Earth Is Now Warming at 0.35°C per Decade — Nearly Double the Rate It Held for 45 Years

The rate at which Earth is heating has roughly doubled over the past decade, according to a study from the Potsdam Institute for Climate Impact Research that strips natural variability out of the temperature record and finds a clear break around 2015.

Writing in Geophysical Research Letters, statistician Grant Foster and PIK's Stefan Rahmstorf report that the planet has warmed at about 0.35°C per decade over the past 10 years. From 1970 to 2015, the rate was roughly 0.2°C per decade — a figure so stable for so long that it became a standard planning assumption in climate policy.

The methodological problem the pair set out to solve is that global temperature bounces around for reasons that have nothing to do with greenhouse gases. El Niño and La Niña cycles, volcanic eruptions and the 11-year solar cycle each push the annual number up or down by enough to hide or fake a trend change over any short window. Foster and Rahmstorf removed the known contributions of those three factors from the observational data, leaving what they describe as the underlying signal.

"We filter out known natural influences in the observational data, so that the 'noise' is reduced, making the underlying long-term warming signal more clearly visible," Foster said.

They then tested the adjusted series two ways — fitting a quadratic trend, and fitting a piecewise linear model with a breakpoint — and asked whether the acceleration was statistically distinguishable from chance. "The adjusted data show an acceleration of global warming since 2015 with a statistical certainty of over 98 percent," Rahmstorf said. The acceleration first becomes visible around 2013 and 2014, and it appears in all five major global temperature datasets: NASA, NOAA, the UK's HadCRUT, Berkeley Earth and the ERA5 reanalysis.

The practical consequence is a schedule change. The Paris Agreement's 1.5°C target is defined as a long-term average rather than a single hot year, and most projections had the world crossing it durably in the early-to-mid 2030s. "If the warming rate of the past 10 years continues, it would lead to a long-term exceedance of the 1.5°C limit of the Paris Agreement before 2030," Rahmstorf said — a difference of several years in a timeline that governments have been treating as fixed.

Why the rate would have jumped is the part the study does not settle. The leading candidates under investigation are a measured decline in Earth's albedo, meaning the planet is reflecting less sunlight back to space as sea ice shrinks and low cloud cover changes, and the international shipping industry's switch to low-sulfur fuel, which removed a pollutant that had been inadvertently shading the ocean. The two explanations are not mutually exclusive.

The finding lands in an argument that has been running since 2023, when global temperatures spiked well above what models predicted and researchers split over whether it was a blip or a signal. Foster and Rahmstorf's answer is that it was a signal, and that it began earlier than the spike itself suggested.