High CO₂ Levels Could Lead to Cloud Loss and a Catastrophic Tipping Point
Last updated April 22, 2019
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Recently, I came across some fascinating, if not alarming, climate research in a piece by Natalie Wolchover at Quanta Magazine. In Wolchover’s story, we learn how extremely high levels of atmospheric carbon dioxide could lead to cloud loss and a catastrophic tipping point in Earth’s climate. Needles to say, these findings have caught the attention of journalists, scientists and activists concerned with climate science. Let’s investigate.
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 published the study results in the journal Nature Geoscience in February 2019. 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 reads more like a gripping adventure than a tedious science piece.
It could happen again
But could the concentration of carbon dioxide in the atmosphere rise to 1,200 ppm again? Yes, if the world increases its use of coal and other fossil fuels and follows a path of unabated emissions—CO₂ levels could climb to 1,100 ppm by the end of this century. 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. Here’s what climate scientist Michael Mann had to say about it on Twitter (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 that 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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