Media release
From: Springer NatureClimate change: Antarctic ice suggests human-induced warming is nearing the 1.5 °C warming limit *PRESS BRIEFING*
Human-induced climate change may have caused approximately 1.5 °C of warming by the end of 2023, compared to before the 1700s, according to a study published in Nature Geoscience. The findings are based on a new approach for assessing the impact of human-induced warming using Antarctic ice core data covering the last two millennia, and suggest that Earth may be closer to the 1.5 °C warming limit than previously thought.
Countries involved in the Paris Agreement have agreed to pursue efforts to keep global temperatures from increasing beyond 1.5 °C above pre-industrial levels, with the Intergovernmental Panel on Climate Change using 1850–1900 global temperature anomaly data as the pre-industrial baseline condition. However, it is known that both emissions and the overall amount of atmospheric carbon dioxide (CO2) were rising well before this period. As such, assessing progress towards the 1.5 °C warming limit depends on having a robust baseline from which to assess the degree of warming that has already occurred.
Andrew Jarvis and Piers Forster reassessed the relationship between global surface temperatures and atmospheric CO2 trends, using Antarctic ice core records to couple with temperature anomaly data and extend their analysis back 2,000 years. They first suggest that, using data from 1850 to 2023, there has been a linear relationship between CO2 and temperature increase. While other factors have influenced temperature trends since 1850, they argue that this linear relationship for the interval is sufficient for a robust assessment of how much warming humans have caused, though it may become non-linear as warming progresses in the future and other climate variables in the Earth system become more pronounced.
The authors then apply this linear relationship to estimate modern warming against a pre-industrial baseline from 13 to 1700 CE — when atmospheric CO2 was approximately 280 parts per million — Jarvis and Forster calculated that human-induced warming likely reached 1.49 °C in 2023, meaning that the 1.5 °C warming threshold has almost been reached. When using the more commonly applied 1850 to 1900 CE interval as a baseline — which the authors argue against owing to uncertain temperature observations at the time and the warming already underway — their human-induced warming estimate is up to 30% more certain than estimates based on other approaches.
The authors acknowledge that their approach does not directly quantify how warming may have been influenced by factors other than atmospheric CO2, though they argue that these factors are incorporated in the linear relationship and that this relationship could be important in tracking changes in the behaviour of the climate system as warming progresses.
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Springer Nature is committed to boosting the visibility of the UN Sustainable Development Goals and relevant information and evidence published in our journals and books. The research described in this press release pertains to SDG 13 (Climate Action). More information can be found here.
