Significant acceleration of global warming since 2015

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Global warming has accelerated since 2015, according to a new study by the Potsdam Institute for Climate Impact Research (PIK). After accounting for known natural influences on global temperature, the research team detected a statistically significant acceleration of the warming trend for the first time. Over the past ten years, the estimated warming rate has been around 0.35°C per decade, depending on the dataset, compared with just under 0.2°C per decade on average from 1970 to 2015. This recent rate is higher than in any previous decade since the beginning of instrumental records in 1880.

Global warming rate (in °C per decade) from the Berkeley Earth global temperature data: The blue line shows the linear trends for the time before and after 2015 (light blue the uncertainty range). The red line shows the linear trend for 10‐year windows of the data, at 1-year intervals. Figure credit: PIK

“We can now demonstrate a strong and statistically significant acceleration of global warming since around 2015,” saids *Grant Foster, a US statistics expert and co-author of the study, which was published in the scientific journal Geophysical Research Letters.

“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 added.

Short-term natural fluctuations in global temperature caused by El Niño, volcanic eruptions, and solar cycles can mask changes in the long-term rate of warming. In their data analysis, which is based on measurement data, the two researchers work with five large, established global temperature data sets (NASA, NOAA, HadCRUT, Berkeley Earth, ERA5)

“The adjusted data show an acceleration of global warming since 2015 with a statistical certainty of over 98 percent, consistent across all data sets examined and independent of the analysis method chosen,” explained Stefan Rahmstorf, PIK researcher and lead author of the study.

Study examines statistical acceleration of warming, not its causes
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After correcting for the effects of El Niño and the solar maximum, 2023 and 2024, which were exceptionally warm years, become somewhat cooler, but remain the two warmest years since the beginning of instrumental records. In all datasets, the acceleration begins to become apparent in 2013 or 2014. To test whether the warming rate has changed since the 1970s, the research team applied two statistical approaches: a quadratic trend analysis and a piecewise linear model that objectively determines the timing of any change in the warming rate.

The study does not investigate the specific causes of the observed acceleration. However, climate models show that an increasing rate of warming is fundamentally within the scope of current climate modelling, according to the authors.

“If the warming rate of the past 10 years continues, it would lead to a long-term exceedance of the 1.5° limit of the Paris Agreement before 2030,” said Stefan Rahmstorf. “How quickly the Earth continues to warm ultimately depends on how rapidly we reduce global CO₂ emissions from fossil fuels to zero."