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Greenhouse Gases Greenhouse Gases

Percent Major Atmosphere Percent Major Atmosphere GasesGases

►NitrogenNitrogen 78.178.1►OxygenOxygen 20.920.9►ArgonArgon .93.93►Water Vapor (HWater Vapor (H220), Carbon Dioxide 0), Carbon Dioxide

(CO(CO22), Methane (CH), Methane (CH44), Nitric Oxide ), Nitric Oxide (N(N22O), Ozone (OO), Ozone (O33) <1) <1

What are Greenhouse GasesWhat are Greenhouse Gases

► Allow sunlight to Allow sunlight to enter atmosphere enter atmosphere freelyfreely mostly in visible light mostly in visible light

wavelengthswavelengths► Sunlight hits surface Sunlight hits surface

and reradiated to and reradiated to space space As longer wavelengths As longer wavelengths

of infrared radiationof infrared radiation► Greenhouse gases Greenhouse gases

absorb reradiated absorb reradiated infrared radiationinfrared radiation

► Warms up earthWarms up earth

Major Greenhouse GasesMajor Greenhouse Gases

►Water VaporWater Vapor 55-7055-70►COCO22 2525

►CFC’sCFC’s 1111►CHCH44 55

►NN22OO 22

►OO33 <1<1

How Does Greenhouse WorkHow Does Greenhouse Work► Glass transparent to most Glass transparent to most

wavelengths of solar wavelengths of solar radiationradiation

► Glass opaque to longer Glass opaque to longer (thermal infrared) (thermal infrared) wavelengthswavelengths Soil, plants, are heatedSoil, plants, are heated Radiate heat to warm airRadiate heat to warm air

► Close car in summer works Close car in summer works the samethe same

► Greenhouse really works Greenhouse really works differentlydifferently Soil, plants heatedSoil, plants heated Air then heatedAir then heated Air rise, cooler air replaces Air rise, cooler air replaces

heated airheated airwww.hardwarezone.com/

These two simple cartoons show the multiple paths sunlight takes as it enters Earth's atmosphere (left) and the basic mechanism of the greenhouse effect (right). The portion of incoming sunlight that is absorbed by Earth is re-emitted as infrared radiation. Some IR energy escapes directly to space, but most is absorbed by greenhouse gases in the atmosphere. This warms Earth's atmosphere.Credit: The COMET Program

Are Greenhouse Gases BadAre Greenhouse Gases Bad

► No, not in No, not in excessive amountsexcessive amounts

► Gases needed to Gases needed to heat atmosphereheat atmosphere

► If not greenhouse If not greenhouse gases, atmosphere gases, atmosphere would be 54oF would be 54oF coldercolder

► If too many gases, If too many gases, atmosphere heats atmosphere heats up too muchup too much

► Various wavelengths of solar EM radiation penetrate Earth's atmosphere to Various wavelengths of solar EM radiation penetrate Earth's atmosphere to various depths. Fortunately for us, all of the high energy X-rays and most various depths. Fortunately for us, all of the high energy X-rays and most UV is filtered out long before it reaches the ground. Much of the infrared UV is filtered out long before it reaches the ground. Much of the infrared radiation is also absorbed by our atmosphere far above our heads. Most radiation is also absorbed by our atmosphere far above our heads. Most radio waves do make it to the ground, along with a narrow "window" of IR, radio waves do make it to the ground, along with a narrow "window" of IR, UV, and visible light frequencies. UV, and visible light frequencies.

► Image courtesy STCI/JHU/NASA.Image courtesy STCI/JHU/NASA.

Household Greenhouse Household Greenhouse ContributionsContributions

► Private car -- Private car -- greatest greatest contributioncontribution

►A kilogram of carbon dioxide will fill a A kilogram of carbon dioxide will fill a large family fridge. A ton of carbon large family fridge. A ton of carbon dioxide will fill a family home.dioxide will fill a family home.

