Although scientists have known since the 1970s that clouds can both improve and contribute to Earth's warming, the role they play in the planet's heating remains one of the singular uncertainties in the field.
Out of the many clouds that help regulate the Earth's climate, the Stratocumulus, those low-lying, grayish-white clouds that are often mistaken for rain clouds, are especially significant. They cover about 20 percent of the tropical ocean, cooling the planet by reflecting sunlight back to the atmosphere.
In February, Schneider's team published a paper stating that Stratocumulus clouds, in their model broke up into smaller Cumulus clouds and actually disappeared when carbon dioxide levels reached 1,200 parts per million (ppm), or levels that are three times higher than today
"The moment you saw the calculations it was shocking, because until then, it was kind of a thought experiment, "Schneider says. "And then it started to feel a bit more real – that it could actually happen, which is scary." Schneider is quick to point out, however, that there are still many uncertainties in the results and that's an extreme scenario that shouldn ' t prompt imminent panic.
"The moment you saw the calculations it was shocking, because until then, it was kind of a thought experiment."
Other climate scientists have criticized the paper, saying the findings are based on a narrow patch of clouds and can not be extrapolated to the whole globe
"It's not enough to run a model of a small box and get some of the small scales correct; all of the intermediate factors have a strong influence on how cloudiness evolves, and that's what's missing from that paper, "says Bjorn Stevens, and director at the Max Planck Institute for Meteorology in Hamburg
Schneider's own surprise, his paper generated and slew of grim headlines, adding to the near-daily feed of news articles about climate calamity. "Climate change kills off clouds," read one headline. Another got even more apocalyptic: "Climate change is eliminating clouds. Without them, Earth burns. "
The California researchers have argued that the dispersal of the Stratocumulus would add some 8 degrees Celsius to Earth's temperature, in addition to the 4 degrees of warming caused by greenhouse gas emissions alone. The last time Earth experienced such conditions was some 50 million years ago when crocodiles swam in the Arctic.
A United Nations Climate Panel has estimated that human activities have contributed between 0.8 degrees and 1.2 degrees Celsius to the planet's temperature since the pre-industrial era.
In May, the concentration of carbon dioxide in the atmosphere hit 415 ppm at the Mauna Loa Observatory 11,000 feet above sea level level in Hawaii, the highest measurement taken at the site since daily observations began in the late 1950s. Carbon dioxide levels are now higher than they have been for millions of years. If emissions continue at their current pace, the scenario modeled by Schneider's team in which Stratocumulus go extinct could be met in a century.