How El Niño could affect U.S. weather : NPR
As warm as Earth’s weather has been in recent years, it’s about to get hotter: El Niño is underway, with warmer sea temperatures promising new weather extremes, US and international forecasters say .
For several years now, a persistent La Niña pattern in the equatorial Pacific Ocean has been mitigating some of the worst temperature increases, as well as disrupting precipitation patterns. But the World Meteorological Organization says all that is about to change.
“We’ve only had eight warmest years on record, even though we’ve had a cooling La Niña for the past three years,” said WMO Secretary-General Petteri Taalas.
In the United States, the change promises relief in other forms, as the outgoing La Niña is associated with more hurricane activity in the East and drought in the West.
Here’s a quick guide to these two influential climate trends:
They affect hurricanes and other weather
El Niño usually brings a quieter Atlantic hurricane season and more Pacific hurricane activity, while La Niña does the opposite – a dynamic that the National Oceanic and Atmospheric Administration be compared to an egg.
The warm waters of El Niño can also push the Pacific jet stream south. When that happens, the NOAA says“areas in the northern United States and Canada are drier and warmer than usual. But in the Gulf Coast of the United States and in the Southeast, these periods are wetter than usual and have increased the flood.”
La Niña said goodbye in March; since then, US forecasters have mounted an El Niño Watch.
“There is a 62% chance of El Niño developing during the May-July period, and more than an 80% chance of El Niño by fall,” according to NOAA’s Emily Becker.
La Niña cools, and El Niño warms
La Niña “acted as a temporary brake on global temperature increase,” Taalas said. This is because the pattern occurs when sea surface temperatures are unusually cold and are forecast to remain so for several months.
We have been seeing La Niña conditions from the end of 2020which led to a forecast of below normal winter temperatures for much of the Northern United States and higher temperatures in much of the South.
But given the new trend of warmer sea surface temperatures, Taalas added, “El Niño is likely to lead to a new spike in global warming and increase the chance of breaking temperature records ” which were established only recently.
It usually takes time for changes to exert their full effects. The WMO says the biggest impact on global temperatures is unlikely to become apparent until 2024.
Patterns change regularly, and irregularly
The basic rule is that El Niño patterns occur more often, but La Niña usually lasts longer – sometimes for years. Most cases of each model usually play out over just nine to 12 months.
“El Niño and La Niña events occur every two to seven years, on average, but they do not occur on a regular schedule,” NOAA says. In addition to the two patterns, ocean temperatures are sometimes considered “neutral,” meaning they are not abnormally warm or cold.
While confidence is growing that a new pattern is taking hold, it is not yet known exactly how strong this coming El Niño could be.
Still, the World Meteorological Organization is urging people and governments to prepare for warmer and more volatile conditions, citing a possible repeat of 2016 — the the hottest year on recordthanks to what the WMO calls the “‘double whammy’ of a very strong El Niño event and human-induced warming from greenhouse gases.”