Researchers examined ice cores from Antarctica to trace human-driven climate change over the past two millennia. Ice cores offer a record of historical atmospheric conditions, allowing scientists to evaluate warming trends before widespread industrialization. "Our study shows that human societies have caused more than 1.5 degrees of long-term warming,” said Piers Forster, a co-author from the University of Leeds. However, Forster clarified that this does not automatically mean the Paris Agreement’s threshold has been breached, as roughly 0.18 degrees Celsius of this warming occurred before systematic temperature records began.

Currently, the Intergovernmental Panel on Climate Change (IPCC), the United Nations body that assesses climate science, uses data from 1850-1900 as the pre-industrial baseline, marking the onset of recorded global temperatures. Yet, researchers argue that greenhouse gas emissions and human-caused warming were rising even earlier, making the IPCC baseline potentially less accurate. Using ice core data, the researchers recalculated the relationship between global surface temperatures and carbon dioxide levels, extending their analysis to 2,000 years ago. Their results, published in Nature Geoscience, reveal that by 2023, long-term human-caused warming has already reached approximately 1.49 degrees Celsius, with an error margin of 0.11 degrees Celsius, suggesting warming likely above 1.5 degrees.

This analysis points to around 0.2 degrees Celsius of warming already embedded within the 1850-1900 baseline. If factored into today’s warming calculations, it suggests the planet is closer to breaching the Paris Agreement limits than previously estimated. Although the 1.5-degree target may appear inevitable, urgent actions could slow the rate of warming and delay reaching this threshold. Forster emphasized the importance of continued commitment to the Paris Agreement’s objectives, stressing that “delivering action commensurate with the noble Paris goal is more important than ever.”

In sum, the study challenges the adequacy of the traditional pre-industrial baseline, suggesting that human activities may have triggered global warming earlier than the IPCC records reflect. This research underscores the urgency of robust climate action and emissions reductions, emphasizing the necessity of meeting the Paris Agreement targets to mitigate climate risks. By accounting for early, pre-industrial warming, this study paints a clearer picture of our climate position, reinforcing the need for swift and effective climate interventions.

(This article is a reworked version of a PTI feed)