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Chapter 15 Air, Weather & Climate 1 Outline • • • The Atmosphere and Climate Convection Currents Greenhouse Effect Weather Winds Frontal Systems Cyclonic Storms Climate ENSO Climate Change Kyoto Protocol 2 The Atmosphere and Climate • Atmosphere – the air surrounding the earth which extends upwards 500km (300 miles) • Weather - daily temperature and moisture conditions in a specific place • Climate - a description of the long-term weather pattern in a particular area (30+ years) 3 Earth’s First Atmosphere • • • Composition - Probably H2, He (common in space) These gases are relatively rare on Earth and were probably lost to space early in Earth's history due to: Earth's gravity was not strong enough to hold lighter gases Earth still did not have a differentiated core (solid inner/liquid outer core) which created Earth's magnetic field (magnetosphere = Van Allen Belt) which deflects solar winds. Once the core differentiated the heavier gases could be retained 4 Earth’s Second Atmosphere • • • • Produced by volcanic out gassing. Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 (ammonia) and CH4 (methane) No free O2 at this time (not part of volcanic gases). Ocean Formation - As the Earth cooled, H2O produced by out gassing could exist as liquid in the Early Achaean, allowing oceans to form. 5 The Atmosphere Today 6 Atmospheric Aerosols • AEROSOLS: Aerosols are minute particles or droplets suspended in the atmosphere which can affect climate. Reflect & scatter sunlight Cause chemical reactions in the atmosphere - ie: ozone depletion 3 sources of Aerosols - 1. Volcanic activity (dust, SO2) - 2. Desert dust - 3. Anthropogenic (burning forests/fuels) 7 Selected Properties of Earth’s Atmosphere 8 Layers of the Atmosphere • • • “Spheres” are layers of air “Pauses” mark boundaries between two “spheres” Due to temperature variations the air in the layers do not mix 9 Troposphere Densest layer (nearest the earth) • Contains 75-80% of all gas molecules • All weather occurs here • Convection currents circulate the air (mix heat & moisture) • Highest air pressure (sea level = 14.7 lbs/in2) • 10 Stratosphere – “Global Sunscreen” • • • • • Contains majority of atmospheric ozone Ozone is produced when O2 interacts with UV radiation. O2 + UV O3 Ozone blocks UV rays allowing life to survive Little mixing of air so aerosols stay many years Commercial jets fly here – avoid turbulence11 Mesosphere • • • • Temperatures drop rapidly in this layer Coldest temps on earth -90°C (-130° F) Least studied due to its position (above weather balloons & aircraft and below orbiting spacecraft) 12 Thermosphere • • • Extremely hot from suns radiation Contains highly ionized (charged) gas molecules When solar radiation hits these ionized molecules they glow – “Aurora borealis” concentrated above Earth’s magnetic pole https://vimeo.com/16917950 13 Sun’s Energy • INSOLATION (incoming solar radiation) About 25% is reflected by clouds and the atmosphere. Another 25% is absorbed by carbon dioxide, water vapor, ozone, aerosols and a few other gases. About 50% reaches the earth’s surface. Insolation is greatest at equator, decreasing toward higher latitudes (the poles) Insolation is short wave radiation (light) which becomes long-wave (infrared/heat) after absorption by surface/clouds/gases. 14 Energy Balance 15 Effects of Albedo (Reflectivity) • Surfaces that reflect energy have a high albedo. Fresh clean snow 80-85% Dense clouds 70-90% White sand 20-30% • Surfaces that absorb energy have low albedo. Forests 5-10% Water (sun overhead) 5% Dark soil/Pavement 3% Absorbed energy causes water to evaporate and allows for photosynthesis. Absorbed energy is released as heat. • • 16 Energy and the Greenhouse Effect • Most insolation reaching the Earth is high energy light (a.k.a. near infrared) of short wavelength. • Energy reradiated (reemitted) by earth is heat (a.k.a. far infrared) of long wavelength. - Longer wavelengths are absorbed in the lower atmosphere, trapping heat close to the earth’s surface. - GREENHOUSE EFFECT: The atmosphere transmits sunlight while trapping heat. 17 GREENHOUSE EFFECT Earth’s average temp. today is 58.30F. Without the greenhouse effect the temp. would be 330F cooler!!! (250F) 18 Contributing Factors to the Greenhouse Effect Gases in the atmosphere, especially carbon dioxide, methane and water vapor, are the substances that retain heat. Burning fossil fuels releases carbon dioxide and particulate aerosols. Cows, melting permafrost, landfills and production of fuels releases methane Increased heat increases evaporation of water Deforestation destroys carbon sinks (absorbers). And, MUCH MORE TO COME ..... 