Global warming has accelerated since around 2015, according to a new analysis published in the scientific journal Geophysical Research Letters by the Potsdam Institute for Climate Impact Research (PIK).
How Scientists Isolated the Long-Term Warming Signal
Researchers analyzed measurements from five widely used global temperature datasets—NASA, NOAA, HadCRUT, Berkeley Earth, and ERA5—to determine that the planet’s warming rate is climbing faster than historical averages. Over the past decade, global temperatures have risen at an estimated pace of about 0.35 degrees Celsius per decade, depending on the dataset used. By comparison, the average warming rate from 1970 to 2015 hovered just under 0.2 degrees Celsius per decade, making the recent pace higher than any previous decade since instrumental temperature records began in 1880.
“We can now demonstrate a strong and statistically significant acceleration of global warming since around 2015,” says Grant Foster, a US statistics expert and co-author of the study. To separate temporary influences from the broader warming trend, researchers filtered out known natural variations like El Niño and the solar maximum. “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 explains.
Statistical Certainty Across Five Independent Datasets
The adjusted data show an acceleration of global warming since 2015 with a statistical certainty of over 98 percent, according to Stefan Rahmstorf, a PIK researcher and lead author of the study. This high confidence level remains consistent across all five temperature records, independent of the analysis method chosen, meaning the pattern is not the result of random data variation.
Did you know? Even after researchers adjusted for natural drivers like El Niño and the solar maximum—which slightly reduced the extreme warmth recorded in recent years—2023 and 2024 remained the two warmest years since instrumental records began in 1880.
The research team employed two distinct statistical approaches to test whether the temperature curve is bending upward rather than rising at a constant rate. The first was a quadratic trend analysis, and the second was a piecewise linear model that objectively identifies when the rate of warming changes. Both independent methods confirmed that the acceleration began to become visible between 2013 and 2014, solidifying around 2015.
Implications for the Paris Agreement 1.5°C Threshold
While the study was designed to detect and measure statistical acceleration rather than determine its exact underlying causes, the authors noted that current climate models can produce periods where warming speeds up.
“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 warns. He notes that permanently restricting global warming to 1.5 degrees Celsius above preindustrial temperatures ultimately depends on how rapidly global carbon dioxide emissions from fossil fuels are reduced to zero.
Frequently Asked Questions
What caused the acceleration in global warming since 2015?
The study measured and detected the statistical acceleration of warming but did not investigate its specific causes. The researchers noted that an increasing rate of warming falls within the expected behavior of current physics-based climate models.
Which datasets were used in the Potsdam Institute study?
The research team evaluated five major global temperature records: NASA, NOAA, HadCRUT, Berkeley Earth, and ERA5.
Does a single year above 1.5°C mean the Paris Agreement limit is broken?
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