Lubna Dada creates clouds from September to December every year. Dada, an atmospheric scientist, has gathered with dozens of colleagues to conduct experiments in a 7,000-gallon stainless steel chamber at CERN in Switzerland. “It’s like a science camp,” Dada said. He studies how natural emissions react with ozone to produce aerosols that affect the climate.
Clouds are the biggest source uncertainty In climate prediction. Depending on the location, it may be cloudy. reflect sunlight away Heat sources from land and sea that would otherwise absorb heat. This is a rare perk in a warming world. But clouds can also do things like: trap Heat on the ice of the Arctic and Antarctic. Scientists want to learn more about what causes clouds to form and whether the effect is cooling or heating. More than anything, Dada says, “I want to understand how we humans have changed the clouds.”
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In the sky, aerosol particles attract water vapor and ice. When the small wet mass becomes large enough, cloud seeds. Half of Earth’s clouds are formed around things like sand, salt, soot, smoke, and dust. The other half nucleates around vapors emitted by organisms and machines. Sulfur dioxide produced when burning fossil fuels.
At CERN, scientists recreate the process by injecting steam representing a particular environment into a steel chamber. (This is called a cloud chamber, in the sense of space that leaves droplets outdoors.) For example, it can mimic the gases found in the sky above a city. But Dada, who normally works at the Paul Scherrer Institute in Switzerland, went to CERN to peer into the past. Her team of scientists from around the world wanted to recreate the air above a forest. That’s because a “pristine” atmosphere suggests what cloud formation was like before industrialization. “To revise climate models, we need to compare them to a time when there were no human emissions,” she says.
Among the published papers this month In Science Advances, Dada’s team established a new dominant player in cloud formation: a type of chemical emitted by trees.trees emanate natural volatiles Potentially flammable, such as isoprene and monoterpenes cloud formation Chemical reaction. Dada’s new book focuses on an often overlooked class of volatile substances called sesquiterpenes, which can be used to smell woody, earthy scents, depending on the molecule and type of plant or microorganism that releases them. scent, citrus, or spicy.
The research team showed that sesquiterpenes were more effective than expected in cloud seeding. The ratio of sesquiterpenes to other volatiles is only 1:50 doubled cloud formation.
The role of trees in seeding clouds is important because it suggests what the skies above some regions might look like if governments were able to curb sulfur emissions. In a world with reduced pollution, plants and trees will become more dominant drivers of cloud formation. This is an echo of the pre-modern world.
This research could help improve estimates of what the pre-industrial atmosphere was like. Perhaps we have overlooked a large portion of aerosols generated by trees and have underestimated the world’s aerosol population. If so, climate models will need to be rebuilt.
“The formation of new particles is a pretty hot topic right now,” says Paquita Zuidema, an atmospheric scientist at the University of Miami who was not involved in the study. “We’re becoming increasingly aware that we don’t know exactly what a pristine atmosphere looks like.”
Anthropogenic emissions dominate cloud formation in populated areas, whereas elsewhere plant volatiles dominate in more natural lands. Lab tools have recently become sensitive enough to understand which tools contribute the most.
Many discoveries regarding sesquiterpenes are relatively recent. In 2010, researchers discovered them Near the Amazon forest floor. Higher in the tree canopy, sesquiterpenes were difficult to track. This suggests that ozone converts sesquiterpenes into aerosols that seed clouds. Dada reported a similar system. Finnish forests and peatlands last year. “We’re seeing more and more because our equipment is much better now,” she says. “They’re not just Amazon.”