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