Sponge by Olly Clarke via Flickr CC
Perhaps it should be net-below-zero.
According to a study in Nature, the planet has already passed the 1.5 °C warming threshold that climate crisis experts are saying is the goal for climate action.
At the 2015 Paris Climate Accords, nations agreed not to exceed 1.5 °C, a main guardrail of climate change. But the problem is that the planet has already passed 1.5 °C of warming, according to a new measuring technique that goes back further in time than current methods. The technique involves dating ancient sponges.
“We have an alternate record of global warming,” said coral-reef geochemist Malcolm McCulloch, at the University of West Australia Oceans Institute in Crawley, and lead author of the study. “It looks like temperatures were underestimated by about half a degree.”
However, McCulloch says that long-lived marine sponges can provide indications of temperature as far back as the eighteenth century. He and his colleagues analyzed the ratio of the elements strontium to calcium in the 300-year-old calcium carbonate skeletons of a coral-like species of sponge, Ceratoporella nicholsoni, that grows off the coasts of Puerto Rico. This ratio changes only with changes in water temperature, making it a sort of thermometer, according to the study published in Nature Climate Change.
The sponges were sampled from one particular section in the Caribbean — the only place where they are found. They were collected at a depth of 33–91 meters, in what’s called the ocean mixed layer. “Sea-surface temperature can be highly variable on top,” McCulloch was quoted as saying. “But this mixed layer represents the whole system down to a couple hundred meters, and it’s in equilibrium with the temperatures in the atmosphere.”
The sponge skeletons suggest that the planet started to warm up in the mid-1860s, during the period currently defined as the pre-industrial baseline.
“The baseline is where we measure our current temperatures from, so when we say 1.5 [degrees of warming], it’s to do with this reference point,” said McCulloch.
McCulloch and colleagues have calculated that global temperatures had in fact increased by 0.5 °C more than what was estimated by the IPCC. “That’s a huge difference relative to the total amount of warming,” says McCulloch. Furthermore, the planet exceeded 1.5 °C of warming by around 2010–2012 and is on track to surpass 2 °C in the next few years.
Climate change is all about calibration and constantly trying to catch up; our planet operates on its own time schedule, no matter how hard we try to understand.
wrdforwrd 