The Strongest El Niño Ever

史上最强厄尔尼诺现象

With all the July runs in, dynamical models give a ~90% chance of a record-setting event. 随着七月份的运行数据出炉，动力学模型显示，此次厄尔尼诺现象创下历史纪录的可能性约为 90%。

I’m generally pretty measured in how I discuss climate data. There has been only one time in recent years when I was truly shocked: when global temperatures came in for September 2023 at a full 0.5C warmer than any prior September on record. Until today, that is. With the July runs now in from 667 ensemble members across 14 different seasonal forecast models, it looks like this year’s El Niño is not only very likely to be the strongest event since reliable records began – it may end up the strongest by a truly mind-blowing margin. 在讨论气候数据时，我通常非常谨慎。近年来，只有一次让我真正感到震惊：2023 年 9 月的全球气温比有记录以来的任何 9 月都要高出整整 0.5 摄氏度。直到今天，情况发生了变化。随着来自 14 个不同季节性预报模型的 667 个集合成员的 7 月运行数据出炉，今年的厄尔尼诺现象不仅极有可能成为自可靠记录开始以来最强的一次，而且最终可能会以令人难以置信的幅度打破纪录。

The multi-model median for the event’s peak (measured as detrended sea surface temperature anomalies in the Niño 3.4 region of the tropical Pacific) currently stands at 3.6C, roughly 0.8C hotter than the prior record of 2.75C set in 2015-16. For context, the gap between the strongest and the fifth strongest El Niño of the past 150 years is only about 0.5C. The models are forecasting something outside the envelope of anything we have ever observed. 此次事件峰值的多模型中位数（以热带太平洋 Niño 3.4 区域的去趋势海表温度异常衡量）目前为 3.6 摄氏度，比 2015-16 年创下的 2.75 摄氏度的前纪录高出约 0.8 摄氏度。作为参考，过去 150 年中最强厄尔尼诺与第五强厄尔尼诺之间的差距仅为 0.5 摄氏度左右。模型预测的情况已经超出了我们以往观测到的任何范围。

A few things stand out in this figure. First, no event in a century and a half of observations has ever pushed meaningfully past 2.75C. The legendary 1877-78 event comes closest, in a statistical dead heat with 2015-16 (2.73C vs 2.75C, well within the uncertainty of 19th-century ship data). Second, the middle 80% of this year’s forecast ensemble sits entirely at or above that all-time record: even the low end of the plume (2.8C) grazes it. Around 91% of ensemble members exceed the 2015-16 record at their peak. 从这张图中可以看出几点。首先，在过去一个半世纪的观测中，没有任何一次事件能显著超过 2.75 摄氏度。传说中的 1877-78 年事件最接近，与 2015-16 年的数据在统计学上不相上下（2.73 摄氏度对 2.75 摄氏度，这完全在 19 世纪船舶数据的误差范围内）。其次，今年预报集合中 80% 的中间值完全处于或高于该历史纪录：即使是预测范围的下限（2.8 摄氏度）也触及了这一纪录。约 91% 的集合成员在峰值时超过了 2015-16 年的纪录。

To see what this would look like as the event unfolds, we can compare the forecast trajectory against the five strongest events ever observed, month by month through the development year and into the following spring. 为了观察事件发展过程中的情况，我们可以将预报轨迹与有史以来观测到的五次最强事件进行对比，按月追踪其从发展年到次年春季的变化。

What is remarkable here is not just the level but the trajectory. The 2026 event is developing faster than 1997-98, the previous gold standard for explosive El Niño onsets. And unlike 2015 which started its year already warm from a precursor event, this one launched from genuinely La Niña-ish conditions in January. 这里引人注目的不仅是强度，还有其发展轨迹。2026 年的事件发展速度超过了 1997-98 年，后者曾是厄尔尼诺爆发式增长的黄金标准。而且与 2015 年不同的是，2015 年初时由于前兆事件气温已经偏高，而今年年初则是从真正的拉尼娜状态开始的。

Of course, a multi-model median can hide a lot of disagreement, so it is worth looking at where each individual model puts the peak. The figure below shows the distribution of member peaks across all 14 models. 当然，多模型中位数可能会掩盖许多分歧，因此有必要看看每个模型对峰值的预测。下图显示了所有 14 个模型中成员峰值的分布情况。

Every single model’s median peak lands at very strong (”super”) El Niño intensity, and all but one (JAMSTEC’s SINTEX-F, at 2.2C) put their median above the 2015-16 record. Model agreement this strong is unusual, though I’d note that agreement is not the same thing as skill as I discuss later on. 每一个模型的峰值中位数都达到了极强（“超级”）厄尔尼诺强度，除一个模型（JAMSTEC 的 SINTEX-F，为 2.2 摄氏度）外，其余所有模型的中位数都超过了 2015-16 年的纪录。如此强的一致性在模型中并不常见，尽管我必须指出，正如我稍后将讨论的那样，一致性并不等同于准确性。

Long-time readers may recall that in a warming world, the raw Niño 3.4 anomaly risks conflating El Niño with the broader ocean warming trend. NOAA’s answer is the relative ONI (RONI), which subtracts the tropical-mean SST anomaly to isolate the ENSO signal. In RONI terms the record holder is actually 1982-83 (a peak monthly value of 2.69C), not 2015-16. However, even using RONI the multi-model median in 11 of the 14 models shows a record event. 长期读者可能还记得，在气候变暖的世界中，原始的 Niño 3.4 异常存在将厄尔尼诺现象与更广泛的海洋变暖趋势混淆的风险。美国国家海洋和大气管理局（NOAA）的解决方案是相对 ONI (RONI)，它通过减去热带平均海表温度异常来分离出厄尔尼诺-南方涛动（ENSO）信号。从 RONI 的角度来看，纪录保持者实际上是 1982-83 年（月峰值为 2.69 摄氏度），而不是 2015-16 年。然而，即使使用 RONI，14 个模型中有 11 个模型的多模型中位数也显示这将是一次破纪录的事件。

Putting the two together: models give a ~91% chance of a record peak in Niño 3.4 terms and ~77% in RONI terms this year. Whichever way you slice the index, the forecast says the same thing: this is more likely than not to be the strongest El Niño ever observed. 综合来看：模型显示今年 Niño 3.4 指数创下历史峰值的可能性约为 91%，RONI 指数创下历史峰值的可能性约为 77%。无论从哪个指标来看，预报结果都指向同一个结论：这极有可能是史上观测到的最强厄尔尼诺现象。

So how did we get here? The forecast has been building all spring. The figure below shows how each model’s projection evolved from its March run through its July run, against observed monthly conditions. 那么我们是如何走到这一步的呢？预报在整个春季不断增强。下图显示了每个模型的预测如何从 3 月份的运行到 7 月份的运行演变，并与观测到的月度情况进行了对比。

Nearly every panel shows the same thing: each successive run warmer than the last, across five months and thirteen independent modeling systems. This pattern of sustained revision as initialization improves is the classic signature of a real intensifying event rather than model noise. The reason is visible in the black line: observed conditions kept outrunning the forecasts. 几乎每个面板都显示出同样的情况：在五个月和十三个独立的建模系统中，每一次连续的运行都比上一次更热。这种随着初始化改进而持续修正的模式，是真实增强事件的典型特征，而非模型噪声。原因在黑线中清晰可见：观测到的实际情况不断超过预报值。