global effects of air pollution 1

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July 22, 2010 IST,JNTUH, Hyderabad 1

GLOBAL EFFECTS OF AIR POLLUTION

Greenhouse effect

Ozone layer Depletion

Acid Rain Photochemical Smog


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Greenhouse effect


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What is Greenhouse effect? The greenhouse effect is a process by which

radiative energy leaving a planetary surface isabsorbed by some atmospheric gases, calledgreenhouse gases.

They transfer this energy to other components ofthe atmosphere, and it is re-radiated in alldirections, including back down towards the surface.

This transfers energy to the surface and lower

atmosphere, so the temperature there is higherthan it would be if direct heating by solar radiationwere the only warming mechanism


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This mechanism is fundamentally different from

that of an actual greenhouse, which works by

isolating warm air inside the structure so that heatis not lost by convection.

The greenhouse effect was discovered by Joseph

Fourier in 1824, first reliably experimented on by

John Tyndall in 1858, and first reported

quantitatively by Svante Arrhenius in 1896


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A modern Greenhouse in RHS Wisley


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History ofGreenhouse effect

The greenhouse effect was discovered by

Joseph Fourier in 1824, first reliably

experimented on by John Tyndall in 1858, and

first reported quantitatively by Svante

Arrhenius in 1896.


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What is Global Warming? An increase in the average

temperature of the Earthsatmosphere and oceans

Global temperature on bothland and sea increased by 0.6 0.2 C over the past century

Volume of atmosphericcarbon dioxide increasedfrom 280 parts per million in1800 to 367 in 2000, a 31%increase over 200 years


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Basic mechanism

The Earth receives energy from the Sun in the form of

visible light. This light is absorbed at the Earth's surface, and re-radiated

as thermal radiation.

Some of this thermal radiation is absorbed by the

atmosphere, and re-radiated both upwards anddownwards; that radiated downwards is absorbed by the

Earth's surface.

Thus the presence of the atmosphere results in the surface

receiving more radiation than it would were the

atmosphere absent; and it is thus warmer than it would

otherwise be.


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MarsAtmosphere: mass 80% CO2Sfc. Temp.: -47rC

GH Effect: 10rC

FAR TOO COLD!

Other planets also have Greenhouse Effects,

but these are unsuitable for life

EarthGH Gases: ~0.04% CO2

~ 1% H2O

Sfc. Temp.: 15rC

GH Effect: 33rC

NOT BAD!

Venus

Atmosphere: mass 90x

earthsGH Gases: >90% CO2Sfc. Temp.: 477rC

GH Effect: 523rC

FAR TOO HOT!

Sun


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The Greenhouse Effect

The Earths surface thus receives energy fromtwo sources: the sun & the atmosphere As a result the Earths surface is ~33rC warmer than it would be without

an atmosphere

Greenhouse gases are transparent to shortwave

but absorb longwave radiation Thus the atmosphere stores energy


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Structure of the Atmosphere

Thermosphere

Mesosphere

OzoneMaximum

Stratosphere

Troposphere

Temperature


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Electromagnetic Spectrum

incoming outgoing


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1. Shorter, high

Energy wavelengthsHit the earths

Surface

2. Incoming energy

Is converted to heat


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3. Longer, infrared

Wavelengths hitGreenhouse gas

Molecules in the

atmosphere

4. Greenhouse gas

Molecules in the

Atmosphere emit

Infrared radiation

Back towards earth


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Our Changing Climate

Global mean surface temperatures have increased0.5-1.0F since the late 19th century

The snow cover in the Northern Hemisphere and

floating ice in the Arctic Ocean have decreased

Sea level has risen 4-8 inches over the past

century

Global surface temp. could rise 1-4.5F (0.6-2.5C)

in the next fifty years, and 2.2-10F (1.4-5.8C) inthe next century


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What causes it? Human Impacts- Atmospheric greenhouse gases trap

some of the outgoing energy, retaining heat

Natural Impacts- Change in suns energy output VolcanoesWater Vapor Clouds

Greenhouse Gases -

CO2 Methane Nitrous oxide Fluorinated compounds

Since industrial revolution, atmospheric concentrations ofcarbon dioxide increased 30%, methane more thandoubled, nitrous oxide risen by 15%.

These increases have enhanced the heat-trappingcapability of the earths atmosphere


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Greenhouse gases

By their percentage contribution to the greenhouse

effect on Earth the four major gases are: water vapor, 3670%

carbon dioxide, 926%

methane, 49% ozone, 37%

The major non-gas contributor to the Earth's

greenhouse effect, clouds, also absorb and emitinfrared radiation and thus have an effect on

radiative properties of the atmosphere.


