At a Glance

Researchers used a 120-year data set to confirm what climate models have been predicting about climate change all along.Extreme precipitation events from hurricanes, tropical storms are more prevalent.This is worsening coastal flooding in places like North Carolina.

Researchers with the University of North Carolina were able to confirm what climate models have been predicting about climate change all along: from tropical systems like hurricanes and tropical storms are becoming more frequent and more extreme.

As a result, coastal flooding from tropical systems is worsening in North Carolina, published this week in the journal Scientific Reports

Professor Hans Paerl, lead author of the study and Kenan professor of marine and environmental sciences at the UNC-Chapel Hill Institute of Marine Sciences, told weather.com six of the seven highest precipitation events on record in North Carolina occurred within in the last 20 years.

"We are certainly into a new normal, so to speak, in terms of the amount of rainfall that's associated with these tropical cyclones," Paerl said. "By that, I mean everything from a depression to a Category 2 or 3 hurricane."

Paerl noted that the 120-year data set, made up primarily of records from the National Oceanic and Atmospheric Administration (NOAA), used for the study is particularly reliable for making the UNC team's determinations.

"We're very fortunate in having a really good, long-term data set in North Carolina," said Paerl. "There's been a long history of marine interest in North Carolina along the coast, so there's been good records. NOAA has done a fantastic job of collating all of this data and they've made accurate measurements of rainfall. So, I think the data is pretty irrefutable."

Satellite image of Hurricane Florence just as it makes landfall off the coast of the U.S. in the Atlantic Ocean on September 13, 2018.

(NOAA via Getty Images)

Paerl pointed out that the strength, or category, of a hurricane does not necessarily predict the amount of destruction or casualties that can occur from a storm. Instead, it's very often the amount of rainfall produced by a storm that can and will likely have the greatest impact.

"When you look at the long-term record that we published in this article, there is some research that says the frequency of hurricanes has increased the past 20 years or so; but really, the outstanding thing is the amount of rainfall that's associated with these events," he said.

More people — — are killed by water than by wind in a hurricane or tropical storm.

(MORE: 88% of U.S. Deaths From Hurricanes, Tropical Storms Are From Water, Not Wind)

Paerl, who has lived in the coastal city of Beaufort, North Carolina, for 41 years, said his personal experience can attest to the fallacy that a hurricane's strength determines the danger associated with these storms.

"Florence was a Category 1, but because it moved so slowly and it absorbed so much water, it has been the most devastating hurricane that I have seen in our neighborhood in the last 41 years. I've also lived here long enough to see sea level rise," he added.

Three storms in the past 20 years — hurricanes Floyd, Matthew and Florence — resulted in abnormally large floods. , which made landfall along the North Carolina coast on Sept. 7, 2018, dumped an average 17.5 inches of rain on a 14,000 square mile area of the Carolinas and became the second wettest tropical system in the United States in the past 70 years.

Areas of Kinston, N.C., remained under water on September 21, 2018, as a result of Hurricane Florence, more than two weeks after Florence came ashore along the coast of North Carolina.

(Scott Sharpe/Raleigh News & Observer/TNS via Getty Images)

The probability of these three major flooding events occurring in such a short time frame is just 2 percent, the researchers determined, and "is a consequence of the increased moisture carrying capacity of tropical cyclones due to the warming climate."

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North Carolina "has one of the highest impact zones of tropical cyclones in the world," Paerl said, but made a point of saying that other regions are experiencing a similar increase in the amount of precipitation associated with tropical events.

"All you have to do is go back to 2017 and along the Texas coastline," Paerl said, referring to the devastating Category 4 hurricane that dropped more than 60 inches of rain on parts of Texas, the all-time rainfall record for a tropical cyclone in the U.S.

"The price we're paying is that we're having to cope with increasing levels of ," Paerl said in a press release. "Coastal watersheds are having to absorb more rain. Let's go back to Hurricane Floyd in 1999, which flooded half of the coastal plain of North Carolina. Then, we had Hurricane Matthew in 2016. Just recently we had Hurricane Florence in 2018. These events are causing a huge amount of human suffering, economic and ecological damage."

An oceanfront home is partially destroyed September 18, 1999, in Oak Island, NC. The eye of Hurricane Floyd passed over the Island leaving a trail of damaged homes and heavy flooding.

(Robert Nickelsberg/Liaison/Getty Images)

Another driver for the uptick in precipitation associated with tropical systems is the increase in population in both North Carolina — which jumped 40 percent from 6.6 million in 1990 to more than 10.3 million in 2018 — and the world.

"Increasing global population is compounding the problem by driving up emissions of greenhouse gases, leading to increases in ocean temperature, evaporation and subsequent increases in precipitation associated with tropical cyclones," according to the study's press release.

A consequence of increased rainfall is nitrogen-rich runoff flowing into estuaries and coastal waters. It's a growing problem in North Carolina, home to not only one of the largest poultry and hog industries in the U.S., but also the country's second largest estuarine complex and a key Southeast fisheries nursery.

More runoff results in more organic matter and nutrient losses from soil erosion, agricultural operations, urbanization and the flushing of swamps and wetlands.

"This scenario increases the overloading of organic matter and nutrients that ecosystems can't process quickly enough to avoid harmful algal blooms, hypoxia, fish and shellfish kills," according to the press release.

(MORE: Florence's Health Threats: Sewage Spilled, Millions of Chickens and Pigs Die, Hog Waste Holding Pond Breached)

Paerl said there are measures that communities can take to protect coastal areas, waterways and the ocean as wetter tropical cyclones threaten, including "being aware in terms of land use."

"That's really where we can make the biggest difference," he said. "For example, not developing all the way to the water's edge, having vegetative buffers, stormwater retention ponds, applying fertilizer wisely ... you know, you don't want to be applying fertilizer in the middle of hurricane season... and lastly, reducing greenhouse gas emissions, which admittedly won't lead to a quick result, but it's absolutely something we have to do."