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SUMMARY:The role of methane for chemistry-climate interactions: rapid radi
 ative adjustments and climate feedbacks    - Laura Stecher\, Deutsches Zen
 trum für Luft- und Raumfahrt (DLR)\, Institut für Physik der Atmosphäre
  (Engl: German Aerospace Center\, Institute of Atmospheric Physics)
DTSTART:20240507T103000Z
DTEND:20240507T113000Z
UID:TALK216460@talks.cam.ac.uk
CONTACT:Dr Megan Brown
DESCRIPTION:Methane (CH4)\, the second most important greenhouse gas direc
 tly emitted by human activity\, is removed from the atmosphere via chemica
 l degradation. The chemical sink of CH4 is influenced by temperature and t
 he chemical composition of the atmosphere. It is further an important sour
 ce of water vapour in the stratosphere and affects the ozone concentration
  in the troposphere and the stratosphere via secondary feedbacks.\n\n \n\n
 The talk will focus on the role of these chemistry-climate interactions in
  numerical simulations with the chemistry-climate model EMAC perturbed by 
 either CO2 or CH4 increase. For both forcing agents\, CO2 and CH4\, so cal
 led rapid radiative adjustments are assessed in simulations with prescribe
 d sea surface temperatures\, as well as climate feedbacks in respective si
 mulations using an interactive oceanic mixed layer.\n\nThe simulation set-
 up uses CH4 emission fluxes instead of prescribed CH4 concentrations at th
 e lower boundary so that changes of the chemical sink can feed back on the
  atmospheric CH4 concentration without constraints.\n\n \n\nThe results sh
 ow a shortening of the CH4 lifetime and\, accordingly\, a reduction of the
  CH4 mixing ratios in a warming and moistening troposphere. This decrease 
 in CH4 also affects the response of tropospheric ozone.\n\nFurthermore\, r
 ecently an additional radiation scheme was implemented into the EMAC model
 \, which represents the direct radiative effect of CH4 better and also acc
 ounts for the absorption by CH4 in the solar shortwave spectrum. With the 
 new radiation scheme the effective radiative forcing for the same perturba
 tion of CH4 emissions is larger\, and individual rapid radiative adjustmen
 ts\, e.g. of clouds\, are changed.
LOCATION:Chemistry Dept\, Unilever Lecture Theatre and Zoom
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