The 2020 Atlantic hurricane season was a record-breaker, and it’s raising more concerns about climate change

It was clear before the 2020 Atlantic hurricane season started that it was going to be busy.


Six months later, we're looking back at a trail of broken records, and the storms may still not be over even though the season officially ended on Nov. 30.

This season had the most named storms, with 30, taking the record from the calamitous 2005 season that brought Hurricane Katrina to New Orleans. It was only the second time the list of storm names was exhausted since naming began in the 1950s.

Ten storms underwent rapid intensification, a number not seen since 1995. Twelve made landfall in the U.S., also setting a new record. Six of those landfalling storms were hurricane strength, tying yet another record.

Tropical storm tracks show how busy the 2020 Atlantic hurricane season was. (Credit: Brian McNoldy, CC BY-ND)

As atmosphericscientists, we target our research at better understanding both what drives the formation of tropical cyclones and how climate change is affecting them on longer time scales.

Here's what research tells us about the 2020 season and what may be ahead.

Why did 2020 have so many storms?

An unfortunate combination of two key factors made this season ripe for tropical storms.

First, a La Niña pattern of cool surface waters developed in the equatorial Pacific, and it was stronger than anticipated.

Ironically, cooling in the equatorial Pacific makes it easier for tropical storms to form and gain strength in the Atlantic. That's because La Niña weakens the vertical wind shear over the tropical Atlantic. Vertical wind shear – a change in wind speeds with altitude – is highly disruptive to storm development.

As the La Niña pattern became established this season, it made the tropical Atlantic much more hospitable for storms to form and intensify.

Atlantic sea surface temperatures in September 2020 were warmer than the 1981-2010 average. (Credit: NOAA)

The second critical factor was the extremely warm temperatures in the Atlantic, including the Gulf of Mexico and the Caribbean.

Hurricanes are powered by the transfer of heat from the ocean to the atmosphere. The sea surface temperature therefore dictates the maximum potential intensity a storm can attain under perfect conditions – it's like a thermodynamic "speed limit" on hurricane intensity.

The sea surface temperature approached record levels in the Atlantic hurricane basin this season, including in September, the most active Atlantic storm month on record.

What does climate change have to do with it?

An important part of this season's story is the Atlantic warming trend we're witnessing, which is unprecedented going back at least several millennia.

The oceans store much of the excess heat trapped by greenhouse gases. With greenhouse gas concentrations still increasing due to human activities, such as the burning of fossil fuels, average sea surface temperatures are likely to continue rising over the coming decades. Whether climate change caused the extremely high number of storms this season is unclear. There is no detectable trend in global hurricane frequency, and computer modeling studies have had conflicting results.

However, the warming climate is increasing the threat posed by hurricanes in other ways.

A growing proportion of high-intensity storms, Category 3, 4 and 5, is being observed around the world, including in the Atlantic. Since ocean temperature controls the potential intensity of tropical cyclones, climate change is likely behind this trend, which is expected to continue.

The U.S. is also seeing more storms with extreme rainfall. Think about Hurricane Harvey's 50 inches of rain in the Houston area in 2017 and Florence's 30-plus inches in North Carolina in 2018. The warming climate plays a key role here, too. With warmer temperatures, more water is able to evaporate into the atmosphere, resulting in greater moisture in the air.

Implications of the 2020 season

Ten storms this season underwent rapid intensification – a 35 mph increase in maximum winds within 24 hours. Rapidly intensifying storms are especially dangerous because 1) they are challenging to accurately predict, and 2) they provide minimal time for evacuations when they intensify just before making landfall.

Satellite instruments capture Hurricane Iota making landfall in Nicaragua on Nov. 16. The image shows the temperature of cloud tops, which tells scientists how tall the clouds are. (Credit: NOAA; James H. Ruppert Jr.)

Hurricanes Laura and Sally both rapidly intensified just before making landfall on the Gulf Coast this season. Eta rapidly intensified to a Category 4 just before hitting Nicaragua, and just two weeks later, Iota essentially repeated the act in the same location.

Forecasts for the tracks or paths of tropical cyclones have dramatically improved in recent decades, as much as five days in advance. However, forecasts of storm formation and intensification have improved very little by comparison.

