Overlaps of AQ and climate policy – global modelling perspectives
David Stevenson
Institute of Atmospheric and Environmental ScienceSchool of GeoSciencesThe University of Edinburgh
Thanks to:
Ruth Doherty (Univ. Edinburgh)Dick Derwent (rdscientific)Mike Sanderson, Colin Johnson, Bill Collins (Met Office)Frank Dentener, Peter Bergamaschi, Frank Raes (JRC Ispra)Markus Amann, Janusz Cofala, Reinhard Mechler (IIASA)NERC and the Environment Agency for funding
Material mainly from 2 current publications:
The impact of air pollutant and methane emission controls on tropospheric ozone and radiative forcing: CTM calculations for the period 1990-2030
Dentener et al (2004) Atmos. Chem. Phys. Disc.(currently open for discussion on the web)
Impacts of climate change and variability on tropospheric ozone and its precursors
Stevenson et al (2005) Faraday Discussions(upcoming discussion meeting at Leeds in April)
Rationale• Regional-global scale AQ legislation has
implications for climate forcing – quantify these for current and possible future policies (use 2 very different models to try and reduce model uncertainty)
• Climate change will influence AQ – use coupled climate-chemistry model to identify potentially important interactions
Modelling Approach• Global chemistry-climate model: STOCHEM-
HadAM3 (also some results from TM3+others)• Three transient runs: 1990 → 2030, following
different emissions/climate scenarios: 1. Current Legislation (CLE)
Assumes full implementation of all current legislation
2. Maximum Feasible Reductions (MFR)Assumes full implementation of all available current emission
reduction technology
3. CLE + climate changeFor 1 and 2, climate is unforced, and doesn’t change.For 3, climate is forced by the is92a scenario, and shows a global
surface warming of ~1K between 1990 and 2030.
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)
Global NOx emissions
0.0
40.0
80.0
120.0
160.0
200.0
1990 2000 2010 2020 2030
Europe North AmericaAsia + Oceania Latin AmericaAfrica + Middle East Maximum Feasible Reduction (MFR)SRES A2 - World Total SRES B2 - World Total
Figure 1. Projected development of IIASA anthropogenic NOx emissions by SRES world region (Tg NO2 yr-1).
CLE
SRES A2
MFR
Global CO emissions
0.0
200.0
400.0
600.0
800.0
1000.0
1990 2000 2010 2020 2030
Europe North AmericaAsia + Oceania Latin AmericaAfrica + Middle East Maximum Feasible Reduction (MFR)SRES A2 - World Total SRES B2 - World Total
Figure 2 Projected development of IIASA anthropogenic CO emissions by SRES world region (Tg CO yr-1).
CLE
SRES A2
MFR
Global CH4 emissions
0
100
200
300
400
500
600
1990 2000 2010 2020 2030
Europe North AmericaAsia + Oceania Latin AmericaAfrica + Middle East Maximum Feasible Reduction (MFR)SRES A2 - World Total SRES B2 - World Total
Figure 3: Projected development of IIASA anthropogenic CH4 emissions by SRES region (Tg CH4 yr-1).
CLE
SRES A2
MFR
Figure 4. Regional emissions separated for sources categories in 1990, 2000, 2030-CLE and 2030-MFR for NO x [Tg NO2 yr-1]
Regional NOx emissions19
9020
0020
30 C
LE20
30 M
FR
Surface O3 (ppbv) 1990s
BAUChange in surface O3, CLE 2020s-1990s
>+10 ppbvIndia
+2 to 4 ppbv overN. Atlantic/Pacific
A large fraction isdue to ship NOx
CLE
CLE Surface Annual Mean O3 2020s-1990s TM3 (top) and STOCHEM (bottom)
Figure 13. Decadal averaged ozone volume mixing ratio differences [ppbv] comparing the 2020s and 1990s for (a) TM3 CLE and STOCHEM CLE.
Surface ΔO3
2030CLE–2000(NB July)
18 Models from IPCC-ACCENTintercomparison
MRF BAUChange in surface O3, MFR 2020s-1990s
Up to -10 ppbvover continents
Figure 13(b) Decadal averaged ozone volume mixing ratio differences [ppbv] comparing the 2020s and 1990s for TM3 MFR and STOCHEM MFR
MFR Surface Annual Mean O3 2020s-1990s TM3 (top) and STOCHEM (bottom)
Surface ΔO3
2030MFR–2000(NB July)
18 Models from IPCC-ACCENTintercomparison
CH4, CH4 & OH trajectories 1990-2030CLE
CLEcc
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3R
ad. F
orci
ng /
W/m
2
CH4O3
CH4 0.167 0.125 0.004 0.003 -0.039 0.221
O3 0.075 0.041 -0.073 -0.072 0.029 -0.03
CLE TM3
CLE STOC
MFR TM3
MFR STOC
MFR-CH4
MFR-pol
If the world opts for MFRover CLE, net reduction in
radiative forcing of 0.2-0.3 W m-2 for the period 2000-2030
Methane controlsare the mosteffective for RF
Part 1 Summary• Co-benefits for both AQ and climate from some
emissions controls• Methane offers the best opportunity (also CO and
NMVOCs)• NOx controls (alone) benefit AQ, but probably worsen
climate forcing (via OH and CH4) (Similarly for SO2)• AQ policies influence climate –
this study gives a quantitative assessment• Use of many models shows results are quite
consistent
ΔO3 from climate changeWarmer
temperatures &higher humidities
increase O3
destruction over the oceans
But also a rolefrom increases
in isoprene emissions from
vegetation &changes in
lightning NOx
2020s CLEcc-2020s CLE
Zonal mean ΔT (2020s-1990s)
Zonal mean H2O increase 2020s-1990s
Zonal mean change in convective updraught flux 2020s-1990s
C5H8 change 2020s (climate change – fixed climate)
Lightning NOx change 2020s(climate change – fixed climate)
More lightning in N mid-lats
Less, but higher, tropical convection
No overall trend in Lightning NOxemissions
HadCM3 Amazondrying
Zonal mean PAN decrease 2020s (climate change – fixed climate)
IncreasedPANthermaldecomposition,due toincreased T
Colder LS
Zonal mean NOx change 2020s (climate change – fixed climate)
IncreasedPANdecomposition
IncreasedN mid-latconvectionand lightning
Lesstropicalconvectionandlightning
Zonal mean O3 budget changes 2020s (climate change – fixed climate)
Zonal mean O3 decrease 2020s (climate change – fixed climate)
Zonal mean OH change 2020s (climate change – fixed climate)
Complexfunction:
F(H2O,NOx,O3,
T,…)
Influence of climate change on O3 – 4 IPCC ACCENT models
Part 2 Summary• Climate change will introduce feedbacks that modify air
quality• These include:
–More O3 destruction from H2O–More stratospheric input of ozone–More isoprene emissions from vegetation–Changes in lightning NOx– Increases in sulphate from OH and H2O2–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