Global warming rate has nearly doubled since 2015, analysis of five datasets confirms

The number is 0.35 degrees Celsius per decade. That is how fast the planet has been warming over the past ten years, depending on which temperature dataset you consult. From 1970 to 2015, the rate was just under 0.2 degrees per decade. The warming has not merely continued. It has accelerated.

A study published in Geophysical Research Letters by researchers at the Potsdam Institute for Climate Impact Research (PIK) provides the first statistically rigorous demonstration of this acceleration. After stripping out the natural fluctuations that can mask long-term trends, the acceleration emerges with over 98% statistical confidence across all five major global temperature datasets.

Filtering the noise

Global average temperatures do not rise in a smooth line. Year-to-year fluctuations driven by El Nino events, volcanic eruptions, and solar cycles can temporarily boost or suppress temperatures, creating enough noise to obscure changes in the underlying warming rate. To detect whether the rate itself has changed, the researchers filtered these known natural influences from five established temperature records: NASA, NOAA, HadCRUT, Berkeley Earth, and ERA5.

Even after correction, 2023 and 2024 remain the two warmest years since instrumental records began in 1880. El Nino and the solar maximum made them somewhat warmer than they would have been otherwise, but even after removing those effects, both years stand out.

Two statistical tests, same answer

The research team applied two independent statistical approaches. The first was a quadratic trend analysis, which tests whether a curve fits the data better than a straight line. The second was a piecewise linear model that objectively identifies the timing of any change in the warming rate without the researchers specifying when to look.

Both methods pointed to the same conclusion: the warming rate shifted upward around 2013 or 2014, and the acceleration has been sustained since. The consistency across methods and datasets makes this finding difficult to attribute to a statistical artifact or a quirk of any single temperature record.

The study does not explain why

Lead author Stefan Rahmstorf and co-author Grant Foster, a US statistics expert, are careful to distinguish between detecting the acceleration and explaining it. Their study establishes what has happened in the observational record. It does not identify the specific causes of the increased warming rate.

Several hypotheses are in circulation among climate scientists. Reduced aerosol emissions from shipping and industrial sources may have diminished the cooling effect that air pollution provides. Changes in cloud cover may be allowing more solar radiation to reach the surface. And the basic physics of greenhouse gas accumulation predicts some acceleration as concentrations continue to rise. Climate models show that an increasing warming rate is within the scope of current projections, according to the authors, but pinpointing the dominant driver requires further research.

Paris Agreement implications

The 2015 Paris Agreement set a goal of limiting warming to 1.5 degrees Celsius above pre-industrial levels. If the current warming rate of 0.35 degrees per decade persists, the 1.5-degree threshold would be breached as a long-term average before 2030.

Whether that happens depends on emissions trajectories. The warming rate is not fixed by physics alone; it responds to how quickly humanity reduces carbon dioxide emissions from fossil fuels. A rapid decline in emissions could slow the rate; continued delays would lock in further acceleration. The 0.35 degrees per decade figure describes recent history, not an inevitable future.

Context and caveats

A decade is a short period for climate statistics. While the statistical significance is high, extending the analysis over longer future periods will either confirm the acceleration as a sustained shift or reveal it as a temporary excursion within natural variability. The authors note that the current rate is higher than any previous decade since 1880, but that distinction comes with the inherent uncertainty of any record that spans less than 150 years.

The study also does not make predictions. It characterizes the current state of warming, using the most rigorous statistical treatment available, and leaves the question of causation and future trajectory to subsequent research. What it does establish, with high confidence, is that the pace of warming the world is experiencing today is measurably faster than what came before.