global effects of air pollution 1
TRANSCRIPT
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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