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SUMMARY:Pre-industrial changes in atmospheric methane: is it possible to d
 ifferentiate between changes in sources and changes in sinks? - Dr James L
 evine\, British Antartic Survey\, Cambridge
DTSTART:20081124T141500Z
DTEND:20081124T151500Z
UID:TALK12556@talks.cam.ac.uk
CONTACT:Dr Francis Pope
DESCRIPTION:The concentration of methane trapped in Antarctic ice shows la
 rge variations over the last 800\,000 years that appear to track changes i
 n temperature.  Our work focuses on the increase in methane from about 360
 ppbv at the last glacial maximum (approximately 20\,000 years ago) to roug
 hly 700ppbv in the pre-industrial era (approximately 200 years ago).  Fund
 amentally\, methane sources (e.g. emissions from wetlands) and/or sinks (e
 .g. oxidation by OH) must have changed during this period\, however\, the 
 balance between changes in sources and changes in sinks remains uncertain.
   As methane is strongly radiatively forcing\, we need to understand what 
 caused the increase in methane if we are to fully understand the accompany
 ing change in climate.  To this end\, we have carried out a number of sens
 itivity experiments using a global atmospheric chemistry-transport model\,
  the aim being to identify any atmospheric chemical signal which could be 
 used to differentiate between changes in methane emissions and changes in 
 oxidising capacity.  We have subsequently assessed whether any such signal
  could be derived from ice-core data.  The results to this work will be pr
 esented\, in addition to preliminary results regarding experiments designe
 d to explore the influence that past changes in temperature and humidity c
 ould have had on oxidising capacity.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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