THINKING LAB
Looking at Global Warming
Background
Some researchers are still uncertain about whether Earth’s
temperatures are really increasing and whether this is
related to anthropogenic sources of greenhouse gases —
especially carbon dioxide. Could various carbon sinks
(including forests and oceans) take any extra amount that
is emitted such that the carbon cycle would continue to
be balanced? This activity will give you an opportunity
to see whether the amount of carbon emitted each year is
correlated with the concentration of carbon dioxide in the
atmosphere. You will also examine whether these variables
are related to temperature.
You Try It
1.Graph the data in this table to discover if there is a
relationship between year, carbon dioxide production,
carbon dioxide concentration in the atmosphere, and
temperature. This graph can be done using spreadsheet
software or drawn by hand. Plotting all the variables on
the same graph will help you see if there is a relationship.
2.Describe the pattern of change over time in the carbon
dioxide and temperature variables.
3.Does a correlation between two variables necessarily
indicate that one variable causeschange in the other?
What other explanations might there be for such a
pattern?
4.Use a library or the Internet to research the following
concepts and areas of controversy related to global
warming, with a focus on answering the associated
questions:
The concentration of carbon dioxide has varied
widely over the history of Earth, and has been much
higher than it is now. Has the rate of change everbeen similar to or greater than the rate between
1960 and 2000?
Gases other than carbon dioxide also contribute
to the greenhouse effect. Are all greenhouse gases
comparable in their ability to trap heat? Might one or
more of them be a more important cause of global
warming?
The data in the table show that there has been only a
small increase in temperature (less than the difference
between winter and summer temperatures in Ontario)
over the time period shown. Can a difference of this
magnitude have any effect on the biosphere?YearCarbon dioxide
emissions
(million tonnes
of C)
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
20001612
2013
2535
3087
3997
4518
5155
5271
5931
6190
6299
Relationship between year, carbon dioxide production,
carbon dioxide concentration in the atmosphere, and
temperature (from The World Watch Institute, 2001)Carbon dioxide
concentration in
the atmosphere
(ppm)Global average
temperature (°C)
not available
not available
316.7
319.9
325.5
331.0
338.5
345.7
354.0
360.9
369.413.83
13.91
13.96
13.89
14.03
13.94
14.18
14.10
14.41
14.39
14.36
Chapter 15 Human Ecology • MHR 527Ozone Depletion
In the atmosphere, ozone (O 3 ) is found both near
Earth’s surface and far from Earth in the upper limits
of the atmosphere. Close to the surface, ozone is
formed by the reaction of oxygen (O 2 ) with various
substances found in car exhaust and industrial
pollution, and it is a toxin that causes damage to
plants and breathing difficulties in humans and
other animals. High in the atmosphere, however,
ozone is beneficial. It forms a thin layer that helps
shield Earth from the harmful effects of the Sun’s
ultraviolet (UV) radiation. This type of radiation
can cause skin cancer in humans, reduce the
effectiveness of the immune system, and produce eye
damage. Although research is ongoing, it is currently
accepted that many other types of organisms,
especially amphibians (which have thin skins) and
the animals and plants inhabiting the top layer of
the ocean, may also be harmed by UV radiation.
Recently, it has been discovered that the ozone
layer has been significantly damaged. It has becomehttp://www.mcgrawhill.ca/links/biology12
Although caution must always be used with respect to the
accuracy of information obtained from the World Wide Web,
there are some very good sites that describe the greenhouse
effect and global warming. Many of these sites provide actual
data. Go to the web site above, and click on Web Links.