Tropospheric Ozone Status and Links to Climate Issues

Transcription

1 Tropospheric Ozone Status and Links to Climate Issues David Simpson 1,2, Birthe Marie Steensen 1 Michael Gauss 1 1. Norwegian Meteorological Institute, Oslo, Norway 2. Chalmers University of Technology, Gothenburg, Sweden

2 My Background Employer: Norwegian Meteorological Institute, EMEP MSC-W Location: Dept. Earth & Space Sciences, Chalmers University of Technology, Gothenburg (% Adj. Prof.) Swedish activities: supervises 1 Post-Doc as part of Swedish MERGE climate initiative + 1 PhD as part of Swedish Clean Air Project (SCARP)

3 IPCC: Ozone as greenhouse gas

4 O 3 -Climate links? As well as being an important GHG, Ozone is a major oxidant in the troposphere Controls OH, hence lifetime of CH 4 and many other gases Conversely, CH 4 is ozone precursor, as are NOx, CO, NMVOC Biosphere-atmosphere links, e.g. N-uptake, VOC emissions, biomass changes (carbon-sink)

5 O 3 -Air quality links? Significant effects on human health vegetation materials Photochemistry (involving O 3, OH) secondary products, e.g nitrates, or organic aerosols, also with environmental consequences.

6 Trends in near-surface ozone (Jenkin, Atmos. Env. 08) Trends driven by: Decreasing peak ozone - European control strategies on NOx and NMVOC Decreasing NOx - increases O 3 in urban areas, and winter Increasing background O 3

7 Hemispheric trends in Ozone Parrish et al. (09) - trends off west coast of USA (blue) and west coast of Ireland (red), compared with historic data. Trends moderately well understood (mainly NOx changes, some (25%?) from CH 4 ), but models still have problems to reproduce fully.

8 Multi-model studies, some examples IPCC, Prather et al., 03, used models - predicted near-surface O 3 increase of ca. 5 ppb in much of N. hemisphere.

9 Multi-model studies, some examples IPCC, Prather et al., 03, used models - predicted near-surface O 3 increase of ca. 5 ppb in much of N. hemisphere. Dentener et al., 05 - used two models to look at impact of air pollutant and CH 4 changes on ozone and radiative forcing (1990-). Used updated (IIASA) emission forecasts, showed that methane control was an efficient option for tropospheric O 3 and RF.

10 Multi-model studies, some examples IPCC, Prather et al., 03, used models - predicted near-surface O 3 increase of ca. 5 ppb in much of N. hemisphere. Dentener et al., 05 - used two models to look at impact of air pollutant and CH 4 changes on ozone and radiative forcing (1990-). Used updated (IIASA) emission forecasts, showed that methane control was an efficient option for tropospheric O 3 and RF. Gauss et al., 06 (ACCENT assessment) - used seven chemistry-climate models to calculate changes between 18 to 00. Illustrated complexity of results - strong spatial dependence, and differing tropospheric - stratospheric responses.

11 Multi-model studies, some examples IPCC, Prather et al., 03, used models - predicted near-surface O 3 increase of ca. 5 ppb in much of N. hemisphere. Dentener et al., 05 - used two models to look at impact of air pollutant and CH 4 changes on ozone and radiative forcing (1990-). Used updated (IIASA) emission forecasts, showed that methane control was an efficient option for tropospheric O 3 and RF. Gauss et al., 06 (ACCENT assessment) - used seven chemistry-climate models to calculate changes between 18 to 00. Illustrated complexity of results - strong spatial dependence, and differing tropospheric - stratospheric responses. Stevenson et al., 06 (ACCENT IPCC-AR4) - used 26 models to assess ozone and RF from 00 to, considered IIASA CLE, MFR and SRES A2 scenarios.

