ESC 301.01 - VII - Global Atmospheric Pollution PDF

ESc 301.01 The Environmental Dimension VII-Global Atmospheric Pollution Ferhan Çeçen Part 1 - Greenhouse effect The atmosphere Electromagnetic Spectrum  Solar Energy Balance Incoming solar radiation strikes Earth's atmosphere in the form of visible light, plus...

ESc 301.01 The Environmental Dimension VII-Global Atmospheric Pollution Ferhan Çeçen Part 1 - Greenhouse effect The atmosphere Electromagnetic Spectrum  Solar Energy Balance Incoming solar radiation strikes Earth's atmosphere in the form of visible light, plus ultraviolet and infrared radiation. Ultraviolet (UV) radiation has a higher energy level than visible light, and infrared (IR) radiation has a weaker energy level. Some of the sun's incoming radiation is absorbed by the atmosphere, the oceans and the surface of the Earth. Much of it, however, is reflected back out to space as low-energy IR radiation. For Earth's temperature to remain stable, the amount of incoming solar radiation should be roughly equal to the amount of IR radiation leaving the atmosphere. As Earth's atmosphere changes, the amount of IR radiation leaving the atmosphere also changes.  The Greenhouse Effect In a greenhouse, visible radiation (visible light) from the sun passes without any intervention through the glass and is absorbed by the plants and the soil inside. The plants and the soil emit thermal radiation (so called blackbody radiation). This radiation is on the far end of the electromagnetic spectrum. Thermal radiation (infrared radiation) is absorbed by the glass and some of it is reemitted back into the greenhouse. Due to this mechanism of emission and reemission, the temperature in the greenhouse increases to many degrees above the ambient temperature. Just as the glass on top of a greenhouse holds the sun’s warmth inside, the atmosphere traps the sun’s heat near the Earth’s surface and keeps the Earth warm. This is called “the natural greenhouse effect” because it makes the Earth a perfect planet for living things.  Major constituents of dry air, by volume Gas Volume(A) Name Formula in ppmv(B) in % Nitrogen N2 780,840 78.084 Oxygen O2 209,460 20.946 Argon Ar 9,340 0.9340 Carbon dioxide CO2 400 0.04 Neon Ne 18.18 0.001818 Helium He 5.24 0.000524 Methane CH4 1.79 0.000179 Not included in above dry atmosphere: Water vapor(C) H2O 10–50,000(D) 0.001%–5%(D) notes: (A) volume fraction is equal to mole fraction for ideal gas only, also see volume (thermodynamics) (B) ppmv: parts per million by volume (C) Water vapor is about 0.25% by mass over full atmosphere (D) Water vapor strongly varies locally  The average surface temperature of the Earth is about 15 ˚C. Without any atmosphere, the average temperature would be -18 ˚C. This average temperature would have been -6 ˚C if the atmosphere contained only N2 and O2. In the atmosphere the water vapor, CO2 and methane are the responsible chemical compounds that absorb sun’s heat. This heat is actually low energy radiation reflected from the Earth’s surface and near surface. Low energy radiation is long wave and is also termed as infrared radiation. In 1827, Jean-Baptiste Fourier (better known as a mathematician) first recognized the warming effect of the greenhouse gases. He also pointed out the similarity between what happens in the atmosphere and in the glass of a greenhouse, which led to the name “greenhouse effect”. ABSORPTION OF RADIATION BY GASES Ozone (O3) and oxygen (O2) absorb most of the ultraviolet light (below 0.3 microns). Carbon dioxide has three large absorption bands in the infrared region at about 2.7, 4.3, and 15 microns. There is already sufficient CO2 in the atmosphere to absorb almost all of the radiation from the sun or from the surface of the earth in the principal CO2 absorption bands. Water has several absorption bands in the infrared, and even has some absorption well into the microwave region. These gases absorb some of the radiation emitted by the Earth’s surface, but then to emit much less radiation out to space. They, therefore, act as a radiation blanket over the surface. Here the outer surface is colder than the lower surface.  Factors affecting Earth’s temperature Solar flux Earth’s reflectivity: albedo Albedo is usually expressed as a decimal fraction of the total incoming (incident) energy reflected from the surface. Amount of warming provided by the greenhouse gases  The Natural Greenhouse Effect The natural greenhouse effect is due to the gases water vapor and carbon dioxide (we have a few more gases of relatively minor effect). The amount of water vapor in our atmosphere depends mostly on the temperature of the surface of the oceans. Therefore, most of it originates through evaporation from the ocean surface and is not influenced directly by human activity.  