Lab Assignment
Lab 2: Globally-Averaged Temperature
Introduction
Since the 19th Century, surface weather stations have recorded temperatures at various locations
around the world. Only the land portions of the globe are sampled in this way, and the density of
stations is greatest in the industrialized nations. Since about 1867, the number and distribution of
stations has been large enough to provide an adequate (though not perfect; the sampling error is
about 0.07 °C) sample of global surface temperature variations from year to year. This record
provides the best documentation of recent global climate change and is at the center of the debate
over humankind's potential to modify Earth's climate. Satellites, with their global coverage, have
been recording a truer estimate of global temperature (in the lower troposphere, not at the Earth's
surface) in recent years. However, satellite data exist only since 1980 and are not included in this
lab.
In this lab you will analyze the global temperature record from 1867 to the present. You will
evaluate long-term trends and shorter-term fluctuations, and you will look for evidence of the
impact of climate forcings and mechanisms of natural variability on the global surface
temperature.
Goal: This lab is to give you a sense of the difficulties encountered in trying to extrapolate recent
temperature trends into the future, and the need for models to make reasoned predictions of
temperature change.
Part 1 (62 points)
A. Fluctuations of the global climate
Transfer the Globally Averaged Temperature file to Excel, save it as an Excel file, and examine
the contents. The data are saved in columns, with the year in column 1, monthly temperatures (in
degrees C) in columns 2-13, annual mean temperature in column 14, and seasonal mean
temperatures in columns 15-18 (e.g., DJF = December-January-February, which is the
climatological definition of Northern Hemisphere winter).
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
Task 1: Use the 10 non-successive years listed below to compare the annual temperature in each
year to that in the following year.
1. Use Excel to create a table for 10 non-successive years, following the format below (11
points):
Table 1: Annual Temperature for 10 Non-Successive Years
Year Annual Mean (°C) Magnitude Abs Magnitude Trend
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Overall Magnitude
2. What is the typical magnitude (= average of absolute magnitudes) of year-to-year global
temperature changes? (1 point)
3. Of your 10 years, how many times did the temperature increase/decrease in the following
year? (1 point)
4. Does it seem possible to predict whether next year is going to be warmer than this year
globally? (1 point)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
Task 2: Compare seasonal temperature data and time-series data.
1. Make a scatter plot of DJF temperature vs. JJA temperature (do not plot either one vs.
time) for the years 1880-2006. Add a linear trendline to the data and display the R^2
value under the legend. This plot is a perspective spanning much more than a human
lifetime; our personal perception of climate change in our daily lives tends to be based on
our experiences over the last few years. (6 points)
a. Include Title, axis titles, trendline, trendline equation, and R^2 value.
2. Now plot the DJF vs JJA data for the 1990-2001 only. (6 points)
a. Include Title, axis titles, trendline, trendline equation, and R^2 value.
3. Is the correlation strong or weak? (1 point)
4. Compare the slopes of the two trendlines from the DJF vs JJA plots (entire series vs.
1990-2001) in Table 2. (1 point)
5. Can we predict with confidence what kind of summer will follow that winter? (1 point)
a. Compare the R^2 values to determine the confidence level of the correlation in
Table 2.
Table 2: Seasonal Temperature and Time-Series Data
DJF vs JJA
(Entire)
DJF vs JJA
(1990~2001)
Annual Mean
(Entire)
Annual Mean
(1975~2006)
R^2
slope
B. Decadal-to-century variability and trends.
Task 3: compare entire data set with various time ranges.
1. Make a chart of annual temperature vs. time for the years 1880-2006; (6 points)
a. Include Title, axis titles, trendline, trendline equation, and R^2 value.
2. How would you describe the general appearance of this curve? (1 point)
3. How much warming has occurred over the entire time series? (1 point)
4. Now make a chart of annual temperature vs. time for only the years 1975-2006.(6 points)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
a. Include Title, axis titles, trendline, trendline equation, and R^2 value.
