Natalie Wolchover has a fascinating and terrifying piece at Quanta that outlines a dire scenario transcending even the most pessimistic recent predictions made by climate scientists. In short, new research suggests that there is a threshold of carbon dioxide beyond which low-lying clouds actually begin to vanish. As Wolchover writes, that triggers a cataclysmic warming cycle:
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.
Nature Geoscience has the nitty-gritty details in the abstract of the report, which relied on simulations run at the California Institute of Technology:
In the simulations, stratocumulus decks become unstable and break up into scattered clouds when CO2 levels rise above 1,200?ppm. In addition to the warming from rising CO2 levels, this instability triggers a surface warming of about 8K globally and10K in the subtropics. Once the stratocumulus decks have broken up, they only re-form once CO2 concentrations drop substantially below the level at which the instability first occurred.
That “8K” represents degrees Celsius, or 14 degrees Fahrenheit, of “extra warming” on top of what we can expect from CO2 emissions alone. At our current rate of emissions, we’ll hit that tipping point in about 100 years.
What’s especially compelling about this model—which remains theoretical—is that it could help explain the intense and mysterious warming cycles that hit Earth in past periods of the planet’s warming cycles. Again, from Wolchover:
When the planet got hot, it got really hot. Ancient warming episodes like the PETM [Paleocene-Eocene Thermal Maximum] were always far more extreme than theoretical models of the climate suggest they should have been. Even after accounting for differences in geography, ocean currents and vegetation during these past episodes, paleoclimatologists find that something big appears to be missing from their models — an X-factor whose wild swings leave no trace in the fossil record.
The work by the CIT researchers provides a possible explanation for that x-factor: The disappearance of stratocumulus clouds.
Please go read the full story at Qanta, which is a terrific piece of climate journalism based on research that might be a complete game-changer…in the most harrowing way imaginable.