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