The forecasts for hurricane rapid intensification are especially poor.

While the official forecasts issued by the National Hurricane Center are issued by human forecasters, they depend on the guidance of prediction models, which aren't very accurate when it comes to rapid intensification.

The complexity of weather models makes this a daunting challenge. However, it becomes more tractable as researchers learn more about how hurricanes form and intensify and identify the root causes for errors in computer model predictions.

Our latest research explores how clouds create their own greenhouse effect, trapping heat that causes hurricanes to form and intensify more quickly. Improving how numerical models account for this cloud feedback may ultimately hold promise for more accurate forecasts. Innovative ways of collecting new measurements in developing storms, down to their smallest scales, will also be necessary for guiding these improvements.

Given the upward trend in high-intensity storms, the risks from these storms will only grow. The ability to accurately predict how and when they will form, intensify and threaten coastal populations is crucial.

James H. Ruppert Jr. is an assistant research professor at Penn State. Allison Wing is an assistant professor of meteorology at Florida State University.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Here's what research tells us about the 2020 season and what may be ahead.

Tribes in the Colorado River basin say they're 'in the dark' as states discuss water conservation
www.kunc.org

Tribes in the Colorado River basin say they're 'in the dark' as states discuss water conservation

As states consider their response to the federal government's call for 2-4 million acre-feet of water conservation, tribal groups say their voices aren't being heard.
Sunrise in the woods

Get our Good News newsletter

Get the best positive, solutions-oriented stories we've seen on the intersection of our health and environment, FREE every Tuesday in your inbox. Subscribe here today. Keep the change tomorrow.

Nev. landowners say they've begun razing wildlife refuge dam
www.eenews.net

Nev. landowners say they've begun razing wildlife refuge dam

Patch of Heaven owner Annette Fuentes said federal officials at the Ash Meadows National Wildlife Refuge have threatened arrest but won't stop them. "They
Low water levels mean Rhine is days from being shut for cargo
www.theguardian.com

Low water levels mean Rhine is days from being shut for cargo

Businesses along the river say they are on verge of having to shut production
Some of the approximately 1,000 people stranded at Death Valley National Park have left in spite of flooding
www.cnn.com

Some of the approximately 1,000 people stranded at Death Valley National Park have left in spite of flooding

Death Valley National Park announced its closure Friday due to substantial flooding within the park, according to a news release.

Peter Dykstra: Greenwashing’s medieval age

Last week I went on an archaeological dig to uncover ancient greenwashers and deniers. This week, I present five more that persist to this very day.

Keep reading...Show less
Axed from climate deal, these ideas might be revived by Dems
www.eenews.net

Axed from climate deal, these ideas might be revived by Dems

Democrats cut more than $170 billion in climate programs to win Sen. Joe Manchin's vote. Some are already looking to resurrect them.
How Republicans are ‘weaponizing’ public office against climate action
www.nytimes.com

How Republicans are ‘weaponizing’ public office against climate action

A Times investigation revealed a coordinated effort by state treasurers to use government muscle and public funds to punish companies trying to reduce greenhouse gases.
From our Newsroom
Colorado fracking

How Colorado is preventing PFAS contamination from the oil and gas industry

And how other states, including Pennsylvania, could do the same.

fracking kids health

PFAS: The latest toxic concern for those near fracking

The “forever chemicals” are used by the oil and gas industry, but a lack of transparency and accountability makes it impossible to know how widespread contamination could be.

supreme court climate change

Op-ed: Reflections on the Supreme Court’s Decision in West Virginia v. EPA

Danger resides in the majority’s having invoked a sweeping “Major Questions Doctrine” to justify its decision in this relatively narrow case.

children health

Derrick Z. Jackson: Children will suffer the consequences of recent Supreme Court rulings

A rash of recent decisions by the high court will irreparably impact our children's health.

summer reading list

Our annual summer reading list, 2022 edition

Happy 4th of July! Here's some summer reading picks from our staff.

environmental injustice

Centering biodiversity and social justice in overhauling the global food system

“The food system is the single largest economic sector causing the transgressing of planetary boundaries.”

Stay informed: sign up for The Daily Climate newsletter
Top news on climate impacts, solutions, politics, drivers. Delivered to your inbox week days.