Six questions about this phenomenon that could raise global temperatures in 2023

He plays sports with his cousin La NiñaIt has a great influence on the climate of the Pacific Ocean and the whole world with it. El Nino It may return in 2023. What characterizes this climate event? Under what conditions does it appear? And what will be the consequences of this reappearance? We count in 6 questions.

1 – El NinoWhat is this?

It is a disruption of the ocean and climate system that usually occurs over a very wide strip in the equatorial Pacific Ocean, from Indonesia to Peru.

The main feature of this system is a very strong inequality in water temperature. “To the west (near Indonesia) there is a warm pool of Pacific Ocean water, with waters over 30°C, and to the east (near Peru) there are cooler surface waters of 23 or 24°C.poses, by way of preamble, Eric Guilyardi, oceanographer at CNRS and president of the Office of Climate Education. “This temperature difference creates a pressure difference in the atmosphere that creates the trade winds (winds from the East). And these trade winds themselves will cause warm water to accumulate in the west and cold water to rise in the east. So, this is a self-sustaining system.”.

But sometimes it happens that this wonderful mechanism becomes a jam. “In some years, a wind anomaly in the western Pacific slows the trade winds and will cause warm water to move from west to east, which will reduce the temperature difference between the two regions, further reducing the trade winds and causing even more heat. let the water move eastward”.

However, these warm waters will move and reach the surface of the ocean, and with the ripple effect, the air temperature there will sometimes rise to 3-4 degrees. This scheme is called: El Nino .

La Niñaagainst cold El Nino follows the rules already written. La Niñasame dynamic as normal except stronger”Eric Guiliardi confirms. “The trade winds are stronger, so more cold water rises to the east. » The sea temperature then becomes even colder, as does the air temperature.

2 – What are the factors necessary for its appearanceEl Nino ?

That’s what this disorder is El Nino it can happen only under two conditions. First, warm water should accumulate well underground (about 300 m below sea level) in the western Pacific Ocean. Then, those famous westerlies should well and truly materialize in the spring when everything is at stake. This is not always the case.

“In 2014, there was this heat storage in the Pacific, but it wasn’t El Nino Because the atmosphere didn’t react.”Eric Guiliardi remembers.

3 – El Nino Will it reappear in 2023?

Early indications suggest this may be possible. On January 23, 2023, the National Oceanic and Atmospheric Administration, the American agency that scans the oceans, reported a one in two chance. El Nino will return by the end of the year.

And for good reason, “Today, one of the predecessors El Nino , there is heat stored underground in the western equatorial Pacific. So there probably is El Nino  passes 50% at the end of the year ».

“But we’ll have a better estimate in March-April.”Eric Gilyard says. We can determine with certainty during this period whether there is an episode of westerly winds, another factor necessary for the episodes to begin. El Nino will actually happen.

4 – Will this return be a significant event?

Yes and no. Yes, because it reappears after three years La Niña Given that the difference in water temperature between the two events is significant, it would constitute a truly large-scale climate change (-1 or -2 °C compared to the average). La NiñaAgainst +3 or +4 °C El NinoMost important).

And not because it’s more or less common for him to reappear at this point. El Nino It returns every 3-7 years”Eric Guiliardi explains. “Episodes La Niñathey return more often, but less strongly »he says.

5 – What consequences could its return have for the global climate?

As Météo France reminds us, El Nino “affects global climate as a whole”especially by mechanically raising the earth’s temperature.

Why? Because the Pacific Ocean is tropical “It’s a quarter the size of a planet”Eric Guilyardi summarizes. “So a 4°C anomaly in this area means a few tenths of a degree warmer globally. »

But the effectEl Nino It far exceeds this simple increase in global average temperature. Because its appearance disrupts a number of oceanic or atmospheric currents and radically changes a certain local climate.

And take that example from Eric Guilyardi “Indonesian Hot Water Pool”one of the regions where the climate system is disturbed El Nino. “It’s an area that gets a lot of rain because the trade winds bring moist air that condenses there, which causes rain. But if we move the warm waters in the central Pacific Ocean, as we have El Ninoall this atmospheric convection moves there and results in a drought in Indonesia or northern Australia.”.

El Nino It causes more rain events in California and changes the areas where cyclones appear (especially less in the Atlantic). alternating with La NiñaThe Horn of Africa also causes floods or droughts depending on the situation. “Furthermore, fish are leaving the coastal waters of South America, where warm waters are poorer in nutrients than typically colder waters.”Adds Météo France.

6 – And for France?

In the Pacific, this change in configuration will have little effect on Europe and France.

Because if the average temperature of the earth is well directed upwards, “It’s not because we have a phenomenon El Nino It is inevitable that the weather will be hotter in France., summarizes Éric Guilyardi. France, which is relatively far from the area where this phenomenon occurs, is actually subject “Other Superior Effects”.

But if it is affected by heatEl Nino perhaps not concretely felt, indeed there is no doubt that there will be greenhouse gases.

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