It is possible that global temperatures surpassed 1.5°C of warming a decade ago.

The 1.5°C limit was exceeded in 2010 or 2011, and the world is already 1.8°C warmer than it was before the industrial revolution, according to researchers using sponges to find out how seawater and air temperatures in the Caribbean have changed through 2018. The researchers who investigated this claim. Past 300 years.

“The increase in Earth's average surface temperature was 0.5 degrees Celsius greater than currently accepted estimates.” Malcolm McCulloch at the University of Western Australia. “What our research shows is that global warming scenarios are 10 years away, or even further.”

But other climate scientists argue that data from a single region is not a reliable way to understand past global temperatures.

The 2015 Paris Agreement called on countries to limit global warming to 1.5 degrees Celsius above pre-industrial levels, but it did not define exactly what this meant. So climate scientists compiling the Intergovernmental Panel on Climate Change (IPCC) report defined it as the average temperature from 1850 to 1900.

By this time, the Earth had already begun to warm as a result of emissions from burning fossil fuels. However, because there were few temperature measurements before 1850, there is great uncertainty about how much warming was caused by fossil fuels during the early industrial era. Therefore, choosing 1850–1900 as the baseline was pragmatic.

But McCulloch and his colleagues think they have discovered exactly what fossil fuel-induced warming was early on after analyzing samples of very long-lived sponges (Ceratoporella nicolsoni) forms a calcium carbonate skeleton.

The 10-centimeter-wide corpora cavernosa could be about 400 years old, team members say amos winter at Indiana State University. “These sponges grow very slowly.”

The sponges were collected by divers at depths of 33 to 91 meters off the coast of Puerto Rico. Although the original goal was to study the ocean's pH in the past, the researchers also measured the ratio of strontium to calcium, which varied with water temperature when calcium carbonate was formed.

Researchers noticed a close correlation between temperatures “recorded” by sponges and the average surface temperature of the Earth measured by instruments, especially after 1960, when measurements became more reliable. That means there is.

“This is kind of a serendipitous discovery, but the connection is very strong,” McCulloch says. “They are changing proportionately to the world average. The main differences occur when instrumental records are the poorest.”

The researchers therefore calculated the average global temperature before the industrial revolution back to 1,700 degrees Celsius, assuming that the sponges accurately reflected this.

The researchers believe their study should be taken into account when assessing whether the IPCC has exceeded the 1.5°C limit. “The bottom line is yes, the IPCC should take this issue seriously,” McCulloch said.

He also thinks climate modelers need to take the findings into account. If previous carbon emissions are causing more warming than thought, the impact of further emissions may be underestimated, he says.

But other climate scientists are far from convinced. “In my view, it would be imprudent to claim that an instrumental record is wrong based on paleocavernoids from one region of the world,” he says. michael man at the University of Pennsylvania. “That doesn't make sense to me. That said, our own early research supports the idea that there was at least another 0.2 degrees Celsius of warming by the late 19th century.”

In fact, anthropogenic warming may have started thousands of years ago. According to the early Anthropocene hypothesis proposed by William Ruddiman The University of Virginia announced that the first farmers' clearing of forests and creation of rice paddies produced enough carbon dioxide and methane to stop the planet from cooling and entering a new ice age.

Recent studies by other researchers have provided increasing evidence to support this hypothesis, but it is still far from being widely accepted.