THE GREENHOUSE EFFECT

The Green House Effect

“The green house effect is a process by which infrared radiation leaving earth’s surface is trapped by some green house gases, so the temperature is higher than it would be if direct heating by solar radiation were the only warming mechanism.”

Warming Mechanism 1. Short wave radiation from the sun penetrates

Earth’s atmosphere (incoming solar radiation = 343 Watt/m2)

2. Some solar radiation is reflected by the atmosphere and earth’s surface (outgoing solar radiation = 103 Watt/m2)

3. Net incoming solar radiation = 240 Watt/m2 4. Solar energy is absorbed by the earth’s surface

(168 Watt/m2) and warms it and is converted into heat causing the emission of longwave (infrared) radiation back to the atmosphere.

Warming Mechanism 5. Some of the infrared radiation is absorbed and re-

emitted by the greenhouse gases. The direct effect is the warming of the earth’s surface and the troposphere. Earth’s surface gains more heat and infrared radiation is emitted again. By this process, some of the infrared radiation is trapped in the atmosphere by greenhouse gases causing a warming of Earth’s climate.

6. Some of the infrared radiation passes through the atmosphere and is lost in space. (Net outgoing infrared radiation = 240 Watt/m2).

The sum up, the green house effect is the rise in temperature that the earth experiences because certain gases in the atmosphere trap energy from the sun.

Warming Mechanism

Earth’s ClimateSystem

Sun

IceOceanLand

Sub-surface Earth

Atmosphere

Terrestrial radiation

About 31%reflected into space

69% absorbed at surface

Solarradiation

Composition of the Atmosphere

Nitrogen N2 78.084% Oxygen O2 20.948%ArgonAr 0.934%

Carbon Dioxide CO2 0.036% (360 ppmv) Methane CH4 1.7 ppmv

Hydrogen H2 0.55 ppmv Nitrous Oxide N2O 0.31 ppmv Ozone O3 10-500 ppbv (troposphere)

0.5-10 ppmv (stratosphere) WaterH2O 100 pptv – 4%

GreenhouseGases

A greenhouse gas is one that absorbs terrestrial (LW)radiation, i.e. emitted from the Earth’s surface/atmosphere

Greenhouse Gases

• Carbon Dioxide (CO2) – Source: Fossil fuel burning, deforestation Anthropogenic increase: 30% Average atmospheric residence time: 500 years

Methane (CH4) – Source: Rice cultivation, cattle & sheep ranching,

decay from landfills, mining Anthropogenic increase: 145% Average atmospheric residence time: 7-10 years

Greenhouse Gases• Nitrous oxide (N2O)

• Source: Industry and agriculture (fertilizers) • Anthropogenic increase: 15%• Average atmospheric residence time: 140-190 years

• Water Vapor (H2O)• The most important Greenhouse Gas!!• Sources: Evaporation• Anthropogenic increase: 35 %

More greenhouse gases means more heat trapped which increases the Earth’s temperature

Burning Natural Gas, coal, oil raises the level of co2 in the atmosphere

Some farming practices and land-use changes increases the levels of methane and nitrous oxide

Many factories produce long lasting industrial gases that do not occur naturally And those gases enhance the greenhouse effect

Even more ways these gases are added to the atmosphere!

Deforestation: Trees use co2 and give off o2 in which helps to create the optimal balance of gases in the atmosphere. As more forests are logged for timber or cut down to make way for farming, there are fewer trees to perform this critical function. In addition when this wood is burned it produces even more co2 in the atmosphere.

Population Growth

As more people use fossil fuels for heat, transportation and industry, the level of greenhouse gases continue to increase. AS more farming occurs to feed millions of new people, more greenhouse gases enter the atmosphere

Effects of Global Warming due to the unbalance of greenhouse gases

Increased Temperature Rising Sea Level

Effects of Global Warming due to the unbalance of greenhouse gases

Habitat Damage and Species Extinction

Changes in water supply; contamination of

fresh water

Effects of Global Warming due to the unbalance of greenhouse gases

More severe storms; hurricanes and floods Droughts, changes in weather patterns

Some Proof of Global Warming

Portage Glacier Alaska then…. Portage Glacier Alaska now….

1.Temperature rising2. Ice melting3. Land submerging4. Sea level rising5. Habitat loss6. Recursive disaster7. Salinity

Effects of global warming on Bangladesh

On nature On human

Effects of global warming on Bangladesh

On nature On human

1. Habitat loss (17 %)2. Migration problem 3. Loss of agriculture

Affected People: 15 %Migration of 27 millionDue to recursive disaster

& salinity in coastal areas

What can we do to help reduce greenhouse gas emissions?

Educate and Use!!

Wind Power Solar Power

Educate and Use!!

Fuel Efficient CarsCompact

Fluorescent

Remedial mearures: (i) Enhance energy efficiency during use by adding insulation to your walls,

using CFL bulbs etc. (ii) Reduce transport sector emissions by less and smart driving. (iii) Promote renewable energy (like solar energy) usage. (iv) Remove subsidies on fossil fuels. (v) Favour sustainable agriculture. (vi) Recover methane emissions through waste management. (vii) Promote afforestation and reforestations, a single tree will absorb

approximately one ton of CO2 during its life time. (viii) Reduce energy consumption by using energy efficient home appliances. (ix) Avoid methane production from biomass decay through controlled

combustion. (x) Enhance energy efficiency during generation, transmission and

distribution. (xi) Reduce waste, prefer reusable products, recycle paper, plastic, metals,

etc. (xii) Eat locally grown fruits and vegetables and not the imported ones. The

later requires the burning of fossil fuels for transport.