Global warming has been accelerating at a faster pace since around 2015, according to a new study from the Potsdam Institute for Climate Impact Research (PIK). By adjusting the global temperature record to remove known natural influences, researchers were able to identify for the first time a statistically significant increase in the rate of warming.
Over the past decade, global temperatures have increased at an estimated rate of about 0.35°C per decade, depending on the dataset analyzed. From 1970 to 2015, the average rate of increase was just under 0.2°C per decade. The more recent trend represents the fastest warming observed in the past decade since thermometer records began in 1880.
“We can now demonstrate that global warming has been accelerating statistically significantly since about 2015,” said Grant Foster, a US statistician and co-author of a study published today in the journal Science. Geophysical Research Letters.
“By removing known natural influences from observational data, we reduce the ‘noise’ and make the underlying long-term warming signal more visible,” Foster added.
Remove natural climate variation from temperature data
Short-term natural events can temporarily increase or decrease global temperatures, making it difficult to detect changes in long-term climate trends. These effects include El Niño events, volcanic eruptions, and fluctuations in solar activity.
To address this challenge, researchers analyzed measured data from five widely used global temperature datasets: NASA, NOAA, HadCRUT, Berkeley Earth, and ERA5. By adjusting the data to account for these natural factors, the researchers were able to more clearly identify the underlying warming trend.
“The adjusted data show an acceleration in global warming since 2015 with over 98 percent statistical certainty, are consistent across all datasets examined and are independent of the analysis method chosen,” explains Stefan Rahmstorff, researcher at PIK and lead author of the study.
Statistical analysis reveals changes in global warming trends
The study focused on determining whether the pace of warming had changed, rather than identifying the causes behind that change.
After accounting for the effects of El Niño and the recent solar maximum, the very warm years of 2023 and 2024 appear slightly cooler in the adjusted analysis. Even with these corrections, it still ranks as the two warmest years recorded since instrumental measurements began. Across all datasets, we see an accelerating trend of warming around 2013 or 2014.
To assess whether the rate of warming has changed since the 1970s, the researchers applied two statistical methods. Quadratic trend analysis and piecewise linear models that identify when changes in warming rates occur.
Impact of the Paris Agreement on climate goals
The study does not attempt to identify the specific reasons behind the accelerated warming. However, the authors point out that climate models already take into account the possibility that the rate of warming will increase over time.
“If the rate of warming of the past decade continues, we will exceed the long-term limit of 1.5°C under the Paris Agreement by 2030,” says Stefan Rahmstorff. “How quickly the planet warms will ultimately depend on how quickly global CO2 emissions from fossil fuels are brought to zero.”
