ch 20: atmospheric change

ozone hole

• loss of ozone over antarctica

• a more accurate term is ozone thinning

  • ozone depletion varies with altitude and location

ozone depletion in the stratosphere

• poses a serious threat to humans, other animals, some primary producers that use sunlight to support the earth’s food webs

• majorly caused by the use of CFCs

chlorofluorocarbon (CFC)

• chemically unreactive, odorless, nonflammable, nontoxic, and noncorrosive compounds

• popular as…

  1. coolants in air conditioners and refrigerators

  2. propellants in aerosol spray cans

  3. cleansers for electronic parts such as computer chips

  4. fumigants for granaries and ships’ cargo holds

  5. gases used to make insulation and packaging

• CFCs also act as greenhouse gases that help to warm the lower atmosphere and contribute to climate change in the trophosphere

CFC conclusions

1. once CFCs are put into the atmosphere, being persistent chemicals they remain there for a long time

2. over 11–20 years, these compounds rise into the stratosphere through convection, random drift, and the turbulent mixing of air in the lower atmosphere

3. once they reach the stratosphere, the CFC molecules break down under the influence of high-energy UV radiation

   1. releases highly reactive chlorine atoms (Cl), as well as atoms of fluorine (F) and bromine (Br), all of which accelerate the breakdown of ozone into and O in a cyclic chain of chemical reactions

   2. process destroys ozone faster than it forms in some parts of the stratosphere

4. each CFC molecule can last in the stratosphere for 65–385 years, depending on its type

   1. each chlorine atom released during the breakdown of CFCs can break down hundreds of molecules

effects of ozone depletion on humans

• worse sunburns

• more eye cataracts and skin cancers

• immune system suppression

effects of ozone depletion on food and forests

• reduced yields for some crops

• reduced seafood supplies due to smallerphytoplankton populations

• decreased forest productivity for UV-sensitive tree species

effects of ozone depletion on wildlife

• more eye cataracts in some species

• shrinking populations of aquatic species sensitive to UV radiation

• disruption of aquatic food webs due to shrinking phytoplankton populations

effects of ozone depletion on air pollution and climate change

• increased acid deposition

• increased photochemical smog

• degradation of outdoor painted surfaces, plastics, and building materials

• while in troposphere, CFCs act as greenhouse gases

reducing exposure to UV raditiation

• stay out of the sun, especially between 10 A.M. and 3 P.M.

• do not use tanning parlors or sunlamps

• when in the sun, wear clothing and sunglasses that protect against UV-A and UV-B radiation

• be aware that overcast skies do not protect you

• do not expose yourself to the sun if you are taking antibiotics or birth control pills

• when in the sun, use a sunscreen with a protection factor of at least 15

montreal protocol

• aimed to cut emissions of CFCs by 35% (1989-2000)

copenhagen amendment

• more meetings that occurred after news spread about seasonal ozone thinning above antarctica

• accelerated the phase-out of CFCs and added other key ozone-depleting chemicals to the agreement

prevention approach

• works for three reasons

  1. scientific evidence of a serious problem

  2. CFCs were produced by a small number of intl companies

     1. less corporate resistance

  3. certainty that CFC sales would decline over a period of years because of government bans unleashed the economic and creative resources of the private sector to find even more profitable substitute chemicals

*substitutes are also mostly available

hydrofluorocarbons (HFCs)

• most widely used substitutes

  • act as greenhouse gases

• can be up to 10,000 times more potent in warming the atmosphere than a molecule of CO2

weather

• short-term changes in atmospheric variables such as the temperature and precipitation in a given area over a period of hours or days

climate

• determined by the weather conditions of the earth or of a particular area, especially atmospheric temperatures, averaged over at least three decades

greenhouse effect

• a natural process that plays a major role in determining the earth’s average atmospheric temperature and thus its climate

natural causes of climate change

1. massive volcanic eruptions and impacts by meteors and asteroids that cooled the planet by injecting large amounts of debris into the atmosphere;

2. changes in solar input that can warm or cool the earth;

3. slight changes in the shape of the earth’s orbit around the sun from mostly round to more elliptical over a 100,000 year cycle;

4. slight changes in the tilt of the earth’s axis over a 41,000-year cycle;

5. slight changes in the earth’s wobbly orbit around the sun over a 20,000-year cycle (Factors 3, 4, and 5 are known Milankovitch cycles);

6. global air circulation patterns (see Figure 8.36);