The Enhanced Greenhouse Effect Increased amount of carbon dioxide is leading to global warming of the Earth’s surface because of enhanced greenhouse effect. Carbon dioxide amount has increased after the industrial revolution due to human involvement: – Combustion generating CO2 Industry Transportation Power generation – Loss of CO2 sinks Deforestation  ANIMATION ABOUT THE GREENHOUSE EFFECT http://www.environment.gov.au/climate-change/climate-science/greenhouse-effect  ANIMATION ABOUT THE GREENHOUSE EFFECT Step 1: Solar radiation reaches the Earth's atmosphere - some of this is reflected back into space. Step 2: The rest of the sun's energy is absorbed by the land and the oceans, heating the Earth. Step 3: Heat radiates from Earth towards space. Step 4: Some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth warm enough to sustain life. Step 5: Human activities such as burning fossil fuels, agriculture and land clearing are increasing the amount of greenhouse gases released into the atmosphere. Step 6: This is trapping extra heat, and causing the Earth's temperature to rise.  Climate Change - Increasing Concentrations of CO2 and other Green House Gases (GHG) CO2 (carbon dioxide) natural and anthropogenic sources recent increase due to fossil-fuel combustion and deforestation CH4 (methane) natural and anthropogenic sources anthropogenic emission sources include landfills, oil and natural gas systems, agricultural activities, coal mining, stationary and mobile combustion, wastewater treatment, and certain industrial processes. N2O (nitrous oxide) natural and anthropogenic sources nitrogen-based fertilizers Other important Greenhouse Gases: CFCs, halons etc. Water vapor Black Carbon (BC) is produced both naturally and by human activities as a result of the incomplete combustion of fossil fuels, biofuels, and biomass.  Global Warming Potential (GWP) of Greenhouse Gases (GHG) Global warming potential (GWP) is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time interval, commonly 20, 100, or 500 years. GWP is expressed as a factor of carbon dioxide (whose GWP is standardized to 1). Relative Contributions to Global Warming  Increase in Greenhouse Gases (GHG) throughout centuries Concentrations of greenhouse gases in the Concentrations of greenhouse gases in the atmosphere from year 0 to the year 1750 atmosphere since Industrial Revolution  Atmospheric CO2 concentration The global CO2 concentration increased from ~277 ppm in 1750 to 419.3 ppm in 2023 (up 51%) Globally averaged surface atmospheric CO2 concentration. Data from: NOAA-GML after 1980; the Scripps Institution of Oceanography before 1980 Source: NOAA-GML; Scripps Institution of Oceanography; Friedlingstein et al 2023; Global Carbon Project 2023  Anthropogenic perturbation of the global carbon cycle Perturbation of the global carbon cycle caused by anthropogenic activities, global annual average for the decade 2013–2022 (GtCO2/yr) CDR here refers to Carbon Dioxide Removal besides those associated with land-use that are accounted for in the Land-use change estimate. The budget imbalance is the difference between the estimated emissions and sinks. Source: NOAA-GML; Friedlingstein et al 2023; Canadell et al 2021 (IPCC AR6 WG1 Chapter 5); Global Carbon Project 2023  Global Fossil CO2 Emissions Global fossil CO2 emissions: 37.1 ± 2 GtCO2 in 2022, 63% over 1990 Projection for 2023: 37.5 ± 2 GtCO2, 1.1% [0.0% to +2.1%] higher than 2022 Uncertainty is ±5% for one standard deviation (IPCC “likely” range) When including cement carbonation, the 2022 and 2023 estimates amount to 36.4 ± 2 GtCO2 and 36.8 ± 2 GtCO2 respectively The 2023 projection is based on preliminary data and modelling. Source: Friedlingstein et al 2023; Global Carbon Project 2023  Emissions Projections for 2023 There are sharp contrasts between the projected emissions changes for the top emitters The 2023 projections are based on preliminary data and modelling. ‘Bunkers’ are fossil fuels (oil) used for shipping and aviation in international territory Source: Friedlingstein et al 2023; Global Carbon Project 2023  Fossil CO2 emissions growth: 2021–2023 Emissions are expected to increase in China, India and international aviation in 2023, and decline in USA, the EU, and the combined rest of the world (Others) The 2023 projections are based on preliminary data and modelling. Source: Friedlingstein et al 2023; Global Carbon Project 2023  Summary of fossil CO2 emissions in 2022 and 2023 2023 projected 2022 emissions 2023 projected 2022 growth emissions Region / Country (billion emissions (percent) growth tonnes/yr) (billion tonnes/yr) (percent) China 11.4 +0.5% +4.0% 11.9 USA 5.1 +0.5% -3.0% 4.9 India 2.8 +5.8% +8.2% 3.1 EU27 2.8 -1.6% -7.4% 2.6 International 1.0 +15.6% +11.9% 1.2 bunkers* All others 15.1 +0.0% -0.4 14.0 World 37.1 +0.9% +1.1% 37.5 World (incl. cement *Emissions 36.4 and maritime +0.9% from use of international aviation +1.1% shipping bunker fuels are not usually included in36.8 national totals. carbonation) Cement carbonation sink only included