19 Arctic Sea Ice Positive feedback loop - poles covered with ice reflect solar radiation back into space. Now that ice is melting, open water is absorbing more heat, which in turn is melting more ice, leading to more warming. (there is no balance – only forward momentum) Arctic Sea Ice Extent http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003893/seaIceArea_2011_Wdate.mp4 20 WEATHER: short term physical conditions of the atmosphere in a specific place 21 Uneven Heating of the Earth • • Insolation is not equal around the earth. Much of solar energy absorbed by the Earth is used to evaporate water. When water evaporates it absorbs energy. (580 calories per gram) Energy stored in water vapor is LATENT HEAT. When water vapor (gas) cools & condenses (turns to liquid), heat energy is released. Heat and water move from warmer areas near the equator towards cooler areas at poles. Heat redistribution prevents extreme temperature fluctuation. 22 Uneven Heating of the Earth • 3 causes of unequal heating: 1. insolation strikes earth at different angles 2. insolation travels through more/less atmosphere where it is absorbed 3. effect of albedo on different surfaces 23 Earth’s Tilt • • Earth’s tilt causes seasonal variations Tropics receive more direct insolation than poles 24 Convection Currents • • Releasing latent heat causes air to rise, cool, and lose more water vapor as precipitation. Warm air close to equator vs. cold air at poles also produces pressure differences that cause weather. Air near surface warms and becomes less dense than the air above it; rises above cool air creating vertical convection currents. - Low pressure - air is rising - High pressure - air is sinking Pressure differences cause winds. Winds move from High to Low 25 Circulation Patterns 26 4 PROPERTIES OF AIR 1. DENSITY: mass of all molecules in a given volume less dense air rises, more dense air sinks 2. CAPACITY TO HOLD WATER VAPOR: warm air holds more water vapor than cold air SATURATION POINT: the maximum amount of water vapor air can hold at a given temp. 3. LATENT HEAT RELEASE: Whenever water vapor condenses, the air becomes warmer and rises 27 4 PROPERTIES OF AIR 4. EFFECTS OF CHANGE IN PRESSURE: ADIABATIC COOLING: the cooling effect of reduced pressure on air as it rises in the atmosphere and expands ADIABATIC HEATING: the heating effect of increased pressure on air as it sinks toward the surface of Earth and decreases in volume 28 29 CONVECTION CURRENTS 1. Insolation reaches Earth’s surface 2. Energy is absorbed and the surface warms 3. Surrounding air warms via conduction 4. Warmer air rises carrying heat upward 5. As air rises, it cools and becomes denser 6. This “new” air displaces other air & spreads 7. Cooled air begins to sink 8. Cool/dry air returns to the surface & warms 30 Convection Currents 31 Weather Happens • WEATHER – short-term, physical conditions in the atmosphere (humidity, temperature, air pressure, wind and precipitation) RAIN/PRECIPITATION: - Air cools as it rises, and water condenses as air cools. - Cooling occurs because pressure decreases as air rises. - CONDENSATION NUCLEI (tiny particles/aerosols) must also be present to have precipitation. Water vapor collects/condenses on them! 32 Weather Happens WIND: - Movement of large air masses - Air moves from areas of high pressure to areas of low pressure - Winds are deflected by the Coriolis effec HUMIDITY: - The amount of water vapor in the air - Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature. 33 CORIOLIS EFFECT Surface air flows do not move straight north and south, but are deflected due to the CORIOLIS EFFECT. The curving pattern results from the rotation of earth in an eastward direction as winds move above it. Winds are deflected because earth’s rotation at the equator is faster than its rotation at the poles. Therefore – air at the equator is moving faster than air at higher latitudes 34 Winds and currents move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. 35 JET STREAMS • JET STREAMS hurricane force winds at the top of the troposphere which follow an undulating path 36 RAIN SHADOW EFFECT • Warm moist air rises, adiabatically cools and precipitation forms on windward side of mountain. Dry, desert-like conditions are found on the leeward side of the mountain. 