What is El Niño, what causes it and can we reduce the risks?

Cracked ground at the dried-up Guarne Lagoon in Arví Park amid drought conditions linked to the El Niño phenomenon in Medellin, Colombia, . Photograph: Juan David Duque/Reuters View image in fullscreen Cracked ground at the dried-up Guarne Lagoon in Arví Park amid drought conditions linked to the El Niño phenomenon in Medellin, Colombia, . Photograph: Juan David Duque/Reuters Explainer What is El Niño, what causes it and can we reduce the risks? This year’s ‘godzilla’ climate phenomenon has already broken temperature records. We ask a climate scientist what is happening This year’s huge El Niño, which comes less than two years since the last one, has already broken temperature records. To understand what is happening, and why, the Guardian interviewed Prof Mat Collins, a climate scientist at the University of Exeter, the author of some of the world’s most important climate reports and an expert on the dynamics of the El Niño southern oscillation. View image in fullscreen Mat Collins. Photograph: supplied What is El Niño? It is a natural climate pattern that affects large parts of the world, often bringing higher temperatures, more droughts and floods. This occurs when the normally cool, dry east Pacific becomes warmer and wetter, shifting rainfall patterns in the tropical Pacific and with other impacts far beyond that. It usually occurs every three to seven years, but is very erratic. The last one was in 2023-24. What’s the best way to describe the relationship between El Niños and human-caused global heating? The easiest way to think about this is that they are two separate things that layer on top of each other. So if you’ve already got drought conditions as a result of global warming, then an El Niño is going to exacerbate that. The harder question is how they interact with each other. With our models, we can use hundreds of years of simulations to work that out but we lack the data to do that from the observational record, although some palaeoclimate reconstructions suggest the present day frequency of El Niño is quite unusual. How strong is this year’s El Niño? Some are calling it a ‘godzilla’ or ‘super El Niño’ It has already broken records and could be on course to be the strongest in a thousand years. The sea surface temperature of the El Niño region of the Pacific has already reached the previous 2015 high of 3C above average, which is almost unthinkable.