12 Multi-model studies, some examples IPCC, Prather et al., 03, used models - predicted near-surface O 3 increase of ca. 5 ppb in much of N. hemisphere. Dentener et al., 05 - used two models to look at impact of air pollutant and CH 4 changes on ozone and radiative forcing (1990-). Used updated (IIASA) emission forecasts, showed that methane control was an efficient option for tropospheric O 3 and RF. Gauss et al., 06 (ACCENT assessment) - used seven chemistry-climate models to calculate changes between 18 to 00. Illustrated complexity of results - strong spatial dependence, and differing tropospheric - stratospheric responses. Stevenson et al., 06 (ACCENT IPCC-AR4) - used 26 models to assess ozone and RF from 00 to, considered IIASA CLE, MFR and SRES A2 scenarios. Fiore et al. 09 used 21 models - calculated source-receptor relationships between continents. Considered NOx, CO, NMVOC, and CH 4. Also found CH 4 effective for reducing long-term O 3. Selected results follow...

13 Caveat... models vary! UM_CAM STOCHEM_HadGEM Altitude [km] Altitude [km] S S S EQ N N 85N 85S S S EQ N N 85N STOCHEM_HadAM3 LMDzINCA Altitude [km] Altitude [km] S S S EQ N N 85N 85S S S EQ N N 85N UIO_CTM2 FRSGC_UCI Altitude [km] Altitude [km] S S S EQ N N 85N 85S S S EQ N N 85N 85S S S EQ N N 85N Fig: Percentage changes in zonal mean O3, from chemical changes, six models. Gauss et al., ACP, 06

14 ACCENT/IPCC-AR4 AOT base-case (S1), 25 model ensemble (Slide: D. Stevenson)

15 AOT, A2-Base (ACCENT /IPCC-AR4, Slide: D. Stevenson)

16 AOT, CLE-Base (ACCENT /IPCC-AR4, Slide: D. Stevenson)

17 AOT, MFR-Base (ACCENT /IPCC-AR4, Slide: D. Stevenson)

18 Peak ozone - can be controlled locally Reduction in number of days exceeding ppb, Fiore etal., ACP, 09

19 Peak ozone - can be controlled locally Reduction in number of days exceeding ppb, Fiore etal., ACP, 09 but - long term O 3 strongly influence by intercontinental transport, especially NOx and CH 4.

20 NOx reductions - more is better! Fiore etal., ACP, 09

21 Ongoing: EMEP global source-receptor

22 Ongoing: EMEP global source-receptor Calculate effects of 15% reduction in NOx emissions Demonstration that EMEP can now calculate global S-R Results will be used by CICERO to calculate radiative forcing Funded by the Norwegian Ministry of the Environment Hot off the press...!

23 EMEP Column O 3 (Calculations by Birthe Marie Steensen, MET.NO)

24 EMEP Column O 3, effects of Europe (left) vs USA (right) (Calculations by Birthe Marie Steensen, MET.NO Caveat: EMEP model extends only to 0 hpa)

25 EMEP Surface PM 2.5, effects of Europe (left) vs USA (right) (Calculations by Birthe Marie Steensen, MET.NO)

26 Carbon-sink, Sitch et al., 07 - suggested that the indirect effect of O 3 on the carbon sink could be as high as the direct RF effect. Mechanism: ozone reduces photosynthesis, preventing CO 2 uptake. Effect: very dramatic! Fig: Temporal changes in land carbon storage and radiative forcing due to ozone. a, b, Simulated change in land carbon storage (a) and indirect radiative forcing due to O3 increases alone (b), for high (red) and low (blue) plant sensitivities to ozone.for comparison, estimates of the direct radiative forcing due to O3 increases are shown by the bars in b. (Sitch et al., 07)

27 Warning - more 03s to come?! What do we know?

28 Conclusions Tropospheric ozone is an important air pollutant and greenhouse gas Strong couplings to other gases and biosphere O 3 predicted to increase in future Stringent controls needed to reduce harmful consequences. NOx control needed for ozone and many other environmental issues, but has undesired side-effect of increasing CH 4 CH 4 control would help reduce both O 3 and RF Synergies, links and uncertainties need to be considered!