The actions that policymakers take in the next couple of years will have "profound impacts on global climate, ecosystems and human societies" for the next 10,000 years and beyond, warns a new report that examines the long-term consequences of the so called "fossil fuel era."
The agreement hashed out at the COP21 Paris climate talks "leaves a lot of leeway" for countries to postpone making critical cuts to their emission outputs—"more than the climate system allows," said report co-author Patrik Pfister from the Oeschger Centre for Climate Change Research at the University of Bern.
The study, published Monday in the journal Nature Climate Change and last month in the open-access journal Environmental Research Letters, warns that delaying global carbon emission reductions by even ten years will have a profound impact on long-term "Earth system variables," such as peak atmospheric warming, sea level rise (SSLR), and ocean acidification.
"Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century," the report states. "The focus on this 250-year window, however, obscures some of the most profound problems associated with climate change."
For example, if global carbon emissions continue to increase at their current rate, peak committed temperatures will rise 3–7.5 times as fast as the global average. Or as Pfister explains, "In 10 years without global reductions, a 2.5°C target will have become about as ambitious as the 2°C target is today."
The long-term impact on the world's oceans is equally grim.
Even if climate change is limited to 2°C, sea levels will still rise by 25 meters over the next 2,000 years—and stay at those levels for at least 10,000 years—significantly impacting the current global landscape, thus driving mass migrations of humans and animals. However, if the burning of fossil fuels continues unabated, the sea could rise as much as 50 meters, "changing the map of the world," as the Guardian notes.
"For islands and coastal cities, the timing and rate of global emission reductions is therefore of existential importance," says Pfister.
What's more, ongoing emissions will only worsen ocean acidification. The study's climate models found that a "near-complete loss" of healthy marine ecosystems such as coral reefs "becomes imminent if emission reductions are delayed by few years to decades...depending on the achievable reduction rate."
"The long-term view sends the chilling message of what the real risks and consequences are of the fossil fuel era," said climate physicist Thomas Stocker, also with the University of Bern, who helped conduct the study. "It will commit us to massive adaptation efforts so that for many, dislocation and migration becomes the only option."
The authors conclude: "The next few decades offer a brief window of opportunity to minimize large-scale and potentially catastrophic climate change that will extend longer than the entire history of human civilization thus far."
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