If temperature-tracking sea sponges are to be trusted, climate change has progressed much further than scientists predicted.
A new study using ocean organisms called sclerosponges to measure average global temperature shows that the world has already warmed by about 1.7 degrees Celsius in the last 300 years; This is at least half a degree Celsius higher than the scientific consensus laid out in United Nations reports.
The finding, published Monday in the journal Nature Climate Change, is surprising, but some scientists say the study authors’ conclusions predict much more about global temperature than what can be safely obtained from sea sponges.
But the study raises an important question: How much warmer did the world get when fossil fuel-powered machines were running but people were not very organized in measuring temperatures around the world? Scientists say this is a critical question and needs to be better understood.
The study’s authors found that pre-1900 industrialization had a larger impact than scientists had previously realized, its impact captured in the skeletons of centuries-old sponges, and the basis we use to talk about climate change policies may be that I was wrong.
Malcolm McCulloch, lead author of the study and professor of geochemistry at the University of Western Australia, said of the sponges: “Basically, they show that the industrial warming period started earlier than we thought, in the 1860s.” “The big picture is that the global warming clock for emissions reductions has been brought forward by at least a decade to minimize the risk of a dangerous climate.”
Scientists not involved with the study said their colleagues were grappling with how much warming occurred in the early years after the industrial revolution but before temperature records became more reliable.
“This is not the only effort to revisit what we call the pre-industrial baseline and suggest that we may be missing the 19th-century warming spikes,” said Kim Cobb, a paleoclimate and oceanographer at Brown University. Brown Institute on Environment and Society. “This is an area of uncertainty and importance.”
In its latest assessment of global warming, the United Nations Intergovernmental Panel on Climate Change (IPCC) estimates that global surface temperatures have increased by 1.2 degrees C since pre-industrial times.
Some scientists think that the IPCC process, which requires consensus, produces cautious results. For example, scientists who study Earth’s ice have expressed concern that Earth’s ice sheet is approaching tipping points sooner than expected and that the IPCC’s sea level rise estimates are too low.
Cobb, who did not contribute to the Nature Climate Change study, said a lot of evidence is needed to change what scientists call the pre-industrial baseline, but other researchers have found some indication that warming before the 1900s was not adequately accounted for. .
“It is currently unknown how large this extra warming increase actually is. Is it important to study this? Cobb said, “Yes, could we be missing a tenth of a degree that has emerged from research over the last 6 to 10 years?” said.
Sclerosponges are one of many climate mediators that scientists use to gather information about past climate conditions. In sclerosponges, skeletal growth layers serve a similar purpose to marine biologists as the rings inside a tree serve those working in forests.
Sclerosponges grow slowly, and as they grow, the chemical content of their skeleton changes depending on the environmental temperature. This means scientists can track temperatures by looking at the ratio of strontium to calcium as the creatures grow steadily.
Each half-millimeter of growth represents about two years of temperature data, the study says. Living things can grow and add layers to their skeletons over hundreds of years.
“These are truly unique specimens,” McCulloch said. “The reason we were able to obtain this unique data is because of the special relationship these animals have with the environment.”
The authors of the study were off the coast of Puerto Rico and St. They collected sponges from waters at least 100 feet deep near the island of St. Croix, analyzed the chemical composition of their skeletons, charted their findings, and compared their data to sea surface temperature measurements from 1964 to 2012. trends closely matched.
Sponge skeleton data dates back to 1700, which is longer than reliable human records. This gives scientists a longer reference point to evaluate what temperatures were like before fossil fuels became popular. The researchers think it does a better job than other data sets, some of which were calculated using temperature measurements taken from seagoing ships in the 19th century.
Sponge data show that temperatures began rising in the 1860s, before the date assessed by the United Nations Intergovernmental Panel on Climate Change.
But some outside researchers have said that too much can be gained from the study’s uniformly representative measurement, especially when the data is tied to a single location on Earth.
“People should be careful when assuming that proxies from one part of the Atlantic always reflect the global average,” Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, said in an emailed statement, adding that the author’s claims were likely spurious. “Don’t overdo it.”
The study authors said they think the waters off Puerto Rico remain relatively consistent and reflect global change as much as anywhere else in the world.
The results show that humanity has already overcome political hurdles, such as world leaders’ goal of limiting warming to 1.5 degrees C.
More studies need to be done with sclerosponges to make sure this study is conclusive, Cobb said. And no matter how hard we push Earth’s temperatures, humanity needs to curb greenhouse gas production.
“Every increase in warming brings with it a set of increasing climate impacts and worsening climate impacts,” Cobb said. “We are already living with unsafe warming increases. … The business hasn’t changed.”
This article first appeared on NBCNews.com.