Maria Montero

Climate change kills clouds over the ocean in a …

We all know that climate change is affecting weather systems and ecosystems around the world, but exactly how and in what way remains a subject of intense study. New simulations made possible by higher-powered computers suggest that cloud cover over the oceans may be completely extinguished once a certain level of CO2 is reached, accelerating warming and contributing to a vicious cycle.

An article published in Nature details the new, much more detailed simulation of cloud formation and the effects of solar radiation at that time. The researchers, from the California Institute of Technology, explain that previous simulation techniques were not granular enough to resolve effects that occur at the scale of meters rather than kilometers.

These global climate models seem particularly poor at predicting stratocumulus clouds hovering over the ocean, and that’s a big problem, they noted:

As stratocumulus clouds cover 20% of the tropical oceans and critically affect the Earth’s energy balance (they reflect 30–60% of the short-wave radiation that strikes them into space1), the problems that simulate their response to climate change filter into the global climate response.

A more accurate and precise simulation of the clouds was necessary to determine how temperatures and greenhouse gas concentrations can affect them. That’s something that technology can help with.

Thanks to “advances in high-performance computing and simulation of large eddies (LES) of clouds,” the researchers were able to “faithfully simulate the statistically stable states of boundary layers capped in stratocumulus in restricted regions.” A “restricted region” in this case means the 5 × 5 km area simulated in detail.

The improved simulations showed something unpleasant: When CO2 concentrations reached about 1,200 parts per million, this caused a sudden collapse of cloud formation, as the cooling at the top of the clouds is interrupted by excess incoming radiation. . Result (as seen at the top): Clouds do not form as easily, letting in more sun, further worsening the heating problem. The process could contribute as much as 8 or 10 degrees to warming in the subtropics.

Naturally, there are caveats: the simulations are just simulations, although this one predicted today’s conditions well and seems to accurately reflect the many processes that occur within these cloud systems (and remember, an inherent error could be against us and not for us). And we are still far from 1,200 PPM; NOAA’s current measurements put it at 411, but it’s steadily increasing.

It would be decades before this happened, although once it did it would be catastrophic and probably irreversible.

On the other hand, major climatic events such as volcanoes can change these measures temporarily but violently, as has happened before; Earth has seen sudden jumps in temperature and CO2 levels before, and the feedback loop of cloud loss and the resulting warming could help explain that. (Quanta has a great review with more context and background if you’re interested.)

The researchers call for further investigation into the possibility of stratocumulus instability, filling in the gaps they had to estimate in their model. The more brains (and groups of GPUs) there are in the case, the better idea we have of how climate change will unfold in specific weather systems like this one.