in global (World) estimate. Source: Friedlingstein et al 2023; Global Carbon Project 2023  Global carbon budget Carbon emissions are partitioned among the atmosphere and carbon sinks on land and in the ocean The “imbalance” between total emissions and total sinks is an active area of research Source: Friedlingstein et al 2023; Global Carbon Project 2023 The consequences of excess heat from greenhouse gas emissions POSITIVE FEEDBACKS Increase in the amount of water vapor in the atmosphere due to higher air and ocean temperatures. The ability of air to hold moisture increases exponentially with temperature, so a warming atmosphere will contain more water vapor, which in turn will enhance the greenhouse effect. Loss of snow and sea ice due to rising temperatures. Melting of permafrost, resulting in the release of methane, a potent greenhouse gas, and CO2 from soil organic matter. Release of carbon from ecosystems due to changing climatic conditions. (accelerated decomposition of soil organic matter in temperate forests and grasslands due to temperature and precipitation changes). NEGATIVE FEEDBACKS Examples of negative feedback: Plants growing in warmer conditions and higher concentrations of CO2 can absorb more CO2 helping to reduce the greenhouse effect. Clouds lead to reflection of incoming solar radiation. Sulfate aerosols (produced due to the industrial release of sulfur dioxide, SO2) are reflective, with a net cooling effect. We can presently say that positive feedbacks are more pronounced in comparison with the negative feedbacks. The Earth as a Greenhouse Consequences of Increases in Greenhouse Gases Together, the Greenland and Antarctic Ice Sheets contain more than 99 percent of the freshwater ice on Earth. Credit: NSIDC IPCC: Intergovernmental Panel on Climate Change  IPCC Reports The IPCC prepares comprehensive Assessment Reports about knowledge on climate change, its causes, potential impacts and response options. The IPCC also produces Special Reports, which are an assessment on a specific issue and Methodology Reports, which provide practical guidelines for the preparation of greenhouse gas inventories. https://www.ipcc.ch/reports/ Others: https://climate.nasa.gov/vital-signs/sea-level/ Video: Global Warming from 1880 to 2020 https://climate.nasa.gov/climate_resources/139/video-global- warming-from-1880-to-2020/  Solutions to Global Warming Reduction of CO2 emissions – Shifting to alternative energy sources or solving the problem of CO2 disposal Carbon capture and storage: Carbon dioxide (CO2) capture and storage (CCS) is a process consisting of the separation of CO2 from industrial and energy-related sources, transport to a storage location and long-term isolation from the atmosphere. Capture of CO2 can be applied to large point sources. The CO2 would then be transported for storage in geological formations, in the ocean, in mineral carbonates, or for use in industrial processes. Part 2 - Ozone Depletion What is the difference between UV-A, UV-B and UV-C? Short-wavelength UV-C (100-280 nm) is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface. Medium-wavelength UV-B (280-315 nm) is very biologically active but cannot penetrate beyond the superficial skin layers. Most solar UVB is filtered by the atmosphere. Human exposure to UV-B increases the risk of skin cancer, cataracts, and a suppressed immune system. UV-B exposure can also damage terrestrial plant life, single cell organisms, and aquatic ecosystems. The relatively long-wavelength UV-A (315-400 nm) accounts for approximately 95 per cent of the UV radiation reaching the Earth's surface. It can penetrate into the deeper layers of the skin and is responsible for the immediate tanning effect. Furthermore, it also contributes to skin ageing and wrinkling. For a long time it was thought that UVA could not cause any lasting damage. Recent studies strongly suggest that it may also enhance the development of skin cancers.  STRATOSPHERIC OZONE Ultraviolet radiation is harmful to life. It can damage molecular bonds, Ieading to a range of undesirable effects in biological organisms, such as skin cancer in humans. At the earth's surface, we are substantially protected from the sun's ultraviolet radiation by the presence of oxygen (02) and ozone (03) in the stratosphere. About 90 percent of all atmospheric ozone is in the stratosphere. Molecular oxygen (02) efficiently absorbs radiation at wavelengths less than 0.24 μm (240 nm). Ozone is an efficient absorber of light with wavelengths of 0.24-0.32 μm (240-320 nm); thus it absorbs UVB radiation.  Stratospheric ozone: the natural cycle The ozone molecule (O3) contains three atoms of oxygen and is mainly formed by the action of the UV rays on oxygen molecules (diatomic oxygen, O2) in the upper part of Earth’s atmosphere (called the stratosphere): Production of ozone: Photolysis of molecular oxygen (by the short-wavelength UV radiation at λ