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 ReflectionScattering Absorption (absorber 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.

incoming radiation Solar energy reaches the Earth’s surface The earth surface absorbs the energy and warms up Earth’s energy balance

Incoming solar radiation infrared radiation (IR) greenhouse gases The warm earth surface radiates infrared radiation (IR) Greenhouse gases absorb IR leaving the surface Earth’s Energy Balance

Incoming solar radiation infrared radiation greenhouse gases Gases are energized, then emit more radiation (IR) Earth’s Energy Balance

Incoming solar radiation infrared radiation greenhouse gases Some of this IR returns to the earth surface, warming it further Earth’s Energy Balance

Incoming solar radiation infrared radiation greenhouse gases 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 (H 2 O) 2.Carbon Dioxide (CO 2 ) 3.Methane (CH 4 ) 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 20 th century, indicating an increasing Greenhouse Effect. Greenhouse Effect: It is increasing…

Greenhouse Gas Increases in the last 100 years Greenhouse GasConcentration 1800s Concentration 1990s Percent IncreaseAnthropogenic Sources CO ppm360 ppm29% burning fossil fuels; deforestation CH ppm1.7 ppm79% agriculture; fuel leakage CFCs00.7 ppb---- refrigerants N2ON2O250 ppb310 ppb24% agriculture; combustion O3O3 15 ppb20-30 ppb33-100% urban pollution Greenhouse gases are increasing. This may be due to both natural and man-made (Anthropogenic) sources.

14 Global Warming Potentials (100 year time horizon)

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Greenhouse Gases The biggest problem is increasing CO 2, carbon dioxide. CH 4, Methane, is also increasing and interacts with IR and has more “global warming potential” than CO 2 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 KnowWater vapor

NOTICE!: 1) The CO 2 -Temp Correlation. Is it cause-effect? 2) The rate and degree of change of C0 2 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 consumption coal mining natural gas systems Waste management landfill gas Agriculture manure management cattle (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)?