Atmospheric & Environmental Chemistry Seminar
Detlev Helmig, University of Colorado, Boulder, will discuss "Reactive Gases in the Global Atmosphere Watch Network."
Long-term observations of atmospheric gases serve multiple research interests, such as for studies on trace gas cycles, assessments of emissions and their changes, and testing of atmospheric chemistry models. The World Meteorological Organization’s (WMO) Global Atmosphere Watch (GAW) program coordinates a network of global observations of reactive gases, including a series of volatile organic compounds (VOC). Example data will be presented, including new results from global observations of acetylene and isoprene. A particular focus will be on ethane, where observations have shown a recent, remarkable reversal of the Northern Hemisphere long-term trend. Global atmospheric ethane peaked around 1970, followed by a downward trend for the next four decades. Surprisingly, the near 40-year trend of declining global ethane halted between 2005-2010 and has since reversed. These changes are occurring at a hemispheric scale, but are most evident in the eastern part of the North American continent, downwind over the North Atlantic, and in the free troposphere over Europe. Network observations provide convincing evidence that these changes are most likely driven by emission increases that are associated to the growth of the North American oil and natural gas industries.
Host: Jianxiong Sheng