Why Half a Degree Matters

Arts and Sciences

The Paris Agreement from 2015 has a goal to hold the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels, and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius above pre-industrial levels. Now a recent study by Tufts scientists projects that aiming for the lower temperature increase could save coastal ecosystems from the dire consequences of global sea-level change. It also shows that even meeting the Paris targets will result in sizeable sea-level rise.Research studies forecast that warming the planet by more than 2 degrees Celsius will result in not only extreme weather events—floods, wildfires, landslides, and hurricanes—but also catastrophic sea level changes, leading to ecosystem loss and mass migration. As temperatures rise, sea levels rise and directly affect coastal areas.
The researchers found that stabilizing global temperature rise at 1.5 degrees Celsius between now and 2150—which would require a swifter reduction in carbon emissions than under the 2-degree Celsius goal—would lower the impact of sea-level rise significantly; the global average sea-level in 2150 would be about 7 inches—or 17.7 centimeters—less than under a 2-degree Celsius rise.
The study’s lead author, Klaus Bittermann, a postdoctoral student in the Department of Earth and Ocean Sciences, said that the 0.5 degree difference could be a matter of life and death, as ecosystems and populations are overwhelmed by tidal flooding and other ecological changes. “For example, salt marshes and mangroves can be drowned if the local rate of relative sea-level rise exceeds their ecological ability” to adapt, he said.
“Some people might argue there will be no sizable difference between the two targets, so we should aim for the higher one, because it’s easier,” Bittermann said. But the findings challenge that idea. “Those differences turn out to be significant,” he said.
Bittermann did the computational research along with Andrew Kemp, an assistant professor in …

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