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Eastern Pacific warming to change surface temperatures in years, not decades

Time is running out to craft policies to deal with the extremes of more frequent El Niño events spurred by warmer ocean temperatures.

(CN) — For some time, scientists believed 2070 was the earliest they would be able to detect a change in the Pacific Ocean’s surface temperature. A study published Tuesday in Nature Communications moves that projection up by four decades, to 2030.

Dr. Tao Geng of the CSIRO Oceans and Atmosphere and Dr. Wenju Cai of the Pilot National Laboratory for Marine Science and Technology focused their study on the El Niño-Southern Oscillation (ENSO), what they called “the strongest and most consequential year-to-year climate fluctuation on the planet.” Every year with some variability in either the equatorial eastern Pacific (EP) or central Pacific (CP), ENSO creates worldwide natural events during its warm El Niño phase or cold La Niña phase.

Previous measurements of EP-ENSO and CP-ENSO had biases when it came to that variability, according to the study.

“Climate models suffer from persistent biases in their simulation of the mean equatorial climate and ENSO dynamics,” said the researchers in their study. Although some of their models continued to simulate a “too-cold climatological Pacific cold tongue,” they never fell before their 85% confidence level, and the researchers accounted for the underestimated EP-ENSO rainfall sensitivity. Combining this with 70 years of ENSO data starting from 1950 and some of the newest climate models, the researchers predict that environmental change will happen, including the Pacific Ocean's rising surface temperature, by 2030.

According to Geng, the rising surface temperature of the eastern Pacific will affect ENSO.

“A strong El Niño is characterized by atmospheric convection (rising motions of warm and moist air) moving eastward from the western Pacific warm pool region towards the eastern Pacific that causes the global impact,” Geng said in an email. “Atmospheric convection occurs where the ocean surface temperature is warmest relative to surrounding regions. The rising surface temperature in the eastern Pacific will facilitate eastward movement of atmospheric convection and favor development of strong El Niño events.”

In the past, strong EP-ENSO events such as El Niño in 1982 and 1997 caused a substantial disruption of the Pacific’s marine ecosystems, according to the study. Large, warm anomalies lead to a displaced atmospheric deep convection toward the eastern Pacific, causing floods in countries on the eastern Pacific Rim but droughts in western Pacific regions, which could become more commonplace as global climate temperatures increase.

Despite this, Cai noted that the greater greenhouse warming-induced strengthening of EP-ENSO over CP-ENSO could benefit research into climate change.

“Because EP-ENSO, featuring strong El Niño events, is a type of more impactful event, the earlier emergence of EP-ENSO sea surface temperature (SST) variability compared to CP-ENSO means that the equatorial eastern Pacific is a preferable place to detect greenhouse warming-induced changes in ENSO SST variability and the associated climate and weather extremes,” Cai said in an email.

Still, future policies to mitigate or adapt to climate change will contend not only with the diverse geography of the two ENSO regimes, as it includes regions such as south Asia and Australia, but also with much less time to create said policies.

“Our findings increase the confidence of projected increase in ENSO sea surface temperature variability and would reinforce the realization that climate change is happening and may have already exerted an influence on our climate that will soon be detectable, highlighting the urgency to cut down greenhouse gas emissions to mitigate the associated impacts,” wrote Cai.

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