We’re on course to destroy the clouds, they said now. Not just the coral, not just the insects, not just all the wild vertebrates living on land. The clouds.
Quanta Magazine, writing about a new Nature Geoscience study on warming and clouds, described the temperature spike known as the Paleocene-Eocene Thermal Maximum, when a sharp increase in atmospheric carbon dioxide led to an even sharper increase in temperature—along with “mass extinctions” of ocean life, immense dislocations of land animals, and “flash floods and protracted droughts.” How did the temperature jump out of normal boundaries into a lethal range?
Clouds currently cover about two-thirds of the planet at any moment. But computer simulations of clouds have begun to suggest that as the Earth warms, clouds become scarcer. With fewer white surfaces reflecting sunlight back to space, the Earth gets even warmer, leading to more cloud loss. This feedback loop causes warming to spiral out of control.
In computer simulations, researchers found that at 1,200 parts per million of carbon dioxide, the level at which temperatures would be expected to be 4 degrees Celsius above the historical baseline, the atmosphere would become too warm and too turbulent to allow sheets of stratocumulus clouds to form. If the clouds fell apart, the extra sunlight could bring on an extra 8 degrees of warming—for a total increase of 12 degrees Celsius, or more than 21 degrees Fahrenheit.
Like the methane-spilling permafrost or the fracturing Antarctic ice sheet, the clouds can’t come back if they’re broken; the runaway heating effect would linger even after carbon dioxide levels dropped. We would have irrevocably ruined the sky.
This was just a limited simulation. Clouds are spectacularly difficult to model, so the intensive supercomputer work by the researchers only replicated a “roughly 5-by-5-kilometer patch of stratocumulus cloud.” There are complicating and mitigating factors to consider—but also factors that might make it all worse.
The lesson that matters is that global warming is not going to be an incremental process.
The specifics don’t matter that much. We will almost certainly not reach 1,200 parts per million of carbon dioxide, but the study helps explain why: again and again, the lesson that matters is that global warming is not going to be an incremental process. Four degrees of warming is 12 degrees of warming; we talk about worry while we stare into doom. Everyone who looks at any little piece of the picture finds things happening faster, and heading more precipitously toward total failure, than the cautiously wary warnings have laid out. The set of planetary conditions under which human beings have up till now thrived, or at least proliferated, is not some unshakeable baseline, but a conditional system, moving and wobbling.
So while Dianne Feinstein lectures children on the limits of political action, as if describing some natural law, the true laws of nature don’t care about how fast imagination or collective action can adapt. Two years ago, wildfires in California killed 46 people and burned 1.2 million acres; last year they killed more than 100 and burned 1.9 million acres. The systems that sustain our complacency are themselves a fragile overlay.
One climate scientist in the Quanta story optimistically predicted that, as solar energy becomes cheaper than fossil fuels, “there will be an exponential transformation of entire industries.” Another, however, “noted that possible economic collapse caused by nearer-term effects of climate change might also curtail carbon emissions before the stratocumulus tipping point is reached.” Theoretically, our way of life could have the power to destroy the clouds; practically speaking, our way of life will almost certainly destroy itself before that can happen.