Environmental Science and Engineering Seminar

Wednesday May 6, 2015 4:00 PM

Resolving Discrepancies in High Global Warming Potential Greenhouse Gas Emissions Using Atmospheric Measurements

Speaker: Ray Weiss, Department of Geosciences Research, Scripps Institution of Oceanography, UC San Diego
Location: Arms 155 (Robert P. Sharp Lecture Hall)

The reported emissions of many anthropogenic greenhouse gases (GHGs) are inconsistent with their measured rates of increase in the atmosphere, most often showing that emissions are underreported.  Emissions of purely anthropogenic industrial GHGs, as distinct from those that also have natural biogenic sources, ought to be comparatively easy to quantify at their sources, but many of these gases show among the largest discrepancies with atmospheric measurements, and also have the largest global warming potentials (GWPs).  The Advanced Global Atmospheric Gases Experiment (AGAGE) has been studying these issues for a number of years and for a wide range of non-CO2 GHGs, using real-time high frequency measurements and archived air samples.  Examples of large inconsistencies in global emissions include SF6 and CF4.  Based on high-frequency measurements of C2F6/CF4 emission ratios using trajectory analysis in East Asia and Australia it is possible to separate and quantify the roles of the aluminum and semiconductor industries in contributing to the global increases of these two potent GHGs.  Measurements of HFC-23 (CHF3), another very potent GHG, are used to locate and quantify its regional emissions through inverse modeling, and to show the role of the Clean Development Mechanism (CDM) in modulating its emissions.  And measurements of NF3, a very potent GHG with rapidly growing uses in the electronics industry, show that despite very large initial discrepancies between reported and measured global emissions, industry can respond positively to such findings and effect major improvements in the percentage of NF3 production that is emitted.  In the context of climate legislation, the solution to discrepancies between bottom-up and top-down emissions assessment lies in the use of improved optimal estimation methods and an expanded observational base to refine emission parameters globally and regionally.

Series Environmental Science and Engineering Seminar

Contact: Kathy Young at 626-395-8732 katyoung@gps.caltech.edu