If Emissions Aren’t Curbed, Clouds May Disappear

A study just published in the journal Nature Geoscience shows that if we continue with business-as-usual fossil fuel emissions, the atmosphere will hold 1,200 parts per million CO2 in about a century from now, which will cause stratocumulus clouds to disappear. Their absence could leave the Earth to warm by a staggering 8 degrees Celsius (8°C).

The computer simulation used in the study showed that once that 1,200 parts per million (ppm) tipping point of atmospheric CO2 is breached, the Earth’s temperature would soar by 4°C just from the CO2. Then, it would increase by another 4°C due to the absent clouds no longer reflecting solar radiation back into space.

Stratocumulus clouds cover around two-thirds of the planet, and play a key role in keeping the planet cool, due to their white color and reflective qualities. Research has shown that planetary warming correlates with the loss of clouds. This is yet another unforeseen climate feedback loop that could catapult us into catastrophic warming.

Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology who is a leading authority on atmospheric physics, told Quanta Magazine that the results of the study still needed to be replicated independently, but that the possibility of the simulation being accurate was “very plausible.”

Crocodiles in the Arctic

It is highly unlikely that most complex life could survive on a planet that has warmed to 8°C. A previous cataclysmic hot spell gives us clues as to what Earth’s future could look like.

The Paleocene-Eocene Thermal Maximum (PETM), which occurred 56 million years ago, was triggered by heat-trapping carbon causing the planet to gain 6°C. (At the time, the Earth was already several degrees Celsius warmer than it is now.)

Global mass extinctions resulted, as the oceans warmed dramatically. Horses, monkeys, and other animals migrated northward as they chased vegetation that moved into the higher latitudes. Mammal life miniaturized over many generations as their food became less nutritious due to the warmer carbon-filled air, and flash flooding and increasingly violent storms became the norm.

During the PETM, the equatorial regions of Earth were scorched and nearly completely lifeless, while crocodiles swam in the Arctic.

“Schneider and co-authors have cracked open Pandora’s box of potential climate surprises,” Matt Huber, a paleoclimate modeler at Purdue University told Quanta Magazine of the study.

Huber added that, “all of a sudden this enormous sensitivity that is apparent from past climates isn’t something that’s just in the past. It becomes a vision of the future.” The tipping point of the loss of clouds, and the instability it causes, is significant: It helps to explain the volatility in Earth’s paleoclimate records.

“Climate transitions that arise from this instability may have contributed importantly to hothouse climates and abrupt climate changes in the geological past,” reads the abstract of the study. “Such transitions to a much warmer climate may also occur in the future if CO2 levels continue to rise.”