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Typical cesspit, with access from the street
By the early 18th Century nearly every residence had a
cesspit beneath the floors. In the best of homes the
nauseating stench permeated the most elegant parlor.
Indoor odors were often worse than of the garbage- and
manure- filled streets. While noxious fumes were ignored
by most people, it was fear of "night air" laden with coal
smoke and sulfurous industrial fogs which alarmed the
Climate Change
Week 7
Lecturer: John Todd
Ecosystem Processes
16 April 2002
Why start a lecture on climate
change with a diagram of a cesspit?
• Disposal of waste has always been a problem
for human societies.
• We are learning the importance of liquid and
solid waste disposal; and we have had some
success in controlling some waste discharged
into the atmosphere.
• We now need to learn that with so many
humans we need to limit all wastes released to
the atmosphere.
Population
World Population
7
Billions of people
6
5
4
3
2
1
0
1600
1700
1800
1900
Ye ar
2000
2100
We have learnt not to
dump solid and liquid
wastes into our rivers.
But we discharge some
20 billion tonnes of
carbon dioxide into
the atmosphere each
year.
Facts and Speculation
•
•
•
•
•
•
Changes to atmosphere
Impact on radiation
Complicating factors
Observed warming
Uncertainty contributes to lack of action
Some possible futures
First Some Facts
1. The chemical composition of the
atmosphere is changing
2. It is almost certain that human activities
are contributing to these changes
3. The average surface temperature is
warming
4. But some argue that point 3 is not linked
to points 1 and 2
Changes to atmosphere
Carbon Dioxide CO2
Ice cores allow CO2 analysis back 400,000 years
Now
Cape Grim, Tasmania’s ‘baseline’ monitoring station
Carbon dioxide (parts per million)
Cape Grim, Tas
is one of the
important global
monitoring sites
for climate change
gases.
1970
1975
1980
1985
1990
1995
2000
2005
There are at least 30 gases, released by human activities, increasing
in the atmosphere that influence the heat escaping by radiation.
Air reaching Cape
Methane (parts per billion)
Grim from the west
1720
1700
and south-west has
1680
1660
travelled ¾ of the
1640
1620
way round the
1600
1580
world without
1560
passing over land.
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
375
370
365
360
355
350
345
340
335
330
325
Gases that interact with energy flow out of the
atmosphere – greenhouse gases
CO2
Sunlight in
0.7
Infrared out
Wavelength
10 20
25ooCC
CH4
N2O
Long time scales
• The energy reaching the Earth each day is large,
so one might expect quick changes
• But we have seen how massive the
atmosphere is 5 x 1015 tonnes
• The earth itself is 6 x 1021 tonnes
• These numbers are so large they are
difficult to comprehend, but the point is, it will
take a long time to heat the Earth up and a long
time for it to cool off again.
Carbon Balance – annual flows
Units 109 tonnes of carbon
About 1 unaccounted for
700 in atmosphere
increasing by about 2 per year
Burning fossil fuels
5
50
1
3
600
800
7000
40,000
3000
1998 hottest ever
2001 second hottest
Uncertainties
• Will climate change lead to
more storms, more droughts, more floods?
• Will feedback processes, such as increased
cloud, faster plant growth, etc. off-set the
changes?
• Will other changes accelerate the warming,
e.g. less ice and snow, CO2 release from
oceans, melting of tundra etc.?
No trends are obvious
Tropical cyclones in the Australian Region
Maybe the proportion
of intense storms is
greater?
Source: Bureau of Meteorology
Some of the uncertainties
• If it gets warmer, there will be more
evaporation.
• This will alter the water cycle slightly, but
we have seen how much energy the
evaporation and condensation of water
transfers to the atmosphere.
• How will this change local weather?
• Will there be more clouds?
• Will there be more rain?
Implications for your
professional work
• Will need informed people in many
disciplines who can deal with this issue
sensibly.
• Reduce the emissions of climate change
gases.
• Facilitate adaptation to changes in weather
patterns
Summary
• We are altering the chemical composition of the
Earth’s atmosphere.
• The Earth is warming.
• The impact this will have on the processes we
have covered in this series of lectures is
unknown
–
–
–
–
Energy flow/radiation
Global circulation
Weather
Water cycle
Know definitions
of identified words
Exam
• Atmospheric composition,
temperature
• Radiation balance
• Global circulation
• Water in atmosphere
• Weather
• Climate change
Need to understand
the basics
Possible question
Possible question
Possible question
Provides examples for
above three topics
Also examples, but not
the topic of a question
Will be one essay question
Next Week
• Professor Jamie Kirkpatrick
• Weathering and erosion
• Chapter 13 of Christopherson.