Air IssuesAtmosphere basics

Air pollutionClimate change

Composition of atmosphere

78% nitrogen21% oxygen1% everything else

Structure of atmosphereMesosphere and thermosphere

52-120 km

Stratosphere12-52 kmtemperature increases upwardimportant ozone layer (19-26 km)

Troposphere ground to 12 kmtemperature decreases upward

Focus on troposphereOur weather

Pollution that affects humans

Usual conditions vs. inversions (change in temperature going upward)

Usual conditions – pollution rises

Inversion – pollution is trapped

Air pollution Outdoor air pollutionIndoor air pollution

Criteria air pollutants (Clean Air Act, EPA)

Carbon monoxideNOx or nitrogen dioxide

SO2 (sulfur dioxide)

tropospheric ozone (O3)

particulate matter (PM)lead (Pb)

Let’s look at sources of each of these.

Carbon monoxide (CO)Incomplete combustion of

coal gasoline (catalytic converters help here)

Why is it harmful to humans?

Nitrogen oxides (many forms)

NOx

Incomplete burning of gasoline

Contributes to acid rainPart of ozone problem in summer in cities

Tropospheric Ozone

Secondary pollutantMonitor VOCs (volatile organic compounds) solvents and vehicle emissions particularly importantOften a summer-time problem

Sulfur dioxide (SO2)Burning of coalVolcanic emissions (natural)

Effects: damages plant chlorophyll, irritates throat and lungs; causes acid rain

Particulate matterIncomplete combustion of fossil fuelsDust from fields, construction, etc.

Size of particles importantWhat ARE those particles?

LeadPrimary source from leaded gasolineMetal processing industries

Effects central nervous system and bioaccumulates

Criteria Air pollutants

Primary sources to atmosphere

Carbon Monoxide

Sulfur Dioxide

Nitrogen Dioxide

Tropospheric Ozone

Particulate Matter

Lead

Secondary pollutantsCreated by a reactionIncludes smog and tropospheric ozone

SmogPhotochemical smog (LA smog)

Industrial smog (London smog)

Photochemical smog (1)Car exhaust

Hydrocarbons and NOx plus solar radiation produces toxic chemicals, particularly ozone

Higher ozone concentrations in late summer afternoons

Photochemical smog (2)Effects of ozone:

Solutions:

Ozone (O3)Stratosphere = good; troposphere = badPart of summertime smogCharlotte area (and many other urban areas) are in non-attainment for ozone levels

Industrial smogOlder industrial citiesOften associated with coal burningParticulates, sulfur dioxide and stagnant air

Acid depositionSulfuric and nitric acids

Travel long distances

Some solutions: industrial scrubbers, catalytic converters

Indoor air qualityIncreasing awarenessDeveloping countries: particulate matter and carbon monoxideIndustrialized nations: cigarette smoke, radon, mold, VOCs

Solutions?

Global air issuesStratospheric ozone depletion

Climate change

Stratospheric Ozone Depletion

What does stratospheric ozone do?

What is happening?

mid 1990s1970s

Antarctic ResearchersRoutinely monitor atmosphere above Antarctica

Significant depletion started in 1980

Rowland and MolinaPredicted CFCs would destroy ozone (1974)CCl2F2 + UV Cl + CClF2

Cl + O3 ClO + O2

ClO + O O2 + Cl

What can we do?Phase out manufacturing of CFCs – done

Phase out use of CFCs – spray cans, styrofoam products, refrigerants – done

Can this happen on a global basis?

Montreal Protocol (1987)Major reduction in production of CFCs and halonsInitially signed by 25 nations, eventually ratified by over 150 nationsCFC production in industrial nations to be cut by 50%Halon production frozen at 1986 levels SUCCESS

NATURAL TEMPERATURE VARIABILITY INCLUDING GREEN HOUSE EFFECT

HUMAN IMPACT ON TEMPERATURES

ADAPTATION, MITIGATION, SUFFERING

Climate Change

Natural Temperature Variability

SeasonsLatitudes - altitudesMilankovitch cyclesEl Nino cycles

How do we know temperatures from long ago?

Human records: actual measurements

Proxies: ice cores, sediment cores for example

Greenhouse effect

What is it?Is it bad or good that Earth has a greenhouse effect?Greenhouse gases

Sources of greenhouse gases

Carbon dioxide : burning fossil fuels and forests, making cement

Methane: decomposition of organic matter in swampy environments; frozen in tundra and ocean floor; stomachs of cows

Nitrous oxides: bacterial decomposition of manure; soil denitrification; some organic fertilizers

Halocarbons (including CFCs): chemical cooling agent; foaming agent; propellant (phased out by Montreal Protocol)

Relative strength of GHG (from IPCC, 2007)

Carbon Dioxide 1

Methane 25

Nitrous oxide 300

1 CFC replacement 15,000

Future of global warming?

Computer modeling

United Nations IPCC

Intergovernmental Panel on Climate Change

•Won the Nobel Peace Prize (along with Al Gore)

•Established in 1988

•2,000 scientists from many nations

•Policy-relevant but policy neutral

•Four assessment reports (latest in 2007)

IPCC Fourth Assessment Report Conclusions

Greenhouse gases such as carbon dioxide help trap heat near Earth’s surface.

Figure SPM.1

IPCC Fourth Assessment Report Conclusions“Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years.”

Highest in 650,000 years

Today = 385 ppmPreindustrial = 280 ppm

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”

IPCC Fourth Assessment Report Conclusions

Figure SPM.3

Future?

Sea level change (3-20 ft rise)Coral reef “bleaching”Changes in locations of plants and animalsMelting of ice caps and glaciers

Sea Ice in Arctic Ocean1979 and 2003

Alaskan glacier1914 and 2004

Solutions?Adaptation

Mitigation

Suffering is inevitable, but how much?

Evaluating SolutionsThe Need for Adaptation

We are already committed to a certain amount of warming

Resources must be devoted to adapting to altered future conditions

Sea levelEcosystems

Focus on mitigation cannot ignore need for adaptation

Mitigation?

Limit dependence on fossils fuelsPlant treesKyoto Protocol and beyond