37 Ocean Currents • Ocean currents are affected by several factors: Temperature, salinity, continents, Coriolis effect, gravity, & surface winds • Ocean currents strongly influence the climate conditions on adjacent land. • As surface water moves, deep water wells up to replace it. Upwelling brings huge amounts of nutrients from the ocean bottom which supports large amounts of producers which in turn support large populations of fish. Most upwelling occurs on the west coasts of continents 38 Ocean Currents Temperature: warm water rises, cold water sinks as water warms, it expands. (tropical water is actually a few inches higher than subtropical water) Gravity: the force of gravity allows the tropical water to flow to higher latitudes Salinity: salty water is denser and sinks Coriolis Effect: like the air masses, water is also defected due to the rotation of the earth. Continents: create barriers that shape currents Surface Winds: create water movement on the surface of oceans called GYRES. 39 OCEAN CURRENTS & GYRES • GYRES: circular surface currents that move between continents 40 THERMOHALINE CIRCULATION • Ocean circulation is also driven by differences in water density due to temperature and salinity of the water – referred to as the Global Conveyer Belt 41 • • CHANGES TO THE THC Lake Agassiz – 11,000 years ago, an ice dam broke and the lake drained into the N. Atlantic. Stopping the THC and created a mini-ice age in Europe. Vast melting of Greenland ice sheets could have similar effects. 42 Seasonal Winds and Monsoons • Monsoon - seasonal reversal of wind patterns caused by differential heating and cooling rates of oceans and continents Most prevalent in subtropical and tropical areas. Tilt of Earth’s axis changes location where the Sun is most intense over the course of the year. Places where the Sun shines most directly have evaporation and convection currents which bring thunderstorms. Seasonal rains support tropical forests and fill great rivers such as the Ganges and Amazon. 43 Summer Monsoons in India Summer cycle: (Monsoon season) Winds from the ocean carry warm, moist air causing rain on land Winter cycle: Winds come from the land are dry and cool, rains occur over the oceans 44 Frontal Weather • COLD FRONT - boundary formed when cooler air displaces warmer air Cold air is more dense and pushes warm air up. - Creates strong, short-lived storms 45 Frontal Weather • WARM FRONT - boundary formed when warm air displaces cooler air Warm air is less dense and slides over cool air, creating a long wedge-shaped band of clouds and precipitation. 46 Cyclonic Storms • • • When rising air is laden with water vapor, latent heat energy released by condensation intensifies convection currents and draws up more warm air and water vapor. (___________ feedback) HURRICANES (Atlantic) (Form off W Coast of Africa) TYPHOONS (Western Pacific) CYCLONES (Indian Ocean) These storms are usually very large and generate high winds. Cause severe wind and flood damage Winds are highest in the center 47 Hurricane Classification Hurricane Katrina – Category 5 Hurricane Matthew – Category 4 Hurricane Sandy – Category 3 48 Cyclonic Storms • TORNADOES - swirling funnel clouds Rotation not generated by Coriolis forces Generated by a “supercell” frontal systems where strong dry cold fronts collide with warm humid air Common in midwest 49 Tornado Intensity 50 Studying Climate • CLIMATE - a description of the long-term weather pattern in a particular area (30+ years) • ICE CORES - collected from glaciers reveal light and dark bands caused by annual snow accumulation on a glacier Gas bubbles can be analyzed for atmospheric composition. Ash and sulfur deposits correlate with volcanic eruptions. Vostok ice core gives us a record back 420,000 years. (from Antarctica – 3,100m in length) 51 • Ice core from Greenland is 3,000 meters and records climate date for 250,000 years. 52 • Climate Data show that: Abrupt climatic change has catastrophic effect on living things as organisms are unable to adjust before conditions exceed their tolerance limits. Species may become extinct. There is a close correlation between carbon dioxide concentration and temperature of the atmosphere. 53 CAUSES OF CLIMATE CHANGE Sunspot & Solar magnetic cycles Cycle of shift in angle of moon alters tides and currents. VOLCANIC ERUPTIONS – dust and sulfur can cool planet suddenly. MILANKOVITCH CYCLES - periodic shifts in Earth’s orbit and tilt which change distribution and intensity of sunlight - Ice cores show drastic changes may have occurred over short periods of time (years to decades). 