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Global Environmental Change CLIMATE CHANGE, GLOBAL WARMING, OZONE DEPLETION… …WHAT’S GOING ON? Stratospheric Ozone Depletion https://www.youtube.com/watch?v=I1wrEvc2URE What are Halogen Gases? Where do CFC’s come from? Where else can we find Ozone depleting chemicals? How long do CFC’s last??? The chlorine atoms can break down tens of thousands of ozone molecules before being removed from the stratosphere. Given the longevity of CFC molecules, recovery times are measured in decades. It is calculated that a CFC molecule takes an average of 15 years to go from the ground level up to the upper atmosphere, and it can stay there for about a century, destroying up to one hundred thousand ozone molecules during that time. What are the effects of Ozone depletion? Skin cancer Cataracts Damage to crops Loss in productivity of phytoplankton in the ocean., Montreal Protocol After a series of rigorous meetings and negotiations, the Montreal Protocol on Substances that Deplete the Ozone Layer was finally agreed upon on 16 September 1987 at the Headquarters of the International Civil Aviation Organization in Montreal. The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere--chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform--are to be phased out by 2000 (2005 for methyl chloroform). Scientific theory and evidence suggest that, once emitted to the atmosphere, these compounds could significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation. Back to the Troposphere Climate change is the fastest-developing area of environmental science What is Climate? Climate = the average and variations of weather over a long period of time (~30 years) The changes in temperature, moisture, wind, precipitation, etc. Above: Global average for atmospheric water vapor. What is Weather? Weather = all natural phenonmena within the atmosphere at a given time (hours to days) Short-term conditions at localized sites What is climate change? Global climate change = describes trends and variations in Earth’s climate Temperature, precipitation, storm frequency Global warming and climate change are not the same Global warming = an increase in Earth’s average temperature Only one aspect of climate change Global warming Climate change and global warming refer to current trends Earth’s climate has varied naturally through time The current rapid climatic changes are due to humans Fossil fuel combustion and deforestation Understanding climate change requires understanding how our planet’s climate works The sun and atmosphere keep Earth warm Four factors exert the most influence on climate The sun = without it, Earth would be dark and frozen Supplies most of Earth’s energy The atmosphere = without it, Earth’s temperature would be much colder The oceans = shape climate by storing and transporting heat and moisture How Earth spins, tilts, and moves through space influence how climate varies over long periods of time The Climate System Oceans Atmosphere The Earth has many Ice Biosphere Land different systems that interact with each other in different ways. The fate of solar radiation • The atmosphere, land, ice, and water absorb 70% of incoming solar radiation Greenhouse gases warm the lower atmosphere As Earth’s surface absorbs solar radiation, the surface increases in temperature and emits infrared radiation Greenhouse gases = atmospheric gases that absorb infrared radiation Water vapor, ozone, carbon dioxide, nitrous oxide, methane, halocarbons [chlorofluorocarbons (CFCs)] After absorbing radiation, greenhouse gases re-emit infrared energy, losing some energy to space Greenhouse effect = energy that travels downward, warming the atmosphere and the planet’s surface Modern Climate Systems Atmosphere and Greenhouse Effect The Earth’s atmosphere keeps it around 30°C warmer than it would otherwise be. This is the Greenhouse Effect The temperature of the Earth depends on the amount of energy we receive from the sun versus the amount of energy lost back out to space. The greenhouse effect is natural Greenhouse gases have always been in the atmosphere We are not worried about the natural greenhouse effect Anthropogenic intensification is of concern Global warming potential = the relative ability of one molecule of a greenhouse gas to contribute to warming Expressed in relation to carbon dioxide (potential = 1) Methane is 25 times as potent as carbon dioxide Carbon dioxide is of primary concern It is not the most potent greenhouse gas, but it is extremely abundant The major contributor to the greenhouse effects CO2 exerts six times more impact than methane, nitrous oxide, and halocarbons combined Deposition, partial decay, and compression of organic matter (mostly plants) in wetlands or marine areas led to formation of coal, oil, and natural gas These deposits remained buried for millions of years The Carbon Cycle What caused levels of CO2 to increase? Burning fossil fuels transfer CO2 from lithospheric reservoirs into the atmosphere The main reason atmospheric carbon dioxide concentrations have increased so dramatically Deforestation contributes to rising atmospheric CO2 Forests serve as