Global warming has accelerated significantly since around 2015, according to a study by the Potsdam Institute for Climate Impact Research (PIK). After accounting for natural influences such as El Niño, volcanic eruptions and changes in solar activity, researchers found that Earth has warmed by about 0.35°C per decade over the past 10 years—nearly twice the average rate recorded between 1970 and 2015.
The exact rate varies among temperature datasets, but all five records examined in the study showed evidence that the pace of warming has increased. The findings provide the first statistically significant evidence that the underlying rate of global warming has accelerated, rather than simply continuing at a steady pace.
“We are now able to demonstrate that global warming has been accelerating statistically significantly since about 2015,” said Grant Foster, a US statistician and co-author of the study published in the journal Geophysical Research Letters.
Separating long-term warming from natural fluctuations
Identifying a change in the fundamental pace of global warming is more difficult than comparing annual temperatures. Natural climate patterns can temporarily make the planet warmer or cooler, potentially obscuring the long-term trend.
El Niño, for example, can raise global temperatures temporarily by releasing heat stored in the tropical Pacific Ocean into the atmosphere. Volcanic eruptions can have the opposite effect: particles released into the atmosphere can reflect sunlight back into space. Changes in solar activity can also alter the amount of energy Earth receives from the Sun.
To account for these effects, the researchers mathematically adjusted temperature observations. Removing the known natural influences reduced short-term “noise” and made it easier to examine whether the long-term warming rate had changed.
“By removing known natural influences from observational data, we reduce the ‘noise’ and make the underlying long-term warming signal more visible,” Foster said.
The team analyzed five major global temperature datasets: NASA, NOAA, HadCRUT, Berkeley Earth and ERA5. These widely used records combine observational measurements, and in some cases additional atmospheric data, to track changes in Earth’s temperature.
The results were consistent across the datasets and statistical techniques. Each showed strong evidence that global warming is accelerating.
“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,” said Stefan Rahmstorf, a researcher at PIK and the study’s lead author.
In statistical terms, this means the evidence for a change in the warming trend is strong enough to distinguish it from normal fluctuations in the temperature record with more than 98 percent confidence.
2023 and 2024 remained the hottest years
The researchers also examined whether the exceptionally high global temperatures recorded in 2023 and 2024 had made the recent warming trend appear steeper than it really was.
Both years were unusually hot, partly because of natural influences including El Niño and an increase in solar activity known as solar maximum. During solar maximum, the Sun reaches the most active phase of its approximately 11-year cycle.
After accounting for these factors, the adjusted temperatures for 2023 and 2024 were slightly lower than the original observations. Even so, both years remained the warmest since instrumental temperature records began.
Signs of accelerated warming had already appeared in 2013 or 2014 in all five datasets. This suggests that the result was not caused solely by the unusually high temperatures of the most recent years.
Two methods point to a faster warming rate
To assess whether the warming rate had changed since the 1970s, the researchers used two statistical approaches.
The first, quadratic trend analysis, searches for curved patterns in the temperature record. Such a curve can indicate that warming is accelerating rather than proceeding at a constant rate.
The second approach, a piecewise linear model, compares warming rates across different time periods and identifies when the rate appears to have changed. Unlike methods that assume the acceleration began in a predetermined year, this model estimates the most likely timing of the shift directly from the data.
Both methods supported the conclusion that global warming is accelerating significantly.
What is driving the acceleration?
The study was designed to detect a change in the rate of warming, not to determine precisely which physical processes are causing it. The researchers stress that identifying an acceleration is different from explaining its cause.
Nevertheless, the observed increase is consistent with what current climate models can produce. These models use established physical principles to simulate how the atmosphere, oceans, ice and land respond to changes in the climate system.
The findings therefore do not show that climate models are fundamentally incapable of representing the recent increase in warming. Instead, they provide additional observational evidence that the pace of climate change can vary substantially over time.
Implications for the 1.5°C Paris Agreement limit
The acceleration has important implications for international efforts to limit global warming. Under the Paris Agreement, countries agreed to pursue measures to keep the long-term increase in global temperature to 1.5°C above pre-industrial levels.
The 1.5°C threshold refers to sustained global warming, not a single unusually hot year. Researchers have warned that if the warming rate measured over the past decade continues, Earth could pass that long-term limit sooner than previously expected.
“If the rate of warming of the past decade continues, we will exceed the long-term limit of 1.5 degrees Celsius under the Paris Agreement by 2030,” said Stefan Rahmstorf. “How quickly the planet continues to warm will ultimately depend on how quickly we can reduce carbon dioxide emissions from fossil fuels to zero.”
The study highlights that the climate challenge involves more than a steady rise in global temperatures. The planet is also warming faster in recent years than it did during previous decades. Whether that accelerated pace continues will have a major influence on how quickly the world reaches key climate thresholds.
Source: www.sciencedaily.com
