In a statement presenting the study, the Potsdam Institute for Climate Impact Research (PIK) in Germany notes that “the estimated warming rate over the last ten years was around 0.35 degrees Celsius (°C), depending on the dataset, compared with just under 0.2°C per decade on average from 1970 to 2015.”
The research team detected, after accounting for known natural influences on global temperature, “for the first time, a statistically significant acceleration of the warming trend.”
According to PIK, “this recent rate is higher than that of any previous decade since the beginning of instrumental records in 1880.”
“We can now demonstrate a strong and statistically significant acceleration of global warming since around 2015,” said Grant Foster, a statistics expert and co-author of the study published in the scientific journal Geophysical Research Letters. “We filtered out known natural influences from the observational data to reduce the noise, making the underlying long-term warming signal more clearly visible,” he added.
Short-term natural fluctuations in global temperature — caused by the El Niño climate phenomenon, volcanic eruptions and solar cycles — can mask changes in the long-term rate of warming.
The researchers used data from five major databases: NASA, the US National Oceanic and Atmospheric Administration (NOAA), the British HadCRUT (which combines data from the Hadley Centre and the Climatic Research Unit at the University of East Anglia), the American organisation Berkeley Earth, and ERA5, linked to the European Union’s Copernicus programme.
To test whether the rate of warming had changed since the 1970s, the research team applied “two statistical approaches: a quadratic trend analysis and a piecewise linear model.”
Read more: Foundation warns Brussels: oceans must be a “fundamental priority” in future European environmental Law
“The adjusted data show an acceleration of global warming from 2015 with a statistical certainty of more than 98%, consistent across all datasets examined and independent of the analytical method chosen,” explained Stefan Rahmstorf, PIK researcher and lead author of the study.
The study does not investigate the specific causes of the observed acceleration, which begins to become apparent in 2013 or 2014 across all datasets.
According to Stefan Rahmstorf, “if the warming rate of the last ten years is maintained, this will lead to a long-term breach before 2030 of the 1.5°C limit of the Paris Agreement.”
The 1.5°C limit of global warming above pre-industrial average values — broadly considered as before 1750 — was established in the 2015 Paris Agreement on greenhouse gas reduction as the threshold beyond which climate change becomes widespread, irreversible and severely consequential.
“How quickly the Earth will continue to warm ultimately depends on how quickly we reduce global CO2 emissions from fossil fuels to zero,” he noted.
Carbon dioxide (CO2) is the gas that contributes most to the greenhouse effect driving global warming.
