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May 8, 2014

Computing the Ozone Pollution Threat

Tiffany Trader
Yellowstone supercomputer

One of the world’s most powerful supercomputers devoted to climate change – the 1.5 petaflop Yellowstone system – is fulfilling its mission to help find solutions to serious climate change issues. Recently a team of researchers from National Center for Atmospheric Research (NCAR) and several partner institutions used Yellowstone, an IBM iDataPlex cluster, to simulate the threat of ozone pollution as temperatures continue to rise due to climate change.

According to the sophisticated simulation, the United States will likely experience a 70 percent increase in unhealthy summertime ozone levels by 2050 – unless serious mitigating actions are implemented.

An article published by NCAR explains that temperature fluctuations spurred by a changing climate will result in higher atmospheric levels of methane and more volatile organic compounds (emitted by plants), setting off further chemical reactions that create excess ozone.

The IBM Yellowstone supercomputer at the heart of this research is among the world’s most powerful computers dedicated to climate and atmospheric science. Funded by the NSF and the University of Wyoming and installed at the NCAR-Wyoming Supercomputing Center (NWSC) in Cheyenne, Wyoming, Yellowstone ran simulations of hourly pollution levels for 39 hypothetical summers. The design allowed the research team to incorporate year-to-year variations in meteorological conditions to arrive at a more detailed and accurate representation of future pollution levels.

Although ozone pollution is invisible, it is triggered by visible pollutions (like smog) that react with sunlight. This type of pollution has long been known to reach unhealthy levels in major cities like Los Angeles, but according to this latest research, regions across the continental United States will begin to experience at least a few days of unhealthy air during the summers. The worst-hit areas will be parts of the East, Midwest, and West Coast that already have above-average levels of pollution and ozone.

“It doesn’t matter where you are in the United States – climate change has the potential to make your air worse,” said NCAR scientist Gabriele Pfister, the lead author of the study. “A warming planet doesn’t just mean rising temperatures, it also means risking more summertime pollution and the health impacts that come with it.”

It’s not all doom and gloom, however. As with many climate change findings, it’s not too late to enact changes. A targeted reduction campaign addressing the worst pollutants will prevent the ozone overload even in the face of rising temperatures.

The study is said to be the first of its kind to employ highly advanced geoscience supercomputing capabilities. Needing to incorporate both global climate and regional pollution conditions, the researchers turned to two well-known models – the Community Earth System Model, and an air chemistry version of the multiagency Weather Research and Forecasting model – both of which were developed through collaborations with the atmospheric science community.

Even with Yellowstone’s leadership-class capabilities, the simulations took months to complete.

“This research would not have been possible even just a couple of years ago,” said Pfister. “Without the new computing power made possible by Yellowstone, you cannot depict the necessary detail of future changes in air chemistry over small areas, including the urban centers where most Americans live.”

Findings will be published this week in the Journal of Geophysical Research-Atmospheres, a journal of the American Geophysical Union. In addition to NCAR, the study co-authors have affiliations with Pacific Northwest National Laboratory, the University of Colorado, Boulder, and North-West University in South Africa.