Trees change climate – by creating clouds: Short Wave: NPR
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Have you ever looked at the clouds and wondered where they came from?
This is exactly what atmospheric researcher Lubna Dada is studying at the Paul Scherrer Institute. She is part of an international project called CLOUD, where she and fellow atmospheric scientists study how clouds form and the role they play in climate.
A recent study from the team was published in the journal Advancement of science Looks at the role of trees and the natural compounds they release into the atmosphere in cloud formation. The goal is to understand more precisely what the climate was like before the Industrial Revolution, and how it has changed since then.
Ultimately, Dada says all this data will improve scientists’ climate models, helping them make more accurate predictions about the future and preparations for it.
What do trees have to do with clouds?
Clouds are not only important to the weather, they also help shape the climate. Some clouds act as a protective layer between incoming solar radiation and the Earth, cooling the atmosphere. Other clouds do the opposite: they act like a blanket and trap heat.
These differences mean that it is important for scientists to know how and what types of clouds are created if they want to predict how the climate will change in the coming decades.
But many current climate models do not take into account the effects of clouds or cooling, or the role that aerosols play in their formation.
“This is the biggest uncertainty in climate science right now,” Dada says.
But the science is clear: When plants emit gases that form aerosol particles (i.e. particles suspended in the atmosphere), they help create cloud seeds. These particles can come from human pollution, or from natural sources such as sea spray and dust.
“Just think about the process of water condensing on your window while cooking,” says Dada. “These aerosols act just like your window. So they form and then act as a surface that can accommodate more gases to grow to form this cloud.”
What are the signals of pre-industrial cloud cover for the future?
In order to incorporate clouds into today’s climate models and predict future climate changes, Dada says we first need to understand how clouds behaved before the Industrial Revolution.
“We don’t know the extent to which humans can change background cloud conditions,” Dada says. “We need to know the background… so we can form that baseline where we can add this contribution from anthropogenic emissions.”
Once scientists know how much human-caused pollution contributes to cloud cover, Dada says scientists will be better equipped to predict the effects of clouds on climate in the future.
Dada and the broader team of researchers at CLOUD are trying to fill some of these past and present gaps using a steel cylindrical chamber that virtually recreates the atmosphere.
To do this, the team covered the box with aluminum foil-like tape. It contains lights that simulate different layers of the atmosphere, and researchers can change the humidity and temperature levels to mimic a specific geographic location they want to study.
Then, Dada and her team can inject specific vapors into the room to study their effect on the phantom atmosphere.
A new consideration of climate forecasting
Dada says previous research has looked at the effects of two types of organic emissions from plants: monoterpenes and isoprene.
But another type of compound, sesquiterpenes, has been largely ignored.
In a recent study from the CLOUD Project, scientists tested the effects of sesquiterpenes on cloud formation. Dada and her team injected the three compounds — monoterpenes, isoprene, and sesquiterpenes — into the cloud chamber to see how many new particles formed. They found that sesquiterpenes formed ten times more molecules than the other two substances at the same concentrations.
Dada says this discovery will help scientists understand the role that natural emissions played in the pre-industrial climate, and the extent to which humans have changed this baseline.
These compounds are released when plants are exposed to stress, so Dada believes they will become more important when factored into climate predictions, as plants are exposed to more extreme weather conditions. By taking these aerosols into account, scientists will be able to make more accurate predictions about the future climate.
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Today’s episode is produced by Rachel Carlson. Edited by Rebecca Ramirez. Brett Hanson checked the facts. Maggie Lothar was the sound engineer.