by If temperature-tracking sea sponges are to be believed, climate change has progressed much further than scientists had anticipated.
A new study using ocean organisms called sclerosponges to measure average global temperatures suggests that the world has already warmed by around 1.7 degrees C over the past 300 years – at least one and a half degrees Celsius more than the scientific consensus. outlined in United Nations reports.
The result, published Monday in the journal Nature Climate Change, is alarming, but some scientists say the study authors’ conclusions extrapolated too much about global temperatures than can be reliably gathered from sea sponges.
But the study hits on an important question: How much warmer was the world when fossil fuel-powered machinery was chugging away but people weren’t very organized about measuring temperatures around the world? Scientists say it’s a critical question and something they need to understand better.
The authors of the study say that industrialization before 1900 had a greater impact than scientists previously realized, that its effect is captured in the skeleton of sponges that are centuries old, and that the baseline we use to talk about the politics of climate change. wrong
“They basically represent the warming industrial era that started earlier than we thought, in the 1860s,” Malcolm McCulloch, lead author of the study who is a professor of geochemistry at the University of Western Australia, said of the sponges. “The big picture is that the global warming clock for emissions reductions to minimize the risk of dangerous climate has been moved forward by at least a decade.”
Scientists not involved in the study said colleagues were grappling with how much warming occurred in the early years after the industrial revolution but before more reliable temperature records became available.
“This is not the only attempt to revisit what we call the pre-industrial baseline that suggests we may be missing warming increments in the 19th century,” said Kim Cobb, a paleontologist and oceanographer. at Brown University who is the director of the University. Brown Institute for Environment and Society. “This is an area of uncertainty and importance.”
The United Nations Intergovernmental Panel on Climate Change (IPCC) estimated in its latest assessment of global warming that global surface temperatures have risen by up to 1.2 degrees C since pre-industrial times.
Some scientists think that the IPCC process – which requires consensus – yields conservative results. Scientists who study the Earth’s ice, for example, are concerned that the Earth is approaching ice sheet tipping points earlier than expected and that the IPCC’s sea level rise projections are far too low.
Cobb, who did not contribute to the Nature Climate Change study, said it would take a lot of evidence to change what scientists refer to as the pre-industrial baseline, but also that other researchers have found some indicators that warming is not being adequately accounted for before the 1900s. .
“It is not yet known how large this additional warming increment really is. Is it important to study this? Could we be missing a tenth of a degree – yes – it looks like it’s been investigated in the last 6-10 years,” Cobb said.
Sclerosponges are one of many climate proxies that scientists use to gather information about past climate conditions. With sclerosponges, skeletal growth layers serve a similar purpose to marine biologists as rings within a tree serve those working in forests.
Sclerosponges grow slowly and the chemical content of their skeleton changes as they grow, based on their surrounding temperature. That 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. The creatures can grow and add layers to their skeleton for hundreds of years.
“These are unique specimens,” McCulloch said.
The study authors collected sponges from waters at least 100 feet deep off Puerto Rico and near the island of St. Croix, analyzed the chemical composition of their skeletons, charted their results and compared their data to sea surface temperature measurements from 1964 to 2012, finding closely matched trends.
The sponge skeleton data dates back to 1700, which is longer than reliable human records. This gives scientists a longer reference point to estimate what the temperature was before the demand for fossil fuels. The researchers think it does a better job than other data sets, some of which were calculated using 19th-century temperature measurements from ships crossing the ocean.
The sponge data shows that temperatures began to rise in the 1860s — before what the United Nations Intergovernmental Panel on Climate Change estimates.
However, some outside researchers said that the study may be drawing too much from any kind of proxy measure, especially when the data is tied to only one location on Earth.
“People should be careful in assuming that proxies from one part of the Atlantic always represent 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 are likely. “around.”
The authors of the study said they think the waters off Puerto Rico are still relatively consistent and reflect global change as well as anywhere in the world.
The findings suggest that humanity has already crossed political guardrails, such as world leaders’ goal of limiting warming to 1.5 degrees C.
Cobb said more work should be done with sclerosponges to make sure this work is accurate. And no matter how far we have already pushed the Earth’s temperature, humanity must prevent the production of greenhouse gases.
“Every increase in warming brings a lot of increased climate impacts and worse climate impacts,” Cobb said. “We are already living with warming increments that are not safe. … The position has not changed.”
This article was originally published on NBCNews.com
