Volume 1, Issue 4
Think Molecularly, Act Globally
When NASA's ER-2 stratospheric aircraft returns from another trip to 70,000 feet above the earth, it may be carrying a special payload back for UC Berkeley professor Kristie Boering. The small canister inside the modified spy plane provides Boering, an assistant professor of chemistry and earth and planetary science, with clues into the human impact on global climate and how the ozone layer may recover over the next century. Amazingly, the canister appears to be empty. That's because Boering's understanding of atmospheric chemistry comes from studying the air up there.
Kristie Boering also studies the atmosphere of Mars to help scientists determine if the Red Planet could ever have supported life.
"We combine measurements on air samples collected in the stratosphere with physical chemistry experiments in our lab and computer models of the atmosphere," Boering says. "It's really a combination of molecular and global scale research."
Boering's goal is to tease apart the coupling of chemistry and air circulation to understand climate change and ozone depletion on monthly to millennial time scales.
"You'd think we'd know everything about how the air circulates from the lower atmosphere where we live, up into the stratosphere, and back down again," she says. "But we're really still working on quantifying it."
The ozone layer, located in the stratosphere six to 30 miles above the Earth, protects our planet from ultraviolet rays. Scientists now agree that ozone depletion is due in large part to the release of chlorofluorocarbons (CFCs) and other industrial chemicals. Boering hopes to put more concrete numbers on the human impact on the ozone layer and climate.
"Even though it's no longer a mystery of how the ozone layer was destroyed over Antarctica, we still need to know how the hole will recover over the next sixty years or so," Boering says. "That depends on the details we're trying to quantify."
The devil may indeed lie in the details. For example, Boering and her students are working to characterize the relationship between the ozone layer and global climate change, spurred by both nature and human forces. Feedback may occur in both directions, she says, but traditional computer models of the atmosphere aren't accurate enough yet to forecast such phenomena.
"Our models are good enough to understand what happened so far and probably enough to prevent a big disaster, but what if we tweak the system in the physical world from where our computer simulations happen to be working?" Boering says.
Two NASA ER-2 high altitude research aircraft used to obtain arm samples from the stratosphere for analysis. The ER-2 is a civilian version of the Air Force's U-2 reconnaissance plane. (courtesy NASA)
To improve the global models, Boering conducts physical chemistry experiments on the air samples retrieved by both the ER-2 plane and arena-sized stratospheric balloons. By measuring the composition of greenhouse gases such as methane, carbon dioxide, and nitrous oxide in samples taken in various parts of the atmosphere on a number of timescales, Boering and her colleagues can help identify where the chemicals come from, where they go, and perhaps most importantly, how they get there.
The new measurements are possible due to analytical techniques that Boering helped pioneer. Previously, measuring greenhouse gases collected in the stratosphere required a sample of thousands of liters of air. Now, the same measurements can be conducted on less than 100 milliliters of air.
Last year, Boering and collaborators from the California Institute of Technology, National Center for Atmospheric Research and UC Irvine published a study in the journal Nature identifying a major sink of hydrogen gas in the environment that had previously been a mystery. The results are essential in assessing the likely impact of additional hydrogen in the atmosphere resulting from an increase in vehicles that run on hydrogen rather than fossil fuel. Boering is currently working to analyze their data to quantitatively predict whether the hydrogen economy will have any unforeseen impact as its main byproduct flows into the skies above.
"We decouple the chemistry from the circulation and then put them back together again in the computer models," she says. "Like a good chemical engineer working in an industrial plant, you need to know both the chemistry and how things move through the pipes."