Chapter 3 Global Climate Change Chapter 3 Global Climate Change

The Ozone DepletionThe Ozone Depletion

The Greenhouse EffectThe Greenhouse Effect

3-1 The Ozone Depletion 3-1 The Ozone Depletion

Ozone: Good Up High, Bad NearlyOzone: Good Up High, Bad Nearly

Ozone-Depleting Substances (ODS)Ozone-Depleting Substances (ODS)

Basic Chemistry of Ozone DepletionBasic Chemistry of Ozone Depletion

The AntarcticThe Antarctic （（南極南極） ） Ozone HoleOzone Hole

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly

Ground-level OGround-level O33—“bad” O—“bad” O33 in troposphere layer in troposphere layer

(( 對流層對流層 )of the atmosphere (0-10 km))of the atmosphere (0-10 km)

VOC + NOx + Sunlight = OzoneVOC + NOx + Sunlight = Ozone Stratospheric Stratospheric ((同溫層同溫層 , 10-30 km, 10-30 km)) O O33 layer —“ layer —“

good” Ogood” O33 , protects life on earth from the sun’s ha , protects life on earth from the sun’s ha

rmful ultraviolet rays (UV-b)rmful ultraviolet rays (UV-b)– ““Good" ozone occurs naturally in the stratosphere and is producGood" ozone occurs naturally in the stratosphere and is produc

ed and destroyed at a constant rate.ed and destroyed at a constant rate.

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly What is happening to the “Good” ozoneWhat is happening to the “Good” ozone

1.1. These ozone depleting substances degrade slowly and can rThese ozone depleting substances degrade slowly and can remain intact for many years as they move through the tropoemain intact for many years as they move through the troposphere until they reach the stratosphere.sphere until they reach the stratosphere.

2.2. There they are broken down by the intensity of the sun's UThere they are broken down by the intensity of the sun's UV rays and release chlorine and bromine molecules, which V rays and release chlorine and bromine molecules, which destroy "good" ozone. 1Cl or Br molecule can destroy 100,destroy "good" ozone. 1Cl or Br molecule can destroy 100,000 O000 O33 molecules, causing ozone to disappear much faster t molecules, causing ozone to disappear much faster t

han nature can replace it. han nature can replace it.

3.3. Gradually being destroyed by manmade chemicals called chGradually being destroyed by manmade chemicals called chlorofluorocarbons (CFCs), halons, and other ozone depletinlorofluorocarbons (CFCs), halons, and other ozone depleting substances (used in coolants, foaming agents, fire extinguig substances (used in coolants, foaming agents, fire extinguishers, and solvents). shers, and solvents).

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly What is happening to the “Good” ozoneWhat is happening to the “Good” ozone

– Satellite observations indicate a world-wide Satellite observations indicate a world-wide thinning of the protective ozone layer. The most thinning of the protective ozone layer. The most noticeable losses occur over the noticeable losses occur over the North and South North and South PolesPoles because ozone depletion accelerates in because ozone depletion accelerates in

extremely cold weather conditions.extremely cold weather conditions.

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly

What is happening to the “Good” ozoneWhat is happening to the “Good” ozone

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly How Does the Depletion of "Good" Ozone Affect HuHow Does the Depletion of "Good" Ozone Affect Hu

man Health and the Environment? man Health and the Environment? – Increased UV-b→skin cancer, cataractsIncreased UV-b→skin cancer, cataracts（白內障）（白內障） , and , and

impaired immune systems. impaired immune systems. – Damage to UV-b sensitive crops, such as soybeans, reduceDamage to UV-b sensitive crops, such as soybeans, reduce

s yield. s yield. – High altitude ozone depletion is suspected to cause decreasHigh altitude ozone depletion is suspected to cause decreas

es in phytoplanktones in phytoplankton（浮游植物）（浮游植物） , in the ocean. → affect , in the ocean. → affect the marine food chain. the marine food chain.

