Climate Change Mitigatons - AQ+CC - Students (4).pdf

Climate Change Mitigation Air Quality and Climate Change – Mitigation Measures Dr Salim Alam [email protected] - Impact of air quality on climate change - Impact of climate change on air quality - Mitigation measures for air pollution and climate change GHG vs AQ pollutants – Test yo...

Climate Change Mitigation Air Quality and Climate Change – Mitigation Measures Dr Salim Alam [email protected] - Impact of air quality on climate change - Impact of climate change on air quality - Mitigation measures for air pollution and climate change GHG vs AQ pollutants – Test yourself (2 min) CO2 NOx Greenhouse Gases (or contribute to warming) Air Quality Pollutants VOC SVOC / IVOC BC N2 O CH4 O3 NH3 SO2 SVOC – Semi volatile organic compounds / IVOC – intermediate volatile organic compounds / BC – black carbon 3 Impact of Air Quality (AQ) on Climate Change (CC) [1] NOx SO2 NH3 VOC Scatter solar radiation back to space All precursors of secondary aerosol tive Reflec Radia tive p roper ties o f clou ds • Aerosols have a negative (cooling) radiative forcing on climate • Reductions in precursors of secondary aerosol likely to lead to increase in temperature 4 Impact of Air Quality (AQ) on Climate Change (CC) [2] • Black Carbon (BC) - A product of incomplete combustion - in UK emitted from diesel vehicles - Black Smoke (AQ) or soot - Can be a substantial part of PM2.5 • Absorbs solar radiation à positive (warming) radiative forcing Black Carbon Emission Trends 2015 (million tonnes) BC +11% -24% 22% 12% % change from 2000 to 2015 -2% 5 Emissions of Black Smoke from Portugal (2003) • Over a dark surface such as an ocean or forest the forcing can be negative • Over a bright surface such as a desert or snow or above cloud, the forcing is positive • Forcing is therefore dependent upon the direction of the wind blowing the smoke (in this example) 6 Impact of Air Quality (AQ) on Climate Change (CC) [3] • Tropospheric O3 - one of the largest single components of the current radiative forcing of climate - NOx, VOC and CO are precursors of ozone (O3) - NO2 emissions need to be controlled (as well as VOC) • • AQ management is concerned with ground level ozone Radiative forcing of climate is more influenced by ozone at higher altitudes hv O3 O2 NO2 7 Impact of Air Quality (AQ) on Climate Change (CC) [4] Radiative forcing due to changes in tropospheric O3 from Radiative forcing due to changes in tropospheric O3 from From Gauss et al., 2003 (IPCC fourth assessment report) From Gauss et al., 2003 (IPCC third assessment report) 1850 – 2000 2000 – 2100 8 Impact of Air Quality (AQ) on Climate Change (CC) [5] Temperatures are low • Greenhouse Gases (GHG) - Most effective high in the troposphere Radiative impact is high • Aerosol - Effect also depends on altitude • Air pollutants - Concentrations at the surface is most important issue in AQ - Distribution is highly inhomogeneous and most are short-lived • Global Warming Potentials (GWP) and Radiative Forcing metrics to describe AQ pollutants such as aerosols on CC is problematic! Also – ozone cannot be assigned a GWP because it is secondary. • The relationship between the effects on regional radiation of pollutants and regional temperature response is far from clear, especially for pollutants that are not evenly distributed. 9 Air Quality Issues linked to Climate Change (5 min task) • In principle, any pollutant that contributes to both local and regional pollution problems and also acts as a radiative forcing agent or changes the distributions of radiative forcing agents, may potentially produce a link between AQ and CC issues Sources Energy Farming Industry Traffic Wastes Compounds SO2 NH3 NOx VOC CO CH4 Effects Receptors Groundwater Acidification Eutrophication Fine Particles Regional O3 Tropospheric O3 Lakes Terrestrial Ecosystems and soils Marine Environment Agricultural crops and forests Climate Health 10 Impact CC on AQ – Increase Temp [1] Increasing Temperatures Stratosphere/troposphere exchange • Will lead to changes in chemistry associated with ozone formation CH4 CO + NMVOC NO NO2 O3 OH H2O • Will lead to increase in water vapour in the atmosphere - ↓ background O3 - ↑ urban O3 where NOx is high • Potential increase in flux of O3 from stratosphere to troposphere Water vapour Deposition Wildfires Anthropogenic Emissions Biogenic Emissions 11 Ozone isopleths O3 (ppm) Should we decrease NOx or VOC in order to decrease O3? 