Air Transportation: Emissions and Effects

Transcription

1 Air Transportation: Emissions and Effects Joyce E. Penner University of Michigan Report Co-ordinator: IPCC Special Report on Aviation and the Global Atmosphere Presentation to the First Regional Symposium on Carbon Management Dhahran, May /14/2006 1

2 Special Report on Aviation and the Global Atmosphere Produced following a request from the International Civil Aviation Authority 10 Chapters, 488 pages, 107 Lead Authors, 108 Contributing Authors 22% of authors from the aviation industry Review comments from over 200 expert reviewers and 48 governments 7/14/2006 2

3 Why a concern about aviation? As a single component aviation was growing quickly The release of CO 2 into the atmosphere by the current fleet of aircraft represents annually 2-3% of all anthropogenic CO 2 emissions. Aviation s identified role in climate change, ~3% of total, is not dominant, but is comparable to California. Studies conducted by aviation specialists suggested that the number of passenger-kilometers could increase by a factor by year 2015 with a corresponding increase of a factor 2-3 in fuel consumption and CO 2 emissions 7/14/2006 3

4 Why a concern about aviation? Aircraft emissions are deposited in a fragile location and may exacerbate several environmental issues: Emissions of O 3 destroying and polluting compounds:» NO x, VOCs Emissions of particles and particle precursors:» H 2 SO 4, soot, SO 2 Emissions of greenhouse gases:» CO 2, H 2 O 7/14/2006 4

5 Aircraft effects on ozone Stratosphere: Ozone depletion Troposphere: Ozone production 7/14/2006 5

6 Nox emissions increase tropospheric ozone with subsequent effects on CH 4 : O 3 OH CH 4 Change in OH concentration in July (106 molecules/cm3) Altitude (km) Latitude 7/14/2006 6

7 The predicted ozone increase from subsonic aircraft differs from model to model: 7/14/2006 7

8 Particle emissions affect cloudiness: 7/14/2006 8

9 Cirrus clouds and contrails cool (by reflecting solar radiation) and warm (by trapping infrared radiation): Long wave warming Flux Change (W/m 2 ) Net effect is a warming Solar radiative cooling 7/14/2006 9

10 Contrail coverage has been estimated from fuel use and estimated conditions of temperature and humidity in the upper troposphere: 7/14/

11 Satellites observations show cloud increases correlated with aircraft corridors 7/14/

12 Cirrus cloudiness increases as aviation fuel consumption increases Change in Cirrus Occurence (%) Number of 3x3 Grid-Boxes Change in cirrus occurrence Fuel Consumption (10-6 kg/yr/m2) 7/14/

13 Radiative Forcing from Aircraft in 1992: Out of 1.5 Wm -2 7/14/

14 New study shows ice number concentration increased and effective radius decreased by soot (Penner and Chen, 2006) Pre-industrial With soot from ground and aircraft sources Ice number concentration Effective radius of ice crystal 7/14/

15 Climate forcing depends on modeling assumptions but is larger than older studies: Total Forcing Shortwave Longwave Anthropogenic sulfate aerosols to to to Anthropogenic surface soot aerosols Aircraft generated soot to to to to to to /14/

16 Aircraft effects for some aspects are smaller in recent assessments, but cirrus impacts could be larger Penner and Chen, /14/

17 Comparison of radiative forcing from all anthropogenic emissions and from aircraft, 1992 (Note scale change on graph) Total: 3.8 Wm -2 ( ) New Total (with cirrus): Wm -2 Radiative Forcing (Wm -2 ) a) CO 2 CH 4 N 2 O CFCs HFCs Trop. O 3 Strat. O 3 Aerosol Radiative Forcing (Wm -2 ) b) CO 2 good O 3 CH 4 from NO x fair poor H 2 O Contrails Cirrus Clouds poor fair very poor Direct Sulfate fair Direct Soot fair Total (without cirrus clouds) 7/14/

18 Q: What can reduce atmospheric CO 2 from Aviation? There is no practical way to keep aviation CO 2 from accumulating. Improve fuel efficiency. 7/14/

19 Q: What about reducing aviation NOx and O 3? NOx will make O 3 in the upper troposphere. The increase in tropospheric O 3 is linearly proportional to the amount of NOx in the exhaust. Only small saturation effects are noted. Thus low-nox engines would reduce the O 3 RF. 7/14/

20 Q: Can Aviation s RF due to contrails be reduced? Can planes fly to avoid contrail regions? 7/14/

21 Contrails form when aircraft fly through air supersaturated with respect to ICE Flying lower could avoid these effects but would use more fuel and may still cause increases in ice number and cloud forcing 7/14/

22 IPCC / Special Report on Aviation & Global Atmosphere Aviation s share of greenhouse gas warming will remain a significant fraction of the world total, when compared to other sub-sectors and to many nations. Significant reductions in Aviation s climate impacts, could be achieved with any of several technologies:» Further improve fuel efficiency per passenger km» Adopt low-nox engines» Avoid meteorological conditions favoring contrails? 7/14/