Earth’s temperature has been climbing for decades.Credit: Mark J. Terrill/AP/Alamy Earth’s temperature has surged in the past two years, and climate scientists will soon announce that it hit a milestone in 2024: rising more than 1.5 °C above pre-industrial levels . But is this sudden spike just a blip in the climate data, or an early indicator that the planet is heating up at a faster pace than researchers thought? Global warming is on the cusp of crucial 1.5 °C threshold, suggest ice-core data That question has been at the centre of numerous studies, as well as a session at last month’s meeting of the American Geophysical Union (AGU) in Washington DC. Some scientists argue that the spike can be mostly explained by two factors. One is the El Niño event that began in mid-2023 — a natural weather pattern in which warm water pools in the eastern tropical Pacific Ocean, often leading to hotter temperatures and more-turbulent weather. The other is a reduction over the past few years in air pollution, which can cool the planet by reflecting sunlight back into space and seeding low-lying clouds. Yet neither explanation fully accounts for the temperature surge, other researchers say. Clouds clearly played a part, according to a study in Science , published in December just before the AGU meeting 1 . A research team identified a reduction in low-lying cloud cover across parts of the Northern Hemisphere and the tropics that, combined with the El Niño, was large enough to explain the temperature spike in 2023. But the cause of this decrease — and whether it can be chalked up to normal climate variations — remains a mystery, the authors say. Decreased air pollution alone doesn’t seem to explain it. They suggest that global warming itself could be causing […]