This has been a record-breaking week for global hurricanes as powerful storms struck both the Pacific and Atlantic Ocean basins, leaving scientists wondering whether they're harbingers of a more destructive climate-warmed future or are outliers that test the limits—but remain within—the realm of normal variability.
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On Sunday, Super Typhoon Goni left a trail of destruction over several smaller Philippine islands, with winds estimated at 195 miles per hour. It was the strongest storm ever to hit land, according to measurements by the National Oceanic and Atmospheric Administration’s National Hurricane Center and the Navy’s Joint Typhoon Warning Center. Luckily, Gomi missed densely-populated Manila and its surroundings. It’s expected to hit Vietnam with heavy rains and lesser winds late Thursday.
And in the Caribbean, the Category 4 Hurricane Eta struck the coast of Nicaragua on Tuesday with 145-mph winds, resulting in “life-threatening storm surge, catastrophic winds, flash flooding, and landslides” across portions of Central America, according to a Tuesday morning advisory by NOAA’s hurricane center. Nicaraguan emergency officials issued an evacuation order for the entire coastline, and the region is expected to be doused with up to 35 inches of rain by Sunday.
Hurricane Eta is the 28th named storm of 2020 in the Atlantic basin, tying the record set in 2005.
The reason that both storms have been so strong and so late is that both the Pacific and Atlantic oceans have stayed warm this year, says John Knaff, a meteorologist at NOAA’s Cooperative Institute for Research in the Atmosphere at Colorado State University. “The Atlantic season is a prototype for what happens when you have very warm sea surface temperatures,” Knaff says. “You have more energy for the storms to become very strong.”
Meteorologically, typhoons and hurricanes are the same phenomenon; it's just traditional to call them typhoons in the western Pacific or hurricanes in the eastern Pacific or Atlantic. They start as storms that pass over hot surface water, at least 80 degrees Fahrenheit, down to 150 feet deep. These storms suck up water from the ocean’s surface, which evaporates into the air. As they rise, the water vapor condenses to form droplets, releasing more energy, while low pressure beneath the rising air masses brings in a rush of more air. A tropical storm officially turns into a hurricane when these counterclockwise winds reach 74 miles per hour. Meteorologists applied the “super” designation to Typhoon Goni after it reached wind speeds of 150 miles per hour.
Earlier this year, NOAA officials predicted that 26 named hurricanes would form in the Atlantic, with between three and six categorized as “major,” and academic research teams separately predicted a “hyperactive” hurricane season. So far in 2020, five of the 28 storms have been major ones. “I was skeptical at the beginning of the season in the Atlantic,” Knaff says. “But it’s been pretty spectacular.”
By contrast, NOAA meteorologists predicted a slower-than-normal storm season in the Pacific, and although Super Typhoon Goni was a big one, that forecast has generally proved correct.
Knaff is an observational meteorologist who studies the environmental conditions that give rise to hurricanes. Others, like Kerry Emanuel, study how climate change is driving the formation of large storms like Goni and Eta, and how that may change in the future as both air and ocean temperatures continue to rise. “What is interesting is we are shattering all kinds of records in general in the last decade,” says Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology.
Globally, seven of the 10 strongest storms that made landfall have occurred since 2006, according to NOAA’s historical hurricane tracks (IBTrACS) database. That’s based on federal records going back to the 1930s. Prior to Typhoon Goni, 20 Category 5 super typhoons with winds of at least 160 mph had hit the Philippines since 1952. It’s almost as if the speed limit is being lifted on big storms, Emanuel says.
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Researchers are getting better at fine-tuning the global climate models that predict the weather patterns we will see as atmospheric carbon dioxide levels continue to climb and the Earth approaches the two degrees Celsius of warming that is expected by the middle of the century. In fact, a recent report by the UN’s World Meteorological Organization states that the planet’s vital signs have barely been slowed by the pandemic’s economic freeze, and that the world is on track to see the warmest five years on record. Warmer air temperatures mean that the atmosphere holds more water vapor from the oceans, water vapor that turns into rainfall from hurricanes. At the same time, storms draw more heat energy from warm surface waters to fuel their development—the hotter the water, the stronger the storm.
Under those conditions, tropical storms will likely increase in intensity, says Thomas Knutson, a research meteorologist at NOAA’s Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. Knutson contributed to the recent WMO report and says that all indications are that climate change is fueling stronger hurricanes. “Our models suggest the intensity of tropical cyclones will increase with warming,” Knutson says. “Something like a 5 percent increase for 2 degrees of global warming. If that happens, we also expect an increase at the high end. Eventually, you would see some record-breaking storms, because the intensity is increasing.”
Knutson says it's still not clear whether global warming will affect the number of hurricanes and typhoons. What is clear is that the storms will cause more damage, because the surge that occurs as winds push water up against the coastline will be bigger. Storm surge is exacerbated by rising sea levels, both because melting polar ice has added more water to the world’s ocean and because water expands as it warms.
Pacific storms are stronger than Atlantic ones, because the ocean is larger, so there’s more space for them to form, and because the Pacific has a deeper layer of warm water on the surface than the Atlantic. In the Atlantic, the warm surface layer gets overturned by currents such as the Gulf Stream, which flows from South Florida all the way to Europe, and the Florida Loop Current which flows around the Gulf of Mexico.
When you add it all up, superstorms like Goni have stronger winds, more rainfall, and bigger surge—which is why they can be more deadly to coastal residents. After its last-minute jog southward, Goni missed Manila and so far has only been responsible for 10 deaths, although a final death count has not been completed and 345,000 people remain in evacuation centers. By contrast, in 2013, Super Typhoon Haiyan killed 6,000 people, according to Phillipine government estimates, with another 1,800 missing.
For NOAA’s Knaff, he hopes that there aren’t too many more hurricanes before the Atlantic season ends officially on November 30. But if there are, he’ll have to rejigger his computer programs to account for more record breakers. “I hope things don’t go on,” Knaff says. “The last time we had storms that existed at the end of the year, it broke a lot of stuff. A lot of software is hardwired to the end of the season.”
Meteorologists and climate researchers say there’s no way to pin a single storm’s genesis or behavior to climate change, so there’s no way to tell if superstorms like Goni and Eta are going to become the new normal. These scientists deal with probabilities and trends over the long term. But as of today, the numbers don’t look so good.