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The Paris Climate Agreements in 2015 set an ambitious (and necessary) goal of keeping global temperatures at 1.5 degrees Celsius above pre-industrial temperatures. But a study says that we may have exceeded that limit several years ago.
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Scientists at the University of Western Australia’s Ocean Institute studied long-living Caribbean sclerosponges and created a chronology of ocean temperature going back to the 1700s.
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While the study claims we exceeded 1.5 degrees Celsius in 2020, other scientists question whether data from just one part of the world is enough to capture the immense thermal complexity of our oceans.
Whatever your position on climate change (it’s real, let’s move on), it’s impossible to miss the call to action almost everywhere to “keep temperatures from exceeding 1.5 degrees Celsius compared to pre-industrial levels.” Over the past few years, the somewhat bureaucratic phrase has become a rallying cry for the climate conscious.
This ambitious target came out for the first time after the Paris Climate Agreement, and describes a kind of climatic threshold—if we go through a long-term average increase in temperature of 1.5 degrees Celsius, and keep at those levels for several years, we will do some serious damage to ourselves and our environment.
Well, a paper from the University of Western Australia’s Ocean Institute has some bad news: the world may have exceeded that limit four years ago.
Published in the journal Nature Climate Changethe paper reaches this conclusion through an unlikely route — it analyzes six sclerosponges, a type of sea sponge that clings to underwater caves in the ocean. These sponges are commonly studied by climate scientists and are called “natural archives“Because they grow so slowly. Like, a fraction of a millimeter a year slowly. This essentially allows them to lock climate data in their limestone skeletons, not at all unlike tree rings or ice cores.
By analyzing the ratios of strontium to calcium in these sponges, the team can actually calculate water temperatures going back to 1700. The sponges home water in the Caribbean is also an advantage, as the major ocean currents do not disturb or distort the temperature readings. This data can be particularly useful, as direct human measurements of sea temperature only go back to around 1850, when sailors threw buckets into the ocean. This is why the Intergovernmental Panel on Climate Change (IPCC) uses 1850 and 1900 as its pre-industrial baseline, according to the website Christ.
“The big picture is that the global warming clock for reducing emissions to reduce the risk of dangerous climate change has been brought forward by at least a decade,” Malcolm McCulloch, lead author of the study, told the Associated Press. “Basically, time is running out.”
The study concludes that the world began to warm approximately 80 years before the IPCC estimates, and that we have already exceeded 1.7 degrees Celsius in 2020. That’s a big “woah, if true” moment, but some scientists are skeptical. One such scientist, talks to him LiveSciencehe said that it “beggars credulity to claim that the instrumental record is wrong based on paleosponges from one region of the world… It honestly doesn’t make sense to me.” Other experts have expressed that they want to see more data before completely changing the IPCC’s climate goal points, which say the Earth is currently hovering around a temperature change of approx. 1.2 degrees Celsius.
Unfortunately, even if the sponges are wrong, there is mounting evidence that we are in the process of crossing that 1.5 degree threshold as we speak. This January was the hottest on record, 1.7 degrees above pre-industrial temperatures. According to New Scientistthis means we have been above 1.5 degrees of change for at least a year. This does not exceed the long-term average on the 1.5 line, but it is certainly a sign that we are fast approaching.
Regardless of the percentage, one thing is certain: climate change is an all-hands-on-deck crisis. In order to save the planet for future habitability, humans need to reduce emissions immediately—after all, sea sponges are telling us so.
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