0.16 0.24 0.40 0.40 NOx (ppm) 0.08 0.36 0.32 0.28 VOC (ppm) 12 Impact CC on AQ – Increase Temp [2] Heatwave 2003 Different models predicting T anomaly as a result of human contribution Yellow line = natural drivers alone Stott et al. (2004) Nature, 432, 610–614 https://doi.org/10.1016/j.atmosenv.2006.06.057 13 Impact of CC on AQ – Heatwaves July 2022 Heatwave 2006 Heatwave 2019 Heatwave 2022 Note: (1) different scales for maps (2) different models and averaging times/methods 14 Impact of CC on AQ – Heatwaves + Temp • Heat waves are predicted to be ‘typical’ by the 2040s • And will lead to ↑ summer pollution events 15 Impact of CC on AQ – Biogenic VOC Increasing Temperature BVOC - High frequency of summer pollution events - Increases in emissions of biogenic compounds e.g. Isoprene Oxidation (OH / O3 / NO3) NOx O3 + secondary organic aerosol https://doi.org/10.1016/j.atmosenv.2006.06.057 16 Impact of CC on AQ – Biogenics and Trees • Emissions of BVOC are different for different tree species • Tree planting schemes aimed at energy production or carbon sequestration should take into account the potential for increased emissions of VOC and their impact on ozone and SOA • Hot/dry summers ↓ the uptake of O3 through the stomata of plants - leading to ↓ damage to plant but ↑ in ground level O3 • Winter smog events likely to be less prevalent because of ↓ winter stagnation events 17 Climate model use for local AQ [1] • Difficult to use output from current climate models to investigate the effects of climate change on regional AQ • Improvements in the temporal resolution are needed to examine processes with daily variations, and seasonal changes in emissions from natural sources • Shorter timescales are also needed for projections (2020 – 2030, for example). • Surface T and soil dryness are key to understanding the likely severity of future summer pollution episodes 18 Climate model use for local AQ [2] • Climate models are becoming more sophisticated, but still need improvement to represent the real world 19 Atmospheric Chemistry for Climate Models • Simplest chemistry models only include chemistry for NOx, O3, CH4 and CO – a total of 20 species • Complex chemistry models simulating urban pollution may need to treat over 100 species • Global tropospheric-climate modelling typically include 50-60 species including isoprene and their oxidation products • NO model can represent all the important chemicals found in the atmosphere 20 Atmospheric Mechanisms Master Chemical Mechanism (MCM) http://chmlin9.leeds.ac.uk/MCMv3.3.1/home.htt - Near explicit mechanism - Describes the degradation of 142 NMVOC emitted in the atmosphere How does it work??? Describes degradation steps from emission to H2O and CO Climate models need detailed atmospheric chemistry 21 Mitigation Measures for Air Pollution and CC • Over the past 20-30 years most attention has been focused on mitigation of AQ impacts through: (1) legislation (2) changes to technology • Little or no consideration has been given to the impacts (beneficial or detrimental) on climate • AQ policies and CC policies have (largely) been developed separately from one another 22 Mitigation Measures for Air Pollution and CC Mitigation measures can be broadly identified and categorised into: - Conservation: reducing the use of resources through energy conservation - Efficiency: reducing use and emissions of AQ & climate active pollutants - Abatement: the application of a technological approach to reduce emissions - Fuel switching: substituting a higher emission fuel with a lower emission fuel - Demand management: implementing policies/measures to control or influence the demand for a product or service - Behavioural change: changing habits of individuals to reduce emissions 23 Air quality emission reductions From 2002 to 2020 UK emissions have shown significant reductions: NOx SO2 VOC PM10 NH3 45% 64% 26% 19% 10% Among DEFRAs top ten AQ priority pollutants CO2 4% AQ Policy vs CC policy / regional vs global Reductions observed because the large emitters have now been controlled – mitigation measures! 