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The Greenhouse Effect
A hot topic…
Energy that drives the Greenhouse Effect starts as solar energy from the sun. The shortwave thermal energy reaches the surface and lower atmosphere, some is reflected or absorbed.
Absorbed shortwave can then be converted into longwave thermal energy, which can then be re-radiated back into the lower atmosphere, where it is reflected or absorbed.
Yellow: shortwave
Red: longwave
Atmospheric influences on radiation
ReflectionReflection ScatteringScattering Absorption Absorption (absorber (absorber warms)warms)
The Greenhouse
Effect:
• 1) Incoming solar energy is called solar radiation• 2) Solar radiation warms the earth• 3) The warmed earth radiates heat. However, this is not
called ‘heat’, but rather in scientific terms it is energy. The correct term is infrared radiation
• 4) The atmospheric ‘blanket’ is gas molecules in the atmosphere.
incomingradiation
Solar energy reaches the Earth’s surfaceThe earth surface absorbs the energy and warms up
Earth’s energy balance
Incomingsolarradiation
infrared radiation (IR)
greenhousegases
The warm earth surface radiates infrared radiation (IR)Greenhouse gases absorb IR leaving the surface
Earth’s Energy Balance
Incomingsolarradiation
infrared radiation
greenhousegases
Gases are energized, then emit more radiation (IR)
Earth’s Energy Balance
Incomingsolarradiation
infrared radiation
greenhousegases
Some of this IR returns to the earth surface, warming it further
Earth’s Energy Balance
Incomingsolarradiation
infrared radiation
greenhousegases
This process is what we call the GREENHOUSE EFFECT!
Earth’s Energy Balance
Greenhouse Gases
• Obviously, those ‘greenhouse gases’ play an important role in trapping the infrared radiation. What are they?
In order of abundance:
1.Water vapor (H2O)2.Carbon Dioxide (CO2)3.Methane (CH4)4.Nitrous Oxide (N2O )5.Ozone (O3)
The energy in the Earth’s atmosphere (Earth’s Energy Balance) in Watts per square meter has increased over the 20th century, indicating an increasing Greenhouse Effect.
Greenhouse Effect: It is increasing…
Greenhouse Gas Increases in the last 100 years
Greenhouse Gas Concentration1800s
Concentration1990s
Percent Increase Anthropogenic Sources
CO2 280 ppm 360 ppm 29% burning fossil fuels; deforestation
CH4 0.95 ppm 1.7 ppm 79% agriculture; fuel leakage
CFCs 0 0.7 ppb ---- refrigerants
N2O 250 ppb 310 ppb 24% agriculture; combustion
O3 15 ppb 20-30 ppb 33-100% urban pollution
Greenhouse gases are increasing. This may be due to both natural and man-made (Anthropogenic) sources.
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Global Warming Potentials(100 year time horizon)
Greenhouse gases GWP
Carbon dioxide (CO2) 1Methane (CH4) 21Nitrous Oxide (N2O) 310Hydrofluorocarbons (e.g., HFC 134a) 1300Perfluorcarbon (e.g., CF4) 6500Sulfur Hexafluoride (SF6) 23,900
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Greenhouse Gases
• The biggest problem is increasing CO2, carbon dioxide.
• CH4, Methane, is also increasing and interacts with IR and has more “global warming potential” than CO2
• Water in the atmosphere is in the gas or vapor form. (In fact if it becomes liquid form then it falls out of the atmosphere.. as..?)
• Water vapor also traps heat and is a greenhouse gas.
• But - It’s a complicated story because vapor as clouds may cool the earth
Things to Know Water vapor
NOTICE!:1) The CO2-Temp Correlation. Is it cause-effect?2) The rate and degree of change of C02 in the past 200 years. How does it compare to the past 150,000 years?
Long-term proxy records show that the earth’s temperature varied considerably over the past 150,000 years
Long Term Records of Carbon Dioxide:
Methane Gas: contributions to Greenhouse Effect
Energy production and consumptioncoal mining natural gas systems
Waste managementlandfill gas
Agriculturemanure managementcattle (enteric fermentation)rice cultivation
Greenhouse Effect and Global Climate Change:
1. The Atmosphere is complicated—often defies short term models, so long term climate models are still being developed.
2. Scientific consensus is that there is a warming happening and that it is at least partially due to the increase in greenhouse gases.
3. Debate: How much is natural vs. man-made (anthropogenic)?