Clouds cover about two-thirds of the planet at any moment, but as the Earth warms, they’re becoming scarcer, risking a feedback loop of runaway warming which could push surface temperatures up by roughly a further 8 °C, according to new research.
The findings: Supercomputer simulations suggest that greenhouse gases are causing the disappearance of clouds over our oceans, and that could drastically speed up global warming over the next century, a paper in Nature Geoscience suggests. Specifically, the tipping point is predicted to come once atmospheric carbon dioxide concentrations reach about 1,200 parts per million. The figure is currently about 410 ppm but could reach 1,200 ppm within the next century.
Past disaster: This scenario would be similar to an event that occurred about 56 million years ago during the Eocene period, according to the authors. During the so-called Paleocene–Eocene Thermal Maximum (PETM), a sudden release of carbon into the atmosphere was followed by a sudden temperature increase of more than 5 °C. It had catastrophic effects. It caused mass extinction in the seas and was hot enough for crocodiles to swim in the Arctic.
Time to worry? Yes and no. It’s undoubtedly a scary prospect. It would mean the end of human civilization.
But there are plenty of assumptions that would have to be borne out, and steps that would have to take place, before we reach that point.
Climate scientist Tapio Schneider, who co-authored the paper, said it's important to note "there are substantial uncertainties about quantitative results. The largest uncertainty is in the CO2 level at which the clouds become unstable—we cannot pinpoint that with precision."
"The central point to me is that our study points to the possibility of previously undiscovered and strong feedbacks in the climate system," he added.
Your response to that possibility might depend on how optimistic you are about the likelihood of humanity tackling climate change before it inflicts further irreparable damage.