54 Milankovitch Cycles 55 ENSO - El Nino Southern Oscillation • Large area of warm surface water in the Pacific Ocean moves back and forth between Indonesia and South America. La Nina: Most years, this warm water is held in western Pacific by steady equatorial trade winds. Surface waters driven westward by trade winds are replaced by upwelling of cold, nutrient rich waters off west coast of South America. Nutrients supply food for fisheries. El Nino: Every 2-7 years the Indonesian low collapses and the mass of warm surface water surges back east. 56 57 El Nino/Southern Oscillation During an El Nino year, the northern jet stream pulls moist air from the Pacific over the U.S. - Intense storms and heavy rains from California to the Midwest - ENSO events are becoming stronger and more irregular due to global warming. During other years La Nina - hot, dry weather is often present. CYCLES AFFECT OCEAN PRODUCTIVITY 58 El Nino/Southern Oscillation THESE CYCLES HAVE MANY EFFECTS: 1. Decrease in upwelling off the SA coast Reduction in productivity in the oceans Reduction in commercial fisheries 2. Cooler & wetter conditions in Southern USA Replenish water in SW USA 3. Warmer conditions in northern US & Canada 4. Drier weather in Africa and SE Asia Reduces hurricanes in N Atlantic 5. Disease frequency changes Wet – increase of mosquitoes Dry – decrease in safe water sources 59 PACIFIC DECADAL OSCILLATION (PDO) a very large area of warm water moving back and forth across the North Pacific every 30 years. Affects fishing harvest on NA west coast. 60 Evidence of Climate Change is Overwhelming “As best as can be determined, the world is now warmer than it has been at any point in the last two millennia, and, if current trends continue, by the end of the century it will likely be hotter than at any point in the last two million years.” American Geophysical Union 61 Global Warming is Happening • Global Surface Temperature, 1884--‐2012 http://svs.gsfc.nasa.gov/vis/a000000/a004000/a004030/2012_GISSTEMP_update_withdates.mp4 • In 2007, the Intergovernmental Panel on Climate Change (IPCC) released its fourth report. Represents a consensus by more than 90% of all scientists working on climate change Gives a probability value of 90% that the warming we are now seeing is anthropogenic Bush administration praised the report but said it opposes mandatory cuts in greenhouse gas emissions because they are too costly. 62 Carbon Dioxide Concentrations on Mauna Loa Mauna Loa observatory was created in 1957 to obtain air chemistry data. CO2 levels have increased from 315ppm in 1958 to 383ppm in 2006 – a .5% increase per year. 63 Rate of Global Warming • • • • Change in temperature is happening quickly! Best predictions of temperature increase are from 1.8 to 4.0°C (3.2 to 7.8°F) by 2100 depending on population growth, energy conservation, etc. In contrast, there has been a 5oC rise since the middle of the last ice age (about 20,000 years ago). Ice core samples can tell scientists the relative abundance of gases in the atmosphere 64 Effects of Global Warming • Most people will experience more extreme weather including droughts, floods, heat waves and hurricanes. These extremes have increased globally in the last decade. • Sea levels are projected to rise 17-57 cm (7 to 23 in). If Greenland’s ice melts it will raise sea level 20 ft. Most of Florida, Manhattan, Hong Kong, Tokyo, Mumbai, and other large cities would be flooded • Coral bleaching worldwide, loss of biodiversity 65 Sources of Greenhouse Gases • Carbon Dioxide - increased 31% since pre-industrial times - fossil-fuel burning, cement production, burning forests, - 30 billion tons of CO2 released annually 8 billion tons of carbon 3 billion absorbed by terrestrial plants 2 billion absorbed by oceans Atmospheric levels increasing steadily could reach 500ppm by 2100. 66 Sources of Greenhouse Gases • Methane – - Increased 151% since pre-industrial times - Accumulating 2x faster than CO2 - Absorbs 23x more infrared than CO2 . - Released by animals (cows/termites), rice paddies, coal mines, landfills, swamps, melting permafrost, pipeline leaks - (methane is produced when decomposition takes place w/o oxygen present) 67 Sources of Greenhouse Gases • Chlorofluorocarbons (CFC’s) a.k.a “Freon” - Absorb large amounts of infrared heat - Used in refrigerants, air conditioners, as a propellant in aerosol cans - Banned in US 1978 due to Ozone depletion - the manufacture of CFC’s has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) 68 Sources of Greenhouse Gases • • Nitrous Oxide - emitted by agricultural fertilizer, industrial activities (synthetic fabric production), combustion of fossil fuels & solid waste, burning organic material - N2O is a natural gas – part of Nitrogen cycle - Global warming impact of 1 pound of N2O is almost 300x that of 1 pound of CO2 . Sulfur Hexafluoride - 23,000 times that of CO2 - electrical insulator, production of magnesium. a filler for cushioning 69 Types of Greenhouse Gases 70 Contributing Activities 71 Country Contribution to Greenhouse Gases • • • U.S. has less than 5% of world’s population but produces 28% of carbon dioxide. China, with 1.3 billion people, is second. Japan and Europe produce half as much carbon dioxide per person as the U.S. 72 Evidence of Climate Change is Overwhelming • • • • Ave. global temperature climbed 0.6°C (1°F) in last century. 