5. How is the slope compared to the 1880-2006 curve in Table 2? (1 point)
6. Carbon dioxide and other greenhouse gases have been increasing in concentration over
the 20th Century. Discuss what this has to do with the temperature time series you
examined. (1 point)
7. What are the 5 warmest years on record? The 5 coldest? (10 points)
Table 3: Warmest and Coldest Years on Record
5 Warmest Years 5 Coldest Years
8. Have we come anywhere close to having one of the coldest years on record during your
lifetime? (1 point)
9. How long a record is needed to see clear evidence of global warming? Why? (2 points)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
Part 2 (40 points)
C. Interannual Variability.
Following is a list of major volcanic eruptions since 1867 and the year that each occurred:
1883 Krakatau
1890 Unidentified
1902 Soufriere/Pelee
1902 Santa Maria
1912 Katmai
1963 Agung
1968 Fernandina Island
1982 El Chichon
1991 Pinatubo
Task 4: For any three of the above eruptions, note the average annual global temperature.
● Make 3 tables showing 3 volcano events including the average annual global temperature
for: (3 x 5 points)
○ the year in which the eruption occurred;
○ the year before the eruption;
○ the year after the eruption;
○ two years after the eruption;
○ and three years after the eruption.
Table 4: Volcanic Eruption
Eruption Year Annual Temperature (°C) Difference Trend
● What is the typical magnitude of the effect of volcanoes on global climate? (3 x 1 points)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
● What is the sign (warming or cooling) of the effect of volcanoes on global climate? (3 x 1
points)
● How long does it take for the climate to return to normal after a major eruption? (3 x 1
points)
Following is a list of El Niño years in recent times: 1951, 1953, 1957, 1963, 1965, 1969, 1973,
1977, 1983, 1987, 1991, 1997-1998, 2002-2003, 2006-2007. (For El Niño events starting near
Christmas time, the following year is listed, since that is when the peak temperature anomaly
usually occurs.)
Task 5: Choose three El Niño events (DON’t Choose the year of a major volcanic eruption).
● Make 3 tables showing 3 ENSO events including the average annual global temperature
for: (3 x 3 points)
○ for the ENSO year;
○ for the year before the ENSO;
○ and for the year after the ENSO (El Niño-Southern Oscillation).
Table 5: El Nino event
El Nino Year Annual T (C) Difference Trend
● What is the typical magnitude of the ENSO event? (3 x 1 points)
● What is the sign (warming or cooling) of the effect of ENSO event? (3 x 1 points)
● Can ENSO be detected in the global temperature even though it is basically a tropical
phenomenon? (1 point)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
Part 3 (24 points)
D. Regional Change:
Task 6: Go to the GISS website (https://data.giss.nasa.gov/gistemp/). Given the dataset
options available to you, decide which data set you should observe to determine the two
warmest years on record. Be sure to include which data set you observed and what you
observed in your results.
1. Make a scatter plot showing both data (from NY central park & Ashland) on the same
plot; (5 points)
a. Label the NY central park data and Ashland data on the scatter plot;
2. Write down the hottest years for both stations in the table below; (4 points)
Table 6: New York vs Ashland
Warmest Year Warmest Temperature New York Ashland
Task 7: Next, click on the "Global Maps" dataset to observe the regional surface temperature
distribution for each of the two years you found above. Before you make each map, be sure that
you have selected all of the appropriate parameters. Your map type should be "anomalies," your
mean period should be "annual," and your time interval should span the chosen year. NOTE: If
oceans are set to "none," you will not be able to see data for the ocean.
1. Screenshot and paste the two figures for New York in your report; (2 points)
2. Screenshot the two figures for station Ashland; (2 points)
3. Are the annual regional anomaly distributions the same for the two years you observed?
(1 point)
4. What do the Zonal Mean vs. Latitude graphs under each map look like? (2 points)
5. Based on the observed maps and graphs for the two chosen years, what areas exhibit the
most warming and cooling? (4 points)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY
6. Can you explain the reason for features observed (or not observed) in the tropical Pacific
(lat: -45 to 45)? (2 points)
7. What anthropogenic and natural factors could influence the amount of warming over the
coming century? (2 points)
Contributor: Robert B. Schmunk, NASA / Goddard Institute for Space Studies, New York, NY