Oops, scientists may have miscalculated our global warming timeline

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• The Paris Climate Agreement in 2015 set an ambitious (and necessary) goal of keeping global temperatures to 1.5 degrees Celsius above pre-industrial temperatures. But a study says we may have crossed that threshold several years ago.

• Scientists at the University of Western Australia’s Ocean Institute studied long-lived Caribbean sclerosponges and created a timeline of ocean temperatures in the 1700s.

• While the study claims we exceeded 1.5 degrees Celsius of warming in 2020, other scientists question whether data from one part of the world is enough to capture the vast thermal complexity of our oceans.

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Whatever your stance on climate change (it’s real, let’s move on), it’s impossible to miss the almost ubiquitous call to action to “keep temperatures above 1.5 degrees Celsius above pre-industrial levels.” Over the past few years, the somewhat bureaucratic phrase has become a rallying cry for climate activists.

This ambitious goal appeared for the first time after the Paris climate agreement, and describes a kind of climate threshold – if we exceed the long-term average increase in temperature of 1.5 degrees Celsius, and for a few years at those levels, we are going to 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 crossed that threshold. Four years ago.

Published in the journal Nature climate changeThe paper takes an unlikely route to this conclusion by analyzing six sclerosposes, a type of marine sponge that burrows into underwater caves in the ocean. These sponges are commonly studied by climate scientists and “Natural records“Because they grow very slowly. Like, a fraction of a millimeter-a-year slow. This essentially allows them to lock climate data into their limestone skeletons, not completely different like tree rings or ice cores.

By analyzing the ratio of strontium to calcium in these sponges, the team could effectively calculate the temperature of the water since 1700. A house full of sponges in the Caribbean is also a plus, as major ocean currents don’t mess up or distort temperature readings. This data can be especially useful, since the only direct human measurement of ocean temperature dates back to about 1850, when sailors dipped buckets into the ocean. That is why the Intergovernmental Panel on Climate Change (IPCC) uses 1850 and 1900 as its preindustrial baseline. According to the website grist.

“The big picture is that the global warming clock has been brought forward by at least a decade to reduce the risk of dangerous climate change,” said Malcolm McCulloch, lead author of the study. The Associated Press. “Basically, time is running out.”

The study concluded that global warming began nearly 80 years earlier than IPCC estimates, and that we will exceed 1.7 degrees Celsius in 2020. That’s a big “wow, if true” moment, but some scientists are skeptical. One such scientist, speaking with LiveScienceHe said, “Claims that the instrumental record based on paleosponges from one region of the world is wrong … it honestly doesn’t make sense to me.” Other experts want to see more data before fully raising the IPCC’s climate goalposts, which say the Earth is currently hovering around long-term temperature changes. 1.2 degrees Celsius.

Unfortunately, even if the sponges were wrong, there is mounting evidence that we are in the process of crossing the 1.5 degree threshold as we speak. It was the warmest January on record, 1.7 degrees above pre-industrial temperatures. According to New ScientistThis means we are above 1.5 degrees of change for at least a year. It doesn’t jump the long-term average above the 1.5-line, but it’s certainly a sign that we’re fast approaching.

Whatever the percentage, one thing is certain: climate change is a hands-down crisis. To save the planet for future habitability, humans need to reduce emissions urgently – after all, that’s what sea sponges are telling us.

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