Scientists predict fewer but higher intensity storms

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PANAMA CITY, Fla. (WMBB) — With about two months left of the 2020 hurricane season, the Atlantic has seen 23 total named storms with eight elevated to hurricane status. 

Thomas Knutson, a research meteorologist with the National Oceanic and Atmospheric Association said that the 2020 Atlantic hurricane season is shaping up to be one of the most active yet.

Data collected by NOAA shows a steady increase in the number of named storms since 1980. The data also shows an increase in storms elevated to hurricane status. However Knutson said that the number of storms to make landfall has not increased. 

Data collected before 1979 on the number of storms in the Atlantic Basin is not accurate due to inadequate satellite technology. 

The latest National Climate Assessment issued in 2018 cited climate change as the main underlying factor for the increase in frequency and severity of extreme weather.

“More frequent and intense extreme weather and climate-related events, as well as changes in average climate conditions, are expected to continue to damage infrastructure, ecosystems, and social systems that provide essential benefits to communities,” the report stated. “Future climate change is expected to further disrupt many areas of life, exacerbating existing challenges to prosperity posed by aging and deteriorating infrastructure, stressed ecosystems, and economic inequality.”

The next National Climate Assessment is slated for release in 2023

Knutson said that the data linking an increase in the number storms to climate change is unclear. He said that the number of hurricanes to have made landfall has remained stable since 1900. He added that the severity of the storms has not.

“We use models to try to figure out how Global Warming might be affecting hurricane activity, and using these models, we estimate that in a warmer climate, hurricanes will be more intense than in the present day climate.”

“The size of that change we estimate to be about a 5% increase in wind speeds for every one degree celsius rise in tropical sea surface temperatures,” Knutson added.

Knutson said so far, models predict that there could have been a 2% to 3% increase in wind speeds due to rising temperatures.

Knutson said the models also predict higher rainfall rates from hurricanes in warmer climates.

“A warmer atmosphere typically holds more water than a cooler atmosphere,” Knutson said. “One thing that happens when you warm the planet globally is the atmosphere in the tropics and elsewhere is holding more water vapor than it did before.”

“And when theses hurricanes are forming,” Knutson added. “The amount of water vapor that’s being converged in from hundreds of miles away in toward the center, that’s been sort of supercharged.”

The size of this effect is a 7% increase in rainfall per one degree Celsius rise in sea surface temperatures. Knutson said that so far, models predict that Atlantic could have seen a roughly 5% increase in rainfall rate.

Knutson added that an indirect factor exacerbating the severity of hurricanes is the rising sea level.

“Whatever storm surge you have coming in due to some hurricane is now riding in on a higher background sea level,” Knutson said. “So all other things equal, you’re going to have a higher inundation level.”

Data shows a steady increase in Category 3 or higher storms since 1979.

Knutson said researchers at NOAA expect to see a possible decease in number of storms with an increase in storms elevated to Category 3 or higher intensity. He added that he expects to see continued increases in wind speeds, rainfall rate and hurricane severity in correlation with rising sea surface temperatures and sea levels. 

But he added that hurricane pattern changes are very complex and can face many other factors besides climate change as well.

For example, Aerosols seem to be suppressing activity in the Atlantic Basin over the 20th century, but as the U.S. began to sort of clean up its air,” Knutson said. “We had less aerosols blowing out over the Atlantic Basin[…] then we seemed to get an increase in storm activity.”

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