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SUMMARY:Radiative heating of the tropical lower stratosphere under climate
  change - Dr Peter Hitchcock\, Cambridge University
DTSTART:20151020T131500Z
DTEND:20151020T141500Z
UID:TALK61019@talks.cam.ac.uk
CONTACT:Paul Griffiths
DESCRIPTION:The upwelling branch of the Brewer Dobson circulation in the t
 ropical lower stratosphere is projected to strengthen in the coming decade
 s\, a fact which has important implications for the rate of recovery of th
 e ozone layer and for surface climate. While the conventional understandin
 g is that the increase in upwelling is driven dynamically\, recent work ha
 s suggested some aspects of the present day upwelling are better thought o
 f as being determined by local radiative heating. Similar arguments sugges
 t that the projected increases may also be radiatively determined. \n\nEva
 luating this hypothesis requires separating changes in the radiative heati
 ng of the tropical lower stratosphere into a 'relaxational' and an 'extern
 al' component. We discuss two diagnostic approaches to this decomposition 
 and argue\, based on output from integrations of the UKCA\, that significa
 nt external heating is indeed expected in the lower tropical stratosphere 
 as a result of increases in carbon dioxide. This external heating can ther
 efore be expected to strengthen the upwelling.  \n\nPreliminary estimates 
 of the magnitude of this change in upwelling will also be presented. 
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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