount of land totally destroyed by over 240 storms from 1900 to 2018.

Instead of comparing single hurricanes and the damage they would cause today, the team examined how big an area could be viewed as an area of total destruction - that is, how large an area would you have to completely destroy to account for the financial loss.

The analysis shows that hurricanes with the greatest area of total destruction are Katrina (2005) and Harvey (2017). They both resulted in an area of total destruction greater than 5,000 square km.

An October 14, 2018, view of Mexico Beach, Florida, shows the aftermath of Hurricane Michael making landfall four days earlier. (K.C. Wilsey, FEMA)

Using the normalization method, the experts found that the frequency of more damaging storms is increasing faster than that of moderately damaging storms.

"We find that hurricanes are indeed becoming more damaging. The frequency of the very most damaging hurricanes has increased at a rate of 330% per century. While the most damaging storms have been increasing by a factor of 3.3% per century, whereas moderate storms have only been increasing at a rate of 1.4× per century. This pattern is consistent with modeling which finds that warming is associated with more-frequent and even stronger major hurricanes in the Atlantic," say the researchers in their findings.

They say, “Our data reveal an emergent positive trend in damage, which we attribute to a detectable change in extreme storms due to global warming. Our record of normalized damage, framed in terms of an equivalent area of total destruction, is a more reliable measure for climate-related changes in extreme weather and can be used for better risk assessments on hurricane disasters.”

The team explains that in previous studies, it proved difficult to isolate the "climate signal" - which is the impact climate change has had on hurricane size, strength, and destructive force. 

"It (climate signal) lay hidden behind variations due to the uneven concentration of wealth, and it was statistically uncertain whether there was any tendency in the destruction. But with the new method, this doubt has been eradicated. The weather has indeed become more dangerous on the south- and east coast of the US," says the team.

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