As the detrimental effects of climate change continue to increase, many scientists have suggested that clouds could help us minimize the detrimental effects of global warming. Their ability to trap infrared or heat radiation has been pinpointed as one potential way of slowing down climate change and stimulate cooling in the atmosphere. However, a new study suggests that clouds might not be able to protect us from the Earth's warming as much as originally thought.
Ivy Tan, a geoscientist at Yale who studies clouds, headed a team of researchers that focused on "mixed-phased" clouds, a unique type composed of ice crystals and supercooled liquid water.
Mixed-phased clouds are important for the Earth's climate not just because they are so abundant - occurring in very high numbers in cold and temperate regions as well as mid-latitude regions and closer to the ground near the poles - but because of their composition.
The liquid regions of mixed-phase clouds are much more effective at deflecting sunlight away from the Earth, and these parts of the cloud are expected to increase as the climate continues to warm, which could help them curb global warming.
"The more liquid you have in your cloud, the more reflective of shortwave radiation, or sunlight, it is," Tan said. "It's a jucier cloud, it's going to be thicker, it's denser, so it's going to reflect more sunlight back out to space than a cloud with ice would. The ice clouds are thinner, wispier and more transparent to sunlight."
However, when the ratio of water to ice is changed, so too does this reflection, and recent satellite observations revealed that there is more water in these clouds than many climate models suggest. Tan claims that water content is "severely underestimated on a global scale."
The balance of water and ice in these clouds alters the impact of carbon dioxide levels on atmospheric temperatures and, if the results from the study are correct, they suggest that as the Earth's climate continues to warm, the clouds will possess less ice to convert to liquid, meaning less sunlight reflection and more warming.
Scientists believe that preventing global temperatures from rising by more than 2 degrees Celsius could prevent some of the detrimental effects of climate change, but with these new findings, this could be more difficult then thought.
"Unfortunately, it means staying below 2 degrees is going to be even harder," said Trude Storelvmo, co-author of the paper and an associate professor in the Yale department of geology and geophysics. "We have to emit even less CO2 to stay below those limits."
The findings will be published in the April 8 issue of Science.