– plants "breathe in" COplants "breathe in" CO22 and "breathe out" O and "breathe out" O2 2 → CO→ CO2 2 ↑ in th↑ in th

e air. Increased UV-b radiation → more ground-level or∴e air. Increased UV-b radiation → more ground-level or∴ "bad" ozone "bad" ozone

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly

What is Being Done About the Depletion of What is Being Done About the Depletion of Good Ozone? Good Ozone?

– TThe Montreal Protocol (effective in 1989)— a series he Montreal Protocol (effective in 1989)— a series of international agreements on the reduction and of international agreements on the reduction and eventual elimination of production and use of ozone eventual elimination of production and use of ozone depleting substances (ODS). depleting substances (ODS).

– Currently, 160 countries participate in the Protocol. Currently, 160 countries participate in the Protocol. →recovery of the ozone layer in about 50 years. →recovery of the ozone layer in about 50 years.

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly What is Being Done About the Depletion of What is Being Done About the Depletion of

Good Ozone? Good Ozone?

– In U.S., the U.S. Environmental Protection Agency In U.S., the U.S. Environmental Protection Agency (EPA) continues to establish regulations to phase out (EPA) continues to establish regulations to phase out these chemicals. The Clean Air Act requires warning these chemicals. The Clean Air Act requires warning labels on all products containing CFCs or similar labels on all products containing CFCs or similar substances, prohibits nonessential ODS products, substances, prohibits nonessential ODS products, and prohibits the release of refrigerants used in car and prohibits the release of refrigerants used in car and home air conditioning units and appliances into and home air conditioning units and appliances into the air.the air.

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly

What Causes "Bad" What Causes "Bad" Ozone?Ozone?

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly What is Being Done About Bad Ozone? What is Being Done About Bad Ozone?

– TThe Clean Air Act Amendments(1990) require EPA, statehe Clean Air Act Amendments(1990) require EPA, state

s, and cities to implement programs to further reduce emis, and cities to implement programs to further reduce emissions of Ossions of O33 precursors from sources, eg., cars, fuels, indu precursors from sources, eg., cars, fuels, indu

strial facilities, power plants, and consumer/commercial pstrial facilities, power plants, and consumer/commercial products. roducts.

– Power plants will be reducing emissions, cleaner cars and Power plants will be reducing emissions, cleaner cars and fuels are being developed, many gas stations are using spfuels are being developed, many gas stations are using special nozzles at the pumps to recapture gasoline vapors, aecial nozzles at the pumps to recapture gasoline vapors, and vehicle inspection programs are being improved to rednd vehicle inspection programs are being improved to reduce emissions. uce emissions.

3-1-1 Ozone: Good Up High, Bad Nearly 3-1-1 Ozone: Good Up High, Bad Nearly What is Being Done About Bad Ozone? What is Being Done About Bad Ozone?

– The ultimate responsibility for our environment is The ultimate responsibility for our environment is our own. our own.

– Minor lifestyle changes can result in major air Minor lifestyle changes can result in major air quality improvements.quality improvements.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS)

Ozone-Depleting Substance(s) (ODS): a compound that cOzone-Depleting Substance(s) (ODS): a compound that contributes to stratospheric ontributes to stratospheric ozone depletionozone depletion

include include CFCsCFCs, , HCFCsHCFCs, , halonshalons, , methyl bromidemethyl bromide, , carbon tetrachloridecarbon tetrachloride, and , and methyl chloroformmethyl chloroform. .

very stable in the troposphere and only degrade unvery stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere.der intense ultraviolet light in the stratosphere.

When they break down, they release chlorine or bWhen they break down, they release chlorine or bromine atoms, which then deplete ozone. romine atoms, which then deplete ozone.

