This much is true: Air pollution from Asia crosses the Pacific Ocean to North America.
Also true: Some of that pollution can hamstring efforts in the western United States to meet federal Clean Air Act standards for ozone, a component of smog.
What’s unclear is how ozone moves through the atmosphere. The uncertainty can be traced to a dearth of emissions data in China and other parts of Asia and to relatively little effort placed on taking a global look at ozone, which has been linked to serious health problems.
"Ozone is changing so rapidly, and there’s been no coordinated effort to look at this," National Oceanic and Atmospheric Administration researcher Owen Cooper said. "Scientists study just one or two regions at a time, use a subset of different data, different analysis and different techniques."
Scientists’ inability to supply clear questions about ozone transport has become a political problem for the Obama administration, which has proposed tightening the national air quality standard for the pollutant from 75 parts per billion to between 65 and 70 ppb. With U.S. EPA poised to release a new ozone limit by a court-ordered Oct. 1 deadline, industry opponents of the proposal are blaming China for Western smog (Greenwire, Sept. 9).
Researchers are scrambling for answers.
From his perch at the Cooperative Institute for Research in Environmental Sciences in Boulder, Colo., Cooper is chairing a worldwide effort with 170 scientists from 35 countries trying to create a searchable database of ozone measurements and a comprehensive set of journal articles on the gas’ trends and distribution. Their goal: to create a baseline for future ozone research and policy.
"There isn’t a clear, coherent picture that’s been put together on what’s going on with the ozone distribution," said David Parrish, a retired NOAA researcher who works as a consultant for the agency.
"The historical record is not as complete as we wish it was. There were measurements made at various locations, but in retrospect, we look back and say, ‘Boy, I wish we would have had more measurements.’"
At issue is what’s going on with ozone in the midtroposphere — 3 to 8 kilometers above the Earth’s surface. Ozone at that altitude can be transported far and wide, winding to the surface at high-elevation sites in the western United States.
The "Tropospheric Ozone Assessment Report," or TOAR, project arose out of the most recent Intergovernmental Panel on Climate Change (IPCC) report on trends in tropospheric ozone.
The report’s authors — Cooper, Parrish and NASA associate research scientist Jerry Ziemke — were allowed 900 words.
"It was just clear to me that this was a highly complicated topic that deserved more than just 900 words," Cooper said in an interview. "The IPCC report has to be short and concise. From that assessment of ozone, we wrote a long peer-reviewed paper, and even then we couldn’t do the topic justice."
The International Global Atmospheric Chemistry Project is sponsoring the TOAR project. NOAA and the World Meteorological Organization are providing support, but Cooper calls the project a "grass-roots effort" that’s not working directly with any government.
So far, researchers have met for an organizing workshop in Colorado last fall and in Spain this spring. They’re planning to meet again in the coming months for another workshop that has yet to be announced.
"There have been international efforts in the past dealing with various scientific questions. This is one of the first concerning ozone, with a focus on ozone," said Allen Lefohn, a Montana-based atmospheric researcher who has contributed to EPA science documents on ozone.
"We’re saying, can we gather a sufficient amount of data from around the world using identical analytical techniques and look for patterns of change, either improvements or increases in ozone? Given what these patterns are showing us, are they giving us a message that’s important?"
Big questions about China
One of the major goals is simply to interpret and coalesce all the existing scientific studies done around the world on the movement of ozone through the atmosphere and its sources, whether man-made or naturally occurring.
Ozone forms when nitrogen oxides and volatile organic compounds react in sunlight, but it can also wind its way from the upper atmosphere and form as a result of lightning strikes and wildfires (Greenwire, Nov. 17, 2014).
"The emissions of ozone precursors in Asia have been increasing dramatically over the past few decades, while emissions in North America and Europe have been decreasing due to air quality regulations," said Meiyun Lin, a TOAR contributor.
"So we’re kind of interested in understanding how changes in Asia emissions affect global tropospheric ozone and in understanding how climate variability and change can affect global distributions of ozone."
Lin, a research scientist at NOAA and Princeton University’s Cooperative Institute for Climate Science, recently published a study in the journal Nature Geoscience that shows shifts in wind patterns have pushed Asian pollution to Hawaii’s doorstep.
A big research gap: China.
China has only a handful of high-quality ozone monitoring sites. There’s been some effort to take satellite observations of ozone distribution above the country, but it’s difficult to tell from those pictures how the distribution of ozone has changed closer to the surface of the Earth.
"The Chinese government and policy people in China are not anxious to have it known how bad the air quality is," Parrish said. "So they’ve been reluctant to release data. But we’ve been working with university scientists, and they’re interested in understanding the ozone over Asia as well as the rest of the world."
Another barrier is that NASA, which has a large satellite monitoring program for air pollution, is prohibited from doing any research with Chinese scientists affiliated with state enterprises or entities under a ban passed by Congress in 2011.
Because pollution makes its way from Asia to the United States, this is a big problem for assessing whether U.S. Western states can comply with a tighter national ozone standard.
"It is well known that there is not much ozone monitoring in China," Lin said. "And hopefully these TOAR reports can bring attention to that."
‘Nice, consistent data set’
The project also aims to get the international researchers and policymakers around the same table to discuss ozone concentrations and their impacts on human beings.
Lefohn, the Montana researcher, is leading a branch of the project focused on "metrics," or ways that researchers can describe ozone concentrations.
How people look at ozone data can steer their conclusions, he said.
For example, someone looking at trends in average ozone concentrations will come away with a different picture of what’s going on in the atmosphere than a person looking at the number of high-ozone days. The number of high-ozone days may decrease while leaving average ozone concentrations the same.
"Just because an exposure or dose index doesn’t appear to behave the way people think, emissions reductions have occurred," Lefohn said. "My response to the policymaker will be, ‘Wait, that’s not necessarily the correct conclusion you’ve made.’"
Using common tools will help researchers get a handle not only on ozone trends — whether pollution is rising or falling in an area — but also on the rates of change in the trends.
Ozone measurements are being fed into a massive online database that will act as a sort of baseline for future research on ozone pollution. Researchers are already looking forward to how that data can be used, such as to make better computer climate models, more clearly understand what controls the long-range transport of ozone, and estimate how reductions in ozone concentrations affect forest productivity and crop loss.
Ozone is a greenhouse gas, and the project may also reveal opportunities to address climate change, Cooper said.
"The goal is to post on a server, so any researcher can get data and do their own analysis using a nice, consistent data set," Cooper said. "If your interest is on ozone’s impact on human health globally, you can be a single researcher and go and get all the data."