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Atmospheric chemistry Day 5 Ozone and air quality Air quality and climate change Impact of air pollution UK 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. 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. Timescales of ozone chemistry 1. Global chemistry. Dominated by NOx + CH4 + sunlight. Timescales are long as are transport distances. 2. 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. 3. Urban chemistry: high concentrations of NO from transport sources. Ozone is depressed by the reaction: NO + O3 NO2 + O2 01/04/2006 01/04/2005 01/04/2004 01/04/2003 01/04/2002 01/04/2001 01/04/2000 01/04/1999 01/04/1998 01/04/1997 01/04/1996 01/04/1995 01/04/1994 01/04/1993 01/04/1992 01/04/1991 01/04/1990 01/04/1989 01/04/1988 01/04/1987 Monthly mean baseline ozone, ug/m3 Ozone mixing ratios at MaceHead W. Ireland, under westerly airflows 110 100 90 80 70 60 50 40 Local effects – Ozone depression due to reaction with high concentrations of NO in London. Transect of ozone concentrations 70 Annual Mean Concentration (in g m-3) 60 50 40 30 20 10 0 465000 475000 485000 495000 505000 515000 525000 535000 545000 555000 Easting PCM 2003 2003 AURN measurements Ascot Rural ADMS-Urban 2003 565000 575000 585000 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). Mechanisms of the radiative forcing due to greenhouse gases and of the direct radiative forcings due to aerosols Global-average radiative forcing (RF) estimates and ranges in 2005 (relative to 1750) for anthropogenic GHGs and other important agents and mechanisms Carbon dioxide and methane mixing ratios versus time (NOAA Climate Monitoring and Diagnostics Laboratory http://www.cmdl.noaa.gov/ccgg/insitu.html) Other GHGs • N2O mixing ratios show an increase from a preindustrial 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. Climate System Schematic description of an ocean atmosphere general circulation model Evolution of models Carbon cycle Processes in an atmospheric chemistry model Sulfur cycle Sulfur emissions Sulfur emissions 1860 - 1990 UK Air quality – comparison of trends in pollutants relative annual mean concentration 120 100 80 60 40 SO2 PM10 CO NOx NO2 20 0 1997 1998 1999 2000 2001 Year 2002 2003 2004 Relative annual mean concentration (monthly intervals): selection of monitoring sites in London. AQEG PM report Global NOx and CH4 emissions scenarios 200.0 160.0 NOx 120.0 80.0 40.0 0.0 1990 2000 Europe Asia + Oceania Africa + Middle East SRES A2 - World Total 2010 2020 2030 North America Latin America Maximum Feasible Reduction (MFR) SRES B2 - World Total 600 500 CH4 400 CLE - current legislation SRES – IPCC analyses MFR – maximum feasible reduction 300 200 100 0 1990 2000 Europe Asia + Oceania Africa + Middle East SRES A2 - World Total 2010 2020 North America Latin America Maximum Feasible Reduction (MFR) SRES B2 - World Total 2030 • • • • • • • 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 resourceefficient 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. Royal Society Report on ozone over next 100 years Level of automobile emission limits in Asian countries, compared with the EuropeanUnion. Source: Clean Air Initiative for Asian cities Impact of improved technologies in Asian countries on assessment of NOx emissions New estimates of CO emissions New estimates of CH4 emissions Predicted lobal temperature rise for different scenarios Surface O3 (ppbv) 1990s Change in surface O3, CLE 2020s-1990s No climate change CLE +2 to 4 ppbv over N. Atlantic/Pacific >+10 ppbv India A large fraction is due to ship NOx BAU 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 2020s CLEcc2020s CLE Atmospheric oxidation of Termination CH4 removed mainly by reaction with OH O 3 NO2 CH4 NO2 OH O3 NO CH3O2 HO2 HO2 NO Low NOx route Ozone destruction (background atmos) Yield of OH and loss of O3 depend on humidity light H2O Termination O1D +H2O 2OH O1D +N2,O2 O3P methane O3 NO2 O3 Termination HO2 High NOx route Ozone formation Polluted atmos 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 Impact of climate change on air quality - ozone Heat wave in Europe, August 2003 • 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? ozone / microg/m3 Budapest, 1 – 31 August 2003 200 180 160 140 120 100 80 60 40 20 0 Széna tér Baross tér Pesthidegkút Kőrakás park Laborc u. 0 100 200 300 400 time 500 600 700 800 NO2 in Budapest and Hungary in 2005 Diurnal variation 13th August 2003 Pesthidegkut ozone/ microg/cm3 200 150 100 Ser i es1 50 0 -1 4 9 14 time of day 19 24 Future summer temperatures 2003: hottest on record (1860) Probably hottest since 1500. 15 000 excess deaths in Europe 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 Emission of biomass smoke from Portugal in August 2003: effects on local albedo