A detailed list of class I and class II substances wiA detailed list of class I and class II substances with their ODPs are available. th their ODPs are available.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS)

Class IClass I include CFC's, Halons, Carbon Tetrachloride, an include CFC's, Halons, Carbon Tetrachloride, and TCA as well as less common substances such as methyl d TCA as well as less common substances such as methyl bromide (fumigant) and HBFCs (no Navy/Marine Corps bromide (fumigant) and HBFCs (no Navy/Marine Corps uses). In general, Class I substances cause greater environuses). In general, Class I substances cause greater environmental harm than Class II substancesmental harm than Class II substances

Class IIClass II include HCFC substances, thatare interim materi include HCFC substances, thatare interim materi

als to allow a "rapid" phaseout of Class I substances. Clasals to allow a "rapid" phaseout of Class I substances. Class II substances are also scheduled for phaseout (HCFC-14s II substances are also scheduled for phaseout (HCFC-141b by 2003; HCFC-22 and HCFC-142b by 2020; and, all 1b by 2003; HCFC-22 and HCFC-142b by 2020; and, all other HCFC's by 2030).other HCFC's by 2030).

TYPICAL CLASS I ODS SUBSTANCES

CLASS I TYPICAL USES** OZONE DEPLETING POTEN

TIAL

CFC-11 CHILLERS 1.0

CFC-12REFRIGERATION,

A/C1.0

CFC-113CLEANING SOLVENT

& REFRIGERANT0.8

CFC-114 AIR CONDITIONING 1.0

CFC-500CHILLERS &

AIRCRAFT ACN/A

CFC-502 FREEZERS N/A

HALON 1211FIRE

EXTINGUISHERS3.0

HALON 1301FIXED FIRE

SUPPRESSION SYSTEMS

10.0

CCL4 CLEANING SOLVENT 1.1

TCA CLEANING SOLVENT 0.1

TYPICAL CLASS II ODS SUBSTANCES

CLASS II TYPICAL USESOZONE DEPLETING

POTENTIAL

HCFC-22 REFRIGERANT 0.05

HCFC-123   0.02

** The "ozone depleting potential (ODP)" is a relative index of damage to the environment. The higher the number, the greater the damage.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS)

Chlorofluorocarbon (CFC, Freon): a compound coChlorofluorocarbon (CFC, Freon): a compound consisting of chlorine, fluorine, and carbonnsisting of chlorine, fluorine, and carbon

CFCs are commonly used as refrigerants, solvents,CFCs are commonly used as refrigerants, solvents, and foam blowing agents. and foam blowing agents.

The most common CFCs are CFC-11, CFC-12, CThe most common CFCs are CFC-11, CFC-12, CFC-113, CFC-114, and CFC-115. Their ODPs are, FC-113, CFC-114, and CFC-115. Their ODPs are, respectively, 1, 1, 0.8, 1, and 0.6. respectively, 1, 1, 0.8, 1, and 0.6.

CFC-11(CClCFC-11(CCl33F) F) 、 、 CFC-l2 (CClCFC-l2 (CCl22FF22) ) 及及 CFC-11CFC-11

3(C3(C22ClCl33FF33) )

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS)

Hydrochlorofluorocarbon (HCFC): a compound cHydrochlorofluorocarbon (HCFC): a compound consisting of hydrogen, chlorine, fluorine, and carbonsisting of hydrogen, chlorine, fluorine, and carbonon

HCFCs have ODP ranging from 0.01 to 0.1. HCFCs have ODP ranging from 0.01 to 0.1.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS) Halon: a compound consisting of Halon: a compound consisting of brominebromine, fluorine, a, fluorine, a

nd carbon (nd carbon (Bromine is many times more effective at destBromine is many times more effective at destroying ozone than chlorine. roying ozone than chlorine. ))

used as fire extinguishing agents, both in built-in systems used as fire extinguishing agents, both in built-in systems and in handheld portable fire extinguishers. and in handheld portable fire extinguishers.

Halon production in the U.S. ended on 12/31/93 because tHalon production in the U.S. ended on 12/31/93 because they contribute to ozone depletion.hey contribute to ozone depletion.

ODPs of halon 1301 and halon 1211 were observed to be ODPs of halon 1301 and halon 1211 were observed to be 10 and 3, respectively. Recent scientific studies, however, 10 and 3, respectively. Recent scientific studies, however, indicate that the ODPs are at least 13 and 4, respectively. indicate that the ODPs are at least 13 and 4, respectively.

