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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 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 • 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
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
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
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
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
Sun Spot Minima and Climate Little Ice ages
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
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
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
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
Geologic Glacial Epochs • Latest ~20,000ya • Pleistocene Ice Age • Mammoths, saber-toothed cats, man • San Francisco Peaks • Moenkopi Plateau linear dune field
Climate Change Weather vs Climate
Glacial Hazards • Surges • Ice & debris avalanches • Huascaran, Peru • 1962, 1970 • Glacial damming • Calving • Lahars
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