Something strange is happening to La Nina, a natural but strong weather event involving more drought and forest fires in the western United States and more hurricanes in the Atlantic. He is becoming an unwanted meteorological guest of the nation, and meteorologists have said that the mega-drought in the West will not disappear until La Nina does.
The current La Nina double dive set a record for strength last month and it is predicted that there will probably be a rare but not quite unprecedented third consecutive winter. And it’s not just that. Scientists have noticed that in the last 25 years, the world seems to be getting more La Ninas than before, and this is the exact opposite of what, according to their best computer simulations, has to happen with man-made climate change.
“They (La Ninas) don’t know when to leave,” said Michel L’Oiro, head of the National Oceanic and Atmospheric Administration’s forecast office for La Ninas and its more famous reverse, El Niño.
The Associated Press’s statistical analysis of La Ninas winters shows that they occurred in about 28% of the time from 1950 to 1999, but in the last 25 winters they boiled almost half the time. There is little chance that this effect is accidental, but if La Nina stays this winter, according to the forecast, it will push the trend above the statistically significant line, which is key in science, said L’Heureux. Her own analysis shows that La Nina-like conditions have been more common in the last 40 years. Other new studies show similar patterns.
What worries many scientists is that their climate simulation models, which tend to create conditions right in the rest of the globe, predict more El Niño than La Ninas, and this is causing controversy in the climate community about this. what to believe, according to Columbia University climatologist Richard Seeger and Hurricane scientist at the Massachusetts Institute of Technology Kerry Emanuel.
What Seeger and other scientists say is happening is that the eastern equatorial Atlantic is not warming as fast as the western equatorial Atlantic or even the rest of the world with climate change. And it is not the amount of warming that matters, but the difference between west and east. The bigger the difference, the more likely La Nina is, the smaller the difference, the more likely El Niño is. Scientists have suggested that this may be related to another natural cycle called the Pacific Decade, or it may be caused by man-made climate change, or both.
“We just don’t know at the moment,” L’Heureux said. “Scientists observe and I know, they are actively studying. But this is really important because of regional conditions. We need to fix this. “
La Nina is a natural and cyclical cooling of parts of the equatorial Pacific Ocean, which changes meteorological models worldwide, unlike the warming of El Niño. Often leading to more hurricanes in the Atlantic, less rain and more wildfires in the West and agricultural losses in the middle of the country, studies show that La Nina is more expensive for the United States than El Niño. Together, El Nino, La Nina and Neutrality are called ENSO, short for El Nino Southern Oscillation, and they have one of the greatest natural impacts on climate, sometimes increasing and sometimes suppressing the major effects of climate change. from man. from burning coal, oil and gas, scientists said.
“They really have a very, very strong effect,” said researcher Azhar Ehsan, who is leading the forecast for El Niño / La Nina at Columbia University. “So the third consecutive La Nina is not welcome at all.
He said the dangerous heat in India and Pakistan this month and in April was linked to La Nina.
The current La Nina is formed in the late summer of 2020, when the Atlantic Ocean set a record for the number of so-called storms. It intensified in the winter, when the drought in the West worsened and in the early summer of 2021 weakened enough that the NOAA said the conditions were neutral. But that pause lasted only a few months, and by the early fall of 2021, La Nina was back, making it double.
La Nina’s second year is usually weaker, but in April La Nina surprised meteorologists by setting a record for intensity in April based on sea surface temperatures, Ehsan said.
“These are very impressive figures for April,” said L’Heureux. Still, since La Nina has historically lost weight in the summer and there are slight signs that it may lose a little weight, there is a small but growing chance that this La Nina will warm up enough to be considered neutral at the end of the summer.
La Nina has the greatest effect in the winter and then it is a problem for the West, because the rainy season has to recharge the areas of the reservoirs. But the West is 22 years old, about the same time as La Nina’s growing frequency.
Three factors – ENSO, climate change and chance – are the biggest when it comes to drought, which in itself is a huge trigger for massive forest fires, said UCLA climatologist Daniel Swain. Without climate change, La Nina and bad luck could make the land the worst in 300 years, but with climate change, it is the worst in at least 1,200 years, said UCLA climate hydrologist Park Williams.
La Nina “is a very important player; he may be the dominant player, “said Swain, who has a blog about Western times. “He may be responsible for a third, perhaps half of the conditions given, if he is sufficiently pronounced.”
“The southwest is much less likely to see at least a partial recovery from the mega-drought during La Nina,” Swain said.
La Nina “amplifies your Atlantic storms” but reduces them in the Pacific, said Hurricane researcher at Colorado State University Phil Klotzbach.
Everything is for winds from 6 to 7 miles (10 to 12 kilometers) above the water surface. One of the key factors in the development of storms is whether there is a shear of the wind, which is a change in the wind from high to low altitudes. Cutting the wind can decapitate or overturn hurricanes, making them difficult to strengthen and sometimes even hold back. Cutting the wind can also leave dry air in hurricanes that suffocate them.
When there is El Niño, there is a lot of cutting in the Atlantic wind and it is difficult for hurricanes to move. But La Nina means a small cut in the Atlantic wind, which makes it easier for storms to intensify and do so quickly, said Kristen Corbosiero, a hurricane researcher at the University of Albany.
“It’s a really huge factor,” Corbosiero said.
“Whatever the reason, the growing frequency of La Ninas may be behind the growing hurricanes,” said Emanuel of MIT.
Some areas, such as Eastern Australia and the dry Sahel region of Africa, do better with more rain during La Nina. India and Pakistan, although receiving extra spring heat, are also getting more needed rain in La Ninas, Colombia’s Ehsan said.
A 1999 economic study found that the La Nina drought cost United States agriculture between $ 2.2 billion and $ 6.5 billion, much more than El Niño’s $ 1.5 billion price. The neutral ENSO is best suited for agriculture.
Seeger from Colombia said there may be some chance and some natural cycles behind the changes in La Nina, because there is probably a climate change factor who thinks there will probably be more.
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