Hurricane season is just on the horizon, and this year rising temperatures are headed toward a “La Niña” effect that could cause bigger and stronger tropical storms in the Atlantic.
The annual hurricane season officially starts on June first and continues through the end of November. Every year, the intensity of its storms is affected by a variety of factors: One is climate change. Another is whether it’s a La Niña or El Niño year.
The names of these cyclical weather events translate from Spanish to “the girl” and “the boy.” The most famous of the two, El Niño, is named after ‘el niño dios,’ is what many Latin Americans call baby Jesus. El Niño conditions, including warmer ocean water, are generally noticed in South America around Christmas, so they’re named after the religious figure.
And as of mid May 2022, it’s looking like the boy has left town, and NOAA thinks we’re getting a visit from his little sister.
What is La Niña?
According to Daniel Gilford, a climate scientist at Climate Central, La Niña is somewhat of an opposite of its “brother” El Niño. Whereas El Niño causes warmer waters that move the Pacific jet stream south, causing more rain on the East Coast of the U.S. and higher temperatures in northern climates; La Niña pushes trade winds south, so the U.S. is hit by a polar jet stream instead.
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“You actually see less rain, more descending air, that causes temperatures to go up a little bit,” Gilford told Earther.
This means that Alaska and Canada will see colder temperatures and some parts of the U.S. like the South and Southwest will become dryer than usual. It also means an active storm season for the second half of the year.
How Does La Niña Impact Atlantic Hurricanes?
In 2020 and 2021 we had two very active hurricane seasons, and both were La Niña years. In 2020, storms formed so fast that we ran through the usual list of storm names starting with consecutive letters of the alphabet, and had to turn to Greek characters. That was a record breaking season that saw the formation of 30 storms. Both years spawned storms so powerful, they saw several billion dollar disasters like Hurricane Laura and Hurricane Ida, according to NOAA’s yearly reports.
But how does La Niña contribute to this? During El Niño years, the way air circulates around the Atlantic causes strong winds in the upper levels of the atmosphere, which then decreases the chance of a storm forming in the region. But during La Niña years, this calms down.
“Hurricanes like really pristine environments to grow in… they like that sea surface temperatures to be warm, but they also need the atmosphere in their surroundings to be generally calm and favorable for development,” Gilford explained.
Remember the higher temperatures in the lower half of the U.S. during La Niña years? That helps build warmer sea surface temperatures, creating some of the fuel needed for hurricanes to form and move to areas like the Gulf of Mexico, the coast of Central America, and up the U.S. east coast. Gilford said that this year is still experiencing La Niña conditions, and might continue to do so until later into the summer.
The climate crisis vs. La Niña and El Niño.
Hurricanes are supposed to happen in the Atlantic. These weather events are part of the natural system— the climate crisis didn’t create them. But our changing climate is making them worse. And our national infrastructure is not well prepared to deal with this.
Gilford explained that being in a La Niña or El Niño year does not tell us exactly what will happen, but they are guidelines for what to expect. On top of that, climate change is its own force. The overall strength of storms have increased in recent decades. Higher category cyclones are more likely to happen as storms around the world become stronger. A 2020 report even found that storms over a category 3 increased by about 8 percent each decade from 1979 to 2017.
“We’re seeing an uptick in sea surface temperatures,” Gilford said. “As we increase carbon dioxide in the atmosphere that traps more heat on the earth… that eventually makes its way down in the ocean and the [warmer] oceans provide more fuel for hurricanes to grow.”
Another example of this seen in droughts. Extreme dry periods are not new, they are part of the natural cycle in many regions of the world, and we expect to see more drought conditions in the U.S. during a La Niña year. But the climate crisis is fueling hotter temperatures and changing precipitation patterns that make droughts even worse. Signs of that are already here. The Southwest is experiencing the worst megadrought in over 1,000 years. Some of the largest water reservoirs in the nation are seeing historic lows— so much so that bodies are even being discovered in areas that used to be covered by dozens of feet of water.
“It’s something we’re still actively trying to understand,” Gilford said.