"It's still early to talk about a 'Super El Niño'; climate risks should still be taken seriously."

Sourced from: China Science News

Recently, topics such as “The next one or two years may become the hottest years in history” and “The Earth may be heading for a super El Niño event” have frequently made it to online trending searches, drawing widespread public attention. On March 23, a report titled “Global Climate Status Report 2025” released by the World Meteorological Organization (WMO) shows that the period from 2015 to 2025 is the hottest 11 years on record, and 2025 is among the three hottest years on record.

The warning bell of global warming is ringing again: when exactly will El Niño arrive? Will it be on a “super” level? This summer, will our country face more ferocious heat waves or a more severe flood season? In response to the above questions, China Science News interviewed multiple experts.

Zheng Fei, a researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences (hereinafter referred to as IAP), said that the forecasting model results of IAP indicate that the likelihood of experiencing a moderate-intensity El Niño in 2026 is highest, with a probability exceeding 70%, while the probability of it developing into an extremely strong El Niño is only around one tenth.

“Under the backdrop of global warming, extreme climate impacts caused by or related to ENSO (El Niño–Southern Oscilllation) are more likely to be amplified—for example, higher temperatures and stronger heavy rainfall become stronger and more frequent. It is still too early to assert that this year will be the ‘hottest year,’ but the associated risks are indeed rising significantly,” Zheng Fei said.

“Spring forecast obstacle” leads to forecast biases

“El Niño” refers to the phenomenon in which sea surface temperatures in the tropical central and eastern Pacific remain abnormally high for an extended period. The corresponding condition with abnormally cooler temperatures is called “La Niña.” This periodic oscillation is the strongest interannual variability signal of the climate system.

Monitoring by the National Climate Center shows that the two-year La Niña state has been trending toward an end, and sea temperatures in the equatorial central and eastern Pacific are warming. Liu Yunyun, director of the climate prediction section at the National Climate Center, explained that, based on historical statistics, after a La Niña event ends, the probability of entering an El Niño state in the same year is about one third.

However, forecasts from different places around the world about when El Niño will arrive differ. The European Centre for Medium-Range Weather Forecasts predicts it could be as early as April; the Australian Bureau of Meteorology believes it may occur in May; Japan Meteorological Agency points to June; and U.S. experts’ voting results cluster in July to September.

Why do different institutions’ predictions about when El Niño will “arrive” vary so widely? Does this mean the forecast models are not accurate?

Zheng Fei explained that this cannot simply be attributed to flaws in the models. Behind it lies a scientific challenge widely recognized by the academic community, known as the “spring forecast obstacle.” Put simply, every spring, there is minimal “interaction” between the tropical Pacific Ocean and the atmosphere; the physical link between changes in sea surface and subsurface temperatures and wind fields is the least clear.

At the same time, the prediction models of different institutions are based on different ways of modeling complex natural phenomena. They differ in how they describe the coupled physical processes of the atmosphere and ocean, and they also differ in their sensitivity to initial conditions.

Zheng Fei explained that over long forecasting cycles, initial errors and random disturbances in the atmosphere will be progressively amplified, causing some models to predict faster warming, others slower warming, and in some cases even evolution in entirely different directions—toward either colder or warmer outcomes. Therefore, it is still too early to conclude that a “super El Niño” will occur this year.

In addition, for intensity forecasting, internationally there is no fully unified standard for categorizing “strong” versus “super” El Niño. Zheng Fei told reporters that in our operational work, the peak sea surface temperature anomaly of 2.0°C and above is usually defined as “strong,” and reaching 2.5°C and above is called “extremely strong.”

Based on this, the conditions for forming a strong or extremely strong El Niño are extremely stringent: it not only requires that the warm water “ammunition” stored in the warm pool of the western Pacific be sufficient, but also needs a series of atmospheric responses, such as a significant weakening of the tropical Pacific trade winds and frequent outbreaks of westerlies, through an extremely strong “positive feedback” between the ocean and the atmosphere to keep piling warm water eastward and sustaining the warming. Historically, 1997 and 2015 both saw strong-to-extremely strong El Niño events, respectively.