reservoirs for carbon Removing trees reduces the carbon dioxide absorbed from the atmosphere Human activities increased atmospheric CO2 from 280 parts per million (ppm) to 389 ppm The highest levels in more than 800,000 years Other greenhouse gases add to warming Methane = fossil fuels, livestock, landfills, crops (rice) Levels have doubled since 1750 Nitrous oxide = feedlots, chemical manufacturing plants, auto emissions, and synthetic nitrogen fertilizers Ozone levels have risen 36% due to photochemical smog Halocarbon gases (CFCs) are declining due to the Montreal Protocol Water vapor = the most abundant greenhouse gas Contributes most to the natural greenhouse effect Concentrations have not changed U.S. emissions of major greenhouse gases Feedback complicates our predictions Tropospheric warming will transfer more water to the air But the effects are uncertain A positive feedback loop = more water vapor … more warming … more evaporation … more water vapor … A negative feedback loop = more water vapor … more clouds … shade and cool Earth OR increase evaporation Minor modifications of the atmosphere can lead to major effects on climate Most aerosols exert a cooling effect Aerosols = microscopic droplets and particles They have either a warming or a cooling effect Soot (black carbon aerosols) causes warming by absorbing solar energy But most tropospheric aerosols cool the atmosphere by reflecting the sun’s rays Sulfate aerosols produced by fossil fuel combustion may slow global warming, at least in the short term Volcanic eruptions reduce sunlight reaching Earth’s surface and cool the Earth Radiative forcing expresses change in energy Radiative forcing = the amount of change in thermal energy that a given factor causes Positive forcing warms the surface Negative forcing cools it Earth is experiencing radiative forcing of 1.6 watts/m2 more than it is emitting to space – enough to alter the climate Milankovitch cycles influence climate Milankovitch cycles = periodic changes in Earth’s rotation and orbit around the sun Alter the way solar radiation is distributed over Earth These cycles modify patterns of atmospheric heating Triggering climate variation For example, periods of cold glaciation and warm interglacial times Solar output and ocean absorption influence climate Solar output = the sun varies in the radiation it emits Variation in solar energy (e.g., solar flares) has not been great enough to change Earth’s temperature Radiative forcing is 0.12 watts/m2 – much less than human causes Ocean absorption = the ocean holds 50 times more carbon than the atmosphere Slowing global warming but not preventing it Warmer oceans absorb less CO2 A positive feedback effect that accelerates warming Ocean circulation influences climate Ocean circulation = ocean water exchanges heat with the atmosphere, Currents move energy from place to place The ocean’s thermohaline circulation system affects regional climates Moving warm tropical water north, etc. Greenland’s melting ice sheet will affect this flow El Niño–Southern Oscillation (ENSO) Shifts atmospheric pressure, sea surface temperature, ocean circulation in the tropical Pacific Direct measurements tell us about the present We document daily fluctuations in weather Precise thermometer measurements over the past 100 years Measuring of ocean and atmospheric chemistry began in 1958 Precise records of historical events Droughts, etc. Atmospheric CO2 concentrations have increased from 315 ppm to 389 ppm How Do We Know about Past Climate Systems 1. Early human record cc. W.V. Bailey Rock paintings provide evidence of fertile Sahara region (now desert) 6,000 years ago. Tourism NT http://www.travelnt.com Past Climate Systems 2. Geomorphology River deltas show where rivers entered the ocean or a lake. Above: A “U” shaped valley shows that it was formed by a glacier. Past Climate Systems 4. Ice cores Ice cores can preserve seasonal layering. Studying the chemistry of each layer can give clues about climate change. GISP2 ice core at 1837m depth with clearly visible annual layers. Ice cores from Antarctica Ice cores let us go back in time 800,000 years Reading Earth’s history across eight glacial cycles Is the Climate Changing? What are the current climate trends? Global temperature for the last 150 years cc. Robert A. Rohde http://www.globalwarmingart.com/wiki/Image:Instrumental_Temperature_Record_png Temperatures continue to increase Average surface temperatures increased 0.74 °C since 1906 Most of the increase occurred in the last few decades Extremely hot days have increased The 16 warmest years on record have been since 1990 The future will be hotter In the next 20 years, temperatures will rise 0.4 °C At the end of the 21st century, temperatures will be 1.8–4.0 °C higher than today’s We will have unusually hot days and heat waves Polar areas will have the most intense warming Sea surface temperatures will rise Hurricanes and tropical storms will increase In power and duration Temperatures will rise globally Projected increases in surface temperature for 2090–2099 relative to 1980–1999 Precipitation is changing, too Some regions are receiving more precipitation than