Influence of future climate change on air quality

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Influence of future climate change on air quality
global model results

• David Stevenson
• Institute of Atmospheric and Environmental
  ScienceSchool of GeoSciencesThe University of
  Edinburgh
• Thanks to
• Ruth Doherty (Univ. Edinburgh)
• Mike Sanderson, Colin Johnson, Bill Collins (Met.
  Office)
• Dick Derwent (rdscientific / Imperial College)
• Frank Dentener, Peter Bergamaschi, Frank Raes
  (JRC Ispra)
• Markus Amann, Janusz Cofala, Reinhard Mechler
  (IIASA)
• Martin Schultz, Guang Zeng, Kengo Sudo, Nadine
  Bell, Sophie Szopa, Veronica Montenaro,
  Jean-Francois Lamarque All the other IPCC
  ACCENT modellers
• NERC and the Environment Agency for funding

dstevens_at_met.ed.ac.uk
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Modelling Approach

• Global chemistry-climate model STOCHEM-HadAM3
  (also some results from others)
• Two transient runs 1990 ? 2030, following same
  emissions, but different climate scenarios
• 1. Current Legislation (CLE)
• Assumes full implementation of all current
  legislation
• 2. CLE climate change
• For 1, climate is unforced, and doesnt change.
• For 2, climate is forced by the is92a scenario,
  and shows a global surface warming of 1K between
  1990 and 2030.

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STOCHEM-HadAM3

• Global Lagrangian chemistry-climate model
• Meteorology HadAM3 prescribed SSTs
• GCM grid 3.75 x 2.5 x 19 levels
• CTM 50,000 air parcels, 1 hour timestep
• CTM output 5 x 5 x 9 levels
• Detailed tropospheric chemistry
• CH4-CO-NOx-hydrocarbons (70 species)
• includes S chemistry
• Interactive lightning NOx, C5H8 from veg.
• these respond to changing climate
• 3 years/day on 36 processors (SGI Altix)

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Surface O3 (ppbv) 1990s
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CLE
A large fraction is due to ship NOx
Change in surface O3, CLE 2020s-1990s
BAU
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?O3 from climate change
Warmertemperatures higher humidities increase
O3 destruction over the oceans
But in polluted regions, more H2O promotes
O3production also a role from increases in
isoprene emissions from vegetation changes
in lightning NOx
2020s CLEcc- 2020s CLE
dstevens_at_met.ed.ac.uk
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Zonal mean ?T (2020s-1990s)
dstevens_at_met.ed.ac.uk
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Zonal mean H2O increase 2020s-1990s
dstevens_at_met.ed.ac.uk
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Zonal mean change in convective updraught flux
2020s-1990s
dstevens_at_met.ed.ac.uk
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C5H8 change 2020s (climate change fixed climate)
dstevens_at_met.ed.ac.uk
11
Lightning NOx change 2020s(climate change
fixed climate)
More lightning in N mid-lats Less, but higher,
tropical convection No overall trend in
Lightning NOx emissions
dstevens_at_met.ed.ac.uk
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Zonal mean PAN decrease 2020s (climate change
fixed climate)
Colder LS
Increased PAN thermal decomposition, due
to increased T
dstevens_at_met.ed.ac.uk
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Zonal mean NOx change 2020s (climate change
fixed climate)
Increased N mid-lat convection and lightning
Less tropical convection and lightning
Increased PAN decomposition
dstevens_at_met.ed.ac.uk
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Zonal mean O3 budget changes 2020s (climate
change fixed climate)
dstevens_at_met.ed.ac.uk
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Zonal mean O3 decrease 2020s (climate change
fixed climate)
dstevens_at_met.ed.ac.uk
16
Zonal mean OH change 2020s (climate change
fixed climate)
Complex function F(H2O, NOx, O3, T,)
dstevens_at_met.ed.ac.uk
17
Influence of climate change on O3 9 IPCC ACCENT
models
dstevens_at_met.ed.ac.uk
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Summary

• Climate change will introduce feedbacks that
  modify air quality
• These include
• More O3 destruction from H2O (background air)
• More O3 production from H2O (polluted air)
• More stratospheric input of ozone
• More isoprene emissions from vegetation
• Changes in convection mixing lightning NOx
• Increases in sulphate from OH and H2O2
• Changes in circulation
• Wetland CH4 emissions (not studied here)
• Changes in stomatal uptake? ()
• These are quite poorly constrained different
  models show quite a wide range of response large
  uncertainties

dstevens_at_met.ed.ac.uk