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Greenhouse Gas Emissions Power Plants

40% of carbon dioxide emissions stem from the burning of fossil fuels for thepurpose of electricity generation

Cars20% of carbon dioxide emissions comes from the burning of gasoline in internal-combustion engines of cars and light trucks with poor gas mileage contribute themost to global warming

TrucksAnother 13% of carbon dioxide emissions come from trucks used mostly forcommercial purposes

AirplanesAviation causes 3.5 percent of global warming, and the figure could rise to 15percent by 2050

Carbon Dioxide from BuildingsBuildings structure account for about 12% of carbon dioxide emissions


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MethaneMethane is more than 20 times as effective as CO2 attrapping heat in the atmosphere 2004 Levels ofatmospheric methane have risen 145% in the last 100 yearsDerived from sources such as rice paddies, bovineflatulence, bacteria in bogs and fossil fuel production . Inflooded fields, anaerobic conditions develop and theorganic matter in the soil decomposes

Nitrous oxideNaturally produced by oceans and rainforests , man-madesources-nylon and nitric acid production, the use offertilizers in agriculture, cars with catalytic converters andthe burning of organic matter

DeforestationResponsible for 25% of all carbon emissions entering theatmosphere by the burning and cutting of about 34 millionacres of trees each year .


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The Carbon Cycle


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Effects of Global Warming

Negative Effects

Rising Sea Level

Change of precipitation and local climate

conditions; acid rainAlteration of forests and crop yields

Expansions of deserts into existing

rangelandsMore intense rainstorms

Destabilization of Ocean currents


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Positive Effects

Can stimulate plant growth in places whereCO2 and temperature are the limiting

factors (preventing photorespiration which

can destroy existing sugars).

Melting Arctic ice may open the NorthwestPassage in summer, which would cut 5,000

nautical miles from shipping routes

between Europe and Asia


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What Can be Done: Alternatives

Renewable Energy Sources


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Solar Energies


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Wind Power


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Biomass


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Geothermal


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Changes In Vehicle Systems


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Hybrid Car


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Fuel Cell


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Battery-Electric


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Kyoto Protocol

1997, Kyoto, Japan ? developed countries agreedto specific targets for cutting their emissions ofgreenhouse gases

Industrialized countries committed to an overall

reduction of emissions of greenhouse gases to5.2% below 1990 levels for the period 2008 -2012

Objective is the stabilization of greenhouse gas

concentrations in the atmosphere at a level thatwould prevent dangerous anthropogenicinterference with the climate system


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Ozone layer Depletion


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Introduction That is, the layer of life-protecting ozone found at the top of the

stratosphere. A brief history of the discovery of the ozone 'hole' isincluded. The general concepts found in this section include thefollowing:

Concentrations of stratospheric ozone represent a balance,established over eons, between creative and destructive forces andthis balance, or dynamic equilibrium, has been changed by humanactivity.

Ozone is formed in the earth's stratosphere and is critical to life onearth as we know it.

There is compelling scientific evidence that ozone is destroyed in thestratosphere and that some human-released chemicals are speedingup the breakdown of ozone in the atmosphere.

CFCs, a human-developed compound, are particularly destructive tothe breakdown of ozone in the atmosphere.

Ultraviolet radiation is present in natural outdoor light and can beblocked or filtered by various substances.


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What is Ozone? Ozone Layer?

Ozone (O3) is a highly-reactive from of oxygen.

Unlike oxygen (O2), ozone has a strong scentand is blue in color.

Ozone exists within both the tropospheric andstratospheric zones of the Earths atmosphere

In the troposphere, ground level ozone is amajor air pollutant and primary constituent ofphotochemical smog

In the stratosphere, the ozone layer is anessential protector of life on earth as it absorbsharmful UV radiation before it reaches the earth.


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CFCs and ozone depletion

Chlorofluorocarbons arecreated and used inrefrigerators and airconditioners. Thesechlorofluorocarbons are notharmful to humans and havebeen a benefit to us. Oncereleased into the

atmosphere,chlorofluorocarbons arebombarded and destroyedby ultraviolet rays. In the

process chlorine is releasedto destro the ozone


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Destruction of ozone by chlorine

Molecular oxygen is broken down in the stratosphere bysolar radiation to yield atomic oxygen, which thencombines with molecular oxygen to produce ozone. The

ozone is then destroyed by chlorine atoms.


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Ozone destruction by UV rays

UV radiation from the sunreleases the radicals Cl andClO.

Ozone is a highly unstable

molecule so it readilydonates its extra oxygenmolecule to free radicalspecies such as hydrogen,

bromine, and chlorine. These compound species

act as catalysts in thebreakdown of ozone

molecules.


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The ozone depletion process


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Responsibility for ozone damage

each year

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