15 of the 16 warmest years on record have occurred during the 21st century. Poles are warming fastest (4°C, 7°F over past 50 years). Permafrost is melting in Alaska and Canada Arctic Sea ice is half as thick as it was 30 years ago, and the ocean area covered by ice has decreased by 1 million sq. km. in 30 yr. Polar bears are dying Droughts are more frequent and widespread Cyclonic storms more common and severe. 73 Evidence of Climate Change is Overwhelming • • • • • • Antarctic ice shelves are disappearing. Penguins declined 50% in last 50 yrs. Greenland’s ice is melting Glaciers are melting all over the world. (Glacier Nat’l Park, Mt Kilimanjaro, Himalayas) Sea level has risen 6 to 8 inches in last century. Oceans have been absorbing some of the extra CO2 but that is acidifying the ocean and damaging coral and shellfish. Growing seasons are lengthening in Northern hemisphere. Some animals are breeding earlier or extending their range. Others are disappearing. 74 Global Warming will be Expensive • • • At present, reducing greenhouse gas emissions would cost 1% of world GDP according to Stern report. (IPCC report says less than that.) If we delay, it could cost as much as 20% of world GDP. Energy production will need to be 80% decarbonized by 2050 to stabilize climate. Ethical issue - Poor will suffer the most; perhaps 200 million people will become refugees of flood and drought. 75 Steps For Combating Climate Change • • • • Emissions trading markets already exist Technology sharing Reducing deforestation Helping poorer countries adapt to climate change Tropical areas will not change as much as middle and high latitudes. If all ice on Greenland and Antarctica melt, 1/3 of Earth’s population will be displaced. - South Pacific island nation of Tuvalu already abandoned due to climate change 76 Combating Climate Change • • • Insurance companies have $2 trillion in insured properties along U.S. coastlines at risk from flooding or severe storms. Infectious diseases will increase as insects that spread them are able to move to places where they could not live before. West Nile, malaria, and dengue fever, Zika have appeared in North America. Melting of permafrost may release stores of methane hydrate. Uncertainty about whether that would increase warming or cooling. 77 International Climate Negotiations • Kyoto Protocol (1997) 160 nations agreed to roll back carbon dioxide, methane, and nitrous oxide emissions about 5% below 1990 levels by 2012. - Sets different limits for different countries, depending on prior output Developing countries exempted (China & India to allow development) 126 countries have ratified the Protocol. U.S. took a leading role in the 1990s, but Bush declined to honor U.S. commitments. Said it would be too costly and was unfair. 78 International Climate Negotiations • • • PARIS AGREEMENT – Drafted Dec. 2015 – Goes into effect Nov 2016 4 main objectives 1. Holding the increase in global average temperature to well below 2 °C & to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels 2. Increase the ability to adapt to adverse impacts of climate change and low greenhouse gas emissions development 3. Make finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development. 4. Countries aim to reach “global peaking of greenhouse gas emissions” as soon as possible 79 Regulating Emissions 2007, the CEOs of 10 of the largest business conglomerates in the U.S. called for legislation to reduce greenhouse gases – working with Environmental Defense Fund, and other groups. A single national standard would be better for business than a patchwork of state and local rules. Companies engaged in international business will have to modify their products anyway to compete abroad. EPA told to uphold the Clean Air Act and regulate greenhouse emissions. 80 Controlling Greenhouse Emissions • Reducing carbon dioxide levels Renewable energy sources - Increase fuel economy - Switch to efficient lighting and appliances - Wind turbines, Solar - Biofuels, Nuclear - Planting vegetation/trees 81 Carbon Management • • • • IDEAS TO COMBAT CO2 Build “trees” in which calcium hydroxide solution would absorb carbon dioxide Fertilize the oceans with iron to permit phytoplankton growth, which would take up carbon dioxide Sequestration into rock layers or deep ocean 82