Worst-Case Temp. Spikes May Not Happen, May Not Be Necessary For Large-Scale, Deadly Consequences

[hatrack]

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The latest forecasts suggest Earth’s ever-thickening blanket of greenhouse gases has it on a path to warm by more than 2 degrees Celsius by 2100 — a threshold scientists and policymakers have emphasized as one that would usher in catastrophic effects. That is despite efforts to keep warming below 2 degrees Celsius through the global treaty known as the Paris agreement, signed at a U.N. climate change conference in 2015. An October report from the United Nations found that if countries uphold even their most aggressive pledges to reduce output of climate change-inducing greenhouse gases, the planet would warm 2.4 degrees Celsius (4.3 degrees Fahrenheit) by the end of the century.

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If moderating projections of global warming are good news, the bad news is what is already unfolding: Average global temperatures have risen more than 1.1 degrees Celsius, or 1.9 degrees Fahrenheit, since the dawn of industry and combustion engines. And that level of warming is less than half what is likely by the end of the century. Take, for example, a heat wave that descended on the Pacific Northwest in June 2021. Portland and Seattle hit record highs of 116 degrees and 108 degrees, respectively. British Columbia broke Canadian high-temperature records three days in a row, peaking at 121 degrees — more than 40 degrees hotter than normal for that time of year. Scientists quickly determined the heat was so extreme, it could not have occurred without the influence of global warming. Further research found that, in a world with 2 degrees of warming above preindustrial temperatures, it may be a once-in-a-decade sort of event.

Elsewhere, communities are facing the near-likelihood of sustained extreme heat. Half a century ago, about 12 million people endured average annual global temperatures greater than 29 degrees Celsius, or 84 degrees Fahrenheit; that number could grow to 3.5 billion people by 2070, one study found in 2020. Climate scientist Timothy Lenton, one of the study’s co-authors, called that “absolutely shocking.” “I cannot believe we’d cope well in a world where billions of people are exposed to these kinds of extremes,” said Lenton, director of the Global Systems Institute at the University of Exeter in Britain.

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There are also risks that scientists are vastly underestimating the effects that could come with any given level of global warming, which has increased at a pace without precedent in the past 100,000 years. So there is no historical guide to analyzing how ecosystems and societies might react to the changes induced by greenhouse gas emissions. That could mean that, even at some best-case scenarios of warming global leaders are aiming for, effects on the planet would be devastating, Seneviratne said. And Kemp said it’s also important not to assume the latest global warming forecasts will become reality, and to keep in mind that what seems remote remains possible.

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https://www.washingtonpost.com/climate-environment/2023/01/06/climate-change-scenarios-extremes/

[Bayard]

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