The big picture is that global warming, and the urgent need for emission reductions to minimize the risk of dangerous climate change, has been brought forward for at least a decade; so this is a major change to thinking about global warming. Malcolm McCulloch, Lead-author of the study and marine geochemist.
A new study published in the journal Nature has found that sclerosponges found off the coast of Puerto Rico behave like a time capsule. They hold data on ocean surface temperatures going back 300 years. Like tree rings the sponge layers tell the story of recent ocean warming.
The research found that the Earth has passed one climate threshold (1.5 C) and is galloping at full speed to break the 2.0 C threshold by the end of this decade. The study finds we have warmed by 1.7C and not 1.2 or 1.3 celsius.
They found human-caused warming may have started earlier than currently assumed and, as a result, global average temperature may have already warmed more than 1.5 degrees Celsius above pre-industrial levels. Researchers say the results also suggest global temperature could overshoot 2 degrees of warming by the end of the decade.
Under the 2015 Paris Agreement, countries pledged to restrict global warming to less than 2 degrees above pre-industrial levels, with an ambition to limit it to 1.5 degrees. The pre-industrial era — or the state of the climate before humans started burning large amounts of fossil fuels and warming the planet — is commonly defined as 1850-1900.
The study authors argue their findings suggest the pre-industrial era should be pushed further back to between the 1700s and 1860. Changing that baseline would mean the world has already warmed at least 1.7 degrees (scientists say long-term global warming currently stands at between 1.2 to 1.3 degrees).
“The big picture is that global warming, and the urgent need for emission reductions to minimize the risk of dangerous climate change, has been brought forward by at least a decade,” Malcolm McCulloch, lead author of the study and marine geochemist at the University of Western Australia, said at a news briefing. “So, this is a major change to thinking about global warming.”
With the help of deep-sea divers, six specimens of Ceratoporella nicholsoni – a sponge that can take hundreds of years to grow between 10cm and 15cm – were removed from areas off the coast of Puerto Rico and the US Virgin Islands.
As the sponges grow, they store strontium and calcium in a ratio that relates directly to the temperature of the water around them.
McCulloch and colleagues reconstructed global ocean temperatures over the past 300 years from signals found in the sponges and then combined them with land-based temperatures to give an estimate of global heating.
The sponges grow deep enough to be unaffected by natural fluctuations in temperature and in an area of the ocean, the authors said, where temperature changes closely match the global average.
Some scientists have pushed back on this study. It is too controversial, too dicey, too controversial for the public to understand paraphrasing other scientists not involved in the study, the articles that I have read say. One Caribbean sponge is not representative of the planet as a whole. It is an interesting study on the warming of the Caribbean but can’t be applied to the entirety of the globe, says another. Current data sets seem to confirm that the Puerto Rican study may be on to something.
It’s 67 degrees in my neck of the woods.