24 Comparing AQ and CC impacts There are inherent methodological difficulties in identifying the impact of measures on emissions of pollutants of concern from an AQ perspective and those that have impacts (directly or indirectly) on climate. e.g. Aerosols and their precursors 25 Win-wins and trade offs [1] ‘End of pipe’ AQ controls Flue gas desulfurisation (FGD) Reduced sulfur in fuel • • • Reduction in SO2 emissions and S limits in fuel Increased (<5%) refinery CO2 emissions These could be offset by improvements to petrol engine efficiencies • • Reduction in SO2 emissions Formation of CO2 (~3%) via use of limestone in wet scrubbing 26 Win-wins and trade offs [2] Diesel fuel vs petrol CO 2 CO 2 CO 2 • Diesel fuel is generally considered to have GHG benefits over petro CO 2 CO 2 CO 2 2 2 O CO 2 CO 2 CO CO 2 C CO 2 • Diesel cars have larger engines than equivalent petrol engines – reduces CO2 benefits • Diesel fuel demand is larger so refinery processes used – reduces CO2 benefits • Diesel leads to BC emissions – contribution to warming effects? 27 Win-wins and trade offs [3] • Selective catalytic reduction (SCR) • Could lead to increased N2O emissions - reduces NOx and CO2 emissions - enables engines to operate with higher efficiencies GWP, radiative efficiencies and lifetimes are large! 28 Win-wins • Energy conservation measures - Benefits of improved efficiencies can be reduced through encouraging increased demand in same (or other) products - Combined heat and power - Fuel switching to lower carbon or renewables (e.g. coal to natural gas) - Reduction in CO2, SO2 and NOx, especially when used with abatement 29 Mitigations measures that could reduce emissions of AQ and climate-active pollutants Measure Effect Power generation Fuel switching to lower carbon or renewables (e.g. coal to natural gas) Reduction in CO2, SO2, NOx (esp., if with abatement) Combined heat and power Reduction in AQ and climate-active pollutants if used to replace conventional electricity generation Transport Use of certain new technologies and fuels (e.g. hybrid vehicles) Reduces point of use and fuel chain emissions of CO2 and AQ pollutants Low emission zones Only if newer (more efficient) vehicles replace older (less efficient) vehicles Efficiency Improvements More efficient domestic appliances/industrial processes; improvements in technology Often a proportionate reduction in climate-active and AQ pollutants; benefits of improved efficiencies can be reduced through encouraging increased demand in same (or other) products Demand Management Road user charging Conservation Home insulation 30 Climate mitigations measures that could increase emissions of AQ pollutants Measure Effect Increased aircraft fuel efficiency Reduction in CO2 but increase in NOx Fuel-switching (transport) Increased use of diesel in place of petrol (increase NOx and PM) Use of biofuels under certain conditions General Use of N-based fertilisers could ↑ NH3 emissions. N2O emissions may ↑ for some fuels Transport fuels Increased emissions at point of use and increased production emissions of AQ pollutants Domestic use If used in place of electricity of natural gas – could ↑ PM emissions Waste Management Incineration instead of landfill. Reduced CH4 but increases AQ pollutants Forests as a sink for carbon Potential to ↑ emissions of BVOC 31 AQ mitigations measures that could increase emissions of Climate-active pollutants Measure Effect Power generation Flue gas delusulfurisation (FGD) Formation of CO2 through wet scrubbing Transport Abatement of AQ emissions SCR potential to increase N2O Reduced sulfur in fuels Increased refinery CO2 emissions. 32 Measures that could result in increased AQ and Climateactive pollutant emissions Measure Effect Increased demand for products / services Aircraft – increased fuel efficiency has been exceeded by increased demand Transport modal shifts Increased use of short-haul flights at the expense of rail Increased use of coal for electricity generation If used in place of renewables, nuclear or natural gas Use of biofuels under certain circumstances Significant increase in N2O if nitrogen-based fertilisers used; transportation emissions over long distances (if imported); increased AQ emissions if used in high proportions at point of use; fuel-chain emissions increase particularly if significant use of fossil fuels 33 Air Quality and Climate Change – hand in hand - Impact of air quality on climate change - Impact of climate change on air quality - Mitigation measures for air pollution and climate change 34 Further reading and literature • Pearson, J.K. and Derwent, R., 2022. Air Pollution and Climate Change: The Basics. Routledge. • Hester, R. and Harrison, R., 2016. Air Quality Management (Issues in Environmental Science and Technology). • Air Quality and Climate Change: A UK Perspective (AQEG) https://uk-air.defra.gov.uk/library/assets/documents/reports/aqeg/fullreport.pdf • Air Quality and Climate Change Research (US-EPA) https://www.epa.gov/air-research/air-quality-and-climate-change-research 35