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Atmospheric chemistry

Atmospheric chemistry. Day 5 Ozone and air quality Air quality and climate change. Impact of air pollution UK Air Quality Strategy, 2007.

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Atmospheric chemistry

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  1. Atmospheric chemistry Day 5 Ozone and air quality Air quality and climate change

  2. Impact of air pollutionUK Air Quality Strategy, 2007 • “Air pollution is currently estimated to reduce the life expectancy of every person in the UK by an average of 7-8 months. The measures outlined in the strategy could help to reduce the impact on average life expectancy to five months by 2020, and provide a significant step forward in protecting our environment.” • Defra estimate the health impact of air pollution in 2005 cost £9.1–21.4 billion pa.

  3. Air Quality Standards: Ozone • European Union Limit Value: Target of 120μg.m-3 (60 ppb) for an 8 hour mean, not to be exceeded more than 25 times a year averaged over3 years. To be achieved by 31 December 2010. • UK Air Quality Objective: Target of 100μg.m-3 (50 ppb) for an 8 hour mean, not to be exceeded more than 10 times a year. To be achieved by 31 December 2005.

  4. Timescales of ozone chemistry • Global chemistry. Dominated by NOx + CH4 + sunlight. Timescales are long as are transport distances. • Regional chemistry. Many VOCs are emitted, e.g. over Europe. Each has its own lifetime governed by its rate constant for reaction with OH. The timescales of ozone production takes from hours to days. The transport distance for a wind speed of 5 m s-1 and a lifetime of 1 day is ~500 km. • Urban chemistry: high concentrations of NO from transport sources. Ozone is depressed by the reaction: NO + O3 NO2 + O2

  5. Ozone mixing ratios at MaceHeadW. Ireland, under westerly airflows

  6. Local effects – Ozone depression due to reaction with high concentrations of NO in London. Transect of ozone concentrations

  7. Radiative Forcing • Radiative forcing: the change in the net radiation balance at the tropopause caused by a particular external factor in the absence of any climate feedbacks. • These forcing mechanisms can be caused by: • change in the atmospheric constituents such as the increase in greenhouse gases (GHGs) • aerosols due to anthropogenic activity, • changes in other components of the Earth/atmosphere system such as changes in the surface albedo (the fraction of incoming radiation that is reflected). Albedo changes are caused, e.g., by changesin vegetation (e.g. burn scars or agriculture).

  8. Mechanisms of the radiative forcingdue to greenhouse gases and of the direct radiative forcings due to aerosols

  9. Global-average radiative forcing (RF) estimates and ranges in 2005(relative to 1750) for anthropogenic GHGs and other important agents and mechanisms

  10. Carbon dioxide and methane mixing ratios versus time (NOAA Climate Monitoring and Diagnostics Laboratoryhttp://www.cmdl.noaa.gov/ccgg/insitu.html)

  11. Other GHGs • N2O mixing ratios show an increase from a pre-industrial value of around 270 ppb (Prather et al., 2001) to 318 – 319 ppb in early 2004 • CFC-11, CFC-12, CFC-13, HCFC-22, and CCl4 concentrations increased from a pre-industrial value of zero to 268 ppt, 533 ppt, 4 ppt, 132 ppt, and 102 ppt respectively (1998 concentrations) - leads to radiative forcings of 0.07 W m-2, 0.17 W m-2, 0.03 W m-2, 0.03 W m-2 and 0.01 W m-2 • Ozone:approximate doubling of concentrations between the pre-industrial and present day.

