Single Line
Graphs
Single line graphs are one method used to show temperature predictions.
readings, and temperatures over
time. Temperature is plotted on the y-axis and time on
the x-axis. The single line makes it easy to calculate mean,
average, minimums and maximums over different time periods for
one site. The single line may represent data from one small specific
site, a province , all of Canada, or the entire ocean
surface of the planet.
Source: Environment Canada
ACTIVITY 1
- Find the
best-fit line.
- In which decade did the minimum
temperature occur?
- In which decade did
the maximum temperature occur?
Several single lines ! Single lines for
temperature change predictions are easier to combine with changes predicted
for other factors, for example, carbon dioxide concentrations, sun spot frequency. This
method allows patterns to be examined for interacting factors, concurrent
cycles, and seasonality. The combined graph may yield more information than a number
of separate graphs. In the graph below, projections using the various Canadian
climate models for global mean surface temperature can be compared using a
single line for each model.
. 
Source: Environment Canada
ACTIVITY
2
Note the location of the present year on the
x axis graph. This divides the past decades from the future. All
models use the same data from the past to model the future. The
first century shows models using directly recorded data to determine
how accurate the models are. The tested models then predict the
annual mean surface temperature in 0C. Plotting several single
lines on this one graph allows comparison of the models.
- Find the best-fit line.
- Change to a graph that shows the range of possible results
in different way.
Isolines "Iso' means equal as seen in an isosceles triangles
with two equal sides. The isolines show the range of temperature
change by joining points that have the same temperature change
predictions on a map of the world. In thenext figure, the colours represent
the annual mean change of temperature . Global mean surface temperatures
for 1961-1990 data are the basis of the 2071-2100 projections
emphasizing regional and economic factors.
Global Mean Surface Temperature Projections
Source: IPCC Climate Change (2001) Synthesis Report Working Group 1,
11, 111 www.ipcc.ch.
ACTIVITY
3
- What similar points do isolines join on contour maps? Weather maps?
- Describe the projected global pattern of change in one sentence.
- What change is predicted for Ontario and your hometown.?
- What causes the North American contour lines to dip lower over Ontario?
Yet another way to represent data!
In the next figure, squares reflect changes in temperature relative to the model's global mean.
DJF=winter months
JJA=summer months
A2 and B2 are the scenarios
used. See Section 2.3 for an explanation of these scenarios.
Source: IPCC Climate Change (2001) Synthesis Report Working Group 1,
11, 111 www.ipcc.ch.
ACTIVITY
4
- a)What range of latitudes has the greatest change in global mean temperature
range predicted on the world map?
b) What is the temperature increase predicted (oC) for this area?
- a) What area has less than average warming in
global mean temperature projected for both winter and summer?
b) What is the temperature increase predicted (oC) for this area? Use
proportional dots to represent similar changes in conditions.
The next figure
shows yet another way to represent data. Check the legend and
note that the dots represent a temperature trend. This type of
visual representation of data provides a quick over view of trends using proportional
dots on a
world map.
Annual Temperature and Precipitation Trends 1976 to 2000 in oC
. 
Source: IPCC Climate Change (2001) Synthesis Report Working Group 1,
11, 111 www.ipcc.ch.
ACTIVITY 5
- Which area of the world shows the greatest heating trends? cooling trends?
- Where is the greatest area that had no change in temperature for this
period.
- Name one area of the world which surprises or differs from the over all
trend in nearby areas. Note: this method of representation also allows for
a quick comparison for general statements.
- Look at all four maps, starting with the earliest.
Write one sentence which describes the trend shown from 1901 to 2000.
Source: IPCC Climate Change (2001) Synthesis Report Working Group 1,
11, 111 www.ipcc.ch.
Statistical analysis for the futures - the bell curve! The mean and variance
of temperature are analyzed for the probability of occurrence. The bell curve
shifts are plotted for 3 different variables. Note the use of blue and red
to indicate temperature.
Source: IPCC Climate Change (2001) Synthesis Report Working Group 1,
11, 111 www.ipcc.ch.
ACTIVITY
6
- What are the effects on extreme temperatures when
the mean increases?
- What are the effects on extreme temperatures
when the variance increases?
-
What are the effects on extreme temperatures when both (a) and (b) increase?
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