Greenhouse Effect &Greenhouse Effect & Global Warming Global Warming

Some Evidence

The global air temperature at the Earth's surface has increased about 0.5oC during the past century

Sun

Earth’s TemperatureEarth’s Temperature

Solar

Energy

Solar

Energy

The Greenhouse

Greenhouses are used to grow plants, especially in the winter.

The glass panels of the greenhouse let in light but keep heat from escaping.

This causes the greenhouse to heat up, like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.

Greenhouse

Glass, the material that greenhouse is made of, 1) transmit short-wavelength visible light, 2) absorbs and redirects the longer wavelengths of energy. These two aspects make the greenhouse warmer than outside air temperature.

Greenhouse effect of the atmosphere

• Light from the sun includes the entire visible region and smaller portions of the adjacent UV and infrared regions.

• Sunlight penetrates the atmosphere and warms the earth’s surface.

• Longer wavelength infrared radiation is radiated from the earth’s surface.

• A considerable amount of the outgoing IR radiation is absorbed by gases in the atmosphere and reradiated back to earth.

The gases in the atmosphere that act like glass in a greenhouse are called greenhouse gases.

Natural Greenhouse effect

The natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present.

Enhanced greenhouse effect

When concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises.

What makes a gas greenhouse gas?

Able to absorb infrared light• Must have molecular vibration(s)• The molecular vibrations must be

non-symmetric, i.e. infrared active– Homonuclear diatomic molecules only

have symmetric vibrations. That’s why N2, O2 are not greenhouse gases.

What are the major greenhouse gases?

• H2O

• CO2

• CH4

• N2O

• O3

• CFCs

Carbon DioxideCarbon Dioxide

Are human beings causing increases

in greenhouse gases?

CO2 Concentrations at Mauna Loa, Hawaii

The average atmospheric CO2 concentrations observed at Muana Loa, Hawaii increased approximately 40 ppmv between 1958 and 1995.

Methane

Atmospheric methane has increased steadily to present day levels; this increase is highly correlated with human population growth and with related activities, including agricultural practices.

Rate of increase: 0.9% annually

Nitrous oxide (N2O)

Rate of increase 0.25%/year

Use of fertilizer increases both nitrification and denitrification increase N2O production

CFC-11

Is the earth getting warmer?

Temperature over the past one century

The global air temperature at the Earth's surface has increased about 0.5oC during the past century

Temperature over the past 1000 years

Carbon DioxideCarbon Dioxide

Sources and sinks of CO2

• Sources– Natural: respiration of vegetation and soil

detritus– Man-made: Fossil fuel combustion,

deforestation

• Sinks: slow exchange of carbon between surface waters and deep layers of ocean.(Seawater is alkaline while CO2 is acidic The oceans are a vast reservoir of CO2).

Worldwide Carbon EmissionsWorldwide Carbon EmissionsC

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1750 1800 1850 1900 1950 2000Year

Liquid fuelLiquid fuelTotalTotal

Gas fuelGas fuelSolid fuelSolid fuel

Future Carbon Dioxide LevelsFuture Carbon Dioxide Levels

• Increasing CO2 emissions, especially in China and developing countries

• Likely to double within 150 years: Increased coal usage Increased natural gas usage Decreased petroleum usage (increased

cost and decreasing supply)

Status of CO2

Pre-industrial Amount: 280 ppm

Present Amount: 382 ppm

Maximum Allowable ≤ 450 ppm

Rate of Change: +2 ppm/year (and growing)

Kyoto ProtocolKyoto Protocol

• Adopted in 1997

• Cut CO2 emissions by 5% from 1990 levels for 2008-2012

• Symbolic only, since cuts will not significantly impact global warming

170170

220220

270270

320320

370370

00200000200000400000400000600000600000Time (YBP)Time (YBP)

CO

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2525262627272828292930303131

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CO2 Concentration Vs. TemperatureCO2 Concentration Vs. Temperature

More Important Data

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World USA OECD Asia

Per Capita Carbon Emissions

Greenhouse Effect & Global Warming

• The “greenhouse effect” & global warming are not the same thing. – Global warming refers to a rise in the

temperature of the surface of the earth

• An increase in the concentration of

greenhouse gases leads to an increase in the the magnitude of the greenhouse effect. (Called enhanced greenhouse effect) – This results in global warming

Consequences of global warming

• Sea level rise– Beach erosion– Coastal wetland loss– Loss of low-lying territories

• Water resources change– Precipitation pattern shift– Increases instances of heavy

precipitation

• Effects on agriculture– Changes in the length of growing season– Growth of undesirable plant species

Consequences of global warming (Continued)• Effects on air quality

– Increase in reaction rates and concentrations of certain atmospheric species increase in O3 in urban areas

• Impacts on human health– Changes in patterns of sickness and death.– Respiratory problems affected by air quality change

• Biodiversity– Some species may grow too quick and overshoot their

reproductive period (e.g. reef corals)

• Change in the pattern of ocean current

Possible Solutions to Global Warming

Possible Solutions to Global Warming

Mitigation of Global WarmingMitigation of Global Warming

• Conservation Reduce energy needs Recycling

• Alternate energy sources

Nuclear Wind Geothermal Hydroelectric Solar