  12. Climate System

  13. Schematic description of an ocean atmosphere general circulation model

  14. Evolution of models

  15. Carbon cycle

  16. Processes in an atmospheric chemistry model

  17. Sulfur cycle

  18. Sulfur emissions

  19. Sulfur emissions 1860 - 1990

  20. UK Air quality – comparison of trends in pollutants Relative annual mean concentration (monthly intervals): selection of monitoring sites in London. AQEG PM report

  21. Global NOx and CH4 emissions scenarios NOx CH4 CLE - current legislation SRES – IPCC analyses MFR – maximum feasible reduction

  22. SRES (IPCC Special Report on Emission Scenarios) scenarios • The A1 storyline is for a future world with very rapid economic growth, global population that peaks in mid-century and declines thereafter, the rapid introduction of new and more efficient technologies and with a substantial reduction in regional differences in per capita income. Within this family are three sub-scenarios with different technological emphasis: • A1FI – A1, fossil fuel intensive • A1T – A1, with non-fossil energy source emphasis • A1B – A1, with a balance across energy sources. • The A2 storyline is a more pessimistic scenario, describing a very heterogeneous world based on self-reliance, regional differences in economic and technological development and continuous increase in global population. • The B1 storyline describes a convergent world like A1, with global population peaking in mid-century, but with rapid changes in economic structures, introduction of clean and resource-efficient technologies, emphasis on global solutions to social and environmental sustainability. • The B2 storyline describes a world with emphasis on local solutions to social and environmental sustainability, less rapid and more diverse than in B1 and A1, with continuously increasing global population, but at a lower rate than A2.

  23. Royal Society Report on ozone over next 100 yearsLevel of automobile emission limits in Asian countries, compared with the EuropeanUnion. Source: Clean Air Initiative for Asian cities

  24. Impact of improved technologies in Asian countries on assessment of NOx emissions

  25. New estimates of CO emissions

  26. New estimates of CH4 emissions

  27. Predicted lobal temperature rise for different scenarios

  28. Surface O3 (ppbv) 1990s

  29. +2 to 4 ppbv over N. Atlantic/Pacific >+10 ppbvIndia Change in surface O3, CLE 2020s-1990s No climate change CLE A large fraction is due to ship NOx BAU

  30. 2020s CLEcc- 2020s CLE ΔO3 from climate change Warmer temperatures &higher humidities increase O3destruction over the oceans O3 + hn O1D + O2 O1D + H2O  2OH O1D + N2, O2  O3P But also a role from increases in isoprene emissions from vegetation &changes in lightning NOx OH+RH(+O2)  RO2 + H2O RO2 + NO RO + NO2 NO2+ hn(+O2)NO+O3

  31. O1D +H2O 2OH O1D +N2,O2 O3P  O3 Termination O3 light NO2 CH4 NO2 O3 OH H2O NO Termination CH3O2 HO2 Termination HO2 HO2 NO NO2 O3 Atmospheric oxidation of methane Yield of OH and loss of O3 depend on humidity CH4 removed mainly by reaction with OH High NOx route Ozone formation Polluted atmos Low NOx route Ozone destruction (background atmos)

  32. PAN – peroxy acetyl nitrate PAN is formed from reactions of the acetyl peroxy radical and NO2: e.g. CH3CHO + OH (+O2)  CH3COO2 + H2O CH3COO2 + NO2 CH3COO2NO2 (PAN) PAN is a reservoir compound for nitrogen oxides and provides a mechanism for their transport, especially in the upper troposphere. It provides a means of carrying nitrogen oxides from polluted to less polluted regions. It is a major player in the intercontinental transport of pollutants

  33. Impact of climate change on air quality - ozone

  34. Monitoring stations in Europe reporting high band concentrations of ozone >15 000 ‘excess deaths’ in France; 2000 in UK, ~30% from air pollution. Temperatures exceeded 350C in SE England. What about Hungary? How frequent will such summers be in the future? Heat wave in Europe, August 2003

  35. Budapest, 1 – 31 August 2003

  36. NO2 in Budapest and Hungary in 2005

  37. Diurnal variation

  38. Future summer temperatures Using a climate model simulation with greenhouse gas emissions that follow an IPCC SRES A2 emissions scenario, Hadley Centre predict that more than half of all European summers are likely to be warmer than that of 2003 by the 2040s, and by the 2060s a 2003-type summer would be unusually cool Stott et al. Nature, December 2004 2003: hottest on record (1860) Probably hottest since 1500. 15 000 excess deaths in Europe

  39. Emission of biomass smoke from Portugal in August 2003: effects on local albedo

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