A groundbreaking study on sea sponges in the Caribbean suggests that Earth may have already surpassed the critical 1.5 degrees Celsius warming threshold, potentially accelerating towards a 2-degree rise, as revealed by researchers.
Examining 300 years of ocean temperature records preserved within Caribbean sea sponges, the findings published in Nature Climate Change indicate a concerning trend. Global mean surface temperatures might have exceeded 1.5 degrees Celsius, with projections hinting at a 2-degree Celsius increase by the end of the decade.
While the Paris Agreement aimed to limit global warming to 1.5 degrees Celsius since the Industrial Revolution, the urgency to keep temperatures well below this mark becomes increasingly apparent. Climate scientists express concern about the diminishing likelihood of achieving this goal.
The study focuses on sclerosponge skeletons in the eastern Caribbean, where natural temperature variability is lower. Analysis reveals stable temperatures from 1700 to 1790 and 1840 to 1860 during the pre-industrial period, with volcanic-related cooling causing a gap. Warming linked to human activity became evident from the mid-1860s, emerging distinctly by the mid-1870s—approximately 80 years ahead of instrumental sea surface records.
Sclerosponges, long-lived species recording chemical changes in their calcium carbonate skeletons, act as natural archives of ocean temperatures. Amos Winter, a professor at Indiana State University, emphasized their exclusivity to the Caribbean, requiring divers to descend up to 100 meters below the sea surface for sample collection.
The study’s implications for global warming projections are profound. The researchers estimate that Earth may have already experienced 1.5 degrees Celsius of warming, with a mean surface warming of 1.7 Celsius potentially occurring between 2018 and 2022.
Malcolm McCulloch, lead author and professor of isotope geobiochemistry at the University of Western Australia, highlighted the unexpected early onset of the industrial era of warming in the mid-1860s. He stated, “Since then, global mean surface temperatures, indicating global warming, have been half a degree greater than the current accepted estimates.”
These revelations challenge prevailing climate estimates, underscoring the urgency for immediate and aggressive climate action to mitigate the escalating impacts of global warming.
