Mild El Niño climatic conditions brewing in the Pacific Ocean will strengthen throughout the year, with an outside chance of a record-breaking event that will further turbocharge already sweltering temperatures around the globe, scientists have forecast. Last month saw a “weak” El Niño form, a periodic climatic event where the circulation of the equatorial Pacific Ocean shifts and its temperature rises, causing knock-on heat around the world, according to an update from the National Oceanic and Atmospheric Administration (Noaa). This Niño, which has replaced a three-year period of its reverse condition, La Niña, which typically cools the globe, will almost certainly strengthen throughout the year, with an 81% chance it will peak with a “moderate to strong intensity” between November and January, Noaa said. There is a one-in-five chance that this event will be of “historic” strength, rivaling the major one experienced in 1997, Noaa said. Even if the record is not threatened, however, “El Niños tend to elevate global mean temperatures, so I would not expect this event to be an exception,” said Michelle L’Heureux, a Noaa meteorologist. The developing event has been closely watched by scientists as it is compounding the excess heat spurred by human activity, primarily the burning of fossil fuels. Last week was, preliminary data suggests, the hottest week ever reliably recorded, following a June that was the hottest ever documented globally. More than 100 million people in the US are currently under heat warnings, with scorching conditions felt across Texas and the south-west in recent weeks. Heatwaves have also roiled China, India, parts of Europe and the Arctic. The heat is not confined to the land, with Noaa confirming on Thursday that ocean surface temperatures were at a record high for a third consecutive month in June, with marine heatwaves sweeping the North Atlantic to the UK, as well as imperiling ailing coral reefs found off Florida. The developing Niño is likely to push the world towards even more record-breaking temperatures, scientists warn, as the tangible impacts of the climate crisis continue to unfold. “We have a major El Niño event on our hands, it will certainly continue to develop, and it will almost certainly contribute to 2023 being the hottest year on record,” said Michael Mann, a climate scientist at the University of Pennsylvania. “The combination of human-caused warming and this emerging event is already wreaking havoc across the northern hemisphere this summer in the form of record heat, drought, wildfires and floods.”