Note: technically, all compounds containing carbon and flNote: technically, all compounds containing carbon and fluorine and/or chlorine are halons, but in the context of thuorine and/or chlorine are halons, but in the context of the Clean Air Act, "halon" means a fire extinguishing agent e Clean Air Act, "halon" means a fire extinguishing agent as described above. as described above.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS) Methyl Bromide (CHMethyl Bromide (CH33Br): An effective pesticide, this Br): An effective pesticide, this

compound is used to fumigate soil and many agricultural compound is used to fumigate soil and many agricultural products with ODP 0.6.products with ODP 0.6.

Production of methyl bromide ended in the U.S. on Production of methyl bromide ended in the U.S. on 12/31/2000. 12/31/2000.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS) Carbon Tetrachloride (CClCarbon Tetrachloride (CCl44): widely used as a raw ): widely used as a raw

material in many industrial uses, including the promaterial in many industrial uses, including the production of CFCs, and as a solvent with ODP, 1.2. duction of CFCs, and as a solvent with ODP, 1.2.

Solvent use ended when it was discovered to be caSolvent use ended when it was discovered to be carcinogenicrcinogenic （致癌的）（致癌的） . .

It is also used as a catalyst to deliver chlorine ions It is also used as a catalyst to deliver chlorine ions to certain processes. to certain processes.

3-1-2 Ozone-Depleting Substances (ODS) 3-1-2 Ozone-Depleting Substances (ODS) Methyl Chloroform (CH3CCl3): used as an industrial Methyl Chloroform (CH3CCl3): used as an industrial

solvent with ODP, 0.11solvent with ODP, 0.11 . .

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

T.E.Graedel and P.J.Crutzen, T.E.Graedel and P.J.Crutzen, Atmospheric ChanAtmospheric Change: an Earth System Perspective, 2nd ed., ge: an Earth System Perspective, 2nd ed., FreeFreeman, New York (1993) Starting on page 141, for a man, New York (1993) Starting on page 141, for a more in-depth treatment of ozone chemistry that is more in-depth treatment of ozone chemistry that is still very readable by the science-layman.still very readable by the science-layman.

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion Formation and destruction of ozone (Formation and destruction of ozone (Up to 98% of the Up to 98% of the

sun's high-energy ultraviolet light (UV-B and UV-C) are sun's high-energy ultraviolet light (UV-B and UV-C) are absorbed)absorbed)

The global exchange between ozone and oxygen is on the The global exchange between ozone and oxygen is on the order of 300 million tons per day.order of 300 million tons per day.

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

UVA: 320 nm<λ<400 nm (UVA: 320 nm<λ<400 nm (just shorter than just shorter than visible violet lightvisible violet light),), not absorbed by ozone. not absorbed by ozone.

UVB: 280 nm<λ<320 nmUVB: 280 nm<λ<320 nm UVC: λ<280 nmUVC: λ<280 nm, extremely dangerous, but it is , extremely dangerous, but it is

completely absorbed by ozone and normal oxygen completely absorbed by ozone and normal oxygen (O2). (O2).

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

Halogen catalysis of ozone degradationHalogen catalysis of ozone degradation– Halogens: a chemical family containing fluorine, Halogens: a chemical family containing fluorine,

chlorine, bromine and iodinechlorine, bromine and iodine– Halocarbon: any carbon compound containing Halocarbon: any carbon compound containing

halogens. halogens. – All halogens have the ability to catalyze ozone All halogens have the ability to catalyze ozone

breakdown, they have an unequal impact on the ozone breakdown, they have an unequal impact on the ozone layer. layer.

– A catalyst is a compound which can alter the rate of a A catalyst is a compound which can alter the rate of a reaction without permanently being altered by that reaction without permanently being altered by that reaction, and so can react over and over againreaction, and so can react over and over again

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

Halogen catalysis of ozone degradationHalogen catalysis of ozone degradation

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

Halogen catalysis of ozone degradationHalogen catalysis of ozone degradation– 1 Cl can degrade over 100,000 O1 Cl can degrade over 100,000 O33 before it is removed from the s before it is removed from the s

tratosphere or becomes part of an inactive compound. tratosphere or becomes part of an inactive compound.

