The landmark report from the UN’s Intergovernmental Panel on Climate Change published last month warned that humans needed to reduce greenhouse gas emissions 45 percent below 2010 levels by 2030 for us to have a shot at limiting global warming to 1.5 degrees Celsius above pre-industrial levels.
Now, another study published in Nature Wednesday found we might have even less time than that. This is because the oceans have been absorbing much more heat than previously calculated, meaning the earth is more sensitive to carbon dioxide emissions than scientists thought.
“We thought that we got away with not a lot of warming in both the ocean and the atmosphere for the amount of CO2 that we emitted,” research leader and Princeton University geoscientist Laure Resplandy told The Washington Post. “But we were wrong. The planet warmed more than we thought. It was hidden from us just because we didn’t sample it right. But it was there. It was in the ocean already.”
How much more warming is this?
In the past 25 years, the oceans have warmed 60 percent more than previously thought.
What does this mean?
It means that policy makers now have even less leeway when it comes to reducing greenhouse gas emissions if they want to keep warming to 1.5 or even 2 degrees above pre-industrial levels. The findings reduce the total amount of carbon dioxide humans can safely burn before crossing those thresholds by 25 percent.
They also have implications for the ocean-related impacts of climate change: the health of marine life and the pace of sea level rise.
“A warmer ocean will hold less oxygen, and that has implications for marine ecosystems,” Resplandy told BBC News. “There is also sea level, if you warm the ocean more you will have more thermal expansion and therefore more sea level rise.”
How do they know?
The scientists didn’t measure ocean temperatures directly. Instead, they calculated the amount of oxygen and carbon dioxide released by the oceans, which let off the two gases as they warm.
Before, researchers relied on a set of around 4,000 Argo floats that recorded salinity and temperature, but could only give accurate data back to 2007, when the floats were installed. This new method allows for accurate estimates back to 1991. Scientifically, it’s an exciting breakthrough.
“I feel like this is a triumph of Earth-system science. That we could get confirmation from atmospheric gases of ocean heat content is extraordinary,” University of Arizona oceanographer Joellen Russell told The Washington Post. “You’ve got the A team here on this paper.”
Now we just need to get the A team in on meaningful climate action!
2017 Was the Hottest Year on Record for Oceans https://t.co/yCUATPhyPx @TheCCoalition @ClimateCentral @wattsupwiththat
— EcoWatch (@EcoWatch) January 28, 2018
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