Climatically Speaking: High CO₂ Levels Could Lead to Cloud Loss and a Catastrophic Tipping Point

Icebergs, Photo by Ghost Presenter from  Pexels

Icebergs, Photo by Ghost Presenter from Pexels

High carbon dioxide levels, clouds and a tipping point; heat and fires in the UK; “gold standard” level of confidence for global warming; and the strongest February typhoon ever recorded


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So far, it’s been a busy week in the world of climate news. Besides the strongest February typhoon on record skirting Guam, the UK experiencing its warmest February day ever recorded, a gorse fire in Ireland and additional fires burning across other parts of the UK, scientists are now more sure than ever that humans are warming the planet. Certainty about human-caused global warming has, in fact, reached the “gold standard” level. But the story from this week’s news that has garnered the most attention from the climate community of journalists, scientists and activists is a piece by Natalie Wolchover at Quanta Magazine on how extremely high levels of atmospheric carbon dioxide could lead to cloud loss and a catastrophic tipping point in Earth’s climate. Let’s investigate. Or, alternately, you can skip down to the short video presentation at the end of the post.

High CO₂ levels, cloud loss and a catastrophic tipping point

By studying our planet’s history from about 56 million years ago—a geological period know as the Paleocene-Eocene Thermal Maximum (PETM)—and using advanced computer simulations to model climate, climate scientists discovered that when carbon dioxide levels reach 1,200 ppm, low-lying clouds disappear. They recently published the study results in the journal Nature Geoscience. Because clouds help cool Earth by reflecting heat toward space, the resulting cloud loss could trigger a catastrophic tipping point, raising temperatures 8°C (14.4°F). That’s in addition to the 4°C (7.2°F) or more of warming that would stem from the high carbon dioxide levels alone.

High CO₂ levels and extreme heat in the Paleocene-Eocene Thermal Maximum

What was our planet like 56 million years ago during the PETM? Unlike anything you could ever imagine: “The ocean turned jacuzzi-hot near the equator and experienced mass extinctions worldwide,” writes Wolchover. And that’s just in the ocean. On land, early mammals and other animals migrated north to areas that still had plenty of plant matter to eat. If you would like to learn more, take a look at Peter Brannen’s fascinating story at the Atlantic on the Paleocene-Eocene Thermal Maximum. It’s an excellent read.

It could happen again

But could the concentration of carbon dioxide in the atmosphere rise to 1,200 ppm again? Yes, unless the world curbs its carbon emissions—eventually bringing them down to net zero—CO₂ levels could climb that high in about 100 years. But a lot of bad things would have already happened, such as Earth’s temperature surging 4°C (7.2°F), along with other unpleasant consequences. So losing clouds and pushing our climate over a tipping point would be just one more unimaginable insult to add to many. As climate scientist Michael Mann said on Twitter this past week (courtesy of Common Dreams), “If we let CO₂ levels get that high we are already in big trouble.” Human civilization would not exist as we know it.

A first for climate models and tipping points

Though it’s important to point out that scientists need to further study how cloud loss might impact climate before they reach firm conclusions. That’s how science works. But as Zeke Hausfather notes at Carbon Brief, “The finding in this paper is important, say scientists, because it represents one of the first firm climate tipping points to come out of modeling exercises.”

All I know is I don’t want atmospheric carbon dioxide levels to climb anywhere near 1,200 ppm! How about you?

Video on cloud loss and tipping point

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