– These inactive compounds, for example ClONO2, are collectivelThese inactive compounds, for example ClONO2, are collectively called 'resevoirs'. They hold Cl in an inactive form but can releay called 'resevoirs'. They hold Cl in an inactive form but can release an active chlorine when stuck by sunlight. se an active chlorine when stuck by sunlight.

– stability of the resevior compounds. stability of the resevior compounds.

– Hydrogen fluoride, HF: very stable & have relatively no known iHydrogen fluoride, HF: very stable & have relatively no known impact on Ompact on O33 . .

– Bromine resevoirs, eg., HBr and BrONO2, much more easily broBromine resevoirs, eg., HBr and BrONO2, much more easily broken up by sunlight ; causing Br to be from 10 to 100 times more ken up by sunlight ; causing Br to be from 10 to 100 times more effective than Cl at destroying Oeffective than Cl at destroying O33 . .

3-1-3 Basic Chemistry of Ozone Depletion 3-1-3 Basic Chemistry of Ozone Depletion

Chlorine RemovalChlorine Removal

In the stratosphere the major mechanisms for chlorine remIn the stratosphere the major mechanisms for chlorine removal involve the formation of HCl: oval involve the formation of HCl:

OH + ClO ---->HCl + O2 OH + ClO ---->HCl + O2

O2H + Cl ------> HCl + O2 O2H + Cl ------> HCl + O2 HCl is water soluble and is eventually precipitated out of tHCl is water soluble and is eventually precipitated out of t

he stratosphere by water droplets or crystals. he stratosphere by water droplets or crystals. The estimated lifetime of HCl in the stratosphere is about 2 The estimated lifetime of HCl in the stratosphere is about 2

years.years.

3-1-4 The Antarctic Ozone Hole3-1-4 The Antarctic Ozone Hole Antarctic Ozone Levels Antarctic Ozone Levels

in Fall 2003 in Fall 2003

(Source: NOAA TOVS (Source: NOAA TOVS satellite )satellite )

The ozone hole is The ozone hole is represented by the represented by the purple, red, burgundy, purple, red, burgundy, and gray areas that and gray areas that appeared over Antarctica appeared over Antarctica in the fall of 2003. The in the fall of 2003. The ozone hole is defined as ozone hole is defined as the area having < 220 the area having < 220 Dobson units (DU) of Dobson units (DU) of ozone in the overhead ozone in the overhead columncolumn

3-1-4 The Antarctic Ozone Hole3-1-4 The Antarctic Ozone Hole The ozone hole is a well-defined, large-scale The ozone hole is a well-defined, large-scale

destruction of the ozone layer over Antarctica destruction of the ozone layer over Antarctica that occurs each Antarctic spring. that occurs each Antarctic spring.

The word "hole" is a misnomer; the hole is The word "hole" is a misnomer; the hole is really a significant thinning, or reduction in really a significant thinning, or reduction in ozone concentrations, which results in the ozone concentrations, which results in the destruction of up to 70% of the ozone destruction of up to 70% of the ozone normally found over Antarctica. normally found over Antarctica.

3-1-4 The Antarctic Ozone Hole3-1-4 The Antarctic Ozone Hole The ozone hole occurs only over Antarctica. The ozone hole occurs only over Antarctica.

Two international organizations issue regular Two international organizations issue regular bulletins about the ozone hole as it develops bulletins about the ozone hole as it develops each year: the British Antarctic Survey and each year: the British Antarctic Survey and the World Meteorological Organization. the World Meteorological Organization.

The University of Cambridge's Ozone Hole The University of Cambridge's Ozone Hole Tour provides detailed explanations, with Tour provides detailed explanations, with graphics, of the ozone hole and its history. graphics, of the ozone hole and its history.

3-1-4 The Antarctic Ozone Hole3-1-4 The Antarctic Ozone Hole

3-1-4 The Antarctic Ozone Hole3-1-4 The Antarctic Ozone Hole The illustration above shows a column of air, 10 deg x The illustration above shows a column of air, 10 deg x

5 deg, over Labrador, Canada. If all the ozone in this 5 deg, over Labrador, Canada. If all the ozone in this column were to be compressed to standard temperature column were to be compressed to standard temperature and pressure (STP) (0 deg C and 1 atmosphere and pressure (STP) (0 deg C and 1 atmosphere pressure) and spread out evenly over the area, it would pressure) and spread out evenly over the area, it would form a slab approximately 3mm thick. form a slab approximately 3mm thick.