7. changes in the sizes of areas of ice that reflect incoming solar energy and cool the atmosphere;

8. changes in concentrations of greenhouse gases

9. occasional changes in ocean currents.

carbon footprint

• refers to the amount of generated by an individual, a country, a city, or any other entity over a given period CO2

*china has the largest national carbon footprint, followed by the US and India

per capita carbon footprint

• the average footprint per person in a population

*US has the largest per capita carbon footprint

aerosols

• suspended microscopic droplets and solid particles

• can affect the rate of global warming

• hinders/enhance the greenhouse effect and cloud formation

*light-colored sulfate particles produced by fossil fuel combustion, tend to reflect incoming sunlight and cool the lower atmosphere

soot

• black carbon particles

• emitted into the air by coal-burning power and industrial plants, diesel exhaust, open cooking fires, and burning forests

• warm the lower atmosphere

aerosols and soot affect on climate change

• relatively marginal

• aerosols and soot fall back to earth/washed out of lower atmosphere within weeks

  • CO2 typically remains in the lower atmosphere for > 100 years

  • aerosol and soot emissions are already being reduced because of their harmful impacts on plants and humans

climate change tipping points

• thresholds beyond which natural systems could change for hundreds to thousands of years

  1. atmospheric carbon level of 450 ppm

  2. melting of all arctic summer sea ice

  3. collapse and melting of the greenland ice sheet

  4. severe ocean acidification, collapse of phytoplankton populations, and a sharp drop in the ability of the oceans to absorb

  5. massive release of methane from thawing arctic permafrost and from the arctic seafloor

  6. collapse and melting of most of the western antarctic ice sheet

  7. severe shrinkage or collapse of amazon rain forest

albedo

• measure of the reflectivity of sunlight by a surface such as ice and snow (high reflectivity because of its optical brightness, or whiteness), soil and desert (medium reflectivity), and ocean water (low reflectivity)

hardest hit species

• cold-climate plant and animals, including the polar bear in the Arctic and penguins in Antarctica

• species that live at higher elevations

• species with limited tolerance for temperature change, such as corals

• species with limited ranges

*most vulnerable ecosystems are coral reefs, polar seas, coastal wetlands, high-elevation forests, and alpine and arctic tundra

preventing climate change

1. cut fossil fuel use

   1. esp coal

2. shift from coal to natural gas

3. repair leaky natural gas pipelines and facilities

4. improve energy efficiency

5. shift to renewable energy resources

6. reduce deforestation

7. use more sustainable agriculture and forestry

8. put a price on greenhouse gas emissions

cleaning up climate change

1. sequester CO2 by planting trees and preserving forests and wetlands

2. sequester carbon in soil using blochar

3. sequester CO2 deep underground (with no leaks allowed)

4. sequester CO2 in the deep ocean (with no leaks allowed)

5. remove CO2 from smokestack and vehicle emissions

carbon capture and storage (ccs)

• remove some of the CO2 gas from smokestack emissions of coal-burning power plants and industrial plants and convert it to a liquid to be pumped under pressure into underground storage sites

four major problems with CCS schemes

1. they can remove and store only part of the CO2 from smokestack emissions, at great cost,

2. they do not address the massive emissions of CO2 from motor vehicle exhausts, food production, and the deliberate burning of forests to provide land for growing food,

3. they require a lot of energy, which could lead to greater use of fossil fuels and higher emissions of CO2 and other air pollutants, and

4. the CO2 that is removed would have to remain sequestered from the atmosphere forever. Large-scale leaks and smaller continuous leaks from CO2 storage sites could dramatically increase atmospheric warming and climate change in a short time.

geoengineering

• trying to manipulate certain natural conditions to help counter the human-enhanced greenhouse effect

carbon and energy taxes

ads

1. simple to administer

2. clear price on carbon

3. covers all emitters

4. predictable revenues

disads

1. tax laws can get complex

2. vulnerable to loopholes

3. doesnt guarantee lower emissions

4. politically unpopular

cap-and-trade policies

ads

1. clear legal limit on emissions

2. rewards cuts in emissions

3. record of success

4. low expense for consumers

disads

1. revenues not predictable

2. vulnerable to cheating

3. rich polluters can keep polluting

4. puts variable price on carbon

mitigation

• use of strategies to slow down climate change

adaptation

• finding ways to cope with climate change since humans have waited too long to address this problem and some of the harmful effects of climate change are inevitable