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A controversial new study claims we could break the climate change threshold of 2 degrees Celsius (3.6 degrees Fahrenheit) by the late 2020s, which is faster than current projections. Almost 20 years early.
The study was published February 5 in the journal nature climate changeclaims that Earth’s surface temperature has risen 1.7°C (3°F) above the pre-industrial average by 2020.
However, other scientists have questioned the findings, saying they have major flaws.
Global warming of 2°C is considered a critical threshold, beyond which warming significantly increases the likelihood of catastrophic and irreversible climate collapse. Under the 2015 Paris Agreement, around 200 countries pledged to limit global temperature rise to ideally 1.5°C, but safely below 2°C.
“The big picture is that the global warming clock has been moved forward by at least 10 years to reduce emissions to minimize the risk of dangerous climate change,” said lead author and coral reef expert at the University of Western Australia. said Malcolm McCulloch. Press conference on Thursday (February 1). “This is a major change in the way we think about global warming.”
A key question in climate science is where to set the pre-industrial baseline before the burning of fossil fuels begins to warm the planet. Until the 20th century, ocean temperature records were a nonstandard patchwork of millions of sporadic observations collected by sailors to chart ocean routes.
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To eliminate false records of the past, climate scientists have traditionally looked to natural records of temperature stored in marine animals such as corals, ice and sediment cores, or inside tree grains. Ta.
But scientists still don’t have exact numbers on the extent of post-industrial warming. A recent analysis using the National Oceanic and Atmospheric Administration’s (NOAA) 2023 dataset suggests that the Earth has warmed by 1.34 °C (2.4 °F) above the 1850-1900 average. According to data from the Met Office, the Earth is warming by 1.54 degrees Celsius (2.7 degrees Fahrenheit). .
sponge for knowledge
In search of a better record of 19th century temperatures, the researchers behind the new study looked at a species of sponge called . Ceratoporella nicolsoni In the Caribbean. Known for its rock-hard exoskeleton, C. Nicolsoni They can live for more than a thousand years, extracting strontium and calcium carbonate from seawater and diligently adding layers to their limestone shells.
As ocean temperatures rise, the ratio of strontium to calcium in certain parts of the cancellous bone skeleton decreases, allowing scientists to measure 300 years’ worth of temperature in a cross-section of the cancellous body, similar to reading tree rings. Records can now be measured.
After collecting and analyzing multiple sponges from depths of 100 to 300 feet (30 to 90 meters), the researchers created a temperature record that they say is comparable to the temperature of the entire Earth’s oceans.
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Their findings suggest that warming began in the 1860s, about 40 years earlier than estimated by the United Nations’ Intergovernmental Panel on Climate Change (IPCC).
They found that by 1990, global temperatures had risen by 0.9 degrees Celsius (1.6 degrees Celsius) compared to the newly defined pre-industrial era. In comparison, the IPCC estimates that by this time he will have warmed by 0.4 degrees Celsius (0.7 degrees Celsius).
Research shows that if current heating rates continue, warming is expected to reach 2°C by the end of the 2020s and 2.5°C (4.5°F) by 2040.
problematic waters
Many climate scientists have strongly criticized the new findings. The researchers said they hypothesized that the ocean is well mixed and that the water temperatures recorded by the sponges primarily came from deep layers in response to heating from the sun.
However, some argue that the sea is still an ocean. very complex engine That is, the temperature is far from uniform.
“Skepticism is warranted here. In my view, it would be imprudent to claim that instrument records are wrong based on paleocavernoids collected in one region of the world.” michael manDirector of the Center for Earth System Science at the University of Pennsylvania told Live Science. “Honestly, I don’t understand what that means.”
Camille Parmesanan ecologist at the University of Texas at Austin, IPCC Sixth Assessment Reportpointed out that temperatures in one part of the ocean are unlikely to be representative of ocean temperatures elsewhere. “You can’t extrapolate the entire world ocean from the Caribbean Sea,” Parmesan told his Live Science.
and David ThornalleyA professor of ocean and climate science at University College London also criticized the researchers’ decision to correct the sponge data with global sea surface temperatures, rather than sea surface temperatures in the areas where the sponges live.
Jochem Marotzke, director of Germany’s Max Planck Institute for Meteorology and professor of climate science, told Live Science: “This study fails by a wide margin, failing to support its global claims with solid evidence. ” he said. “The extrapolation from that small ocean to the global scale is simply implausible.” The claim that the increase in Caribbean temperatures since the 1860s is due solely to the sun, rather than ocean mixing, is also implausible. , he added.
Meanwhile, the researchers argue, citing a 2018 paper, that trends in sea surface temperatures in the Caribbean are proportional globally.
Even if a study’s conclusions are questionable, especially regardless of the combination of evidence used or where the baseline is set, this study is an important step forward in global climate information, especially as rapid climate change approaches. scientists said it could still serve as a piece of the jigsaw puzzle.
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