Heat “stacks,” making extreme heat possible to last longer, arrive earlier, and be more “hard to endure”

If this El Niño develops, will it layer on top of the already ongoing global warming background for many years, making extreme heat events even more intense?

Li Kexin from IAP described this risk using the “stacking effect.” She explained that El Niño itself releases a huge amount of heat from the ocean to the atmosphere, bringing natural interannual warming. When this layer of “natural warmth” stacks on top of long-term “human-caused warmth,” the baseline of global average temperature is raised. This means heat events are not only more likely to occur, but may also be stronger and more persistent, even arriving earlier.

Historical records confirm this. An extremely strong El Niño occurred in 2015, and the historical record for global average temperature was broken in 2016. The El Niño event in 2023 helped drive 2024 to become the first year in which the global average land surface temperature exceeded the 1.5°C threshold above the pre-industrial level. The warming effect of El Niño often has lag; it usually peaks in the following year.

Therefore, although it is still too early to assert that this year will be the “hottest year,” the related risks are indeed rising significantly.

Focusing on our country, Li Kexin said that existing research is fairly certain: El Niño will significantly promote extreme heat and heat waves, and it has clear regional and phase-based characteristics. Especially in the summer of the year after an El Niño, the world is more likely to experience heat waves that are stronger, longer-lasting, and more intense. Under the backdrop of global warming, this “amplification” effect will be even more pronounced.

Li Kexin said, “This means that if El Niño forms as expected in the second half of this year, then in the summer of 2027—especially in northern regions of our country—we may need to prepare in advance, psychologically and with material reserves, for ‘ultra-long standby’ heat.”

El Niño cannot “set droughts and floods” with a single click

Our country is a typical monsoon climate region, and besides high temperatures, El Niño’s impact on drought and flooding during our flood season is even more complicated. Sometimes, El Niño becomes a label for “extremely heavy rain” or “nationwide severe drought.” What biases exist in this kind of understanding?

Zheng Fei pointed out that such simplification first ignores the climate system’s “chaotic nature”—the so-called “butterfly effect.” El Niño is indeed a powerful external forcing signal, but it is not a definitive switch that determines whether a particular place in our country will be wet or dry.

More importantly, El Niño has never been a “one-person operation.” Our country lies in a typical East Asian monsoon region. The intensity and location of summer precipitation are the result of multiple factors working together, such as the western Pacific subtropical high, the East Asian summer monsoon, the atmospheric circulation of mid and high latitudes, local topography, and even typhoon activity. Even in the same El Niño year, the distribution of the rain band may differ drastically.

Peng Jingbei, a senior engineer of the IAP, mentioned that, according to historical patterns, El Niño’s impact on precipitation in our country shows prominent phase-based characteristics. The most typical and strongest impact usually occurs from the winter of the El Niño peak through to the summer of the following year.

“For example, taking the strong El Niño of 2015–2016: the huge flood-prevention pressure people associate with the Yangtze River basin mainly corresponds to the summer of 2016, not to 2015 when El Niño had just begun to form,” Peng Jingbei said.

Peng Jingbei analyzed that, in terms of this year, with the ongoing transition process from La Niña to El Niño, together with the influence of an interdecadal climate background, there is a greater possibility that the flood-season rain band will fall in northern parts of our country; “but the real test may be yet to come.”

“If an El Niño event forms in the second half of this year, the more significant impact on our country will appear from this winter through next summer. At that time, risks should be given more focused attention: in the winter and spring, precipitation in the south tends to be above normal, and in summer, there is a risk of more rainfall in the Yangtze River basin,” Peng Jingbei said.

Facing this new normal of “less stable weather and climate,” what can we do? Zheng Fei said that the truly key is to initiate a series of “invisible” preparatory work. This includes strengthening rolling monitoring and refined forecasting of key factors such as sea surface temperatures and monsoons; coordinating water resources and scheduling allocations to achieve “mutual support between wet and dry” among reservoir groups; sorting out potential urban waterlogging hotspots and hidden risks in mountain torrent channels in advance; for electricity peak demand, improving power peak-shaving contingency plans; and more importantly, improving the efficiency of cross-department coordination and public communication, so as to minimize the harm that extreme weather may cause.

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