1 Dobson Unit (DU) is defined to be 0.01 mm 1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP; the ozone layer over Labrador then thickness at STP; the ozone layer over Labrador then is 300 DU.is 300 DU.

The unit is named after G.M.B. Dobson, one of the first scientists to investigate The unit is named after G.M.B. Dobson, one of the first scientists to investigate atmospheric ozone (~1920 - 1960). He designed the 'Dobson Spectrometer' - the atmospheric ozone (~1920 - 1960). He designed the 'Dobson Spectrometer' - the standard instrument used to measure ozone from the ground. standard instrument used to measure ozone from the ground.

The Dobson spectrometer measures the intensity of solar UV radiation at four The Dobson spectrometer measures the intensity of solar UV radiation at four

wavelengths, two of which are absorbed by ozone and two of which are not.wavelengths, two of which are absorbed by ozone and two of which are not.

3-2 The Greenhouse Effect 3-2 The Greenhouse Effect

What is the Greenhouse Effect?What is the Greenhouse Effect?

What Gases are Responsible?What Gases are Responsible?

What are the Solutions to Greenhouse Gas What are the Solutions to Greenhouse Gas Warming?Warming?

3-2 The Greenhouse Effect 3-2 The Greenhouse Effect

What is the Greenhouse Effect?What is the Greenhouse Effect?

Greenhouse gases (GHGs) allow incoming solar radGreenhouse gases (GHGs) allow incoming solar radiation to pass through the Earth’s atmosphere, but iation to pass through the Earth’s atmosphere, but prevent most of the outgoing infra-red radiation frprevent most of the outgoing infra-red radiation from the surface and lower atmosphere from escapiom the surface and lower atmosphere from escaping into outer space. ng into outer space.

↓ ↓Keep the earth’s temperature about 59 Keep the earth’s temperature about 59 ooF(~30F(~30ooC) waC) wa

rmerrmer

3-2-1 What is the Greenhouse Effect? 3-2-1 What is the Greenhouse Effect?

http://earthguide.ucsd.edu/earthguide/diagrams/grhttp://earthguide.ucsd.edu/earthguide/diagrams/greenhouse/eenhouse/

3-2-1 What is the Greenhouse Effect?3-2-1 What is the Greenhouse Effect?

3-2-1 What is the Greenhouse Effect?3-2-1 What is the Greenhouse Effect?

3-2-2 What Gases are Responsible?3-2-2 What Gases are Responsible?

Gases absorb the longer-wavelength energy radiatGases absorb the longer-wavelength energy radiated from the earth (GHG)ed from the earth (GHG)

HH22O (vapor)—dominant GHG, but very little of it O (vapor)—dominant GHG, but very little of it

is the result of human activities. is the result of human activities. Principal GHG resulting from human activities, ePrincipal GHG resulting from human activities, e

g., increased economic activity and changing agrig., increased economic activity and changing agricultural practices...:cultural practices...:

3-2-2 What Gases are Responsible? 3-2-2 What Gases are Responsible?

OO33—a gaseous molecule contributes to smog, is a—a gaseous molecule contributes to smog, is a

lso a GHG, but exists for only a brief period of tilso a GHG, but exists for only a brief period of time in the lower atmosphere (me in the lower atmosphere ( ～～ weeks) →contriweeks) →contribution is still uncertainbution is still uncertain

Since mid-1800s, atmospheric levels of Since mid-1800s, atmospheric levels of

COCO22↑30% (280 ppm → 360 ppm)↑30% (280 ppm → 360 ppm)

CCHH4 4 ↑100% (→ 1.72 ppm)↑100% (→ 1.72 ppm)

NN22O↑8-15%O↑8-15%

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

COCO22

Production:Production:

