Three Tropical Cyclones in a Row Break Records
It’s long been known that climate change will make hurricanes more dangerous in a variety of ways. Sea level rise from ice melt allows their storm surge to penetrate further inland. Warmer oceans provide more favorable conditions to hurricane formation, and over longer stretches of the year. The range of ocean that is sufficiently warm to allow for hurricanes is also growing steadily. As the atmosphere warms it can hold more water vapor, increasing the amount of precipitation during hurricanes. New studies suggest that climate change has slowed the rate of hurricane translation (movement of the whole system, not to be confused with wind speed).
Slower translation speeds and increased precipitation were the dominant features that made hurricanes Harvey, Imelda, Dorian, Florence, and Idai so devastating. Each of these storms slowed to a crawl at or over land, allowing them to dump massive amounts of rain that led to catastrophic flooding. Perhaps it’s not so surprising then, given the recent track record, that each of the last 3 hurricanes to form in the world were all record breakers.
These hurricanes are breaking records, almost certainly, because of climate change. Not only was April the warmest April ever, but the previous 12 month stretch is the hottest on record, “The average temperature for the twelve months to April 2020 is close to 1.3°C above the level”.
Typhoon Amphan is the strongest Tropical cyclone to form in the Bay of Bengal in history. The Tropical Cyclone reached sustained wind speeds of 165 mph, the equivalent of a Category 5 hurricane. On the other side of the world, Tropical Storm Cristobal is the earliest tropical storm to form in the Bay of Campeche (south gulf of mexico) in a history going back to the 1850's! The Bay of Campeche has never had a tropical cyclone before August 1st. Remarkably, it formed from the remains of tropical storm Amanda, despite Amanda having crossed over central America from the Pacific ocean. It’s poised to cross the Gulf of Mexico and strike the Southern Gulf Coast later this week.
In the Arabian Sea yesterday, Typhoon Nisarga went from nothing to something in about two hours. It just made landfall Mumbai in the last 24 hours, Mumbai’s first tropical cyclone in 129 years. This will prove challenging for Mumbai’s covid-19 prevention efforts, as it already has 50,00 confirmed cases of the disease.
As noted, hurricanes form on warm ocean water. This year, as is the case almost every year for last 30 years, global ocean heat content is at an all-time. It’s one of our strongest pieces of evidence for climate change. Sea level is also higher from melting ice and thermal expansion of the oceans, and an atmosphere 1.3°C above the pre-industrial average can hold more moisture and lead to more rainfall. Consequently, the warmer the planet gets, the more devastating tropical cyclones/hurricanes will be: larger storm surges, longer hurricane seasons, more powerful winds, and more rain.
The climatic factors above undoubtedly contributed to the record breaking tropical cyclones from June this year. As noted in Mumbai, this compounds with whatever other crises arise on the ground, such as our current global pandemic. Covid-19 infection rates in the American Southeast will be worth keeping an eye on going into hurricane season, as will the El Niño/La Niña index, as La Niña conditions have historically been linked to worse hurricane seasons in the Atlantic.
If the central Pacific Ocean leans more towards La Niña conditions and the Southeast sees a breakout of Covid-19, Atlantic Hurricanes could cause record damage and hasten the spread of the deadly disease. With the possibility of a record hurricane season looming, Southeastern States should look to get Covid-19 under control now, to mitigate the compounding effects of concurrent crises.