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 = -15 C• With GH = 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?