EXPLORING CLIMATE CHANGE
Name______ANSWER KEY___________
DATA SHEETS
Additional Important Information

During cooling climate, O-18ice decreases, O-18seawater increases, H-2 decreases; during warming
climate, O-18ice increases, O-18seawater decreases, H-2 increases.

Based on a variety of geological evidence, the last major glacial period extended from about 110,000 to
12,500 years ago.

According to archaeologists, cultivation of agricultural crops by humans began about 10,000 years ago
in Mesopotamia (present-day Iraq, Turkey, Syria, and Iran).
DATA SHEET 1
The blue curve on this graph shows global average temperature from 1880-2006, the
approximate period of reliable records for direct measurements of atmospheric
temperatures. Direct measurements of atmospheric carbon dioxide, from the Mauna Loa
atmospheric observatory (yellow curve), are available only for about the last 50 years
(1958-2006) of this time interval. For years prior to 1958, CO2 values were determined from
air bubbles in an Antarctic ice core (reddish curve). Temperature is graphed on the
vertical axis at the right of the graph, and CO2 concentration is on the vertical axis at the
left of the graph.
1) From the yellow curve, determine the concentration of CO2 in the atmosphere in 1958 (the
first year of data collection at Mauna Loa)? What was the concentration in 2006? Use the
following equation to find the percent change in CO2 concentration from 1958 to 2006:
Percent Change = [(Later Concentration – Original Concentration ) / Original Concentration] * 100
Answer should be around 20%, give or take a couple percent - depending on how
carefully they read the graph
2) Use the same equation to determine percent change in atmospheric CO2 concentration
between 1880 and the mid-1950s (reddish curve).
Answer should be around 6-7%
3) Which of the two time periods had a greater percentage increase in CO 2 concentration?
What do you think caused the percentage increase?
1958-2006; a possible cause is increased generation of greenhouse gases
4) Which of the two time periods, 1880 to mid-1950s or 1958-2006, show a closer
correspondence between trends in atmospheric CO2 and global average temperature?
1958-2006
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DATA SHEET 2
Notice that the time span of this graph extends much farther into the past than in Data
Sheet 1.
1) Based on the oxygen isotope data in this graph, briefly describe what has happened to the
atmospheric temperature in Greenland from between 120,000 years ago and the present.
Temperature was relatively lower, with large fluctuations (wiggles) in the curve,
then at about 12,500 years ago, it rose sharply, and it has remained relatively
high, with much smaller fluctuations and almost a flattening or “plateau” of the
curve
2) At what time did the greatest change in O-18, and thus temperature, occur? What most
likely caused this sharp change? Were temperatures higher or lower after the change?
About 12,500 years ago - the end of the last major glacial period (from the box of
info. at the beginning of this worksheet
3) What do you think causes the relatively consistent high O-18 values in the most recent part
of the curve? What other information do you have that might support this?
Possibly human influence- generation of greenhouse gases, also with the advent
of widespread agriculture there was cutting of forests that were carbon dioxide
sinks (see data box at beginning of worksheet). Other info.: the previous info.
discussed, such as rise in carbon dioxide levels on data sheet 1, shrinking of the
north polar ice, etc., from the earlier exercise
DATA SHEET 3
These graphs compare O-18 data from Greenland ice cores with H-2 data from Antarctic
cores, with the Antarctic cores extending farther back in time.
1) Is there relatively close correspondence between the Antarctic data and the Greenland data?
What does this suggest about the reliability of ice cores for tracing global climate trends?
Yes, close correspondence of data from opposite poles and using different
(oxygen vs. hydrogen) isotopes - this suggests that ice cores are reliable
2) What caused the pattern of relatively low O-18 and H-2 values extending from about
110,000 years to about 15,000 years before present?
The last major glacial period
3) What caused the sharp increase in O-18 and H-2 values between about 10,000 and 15,000
years ago?
End of the last major glacial period
4) What do you think has caused the relatively “flat” pattern of elevated values in the most
recent part of the curves?
Possible human influence - greenhouse gases, clearing of forests
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DATA SHEET 4
Note that the curves from the two Antarctic ice cores extend considerably farther back in
time than on any of the previous graphs.
1) What do you think causes the curves to be smoother with increasing years before the
present?
Fewer data points - ice is very deformed at these depths
2) According to the data on these graphs, are our modern warm temperatures unusual?
No, there have been several temperature peaks in the past, some are even higher
at maximum than the present
3) From examination of these graphs and the graphs on Data Sheets 2, 4, and 5, what is
distinctive about our modern temperature peak, compared to earlier peaks?
Instead of dropping sharply as in the past temperature peaks, the temperatures
remain high and have a “flattened” or “plateau” pattern, suggesting possible
human influence - as for the future, ???
DATA SHEET 5
This data sheet compares carbon dioxide concentrations and temperature change over a
period of about 450,000 years. Note that the temperature change curve is the same as the
curves in Data Sheet 4, but with the X-axis values decreasing to the right.
1) Based on the two curves, does there appear to be a general correspondence between carbon
dioxide concentrations and temperature change during the period for which data are
available?
Yes, peaks and “troughs” on both curves are similar in appearance, magnitude,
and timing.
2] Based on these curves, is there any apparent human influence on factors related to climate
change? Explain.
Yes, there is a very pronounced “spike” in recent carbon dioxide levels that is not
matched by any of the earlier carbon dioxide data.
DISCUSSION AND CONCLUSIONS:
1) Based on these data sheets and the earlier information in this lesson, list some of the
evidence that human activities are likely to have contributed to the current global warming
trend. Is the evidence for human influence easy to determine? Explain.
Evidence: shrinking north polar ice cover, shift of species, & other evidence
mentioned in the first part of the lesson& in the Frozen Assets exercise; sharp
increase in carbon dioxide levels in the last 150 years; “plateau” pattern of ice
core isotope curves.
Although there is considerable evidence that humans have played at least some
part in the most recent pattern of climate change, it is not easy to sort out the
human influence because (1) climate change is complex, (2) climate is influenced
by many variables, all of which interact and which must be examined together to
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understand climate patterns, (3) there are pre-human patterns of warming and
cooling climate, which must be compared with recent trends and indicators
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