OceansOceans→90 billion tonnes +→90 billion tonnes +

Decaying vegetationDecaying vegetation→30 billion tonnes +→30 billion tonnes +

Natural respiration of living creatures and Natural respiration of living creatures and

plantsplants →30 billion tonnes+ →30 billion tonnes+

Human activitiesHuman activities→3% or 7 billion tonnes→3% or 7 billion tonnes

per yearper year

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

COCO22

Removal:Removal:

Absorption by the oceans & photosynthesis process Absorption by the oceans & photosynthesis process of green plants of green plants

Net of “carbon cycle”→↑3.1-3.5 billion tonnes per yNet of “carbon cycle”→↑3.1-3.5 billion tonnes per yearear

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

COCO22

Manmade: burning of fuelsManmade: burning of fuels

Chemically stable→remain for manyChemically stable→remain for many

decadesdecades

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

MethaneMethane

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

MethaneMethane

Main sources: “Marsh gas (Main sources: “Marsh gas ( 沼氣沼氣 )” from aerobic decay of ve)” from aerobic decay of vegetation in wetlands and from rice paddies+getation in wetlands and from rice paddies+

natural gas+ Cattle, termites, and other animals release as natural gas+ Cattle, termites, and other animals release as part of the digestive processpart of the digestive process

Industrial revolution, 0.8 ppm →1.72 ppmIndustrial revolution, 0.8 ppm →1.72 ppm 600 million tonnes is released & 560 million tonnes is abs600 million tonnes is released & 560 million tonnes is abs

orbed, annually → 35-40 million tonnes netorbed, annually → 35-40 million tonnes net Can be destroyed by reactions with other chemicals in the Can be destroyed by reactions with other chemicals in the

atmosphere and soil → lifetime~10 yearsatmosphere and soil → lifetime~10 years A much greater energy absorber than COA much greater energy absorber than CO22 (27 times) (27 times)

3-2-2 What Gases are 3-2-2 What Gases are Responsible? Responsible?

Nitrous OxidesNitrous Oxides (laughing gas) (laughing gas)

Major source: Major source: bacterial breakdown of nitrogen components ibacterial breakdown of nitrogen components in soilsn soils →↑ when land is deforested and then cultivated, parti →↑ when land is deforested and then cultivated, particularly if nitrogen-containing fertilizers are used +cularly if nitrogen-containing fertilizers are used +

ocean upswellings during tidal actionocean upswellings during tidal action + +

fossil fuel combustionfossil fuel combustion (~3% ) (~3% ) Worldwide, 13-20 million tonnes emitted, but 10-17 millionWorldwide, 13-20 million tonnes emitted, but 10-17 million

s tonnes are chemically broken down in the stratosphere or s tonnes are chemically broken down in the stratosphere or otherwise removed from the air →↑4 million tonnes per yeaotherwise removed from the air →↑4 million tonnes per yearr

More potent than methane (~165 times than COMore potent than methane (~165 times than CO22))

3-2-2 What Gases are Responsible? 3-2-2 What Gases are Responsible? Chlorofluorocarbons(CFCs) & Hydrofluorocarbons(HFCs)Chlorofluorocarbons(CFCs) & Hydrofluorocarbons(HFCs)

CFCs—most potent GHG, eg., CFC-12 (Freon-12) is 17,700 tiCFCs—most potent GHG, eg., CFC-12 (Freon-12) is 17,700 times than COmes than CO22

Although minute, responsible for ~ 24% greenhouse effect.Although minute, responsible for ~ 24% greenhouse effect. CFCs do not exist naturally. Main concern is their role in destrCFCs do not exist naturally. Main concern is their role in destr

oying Ooying O33 →Montreal Protocol: phase out their use by 2000 →Montreal Protocol: phase out their use by 2000

HFCs has been developed to replace CFCs.HFCs has been developed to replace CFCs. Rare before 1990 and increasing rapidly because in 1994, HFRare before 1990 and increasing rapidly because in 1994, HF

C-134a was adopted as the standard motor vehicle AC refrigereC-134a was adopted as the standard motor vehicle AC refrigerentnt

3-2-2 What Gases are Responsible? 3-2-2 What Gases are Responsible? AerosolsAerosols—cooling effect—cooling effect

