Effects of biogenic emissions on
atmospheric composition
Centre for Atmospheric Science, University of Cambridge, UK
Paul Young
JULES Meeting, Exeter, 28-29th June 2007
Outline
1. Why biogenic VOCs?2. BVOCs and atmospheric chemistry3. Future (?) BVOC emissions
• The experiment• Some results• Some conclusions & caveats
4. Where next? (JULES)
Why are we interested?
BiogenicVOCs
Anthropogenic VOCs
~ 1000 Tg C yr-1
Why are we interested?
T, light, H2O, CO2, species, nutrients
Ethene, acetone, methane (?), terpenes(isoprene, α-pinene, β-caryophylene
May be highly reactive→ large contribution to O3 chem
Oxidation products important globally
Role in organic aerosol formation
Chemistry 101 – Tropospheric ozone
based on a diagram by Oliver Wild
VOCs ‘fuel’ O3production
HO2+O3
HO2+NO OH+NO2
Ocean
ModeratelyPolluted areas
Urban
Climate-chemistry links
based on Ramanathan et al. [1987]
Climate feedbacks on emission:temp, light, CO2, soil moisture…
Atmospheric chemistry
Increasing isoprene emissions in a
pessimistic (A2) future
The experiment (a)• Increase isoprene to a 2100 (2xCO2) level
using Guenther et al. [1995] algorithms and HadCM3 surf temperature output*
Present day Future (2100)
398 Tg C yr-1 771 Tg C yr-1
*ΔT ~ 4K
• Just consider potential isoprene response to temperature (e.g. no vegetation shifts)
Isoprene emissions
Isoprene emissions / Tg month-1 (non-linear scale!)
(a) BASE: 398 Tg C yr-1 (b) 2100: 771 Tg C yr-1
The experiment (b)
210021002100ALLcc200021002100ALL200020002100ANTH
20002000
20002100
20002000
BASEISOP
ClimateIsoprene“Anthro.”*
• Experiment matrix
*e.g. NOx, CO, NMHCs (all non-isoprene emissions); based on SRES A2 Scenario
ΔO3 boundary layer [Jul] / ppbv
ANTH - BASE
ΔO3 boundary layer [Jul] / ppbv
ANTH - BASE
ALL - BASE
ΔO3 boundary layer [Jul] / ppbv
ANTH - BASE
ALL - BASEALL - ANTH
Tropospheric methane lifetime [Yr avg]
10.5
8.08.7
7.4
6
7
8
9
10
11
BASE ANTH ALL ALLcc
Year
s
Impact of OH changes…
Tropospheric NOy speciation [Yr avg]
4.2
12.4
42.8
2.3
30.4
6.2
3.4
11.1
55.6
2.1
21.8
3.8
2.79.7
47.3
1.9
31.1
5.2
2.6
10.5
55.1
1.8
22.2
5.7
0%
20%
40%
60%
80%
100%
BASE ANTH ALL ALLcc
ORG NPANINORG NHNO3NO2NO
2.60ALLcc3.09ALL2.92ANTH1.15BASE
Tg N (as NOy)
What is the potential for NOx redistribution?
Conclusions & Caveats
Isoprene changes are important for atmospheric composition [Sanderson et al., 2003; Hauglustaine et al., 2005; Steiner et al., 2006; Wiedinmyer et al., 2006]
Conclusions & Caveats
Isoprene changes are important for atmospheric composition [Sanderson et al., 2003; Hauglustaine et al., 2005; Steiner et al., 2006; Wiedinmyer et al., 2006]
Impact is heterogeneous and complex: balance of HOxand NOy changes; depend on chemical characteristics of the region → sensitive to future emission estimates
Conclusions & Caveats
Isoprene changes are important for atmospheric composition [Sanderson et al., 2003; Hauglustaine et al., 2005; Steiner et al., 2006; Wiedinmyer et al., 2006]
Impact is heterogeneous and complex: balance of HOxand NOy changes; depend on chemical characteristics of the region → sensitive to future emission estimates
But models obviously over-simplify the problem: chemistry, canopy processes, sub-grid scale phenomena, vegetation-climate feedbacks, etc. etc.
Where next?
• Conducting model study using emissions estimated from LPJ-GUESS [Arneth et al., 2007]
• Comparison with results from Juliette et al.’s work with JULES (‘ensemble chemistry/emissions’)
• …If isoprene CO2-effect counteracts T effect, changes in land use become important
Tropospheric OH [Yr avg]
ALL versus ANTH
ΔO3 boundary layer [Jul] / ppbv
ΔO3 boundary layer [Jul] / ppbv
ΔO3 boundary layer [Jul] / ppbv
ΔO3 boundary layer [Jul] / ppbv
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