► Major GasesMajor Gases Carbon Dioxide Carbon Dioxide

(CO2) is most(CO2) is most ChlorofluorocarboChlorofluorocarbo

n (CFCs)n (CFCs) Methane (CO)Methane (CO) Ozone (OOzone (O33)) Nitrous oxide Nitrous oxide

(NO(NO22)) Water vapor not Water vapor not

includedincluded

Carbon CycleCarbon Cycle

► Carbon moves from the atmosphere to plants.Carbon moves from the atmosphere to plants.► In the atmosphere, carbon is attached to In the atmosphere, carbon is attached to

oxygen to form carbon dioxide (CO2). With the oxygen to form carbon dioxide (CO2). With the help of the Sun, through the process of help of the Sun, through the process of photosynthesis, carbon dioxide is pulled from photosynthesis, carbon dioxide is pulled from the air to make plant food from carbon. the air to make plant food from carbon.

► Carbon moves from plants to animals.Carbon moves from plants to animals.► Through food chains, the carbon that is in plants Through food chains, the carbon that is in plants

moves to the animals that eat them. Animals moves to the animals that eat them. Animals that eat other animals get the carbon from their that eat other animals get the carbon from their food too.food too.

► Carbon moves from plants and animals to the Carbon moves from plants and animals to the ground.ground.

► When plants and animals die, their bodies, wood When plants and animals die, their bodies, wood and leaves decay bringing the carbon into the and leaves decay bringing the carbon into the ground. Some becomes buried miles ground. Some becomes buried miles underground and will become fossil fuels in underground and will become fossil fuels in millions and millions of years.millions and millions of years.

► Carbon moves from living things to the Carbon moves from living things to the atmosphere.atmosphere.

► Each time you exhale, you are releasing carbon Each time you exhale, you are releasing carbon dioxide gas (CO2) into the atmosphere. Animals dioxide gas (CO2) into the atmosphere. Animals and plants get rid of carbon dioxide gas through and plants get rid of carbon dioxide gas through a process called respiration. a process called respiration.

► Carbon moves from fossil fuels to the Carbon moves from fossil fuels to the atmosphere when fuels are burned.atmosphere when fuels are burned.

► When humans burn fossil fuels to power When humans burn fossil fuels to power factories, power plants, cars and trucks, most of factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as the carbon quickly enters the atmosphere as carbon dioxide gas. Each year, five and a half carbon dioxide gas. Each year, five and a half billion tons of carbon is released by burning billion tons of carbon is released by burning fossil fuels. That’s the weight of 100 million fossil fuels. That’s the weight of 100 million adult African elephants! Of the huge amount of adult African elephants! Of the huge amount of carbon that is released from fuels, 3.3 billion carbon that is released from fuels, 3.3 billion tons enters the atmosphere and most of the rest tons enters the atmosphere and most of the rest becomes dissolved inbecomes dissolved in

The Carbon CycleThe Carbon Cycle

► More Carbon going More Carbon going to atmosphere than to atmosphere than is usedis used Therefore more Therefore more

greenhouse gas in greenhouse gas in atmosphereatmosphere

Earth warmsEarth warms

MethaneMethane

►Concentration is far less than that of Concentration is far less than that of COCO22

►Methane is 21 times as potent a Methane is 21 times as potent a greenhouse gasgreenhouse gas

►May now be responsible for ~20% of May now be responsible for ~20% of the predicted global warmingthe predicted global warming

Methane SourceMethane Source► Non-biogenic & biogenic sourcesNon-biogenic & biogenic sources► Non-biogenicNon-biogenic

emissions from fossil fuel mining and burning (natural gas, emissions from fossil fuel mining and burning (natural gas, petroleum and coal), biomass burning, waste treatment and petroleum and coal), biomass burning, waste treatment and geological sourcesgeological sources

(fossil CH4 from natural gas seepage in sedimentary basins and(fossil CH4 from natural gas seepage in sedimentary basins and geothermal/volcanic CH4)geothermal/volcanic CH4)

► Biogenic SourcesBiogenic Sources 70% of the global total70% of the global total wetlands, rice agriculture, livestock, landfills, forests, oceans and wetlands, rice agriculture, livestock, landfills, forests, oceans and

termitestermites► AnthropogenicAnthropogenic

rice agriculture, livestock, landfills and waste treatment, some rice agriculture, livestock, landfills and waste treatment, some biomass burning, and fossil fuel combustionbiomass burning, and fossil fuel combustion