usual, and others are receiving less Droughts have become more frequent and severe Harming agriculture, promoting soil erosion, reducing water supplies, and triggering fires Heavy rains contribute to flooding Killing people, destroying homes, and inflicting billions of dollars in damage Projected changes in precipitation Precipitation will increase at high latitudes and decrease at low and middle latitudes Melting snow and ice Mountaintop glaciers are disappearing Glaciers on tropical mountaintops have disappeared The remaining 26 of 150 glaciers in Glacier National Park will be gone by 2020 or 2030 Reducing summertime water supplies Melting of Greenland’s Arctic ice sheet is accelerating Warmer water is melting Antarctic coastal ice shelves Interior snow is increasing due to more precipitation Melting ice exposes darker, less-reflective surfaces, which absorb more sunlight, causing more melting Coral reefs are threatened Coral reefs are habitat for food fish Snorkeling and scuba diving sites for tourism Warmer waters contribute to coral bleaching Which kills corals Increased CO2 is acidifying the ocean Organisms can’t build their exoskeletons Oceans have already decreased by 0.1 pH unit Enough to kill most coral reefs Climate change affects organisms and ecosystems Organisms are adapted to their environments They are affected when those environments change Global warming modifies temperature-dependent phenomena (e.g., timing of migration, breeding) Animals and plants will move toward the poles or upward in elevation 20–30% of species will be threatened with extinction Rare species will be pushed out of preserves Droughts, fire, and disease will decrease plant growth Fewer plants means more CO2 in the atmosphere Climate change affects people Societies are feeling the impacts of climate change Agriculture: shortened growing seasons, decreased production, crops more susceptible to droughts Increasing hunger Forestry: increased fires, invasive species Insect and disease outbreaks Health: heat waves and stress can cause death Respiratory ailments, expansion of tropical diseases Disease and sanitation problems from flooding Drowning from storms Impacts of climate change The Arctic has suffered the most so far U.S. temperatures will continue to rise Impacts of climate change will vary Predictions from two climate models By 2050, Illinois will have a climate like Missouri’s By 2090, it will have a climate like Louisiana’s Causes and consequences of climate change Shall we pursue mitigation or adaptation? Most people accept that our planet is changing They are searching for solutions Mitigation = pursue actions that reduce greenhouse gas emissions to lessen severity of future climate change Energy efficiency, renewable energy, protecting soil, preventing deforestation Adaptation = accept that climate change is happening Pursue strategies to minimize its impacts on us Seawalls, leaving the area, coping with drought, etc. Both are necessary Electricity generation A coal-fired, electricity-generating power plant The largest source of U.S. CO2 emissions 70% of electricity comes from fossil fuels Coal causes 50% of emissions To reduce fossil fuel use: Encourage conservation and efficiency Switch to cleaner and renewable energy sources Conservation and efficiency We can make lifestyle choices to reduce electricity use Use fewer greenhouse-gas-producing appliances Use electricity more efficiently The EPA’s Energy Star Program rates appliances, lights, windows, etc. by their energy efficiency Replace old appliances with efficient ones Use compact fluorescent lights Use efficient windows, ducts, insulation, heating and cooling systems Sources of electricity We need to switch to clean energy sources Nuclear power, biomass energy, solar, wind, etc. We need to consider how we use fossil fuels Switching from coal to natural gas cuts emissions 50% Cogeneration produces fewer emissions Carbon capture = removes CO2 from power plant emissions Carbon sequestration (storage) = storing carbon underground where it will not seep out Use depleted oil and gas deposits, salt mines, etc. We can’t store enough CO2 to make a difference Transportation 2nd largest source of U.S. greenhouse gases Cars are inefficient Ways to help: More efficient cars Hybrid or electric cars Drive less and use public transportation Live near your job, so you can bike or walk U.S. public transportation saves 4.2 billion gallons of gasoline and 37 million metric tons of CO2 emissions We can reduce emissions in other ways • Agriculture: sustainable land management lets soil store more carbon Reduce methane emissions from rice and cattle Grow renewable biofuels Forestry: reforest cleared land, preserve existing forests Sustainable forestry practices Waste management: treating wastewater Generating electricity by incinerating waste Recovering methane from landfills Individuals can recycle, compost, reduce, or reuse goods Questions to be answered… How fast will the sea level rise? How much warmer will it get? When will the Arctic Ocean be ice-free? Will the water cycle accelerate? Are climate extremes increasing? Will there be abrupt changes? Boiling Frog Syndrome