The countdown has begun: El Niño is coming. Next year, the phenomenon will increase flood risks in Peru, increase heavy rainfall in California, drain Indonesia, and impoverish fisheries off Chile. Some crystal ball climatologists predict a very strong episode; Others think it’s too early to predict its severity. One thing is certain: the burning link between El Niño and global warming will drag the world towards new temperature records.
In mid-May, the World Meteorological Organization (WMO) spoke from Geneva. “A warm El Niño is expected to develop in the coming months, which, combined with man-made climate change, will push global temperatures into uncharted territory,” said Mr. Petteri Taalas, Secretary General, World Meteorological Organization (WMO). . “This will have far-reaching implications for health, food security, water management and the environment,” he added.
Over the past three years, a major episode of La Niña — El Niño’s nemesis sister — has tended to contain slightly higher atmospheric temperatures by pumping more heat into the ocean. The global thermometer still records temperatures 1.15°C higher than those recorded in the period 1850-1900. This moment of respite ended last March with La Niña fainting. WMO is thinking now almost certain That the world temperature record set in 2016 (+1.28°C), during the recent “super El Niño”, will be broken within five years.
What will be the power of the Terrible Kid who is currently preparing his weapons? “It’s hard to say,” answers American climatologist Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies. This spring has seen “rapid” and “very pronounced” warming in the ocean off Peru. “Because it is developing so quickly, people say it will be a very strong El Niño phenomenon. But at the moment, according to statistical and dynamical models, the range of possible answers is still very wide, ”he explains in French in an interview. It will become clear in a few months. »
complex mechanism
El Niño returns at relatively regular intervals, every two to seven years. Each episode, usually lasting 12 to 18 months, begins with the slowing of the trade winds, winds that blow westward in the equatorial Pacific. Usually, these trade winds push the surface waters along the Peruvian coast offshore. It follows that, through the effect of suction, an upwelling of deep waters near the continent accompanied by ample supplies of nutrients – for the fish (and fishermen), feast!
When the trade winds slow down, El Niño begins. Near the continent, the flow of cold water stops and the ocean surface warms under the rays of the equatorial sun. Above this superheated pool, warm, moist air rises skyward, bringing heavy rains to southwestern South America. Also, the rising air has to come down somewhere. Once in the upper atmosphere, it slides to higher latitudes – 30°N and 30°S – and then disrupts the jet streams (jet streams) that bring rain and shine elsewhere in the world.
Among the more frequent long-range effects of El Niño – effects that climate scientists aptly call “telecommunications” – are decreased rainfall in Indonesia and northern South America, as well as increased precipitation in eastern Africa and the southern United States. These climatic hazards destroy crops and flood cities. In Canada, a bout of El Niño could moderate winters in the west of the country. This phenomenon, however, did not Very few consequencesin Quebec.
Reaching 1.5°C with El Niño
On a planetary scale, El Niño episodes cause Mercury to rise slightly. Because during these events, the upwelling of deep, cold Pacific waters slows, less heat can be absorbed there. He should take the atmosphere a little more on his shoulders. Schmidt said an El Niño of moderate intensity is pushing the global thermometer about 0.06°C. If such an episode occurs by the end of the year, we can already expect that many temperature records will be broken in 2024.
“The next few years are likely to be really hot because of an El Niño that pops up which has a good chance of being strong,” notes climatologist Philippe Lucas Bécher of the University of Quebec in Montreal. It is very solid scientifically. In five years, we will likely be close to the 1.5°C rise we’ve been talking about for years. This symbolic mark would first be reached temporarily, at the time of an El Niño episode, before being reached definitively, a few years later, due to the buildup of greenhouse gases in the atmosphere.
At this time, scientists don’t know if climate change is altering the Waltz between El Niño and La Niña. “It’s a chaotic system, very rich and very dynamic, and so it’s hard to see a trend there,” Mr. Schmidt explains. Climate science over the past 40 years indicates that La Niña is in control, but forecast models indicate otherwise. Even if there is a small trend associated with the effect [climatique]the phenomenon will have almost the same natural contrast.
