Earth Has Good Chance of Soon Hitting a 'Global Guardrail': UN

There's a two-out-of-three chance that the world will temporarily hit a key warming limit within the next five years, the United Nations weather agency said Wednesday. But it likely would only be a fleeting and less worrisome flirtation with the internationally agreed upon temperature threshold. Scientists expect a temporary burst of heat from El Niño—a naturally occurring weather phenomenon—to supercharge human-caused warming from the burning of coal, oil, and gas to new heights. Temperatures are expected to then slip back down a bit, per the AP. The World Meteorological Organization forecasts a 66% likelihood that between now and 2027, the globe will have a year that averages 1.5 degrees Celsius (2.7 degrees Fahrenheit) warmer than the mid-19th century. The WMO report is based on calculations by 11 different climate science centers across the globe.

• Why it's important: That number is critical because the 2015 Paris climate agreement set 1.5 degrees Celsius as a global guardrail in atmospheric warming, with countries pledging to try to prevent that much long-term warming if possible. Scientists in a special 2018 United Nations report said going past that point would be drastically and dangerously different, with more death, destruction, and damage to global ecosystems.
• When it will happen: "It won't be this year probably. Maybe it'll be next year or the year after" that a year averages 1.5 degrees Celsius, said report lead author Leon Hermanson, a climate scientist at the UK's Met Office.
• Context: Those 66% odds of a single year hitting that threshold in five years have increased from 48% last year, 40% the year before, 20% in 2020, and 10% about a decade ago.

• What's behind it: The world has been inching closer to the 1.5-degree threshold due to human-caused climate change for years. Key in all this is the El Niño cycle. The world is coming off a record-tying triple dip La Niña—three straight years of El Niño's cooler cousin restraining the human-caused warming climb—and is on the verge of an El Niño that some scientists predict will be strong. La Niña somewhat flattened the trend of human-caused warming so that the world hasn't broken the annual temperature mark since 2016, during the last El Niño, a supersized one, Hermanson said. And that means a 98% chance of breaking the 2016 annual global temperature record between now and 2027, the report said. There's also a 98% chance that the next five years will be the hottest five years on record, per the report.

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• Why it's important: Each year at or near 1.5 degrees matters. "We see this report as more of a barometer of how we're getting close, because the closer you get to the threshold, the more noise bumping up and down is going to bump you over the threshold randomly," Hermanson said. He added the more random bumps over the mark occur, the closer the world gets to the threshold.
• Don't panic: Still, climate scientists said what's likely to happen in the next five years isn't the same as failing the global goal. "We don't expect the longer-term average to pass 1.5 [Celsius] until the early to mid-2030s," says climate scientist Zeke Hausfather, who wasn't part of the WMO report. "It's important to realize that if we pass 1.5 degrees, it's not a reason to give up," Hermanson said. "We have to continue working out how much we can reduce emissions of greenhouse gases as much as possible, even after that, because it will make a difference."

(More global warming stories.)