A new study shows just how hard it may be to limit global warming to 1.5 degrees Celsius over preindustrial times.
The worlds existing power plants, industrial equipment, vehicles and other CO₂-emitters are on track to pump out enough carbon dioxide to blow past that target by midcentury, researchers report July 1 in Nature. Add in future power plants that are already planned, permitted or under construction, and we could emit enough by 2033 to raise average global atmospheric temperatures by 1.5 degrees, the researchers say.
If we want to limit warming to 1.5 degrees, then “we cannot invest more in fossil fuel power or infrastructure,” says Thorsten Mauritsen, a physical climate scientist at Stockholm University who was not involved with the work. “Everything we do from now has to change direction and not use fossil fuels.”
In the 2015 Paris Agreement on climate change, nearly all the worlds nations agreed to try to reduce greenhouse gas emissions enough to limit warming to “well below” 2 degrees by 2100 (SN: 1/9/16, p. 6). The United States has said it would pull out of the agreement (SN Online: 6/1/17), though the exit wouldnt be complete until 2020.
Still, calls have increased since 2015 for the more ambitious goal of keeping warming to 1.5 degrees. That would mean fewer heat waves, spells of extreme weather and species extinctions (10/27/18, p.7).
Human activity has already increased global temperatures by 1 degree. Emitting an additional 420 to 580 gigatons of CO2 could warm the planet to 1.5 degrees above preindustrial levels, the Intergovernmental Panel on Climate Change estimated in 2018. Current infrastructure could emit that much CO2 between 2018 and as early as 2035, though it could take until 2046 to reach those totals, the new study found.
Existing infrastructure, over its expected lifetime, would emit about 658 gigatons of CO2, says Steven Davis, an earth systems scientist at the University of California, Irvine, and his colleagues. About 41 percent of those emissions would come from China, 9 percent from the United States and 7 percent from the European Union.
Those expected global emissions rise to about 850 gigatons when proposed power plants are included. Thats enough to hit the 1.5 degree budget by 2033, and makes up roughly two-thirds of the 1,170 to 1,500 gigatons of CO2 to reach 2 degrees of warming.
“This analysis … lends some concrete context to what a 1.5 degree target would mean,” Davis says. “These targets that get bandied about are very ambitious” and will require more than a few solar power projects and incremental emissions reductions, he says.
Nearly 10 years ago, Davis and some colleagues performed a census of CO2–emitting infrastructure. The new study updates that census to Read More – Source