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Chapter 5

Geography 2153A chapter 5 lecture notes.docx

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Western University
Geography 2153A/B
Jamie Baxter

Geography 2153A Chapter 5- Lecture Notes Our Changing Atmosphere Atmospheric concerns • Climate systems • Changes, atmospheric composition • Greenhouse effect and climate change • Ozone layer • Airborne contaminants • Acidic deposition • Policy responses • Challenges to air quality sustainability Human activities that alter earth’s atmosphere Activity Substances with Negative Atmospheric Effect Industrial SO2, particulates (PM), CFCs heavy metals, reactive hydrocarbons (HCs) Burning fossil fuels GHGs, SO2 Transportation GHGs, smog, NOx, Sox, polycyclic aromatic HCs (PAHs), Carbon monoxide (CO) Deforestation GHGs, CO, PAH’s, PM, loss of carbon sinks Agricultural practices CH4 Earth’s Natural Climate System - dynamic atmosphere +circulating ocean +changing earth surface - All the systems are connected and theres feedbacks - Affecting on one part of the system can affect others - Look at diagram on slide 4 Natural green house gas effect Natural and anthropogenic process • 0.6 average global surface air increase in temperature last 100 years • Accelerating in recent decades (most likely) due to anthropogenic causes • Time lag - changes now may not have effects for decades Not many… - Radiation coming into earth is the first component, uva, uvv to heat up the surface - Reradiated back, 10% leaves earth, 90% is absorbed - Ecosystems are fragile - Need a stable temperature range to survive - Its accelerating, a steep increase which is a concern GHGs are both natural and anthropogenic: • carbon dioxide (CO );2 • methane (CH ); 4 • nitrous oxide (N O2; • water vapour; • ozone (0 )3 - Plastic and food industry’s by product may contain N2O - Recycling of heat, the brown arrow in the diagram - Green house gas effect is a good thing, but the acceleration is not - Which ones are from pre industrialization… - Methane, co2, water vapour - Methane from animals - Volcanic eruptions - Forest fires - The increase is substantial which is why we are concerned, the add on since industrialization is the issue Enhanced Greenhouse Gas Effect Concentrations of: • CO 2ncreased 31 +/- 4% • CH 4ncreased 151 +/- 25% • NO 2ncreased 17 +/- 5% exceed any past levels detectable in fossilized air bubbles of ice cores over the past 420,000 years unprecedented rate of increase in last 20,000 years “halocarbons”: clearly human sources Halocarbon – carbon attached to chlorine, fluorine, bromine, iodine - all the green house gas effects have increase - Fossil fuel consumption and burning - Fossilized air is the air inside ice, ice coring - Transportation energy Characteristics of changes in GHGs • GWP Global Warming Potential – the climate forcing potential of greenhouse gases as CO e2(uivalents) • changes in chlorofluorocarbons and halons: synthetic • changes in aerosols: small solid or liquid particles suspended in the air, contribute to photochemical smog, acid deposition, etc. (volcanic eruptions, aircraft emissions) • Carbon dioxide, methane and nitrous oxide • GWP – The Global Warming Potential (GWP) for a gas is a measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide. The larger the GWP, the more warming the gas causes. For example, methane's 100-year GWP is 21, which means that methane will cause 21 times as much warming as an equivalent mass of carbon dioxide over a 100-year time period. But the amount released also matters! • Characteristics of changes in GHGs • changes in human-made chlorofluorocarbons and halons (both derivative of methane) • changes in aerosols: small solid or liquid particles suspended in the air, contribute to photochemical smog, acid deposition, etc. (e.g.,volcanic eruptions, aircraft emissions) - Coal is the worst emitter of GHG - Coal is cheap to create large amounts of energy - Very efficient but makes GHG Though CO2 has the lowest GWP, it is still currently the most important anthropogenic contribution to global climate change - Not yet understood - Caused by globalization - Co2 is released in such large amounts looking at the relative contribution over 100 years - Co2 is from energy production and methane is agriculture - Look at how do we get to the relative contribution and how is emitted Proposed causes of climate change Changes in: • solar intensity • stratospheric and tropospheric aerosol concentrations • concentrations of GHGs • ozone layer thickness • ocean - atmosphere systems (e.g., El-Niño) - Ozone layer protects us from the sun’s rays - Ozone gas is a green house gas Impacts of global climate change - drought and flooding - glacier retreats leads to flooding, erosion and alters hydrological cycle - Increases chance of malaria - Spread of diseases, droughts and floods - See more shrinking of glaciers than growing Thinning of the (Stratospheric) Ozone Layer Ground-level ozone vs stratospheric ozone • stratospheric: 15-40km, but maximum concentration 20-25 km above the Earth’s surface • “ozone hole”, polar vortex, polar stratospheric clouds - Chemical processes created ozone and stratospheric ozone - To protect solar radiation - Absorb uv radiation to keep making the ozone layer Ozone (O )3depleting substances (ODS) • e.g., volcanoes, chlorofluorocarbons (CFCs) • Sunlight breaks Cl away from various forms of CFC then... Cl + O3 ClO + O 2 ClO + O Cl + O2 one Cl can destroy 100,000 0 3 - Small amount of CFC can have high impact - CFCs used to be common propellants in aerosol cans (now petroleum products are used- GHGs) Spatial variations in ozone depletion • Antarctic - severe “polar vortex” “polar stratospheric clouds” • Arctic – less severe • Tropical/Mid-Latitude – least - seasonally, daily, and spatially - The artic pole is also thin but not as mu
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