Envir Studies Ch 13 – climate change & ozone loss
Start chapter off with a “pleasant” story about an enlightened populace in
year 2060, with many environmental problems solved.
13-1 – Past climate change and the natural greenhouse effect
how have Earth’s temperature and climate changed in the past?
“climate change is neither new nor unusual” – this is an important
point….Earth’s climate has changed dramatically in the past with no help
from humankind at all
Fig 13-2 shows how climate has changed over several diff time frames:
 Last 900,000 years
 Last 22,000 years
 Last 1,000 years
 Last 140 years
What is the greenhouse effect?
Incoming solar radiation heats the Earth; Earth re-radiates the energy as
long-wave IR (heat) energy, keeps things warm. This is the principle behind
a greenhouse for growing plants.
As IR radiation is leaving Earth and passes back out through troposphere,
greenhouse gases can act to absorb the radiation. This causes molecular
vibration in the gases, which then transform the IR radiation at longer
wavelengths. This process adds heat to the lower troposphere. (fig 6-11,
p.127)
The 2 main greenhouse gases are H2O and CO2. Trapped gases in glacial
ice indicate that H2O has stayed pretty steady over last 160,000 yrs, but CO2
levels have fluctuated, and correlate with estimates of global temperature
(Fig 13-3).
13-2 Climate change & Human activities
 beginning of Indus Revolution in 1750 marks sharp rise in use of
fossil fuels
 fossil fuels are combos of H and C, so much add’l added to
atmosphere
 C + O2 from atmosphere = CO2
Industrialized nations contribute disproportionately to CO2 emissions.
1999 world CO2 emissions
US – 26.5%
European Union – 14.5%
China – 13.5%
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“US emissions alone exceeded combined emissions from 146 nations,
which contain 75% of world’s people”
Miller makes the point that continuing increases in man-generated
greenhouse gases could “enhance the Earth’s natural greenhouse effect”
If the effects are significant enough, we could experience some climate
change (generally warmer winters and summers) which coulod produce:
 Shift evaporation-precipitation patterns
 Shift crop farming belts
 Change average sea levels
 Alter the structure and location of biomes
Modeling climate change
Supercomputers allow us to model how climate might change as various
input parameters change (fig 13-6).
These models have a huge range of results – see fig 13-8
Miller makes some claims about “scientific consensus” and cites quotes
that indicate that man is primarily responsible for global warming
In reality, there is still much debate over the factors contributing to climate
change, and what role man plays…there is no “consensus view”, contrary
to what Miller says.
Your assignment #4 – go to the Net,
 find at least one source stating that warming is a “bad” thing
 find at least one source stating that warming is not a “bad thing”
 summarize both positions in approx 250 words
13-3 – Factors affecting changes in Earth’s avg temp
 solar output – there are sunspot cycles of varying periods that result
in more or less solar output, but sunspots alone can’t account for
rise in earth’s temp
 earth reflectivity could change as ice melts (see p. 308)
 world’s oceans store both CO2 and heat, act as a buffer to dampen
swings in heating and cooling
 clouds – can act to both hold heat in and keep heat out
 air pollution – aerosols may cause more condensation and cloud
formation, helping to reflect sunlight back out during the day but
holding heat in during the night…
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13-4 – Poss effects of a warmer world
lots of diff possibilities that Miller lists associated with a warmer world
 more deserts
 warmer soils
 melting glaciers, decreased albedo
 climate belts shifting toward poles, along with corresponding
animals and plants such as trees (Fig 13-12)
 ocean current patterns may change
 global sea level may rise
13-5 – dealing with threat of climate change
what are our options?
 Do nothing – “a dozen or so scientists contend that climate change
… is not a threat”
this is total, misleading BS – there are PLENTY
of scientists who continue to be unsure of what the long-term looks
like…this time Miller has crossed over the line, and is clearly not in
touch with the scientific literature
 Do more research before acting
 Act now – precautionary strategy – take preventive action now
 Act now to take some key actions, like reducing fossil fuel
consumption
How do we use govt regs to reduce greenhouse gas emissions?
 Phase out govt subsidies (WHAT govt subsidies?) for coal and oil
 Retain subsidies for natural gas (what subisidies?)
 Reduce methane (CH4) emissions
 Agree to limits and encourage trading of polluting rights
 Allocate emissions equally throughout world
 Phase in “carbon taxes”
 Increase govt subsidies for energy efficiency
 Make countries agree to improve energy efficiency
 Facilitate transfer of new technology from developed to developing
countries
 Increase use of nuclear power (produces less CO2)
Can we remove CO2 from atmosphere?
There are several ways to remove CO2
 Plant trees
 Pump it underground
 Pump it into deep ocean
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Can technology “save us”?
Miller cites some pretty “far out” ideas, but thinks best approach is more
conservative: improve energy efficiency, and move to fuels that produce
less CO2.
13-6 – Ozone Depletion in the Stratosphere
ozone layer thins seasonally, espec over the poles.
Thinning is a long-term threat.
What causes O3 depletion?
First CFCs produced around 1930. trade name Freon.
Many uses:
 Coolants
 Aerosol propellant
 Cleaners
 Sterilizers
 Fumigants
By 1974, CFCs were found to be harmful, and lowering the ozone level
One of the main problems is that CFCs are stable, non-reactive, so they
hang around a long time.
In the stratosphere, CFCs get broken down by UV radiation, and free
chlorine becomes available. This can lead to permanent breakdown of O3 to
O2 + O.
This takes O3 out of circulation permanently. See Fig 13-16
Some estimates are that one free Cl- atom can act to permanently convert
100,000 O3 atoms to O2.
Ultimately, researchers who first discovered harmful effects of CFCs were
awarded Nobel Prize in chem. (1995)
We talk about an ozone hole, but in reality ozone is thinning. Note too the
seasonal variation..Fig 13-18…summers are the times when O3 is reduced.
Data from 1979 to 2000 is showing that the O3 “hole” or area of thinning
over Antarctica continues to grow.(Fig 13-19)
The annual mechanism is complex…each winter(our summer in the North),
small ice xls form over the pole. CFCs are attracted to ice, then yield Cl2O2,
which during cold winter does not react with O3. However, when things
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begin to warm up, Cl- is once again released, and starts destroying
O3…cycle repeats itself each year.
Why worry about loss of O3?
To humans, this is dangerous because it allows more damaging UV
radiation to reach surface of Earth.
How do we protect the ozone layer?
We have already reached worldwide consensus (175 countries) as of 1987,
and signed agreements limiting CFCs….new products have been
developed to replace Freon and other CFCs.
We apparently are still facing a “lag factor” problem…..11- to 20-year lag
between time CFCs are released and the time they reach the stratosphere,
and then there is a time of persistence in the stratosphere. So there will be
a lag from the time CFCs were reduced to the time we see improvement.
Scientists indicate we should see a return to 1980 ozone levels by 2050,
and to 1950 levels by about 2100.
This is a great story of how the international community can act very
effectively and work together, when there is CONSENSUS (Fig 13-21).
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