Agriculture—flood rice production, livestock most abundantAgriculture—flood rice production, livestock most abundant► Non-Anthropogenic (Natural)Non-Anthropogenic (Natural)

wetlands, oceans, forests, fire, termites and geological sourceswetlands, oceans, forests, fire, termites and geological sources

Summary of SourcesSummary of Sources

►Methane ( marsh gas) released by:Methane ( marsh gas) released by: Natural processesNatural processes

►Decay in swampsDecay in swamps Human activitiesHuman activities

►mining, processing, and use of coal, oil, and mining, processing, and use of coal, oil, and natural gas; natural gas;

►growing rice in paddies; growing rice in paddies; ►burning forests; burning forests; ►raising cattle (fermentation in their rumens raising cattle (fermentation in their rumens

produces methane that is expelled from their produces methane that is expelled from their GI tract)GI tract)

Ozone SourcesOzone Sources► Ozone molecule consists of 3 Ozone molecule consists of 3

oxygen atomsoxygen atoms► Good when up high in Good when up high in

atmosphereatmosphere Blocks ultraviolet radiationBlocks ultraviolet radiation

► Bad when lowerBad when lower Irritates respiratory systemIrritates respiratory system Harms vegetation an cropsHarms vegetation an crops

► A major component of smogA major component of smog Formed through conversion Formed through conversion

of nitrogen oxides and of nitrogen oxides and volatile organic compounds volatile organic compounds through heat and sunlightthrough heat and sunlight

Industry, utilities, and Industry, utilities, and vehicle exhaust contribute vehicle exhaust contribute most nitrogen oxide.most nitrogen oxide.

Plants emit VOC and soil Plants emit VOC and soil emits NOemits NO

Formed only during the dayFormed only during the day

Ozone HoleOzone Hole

► From CFCsFrom CFCs► Some natural Some natural

depletion from depletion from volcanoes, sunvolcanoes, sun

► Allows more uv lightAllows more uv light Ultraviolet rays can Ultraviolet rays can

cause skin cancer, cause skin cancer, cataracts, and may cataracts, and may depress the immune depress the immune systemsystem

Source of Nitrogen DioxideSource of Nitrogen Dioxide

► Reddish brown gasReddish brown gas Very reactiveVery reactive

► produced by motor vehicles produced by motor vehicles (55%), power plants (22%), (55%), power plants (22%), and other industrial, and other industrial, commercial, agricultural, commercial, agricultural, and residential sources that and residential sources that burn fuels or biomass (22%)burn fuels or biomass (22%)

► Lightning and microbial Lightning and microbial activity also form nitrogen activity also form nitrogen oxideoxide

► Mixes with water to form Mixes with water to form acid rainacid rain

► Can also form particles and Can also form particles and aerosolsaerosols

EPA

Nitrogen Oxide ContinuedNitrogen Oxide Continued

► Reacts with Reacts with sunlight to sunlight to form ozoneform ozone

► Is a nutrient Is a nutrient in waterin water Leads to Leads to

over-over-productivitproductivity, death in y, death in ocean, low ocean, low oxygenoxygen

Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)

► Synthetic gases in which the hydrogen atoms Synthetic gases in which the hydrogen atoms of methane replaced by atoms of fluorine and of methane replaced by atoms of fluorine and chlorine (e.g., CHF2Cl, CFCl3, CF2Cl2). chlorine (e.g., CHF2Cl, CFCl3, CF2Cl2).

► Gases are noninflammable, nontoxic, and Gases are noninflammable, nontoxic, and very stablevery stable

► Used in industry as:Used in industry as: refrigerants (e.g., in refrigerators and air refrigerants (e.g., in refrigerators and air

conditioners) conditioners) solvents solvents propellants in aerosol cans (now banned in some propellants in aerosol cans (now banned in some

countries) countries) in the manufacture of plastic foamsin the manufacture of plastic foams

CFCs ContinuedCFCs Continued

►Non-reactiveNon-reactive Remain in atmosphere for 60-100 yrs to Remain in atmosphere for 60-100 yrs to

decomposedecompose

►Pose threat to ozone layerPose threat to ozone layer

Carbon DioxideCarbon DioxideIPCC ReportIPCC Report

► Atmospheric CO2 concentration has increased from pre-industrial value of about 280 ppm to 379 ppm in 2005 Atmospheric CO2 concentration increased by only

20 ppm over 8000 years prior to industrialization► Since 1750, CO2 concentration has risen by

nearly 100 ppm► Annual CO2 growth rate larger during last 10

years (1995–2005 average: 1.9 ppm yr–1) than since continuous direct measurements began (1960–2005 average: 1.4 ppm yr–1).

