New Climate Pledges More Likely to Prevent Worst of Global Warming

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New Climate Pledges More Likely to Prevent Worst of Global Warming

On November 22, 2021, Posted by , In News, By , With Comments Off on New Climate Pledges More Likely to Prevent Worst of Global Warming

Over 100 nations have issued new commitments to reduce greenhouse gas emissions for the United Nations Conference of the Parties. A new analysis published in the journal Science assessed those new pledges, or nationally determined commitments (NDCs), and how they could shape Earth’s climate.

The study’s authors find the latest NDCs could chart a course where limiting global warming to 2°C (3.6°F) and under within this century is now significantly more likely.

Under pledges made at the 2015 Paris Agreement, the chances of limiting temperature change to below 2 and 1.5°C (2.7°F) by 2100 were 8 and 0 percent, respectively.

Under the new pledges—and if those pledges are successfully fulfilled and reinforced with policies and measures of equal or greater ambition—the study’s authors estimate those chances now rise to 34 and 1.5 percent, respectively. If countries strike a more ambitious path beyond 2030, those probabilities become even more likely, rising to 60 and 11 percent, respectively.

Further, the chance of global temperatures rising above 4°C (7.2°F) could be virtually eliminated. Under the 2015 pledges, the probability of such warming was, at 10 percent, more likely.

“We are so much closer to getting to the 2-degree goal than six years ago when the Paris Agreement was first signed,” said corresponding author Haewon McJeon, a research scientist at the Department of Energy’s Pacific Northwest National Laboratory. “The wave of strengthened climate pledges and net-zero targets significantly increased our chance of staying under 2°C. And we practically ruled out the possibility of the worst climate outcomes of 4 degrees or higher.” But making the 1.5°C limit more likely will take more ambition, cautioned lead author Yang Ou, a postdoctoral researcher at the Joint Global Change Research Institute, a partnership between PNNL and the University of Maryland.

“We find there’s a roughly one in three chance that we’ll stay under 2°C, but even with increased ambition, we’re still far away from getting down to 1.5 degrees in this century.”

Yang Ou

The researchers used an open-source model called the Global Change Analysis Model (GCAM) to simulate a spectrum of emissions scenarios. They then evaluated the probabilistic temperature outcomes for those scenarios.

At one end of the spectrum is a hypothetical future in which current climate mitigation measures and policies remain largely the same through 2100. At the other, nations commit to more ambitious targets for limiting emissions and increasing the global decarbonisation rate. Such modelling illustrates the range of climate outcomes that lie beyond different courses of action.

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