The Green House Effect
ISCI 2001
• (1). The fate of solar radiation
– 26% reflected back into space
• 20% clouds; 6% by atmosphere
– 19% absorbed by clouds, ozone gas (O3)
– 55% reaches surface
• 4% reflected at surface; 51% absorbed by surface
• (1). Short-wave radiation from Sun
– As it hits the surface converted into sensible heat
• Heats ground and lower atmosphere
• (2). Surface Radiation (infrared radiation)
– Directed back into space as long-wave radiation
– 90% absorbed by ‘greenhouse’ gases
• CO2 (main GH gas); O3 ; water vapor; methane; N2O
• (3). Gases are ‘warmed’ and heat Earth’s
atmosphere
• (1). Gases absorb (trap) heat to warm up our
atmosphere
• Absorbing longwave radiation from the surface
• (2). Without GH Effect
• Ave. Global Temp =
• With GH = 15 C
-15 C
• (1). Carbon dioxide
– Fossil fuels; deforestation; organic decay; forest fires
• (2). Ozone
– Sunlight chemically reacts with O2 (natural)
– Photochemical smog production
• (3). Methane
– Wetlands; biomass burning; termites; organic decay
• (4). Chlorofluorocarbons
– Refrigerants; aerosol spray propellants; cleaning solvents
• (5). Nitrous Oxide
– Fertilizers; burning of fossil fuels; forests; grasslands
• (1). Rising levels
– 1700’s (280 ppm) ------------- 2005 (380 ppm)
• (2). Causes of increased CO2
– Fossil fuel combustion (65% of increase)
– Deforestation/ Natural habitats to agricultural
areas
• Natural ecosystem hold 20-100 times more CO2
• (1). Methane (CH4)
– 150% increase in levels since 1750
– See sources
• (2). CFC’s destroy Ozone
– Freon; Sprays
– Damage near the poles
– UV light
• (1). Temperature and Clouds
– As GH gases increase, temperature increases
– Causes more cloud formations
– Clouds reflect more energy into space
– Reduce the amount of energy absorbed and
retained in the atmosphere
• (2). Counters the GH effect?
• (1). National Academy of Science
– Increase of 1 F in 20th century
• (2). Recent Data (National Geographic)
– 1.4 F increase since 1880
– Last (2) decades hottest in 400 years
– Arctic temperatures risen 2x average
– Glacier Ntl. Park 27 glaciers
• 150 in 1910
• (1). 2500 scientist/130 countries
– Industry, deforestation, increased greenhouse
gases and pollution
– Combustion and carbon dioxide
• (2). Natural climatic cycles?