A class of gases (eg., SOA class of gases (eg., SO22) create aerosols in the atmosphere ) create aerosols in the atmosphere

→ act as nuclei for water droplets to collect and form clouds → act as nuclei for water droplets to collect and form clouds → reflect sunlight back into space, cooling the planet→ reflect sunlight back into space, cooling the planet

The emissions of these gases are now sharply regulated and haThe emissions of these gases are now sharply regulated and have declined considerably in recent refrigerentve declined considerably in recent refrigerent

3-2-2 What Gases are Responsible? 3-2-2 What Gases are Responsible?

Global Warming Potential (GWP): the ratio of the radiative Global Warming Potential (GWP): the ratio of the radiative forcing that would result from the emissions of 1 kg of a Gforcing that would result from the emissions of 1 kg of a GHG to that from emission of 1 kg of COHG to that from emission of 1 kg of CO22 over a period of ti over a period of ti

me (usually 100 years), i.e, Carbon Dioxide Equivalentme (usually 100 years), i.e, Carbon Dioxide Equivalent

3-2-2 What Gases are Responsible? 3-2-2 What Gases are Responsible?

3-2-3 What are the Solutions to 3-2-3 What are the Solutions to Greenhouse Gas Warming? Greenhouse Gas Warming?

1. Boosting Power Plant Efficiency—most immedia1. Boosting Power Plant Efficiency—most immediate and cost effective ways to reduce GHGste and cost effective ways to reduce GHGs

From 1995 to 2015, world’s use of electricity wiFrom 1995 to 2015, world’s use of electricity will double and ~60 % from power plants that burll double and ~60 % from power plants that burn either coal or natural gas.n either coal or natural gas.

2. Sequestering Carbon—capturing and storing CO2. Sequestering Carbon—capturing and storing CO22

3. Reducing Coal Bed Emissions—methane3. Reducing Coal Bed Emissions—methane4. More Efficient Use of Fossil Fuels in Buildings, I4. More Efficient Use of Fossil Fuels in Buildings, I

ndustry, and Transportationndustry, and Transportation

3-2-3 What are the Solutions to 3-2-3 What are the Solutions to Greenhouse Gas Warming? Greenhouse Gas Warming?

4. More Efficient Use of Fossil Fuels in Buildings, Industry,4. More Efficient Use of Fossil Fuels in Buildings, Industry, and Transportation (each ~ 1/3) and Transportation (each ~ 1/3)

(1) Potential Buildings Sector Savings— “Green” Buildin(1) Potential Buildings Sector Savings— “Green” Buildings, combined heat and power (CHP)gs, combined heat and power (CHP)

(2) Potential Industry Sector Savings—cogeneration & ad(2) Potential Industry Sector Savings—cogeneration & advanced turbines of natural gas and biomass.vanced turbines of natural gas and biomass.

(3) Potential Transportation Sector Savings—President’s (3) Potential Transportation Sector Savings—President’s Partnership for a New Generation of Vehicles (PNGV): Partnership for a New Generation of Vehicles (PNGV): cars 3 times more efficient than current vehicles with ncars 3 times more efficient than current vehicles with no compromise in size, safety, comfort or cost.o compromise in size, safety, comfort or cost.

hybrid vehicle design, advanced engines, regenerative hybrid vehicle design, advanced engines, regenerative braking and lightweight materialsbraking and lightweight materials

3-2-3 What are the Solutions to 3-2-3 What are the Solutions to Greenhouse Gas Warming? Greenhouse Gas Warming?

Carbon neutral fuels—ethanol (Carbon neutral fuels—ethanol ( 乙醇乙醇 ,, 酒精酒精 ) from ) from cellulsoic waste (eg. crop waste) and dedicated cellulsoic waste (eg. crop waste) and dedicated crops (eg., swithgrass) ←capture COcrops (eg., swithgrass) ←capture CO22 when the when the

y grow and release it during combustion.y grow and release it during combustion.

$3.6 /gallon in 1980 → 1.2 /gallon today$3.6 /gallon in 1980 → 1.2 /gallon today