Climate Change Study Guide Chapter 20
1. The earth’s average surface temperature for the past 900,000 years has had many
fluctuations of several degrees Celsius. Over the past million years, glacial periods lasting
about 10,000 years have alternated with interglacial periods lasting about 100,000 years.
2. The greenhouse effect is best described as consensus science. If the greenhouse effect
did not exist life on the planet would cease to exist, as we know it.
- The amount of heat trapped in the troposphere depends on concentrations of
greenhouse gases.
- Heat trapped by the greenhouse gases keep the planet warm enough for life.
- The two predominant greenhouse gases are water vapor and carbon dioxide.
- The greenhouse effect has been confirmed by numerous lab experiments and
measurements of atmospheric temperatures at different altitudes.
3. The major greenhouse gases include methane, carbon dioxide, water vapor, and nitrous
oxide. The two predominant greenhouse gases in the troposphere are carbon dioxide and
water vapor. Chlorofluorocarbons (CFC’s) although not a major greenhouse gas, they do
contribute to the greenhouse effect. All of the greenhouse gases listed has increased in
recent decades except water vapor.
4. The estimate variations in earth’s mean surface temperature over the past 135 years
correlate closely with atmospheric carbon dioxide levels. The concentration of carbon
dioxide in the troposphere around 1900 was about 280 ppm. Today carbon dioxide. levels
are approaching 400 ppm . Since 1861, mean global temperatures have risen .6-, 8
degree(s) Celsius or Centigrade.
5. Scientists rely on complicated computer models to predict the effects of climate
change. There are many uncertainties in climate models because scientists do not
completely understand the ecosphere with all its physical feedbacks and processes of the
climate system. Two of the largest uncertainties in climate models are predicting the
effects of clouds and ecosphere interactions on climate. (Effects of clouds page 472)
6. Major climate models project
- A 2.4 to 5.4 degree centigrade rise in earths mean surface temperature.
- An earth warmer than in any time in the last 10,000 years
- More warming in the Northern Hemisphere than the Southern Hemisphere (Why)
- Human responsibility for the changes in temperature.
7. Signs of global warming include
- Spreading of some tropical diseases away from the equator.
- Bleaching of the coral reefs in tropical areas with warmer waters
- Increased retreat of some glaciers on the tops of mountains in the Northern Cascades.
- Northward migration of some warm-climate fish.
8. Climate Scientists are uncertain about how
- Carbon dioxide will affect the rate of photosynthesis
- Increased temperatures will affect insect populations
- Gas trapped in the permafrost will affect global warming
- How air pollution might affect climate
9. What happens to the carbon dioxide released into the atmosphere by human activities?
Almost half of it absorbed by the oceans. Some is absorbed by the growth of plants the
remains in the atmosphere.
10. As global warming progresses, increased amounts of methane may be released from
oceanic mud as ocean waters warm. In the event of global warming, food production
might be negatively affected by
- Poorer soil in new crop-growing regions
- Increased insect populations
- Lack of irrigation waters in some areas
- Change in crop yields – some increases and some decreases
11. The consequence of rapid climate change over decades might include
- Premature deaths from lack of foods
- Reduction in earth’s biodiversity
- Social and economic chaos
- Increased death from heat and disease
In a warmer world we will expect more droughts, hurricanes, prolonged heat waves, and
desert expansion.
12. An influx of freshwater from increased rain in the North Atlantic Ocean and thawing
ice in the Artic region may disrupt the oceanic conveyor belt current. (How does this
work and what is its function?)
13. So who is going to be most affected by global warming? Definitely organisms who
already live in a tropical or desert like climate. Specialists or generalists??
14. How can we reduce carbon dioxide levels in the troposphere??
Carbon sequestration can be achieved by
- planting more trees
- pumping excess carbon dioxide deep underground
- growing more switch grass or similar carbon absorbing vegetation
- injecting it into the deep oceans
More Techno fixes include
- adding iron to the ocean
- using foil- surfaced sun shields in space
- injecting sulfate particles into the stratosphere
- releasing billions of helium filled reflective balloons into the atmosphere
15. We – you, me, and others – can address the threat of global warming by
- using energy more efficiently
- halting deforestation
- slowing population growth
- shifting to renewable resources
16. 1992 Earth Summit in Rio de Janeiro 161 nations committed themselves to reducing
greenhouse gas emissions to 1990levels by the year 2000.
1997 Kyoto Treaty to reduce global warming would
- not require developing countries to make any cuts in their greenhouse gas emissions
unless they chose to do so
- allow emissions trading among participating countries
- allow forested countries to get a break in their quotas
17. Stratospheric Ozone is most effective in blocking UV-C, the highest-energy UV
band.
Tradeoff?? According to a study by the World Meteorological Organization, ozone
depletion in the stratosphere has been cooling the troposphere and has helped offset or
disguise the global warming from our emissions of greenhouse gases by as much as 30
%. Remember that the formation of the ozone layer enabled life on land to evolve.
18. What is causing the shrinking of the stratospheric Ozone layer? One of the main
chemicals breaking down the Ozone layer is Chlorofluorocarbons other wise known as
CFC’s. CFC’s are used in air conditioners, aerosol cans, sterilants for hospital
equipment, and cleaners for computer chips. CFC’s are light (in mass), odorless and
stable gases. They are nonflammable, nontoxic,, noncorrosive and cheap to produce.
19. Over 44 years passed from the first production of CFCs until the first awareness that
they could cause environmental damage. In the 1980’s researchers discovered a 40 -50
% loss in the upper stratosphere over the Antarctic. CFC’s are found in the bubbles of
Styrofoam and insulation. CFCs remain in the troposphere because they are insoluble in
water and chemically unreactive.
20. Ultraviolet radiation will CFC’s to break down and release chlorine – one chlorine
molecule may convert 100,000 molecules of ozone to molecular oxygen.
21. CFC’s are not the only chemicals that are stratospheric ozone-eaters others include
methyl bromide, halons, methyl chlorform
-Halons are used as fire extinguishing agents, both in built-in systems and in handheld
portable fire extinguishers. Halon production in the U.S. ended on December 31, 1993,
because they contribute to ozone depletion. (very powerful O3 depletion chemical)
-Methyl chloroform is an industrial solvent
22. It takes CFC’s 10 -20 years to reach the atmosphere. The single greatest contributor
to CFC emissions in the United States is leaking air conditioners.
21. If all of the ozone- depleting substances were banned tomorrow it would take about
100 years fro the earth to recover to pre-1950 levels. We can slow the rate of ozone hole
creation by stopping production of Ozone- depleting chemicals, recovering and reusing
ozone-depleting chemicals, and finding substitutes for CFC’s.
22. Increases in ultraviolet radiation will cause an increase in skin cancer, eye cataracts,
suppression of the human system, increased breakdown of materials such as paints and
plastics.
23. In 1987, 36 nations meeting in Montreal, Canada, developed the Montreal Protocol to
reduce production of CFC’s
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