Modern Hurricanes Are Rewriting the Rules of Extreme Storms

 

Modern Hurricanes Are Rewriting the Rules of Extreme Storms

The behavior of the world's most powerful storms is evolving. As hurricanes become more destructive, understanding their changing nature is crucial for adaptation. Fueled by heat from ocean waters, hurricanes function as nature's steam engines, converting oceanic heat into kinetic energy. This energy can flatten islands and inundate coastal cities, requiring extensive repair efforts. With ocean temperatures reaching record highs, hurricanes are changing their paths, slowing down, and becoming more unpredictable and dangerous. There is an urgent need to understand these changes to adapt effectively.

A Longer Hurricane Season

Hurricanes in the Atlantic follow a distinct seasonal cycle, peaking in September with few or none in the winter. According to James Kossin, a retired climate and atmospheric scientist from the US National Oceanic and Atmospheric Administration (NOAA), the early start of the hurricane season aligns with climate change expectations. "Hurricanes respond to their environment," Kossin says. "If June's environment resembles August or September, hurricanes will behave as if it were those months. They don't follow a calendar."

Climate change is driving the extraordinarily warm ocean conditions we're seeing now, along with other factors such as the transition from El Niño to La Niña, which tends to increase storm activity. Kristen Corbosiero, an associate professor at the University at Albany, New York, states, "In a warming climate, we expect earlier and longer hurricane seasons."

Are Hurricanes in the US Getting Worse?

The intense early start to the 2024 hurricane season, marked by Hurricane Beryl, aligns with climate change projections. However, Suzana Camargo, a professor of ocean and climate physics at Columbia University, notes that it's too early to see a consistent shift in the season. "It's not yet clear in the data," she says.

The Impact of Wind Shear

Hugh Willoughby, a research professor at Florida International University, notes that one of the strongest recent Atlantic storms, Hurricane Lee, intensified despite conditions that should have prevented its formation. El Niño generally increases wind shear, which disrupts hurricanes. "Shear is death for hurricanes," Willoughby explains, comparing it to knocking blades out of a turbine engine.

However, in September 2023, Hurricane Lee rapidly intensified into a category five storm despite significant shear. The extraordinary ocean warmth at the time might have overridden the shear's influence. "We need to understand why," says Willoughby.

Faster Intensification

Most Atlantic hurricanes don't reach their full potential due to landfall or high wind shear. However, when conditions are ideal, hurricanes can rapidly intensify, reaching their maximum potential based on ocean surface temperatures. Kossin notes that intensification rates are increasing as oceans get hotter. "It's like changing jets in a carburetor," he says. "More fuel means faster intensification."

Stronger Peak Intensity

Hurricanes are also reaching stronger peak intensities. Kossin's 2020 study found that storm intensity increased by about 6% per decade from 1979 to 2017. Major hurricanes, with winds exceeding 111 mph, are now 25% more likely than 40 years ago. The International Panel on Climate Change (IPCC) reports that the proportion of category three or higher storms is likely increasing.

Slower Movement

While wind speeds within hurricanes are increasing, their movement across oceans and land is slowing. Kossin's 2018 study found that hurricanes near the US have slowed by around 17% since the early 20th century. Tropical cyclones in the western North Pacific slowed by up to 20%.

This slowdown is linked to uneven global warming, with the Arctic warming faster than the tropics, reducing the temperature gradient that drives winds. "Hurricanes move where the wind takes them," Kossin explains. Slower winds mean slower-moving hurricanes, which can cause more rain and damage.

Increased Rainfall

Slower-moving hurricanes have more time to dump rain, exacerbating flooding. "When hurricanes slow down or stall, it's devastating," Kossin says. Warmer air also holds more moisture, leading to wetter hurricanes. However, the biggest impact on rainfall comes from hurricanes stalling out.

Deeper Ocean Warmth

Warmer surface waters allow hurricanes to maintain strength, but if deeper layers are also warm, hurricanes can continue intensifying. Corbosiero notes that current Atlantic conditions feature both warm surface and deep waters, enabling hurricanes to strengthen continuously.

Changing Tracks

Hurricanes are also changing their paths. Kossin's 2014 study found that storms in the northern hemisphere are moving northward, while those in the southern hemisphere are moving southward. This shift could expose new regions to extreme storms. For example, tropical cyclones are now posing a greater risk to Japan, which is less accustomed to them than the Philippines.

Erosion of the Protective Barrier

Climate change is altering wind shear patterns over the Atlantic. High shear in the Main Development Region (MDR) can weaken storms before they reach the US. However, Kossin's research suggests this protective barrier is eroding with climate change. "It seems the news is always bad," he says.

Loss of a Smog Shield

Decreased air pollution in Europe and the US since the 1970s has also unintentionally warmed the Atlantic. Previously, industrial pollutants had a cooling effect by blocking sunlight. With reduced pollution, this cooling effect has diminished, contributing to warmer ocean temperatures.

Rising Sea Levels

Rising sea levels exacerbate storm surge damage from hurricanes. A study found that storm surge waves in the Caribbean, Mexico, and the US grew in area by 80% since 1979, with global storm surge waves getting around 3% higher per decade.

Adaptation Strategies

To mitigate hurricane impacts, limiting coastal development is crucial. Camargo advises against policies promoting real estate development in hurricane-prone regions. For existing coastal communities, adapting buildings and infrastructure can help preserve them. Early-warning systems are vital for safety, and natural solutions like planting grass to stabilize slopes and replenishing oyster beds can bolster coastal defenses.

Conclusion

Understanding and adapting to the evolving nature of hurricanes is essential. As climate change progresses, hurricanes are becoming more intense, slower, and less predictable. By studying these changes and implementing effective adaptation strategies, we can reduce the devastating impacts of modern hurricanes on communities and the environment.