Overshoot Tucked Into Govt Assumptions; i.e. We'll Blow By 2C Or 2.5C, And Then Fix It Later
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The topic of overshoot has actually been lingering beneath the surface of public discussion about climate change for years, often implied but rarely mentioned directly. In the broadest sense, overshoot is a future where the world does not cut carbon quickly enough to limit global warming to 1.5 degrees Celsius above pre industrial levels — a limit often described as a threshold of dangerous climate change — but then is able to bring the temperature back down later on. A sort of climate boomerang.
Here’s how: After blowing past 1.5 degrees, nations eventually achieve net-zero emissions. This requires not only reducing emissions, but also canceling out any remaining emissions with actions to suck carbon dioxide out of the atmosphere, commonly called carbon removal. At that point, the temperature may have only risen to 1.6 degrees C, or it could have shot past 2 degrees, or 3, or 4 — depending on how long it takes to get to net-zero. The global temperature will begin to stabilize, but it will not decline. So next, nations will aim to scale up carbon removal even further. This will lower the concentration of greenhouse gases in the atmosphere, and bring the temperature on earth back down below 2 degrees C, if not to 1.5, or even lower, by the end of this century.
This possibility of overshoot was first conceived by scientific models that map out potential pathways for climate policy. And in the realm of a computer model, overshoot is a success story. We may fail to meet global climate targets in the next few decades, but hey, we can always turn things around and achieve them by 2100. But (Ed. - ecologist Camille) Parmesan and other scientists are warning that overshoot should not be considered lightly. While the rise in temperature is theoretically reversible, many of the consequences of a temporarily hotter planet will not be.
In a sense, we are on the pathway to overshoot right now. Warming is already dangerously close to 1.5 degrees, emissions are not going down, and existing policies put the world on track to warm 3 degrees by the end of the century. Policymakers are also beginning to seriously invest in carbon removal research and development, however, these solutions are still nowhere near being able to turn temperature rise around. When I reached out to Parmesan to ask about her statement in the press conference, she was eager to talk about overshoot. “It’s so important, and really being downplayed by policymakers,” she wrote. “I think there’s very much an increased awareness of the need for action,” she told me when we got on the phone. “But then they fool themselves into thinking oh, but if we go over for a few decades, it’ll be okay.”
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https://grist.org/science/can-the-world-overshoot-its-climate-targets-and-then-fix-it-later/
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