How Climate Change Intensifies Hurricanes

Hurricanes are among the most destructive weather events globally, and climate change is making them even more intense and costly. Warmer ocean waters, the primary fuel for hurricanes, intensify these storms, leading to stronger winds, heavier rainfall, and more flooding when they hit land. The impact of rising temperatures on hurricane strength is evident, with an increase in the upper limit of hurricane intensity and rainfall rates. Warmer oceans also contribute to rising sea levels, exacerbating the effects of storm surges and pushing water further inland during hurricanes. While the total number of hurricanes remains uncertain, climate change is expected to result in more major storms, causing greater damage and loss of life.

Warmer oceans fuel storms

Hurricanes are powered by the release of heat when water evaporates from the ocean's surface and condenses into the storm's rain. Warmer ocean temperatures produce more evaporation, which means more water is available to the atmosphere. Warmer air can also hold more water, allowing for more rain. This cycle results in stronger hurricanes.

The formation of a hurricane is a complex process that depends on three key factors: warm water, moist air, and converging winds. The ocean's surface must be at least 80 degrees Fahrenheit (27 degrees Celsius) for a hurricane to form. When a cluster of thunderstorms moves across the ocean's surface, the storm sucks up heat energy from the warm water, creating moisture in the air. If the wind conditions are right, the storm becomes a hurricane.

The heat energy from the warm ocean water acts as fuel for the storm. The warmer the water, the more moisture is in the air, leading to bigger and stronger hurricanes. Satellite data has shown that hurricanes leave a trail of cooler water in their wake, as they evaporate the warm surface waters.

Recent studies have confirmed a link between ocean surface temperatures and tropical storm intensity. Warmer waters fuel more energetic and destructive storms. As the ocean temperatures continue to rise due to climate change, we can expect more intense and powerful hurricanes.

The impact of warmer oceans on hurricane formation and intensity is a critical area of research. Scientists use satellite data and climate models to improve their understanding and forecasting capabilities. By studying the complex interactions between the ocean, atmosphere, and climate, we can better prepare for and mitigate the impacts of these powerful storms.

Sea level rise makes storm surges worse

Storm surges are a deadly force during hurricanes and are considered the greatest threat to life. Storm surges are caused by the winds of a hurricane pushing water onshore. The amplitude of the storm surge depends on the orientation of the coastline with the storm track, the intensity, size, and speed of the storm, and the local bathymetry.

Sea level rise, triggered by human-caused global warming, makes storm surges worse. Warmer ocean water expands, and land ice melts, causing the sea level to rise. This results in higher water levels being pushed inland during hurricane-related storm surges. For example, the levees in New Orleans failed during Hurricane Katrina due to the storm surge, leading to widespread destruction.

The average global sea level has risen by over half a foot since 1880, with nearly four of those inches occurring since 1993. This rise in sea level can push more water inland during storm surges, leading to extreme flooding in coastal areas. The combination of storm surge and normal high tide, known as storm tide, can result in water levels rising up to 20 feet or more.

The impact of sea level rise on storm surges is a significant concern for coastal communities, as it increases the potential for flooding and the destructive power of the storm. With rising sea levels, communities will need to prepare for increasingly extreme weather events caused by hurricanes and take action to mitigate the impacts of climate change.

Hurricanes are stronger, intensify faster

Hurricanes are fuelled by warm ocean waters, which heat the air above them. This warm, moist air rises, creating a low-pressure zone beneath. This low pressure allows more air to rush in from surrounding areas, fuelling the cyclone and making it more powerful. Warmer ocean temperatures, therefore, create conditions that allow hurricanes to undergo rapid intensification.

A hurricane undergoes rapid intensification when its wind speed increases by 35 mph or more within 24 hours. For example, in 2023, Hurricane Otis strengthened from a tropical storm to a Category 5 hurricane before making landfall near Acapulco, Mexico. Its wind speed increased by 100 mph, from 60 mph to 165 mph. The month before, Hurricane Lee, a major hurricane travelling up the Atlantic, underwent the third-fastest case of rapid intensification ever recorded. On 7 September, its wind speed more than doubled, increasing from 80 mph to 165 mph.