Classic CO2 GraphClassic CO2 Graph

► Carbon Dioxide has Carbon Dioxide has steadily increased—steadily increased—anthropogenic causeanthropogenic cause Probably began in Probably began in

industrial revolutionindustrial revolution

► Superimposed are Superimposed are variations with variations with seasonsseasons More CO2 in winter, More CO2 in winter,

less in winterless in winter Due to photosynthesisDue to photosynthesis

Globally Go Forth and Multiply!

World Population CO2

World Population vs. CO2

The concentrations and radiative forcing by (a) carbon dioxide (CO2), (b) methane (CH4), (c) nitrous oxide (N2O) and (d) the rate of change in their combined radiative forcing over the last 20,000 years reconstructed from Antarctic and Greenland ice and fi rn data (symbols) and direct atmospheric measurements (panels a,b,c, red lines). The grey bars show the reconstructed ranges of natural variability for the past 650,000 years (IPCC)

Carbon Dioxide SourcesCarbon Dioxide Sources

►Carbon in nonliving environment as: Carbon in nonliving environment as: carbon dioxide (CO2) in atmosphere and carbon dioxide (CO2) in atmosphere and

dissolved in waterdissolved in water

►Carbonate rocks (limestone and coral = Carbonate rocks (limestone and coral = CaCO3) CaCO3)

►Deposits of coal, petroleum, and natural Deposits of coal, petroleum, and natural gas derived from once-living things gas derived from once-living things

►Dead organic matter, e.g., humus in the Dead organic matter, e.g., humus in the soilsoil

Carbon Intake & ReleaseCarbon Intake & Release

►Used by plantsUsed by plants PhotosynthesisPhotosynthesis Convert carbon dioxide to organic matterConvert carbon dioxide to organic matter

►Carbon returns to the atmosphere and Carbon returns to the atmosphere and water by water by respiration (as CO2) respiration (as CO2) burning burning decay (producing CO2 if oxygen is decay (producing CO2 if oxygen is

present, methane (CH4) if it is not.present, methane (CH4) if it is not.

Anthropogenic CausesAnthropogenic Causes

► Burning fossil fuels (coal, oil, natural gas)Burning fossil fuels (coal, oil, natural gas) Carbon returns to atmosphere that has been locked within Carbon returns to atmosphere that has been locked within

earth for millions of years. earth for millions of years. ► Land use change. Clearing and burning of forests, Land use change. Clearing and burning of forests,

especially in the tropics. Recently, large areas of especially in the tropics. Recently, large areas of the Amazon rain forest have been cleared for the Amazon rain forest have been cleared for agriculture and cattle grazing.agriculture and cattle grazing. Burning vegetation increases CO2Burning vegetation increases CO2 Cutting trees decrease use of CO2 during photosynthesis, Cutting trees decrease use of CO2 during photosynthesis,

more in atmospheremore in atmosphere► Since 1750, about 2/3rds of anthropogenic CO2

emissions from fossil fuel burning and about 1/3rd from land use change

Clearing of the Amazon Clearing of the Amazon RainforestRainforest

► Without people, a yearly Without people, a yearly fire season in the fire season in the Amazon Rainforest Amazon Rainforest would be almost as would be almost as unlikely as a hurricane unlikely as a hurricane season in Antarctica. season in Antarctica. Today, however, the Today, however, the Amazon is a frontier, Amazon is a frontier, and settlers are burning and settlers are burning hundreds of thousands hundreds of thousands of acres of rainforest of acres of rainforest each year for cattle each year for cattle pasture and farms. pasture and farms. Accidental fires degrade Accidental fires degrade thousands of acres thousands of acres more.more.