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Climate Change

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Climate Change. Weather vs Climate. Weather consists of the short- term (minutes to months) changes in the atmosphere Think of in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure, as in high and low pressure

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Climate Change

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  1. Climate Change Weather vs Climate

  2. Weather consists of the short- term (minutes to months) changes in the atmosphere • Think of in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure, as in high and low pressure • Weather can change from minute-to-minute, hour- to-hour, day-to-day, and season-to-season • Components of weather include: • Sunshine • Precipitation • Cloud cover • Winds • Flooding • Blizzards • Thunderstorms • Cold front or warm front • Excessive heat • Heat waves Weather vs Climate

  3. Climate is the description of the long-term pattern of weather in a particular area • Some scientists define climate as the average weather for a particular region and time period, usually taken over 30-years • Can include looking at averages of precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and hail storms Weather vs Climate

  4. Atmospheric Composition • Permanent Gases – remain essentially constant in % • 99% by volume • N, O, Ar • Variable Gases – amounts vary for many reasons • Exert great influence on climate patterns • CO2, methane, water vapor, O3, Nitrogen oxides, aerosols

  5. Variable Gases • Carbon Dioxide • 0.036% of atmos • Natural - Volcanic, plant & animal respiration, & decay of organics • Anthropogenic - Burning of fossil fuels • Today influx exceeds removal • Water Vapor • Hydrologic cycle • Ozone • Partial UV shield in upper atmos • Smog, skin cancer, cataracts, crop failures • Chemical pollutants (CFC’s) deplete upper ozone layer • Methane • Natural - Bacterial decay in < O2 environments, intestinal tracks • Anthropogenic - Coal mines, oil wells, leaking gas pipelines, rice cultivation, landfills, & livestock • Nitrogen Oxides • Natural – microbiological, forest fires, lightning strikes • Anthropogenic – autos & power plants, aircraft engines • Aerosols • Natural – forest fires, volcanoes, wind/dust, evaporation • Anthropogenic – pollution, landfill fires, construction, agriculture

  6. Greenhouse Effect • Needed or Earth would be ~60F cooler • Compare Earth & Venus conditions • Industrial Revolution (1750) burning of fossil fuels & extensive clearing of native forests = 40% > in the atmospheric concentration of CO2 (280 to 392.6ppm) in 2012 • Change in proportion of variable gases destabilizes equilibrium • Similar in size to wavelength of Thermal IR energy

  7. Main Greenhouse Gases

  8. Per capita GHG emissions2005

  9. Atmospheric Carbon Dioxide concentrations over time

  10. Global temperature rise over last 130yrs

  11. Sun Spot Minima and Climate Little Ice ages

  12. North cap “floats” • South cap rests on continental landmass • Determines impact on sea-level changes • Earth's polar caps have changed dramatically over last 12,000 years • We have been exiting from high glacial period since last Ice Age • Seasonal variation takes place due to varied solar energy absorption as the planet revolves around the Sun • For geologic time scales, the caps may grow or shrink due to climate variation Earth Polar Caps

  13. Seasonal Changes in Northern Ice Cap Extent of the Arctic sea-ice in September, 1978-2002 Extent of the Arctic sea-ice in February, 1978-2002

  14. Atmospheric methane concentrations over time

  15. Ocean Circulation • Reservoir of solar energy • Moderates global climate • Warm water • Keeps N. Europe 9-18F warmer • Moves west and north • > salinity due to evaporation • Cools and sinks from contact w/Arctic air • Cold water • Moves south and east • Upwelling brings nutrients to surface

  16. Geologic Glacial Epochs • Glacial vs interglacial intervals • Temp today similar to 125,000ya (last inter period) • 10% of surface covered by ice • Reflects solar energy • Shrinking every year • Isostatic rebound

  17. Geologic Glacial Epochs • Latest ~20,000ya • Pleistocene Ice Age • Mammoths, saber-toothed cats, man • San Francisco Peaks • Moenkopi Plateau linear dune field

  18. Climate Change Weather vs Climate

  19. Glacial Hazards • Surges • Ice & debris avalanches • Huascaran, Peru • 1962, 1970 • Glacial damming • Calving • Lahars

  20. What causes global climate change? • Changes in the percentage composition of the variable gasses in the atmosphere (Greenhouse Effect) • Large-scale volcanic eruptions (outgassing & particulates) • Large-scale asteroid impacts • Plate Tectonics • 300mya Pangaea (Fig. 18.31) • Higher latitude location of continents in past • Changes in ocean currents = changes in climate • Earth’s orbital variations • Orbital shape • From circular to elliptical • Axial tilt • From 22-25degrees? • Precession • Wobbles around vertical

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