In the past, it has been difficult to forecast rapid intensification, as so many shifting conditions need to align to trigger it. However, scientists are now developing new methods to help them warn people of this rising threat. For example, in 2020, a study found that satellite data and readings from buoys in the Gulf of Mexico showed a marine heatwave was underway during Hurricane Michael's approach. Similar data could warn meteorologists in the future that an incoming hurricane is about to intensify.

According to Andra Garner, a climate scientist at Rowan University, the fact that storms that intensify especially quickly can often be hard to forecast, "creates challenges when you add to that the fact that they’re also hard to plan for". Garner's research found that across 12-, 24-, and 36-hour windows, hurricanes now see mean peak intensification rates that are at least 26% higher than five decades ago. There is now an 8% chance that a given storm will move from category 1 to category 3 or above within 24 hours, compared with 3% in the past.

The warming of the oceans is clearly linked to human-caused climate change. Garner notes that "we know that as humans have warmed the planet, about 90% of that excess energy and warmth has gone into our oceans. We also know that hurricanes require warm water to intensify, and especially to intensify quickly".

Hurricanes are moving more slowly

Hurricanes are indeed moving more slowly, and this is having a significant impact on the destruction they cause. Slower-moving hurricanes, like Hurricane Harvey in 2017, result in a longer period of rainfall accumulation, leading to more flooding. The slow movement of Hurricane Harvey, for example, contributed to the unprecedented 60 inches of rain that fell in southeast Texas.

Scientists are still debating the exact mechanism linking the slowdown of hurricanes to climate change. However, the leading theory suggests that the steering winds that direct hurricanes move more slowly in a warmer climate. This theory is supported by a 2018 study by James Kossin of NOAA, which discovered a 10% global reduction in the forward speed of tropical cyclones since 1949. The slowdown is even more pronounced over land areas, with a 21% reduction in the western North Pacific and a 16% reduction in the North Atlantic.

The decrease in the speed of hurricanes is a critical factor in the total rainfall amounts at a given location. The longer duration of high winds, storm surges, and heavy rainfall associated with slower-moving hurricanes results in more significant destruction and damage to coastal regions.

While the specific cause of the slowdown in hurricane speed is still under investigation, the available data and observations clearly indicate that hurricanes are, indeed, moving more slowly. This trend has important implications for preparing and mitigating the impacts of these powerful storms on vulnerable coastal communities.

Higher temperatures mean more energy to form hurricanes

The formation of hurricanes is a complex process that depends on several factors, but one of the most critical elements is the presence of warm water. The ocean acts as a major heat sink for the planet, absorbing over 90% of the excess heat trapped by greenhouse gases in the Earth's atmosphere in recent decades. As the ocean absorbs heat, sea surface temperatures rise, and this increase in temperature plays a crucial role in strengthening hurricanes.

The relationship between higher temperatures and hurricane formation can be understood by examining the basic physics of these storms. Hurricanes are essentially clusters of thunderstorms that build strength as they move across warm tropical waters. The warm ocean waters heat the air above them, causing the warm, moist air to rise. As this moist air ascends, it cools and condenses, forming clouds and creating a low-pressure zone beneath. This low pressure allows more air to rush in from the surrounding areas, fuelling the storm. Warmer ocean temperatures provide more energy for this process, leading to more intense and destructive hurricanes.

The impact of higher temperatures on hurricane formation is further exacerbated by the fact that warmer air can hold more water vapour. As surface temperatures rise, more liquid water evaporates from the ocean, adding moisture to the air. This increased moisture leads to more intense rainfall during hurricanes. Condensation also releases heat, providing additional energy to fuel the storm and contributing to its intensification.

The combination of higher ocean temperatures and increased moisture in the air creates a positive feedback loop that strengthens hurricanes. The warmer ocean provides more energy for the storm, leading to higher wind speeds and more intense rainfall. This, in turn, causes greater evaporation, adding more moisture to the storm system. As a result, hurricanes fuelled by higher temperatures have the potential to cause significantly more damage when they make landfall.

In summary, the relationship between higher temperatures and hurricane formation is clear. Warmer ocean temperatures provide more energy for the formation and intensification of hurricanes, leading to stronger wind speeds and more intense rainfall. This, combined with the fact that warmer air can hold more moisture, creates the conditions for bigger, more destructive storms. As global temperatures continue to rise due to climate change, communities along the East and Gulf coasts can expect to face increasingly severe and costly impacts from these powerful weather events.

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