GlobalTempLab-2
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Dec 6, 2023
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Laboratory Exercise #1: Global Average Temperatures
I. Introduction
Since the mid-19th century, weather stations have recorded temperatures at various locations on land and
water around the world. From about 1880 onwards, the number and distribution of stations have been
large enough to provide an adequate sample of global surface temperature variations from year to year.
This temperature record provides central evidence of recent global climate change and demonstrates
humankind's potential to modify Earth's climate. Satellites, with extensive global coverage, have been
recording even more accurate estimates of global temperature (in the lower troposphere, not at the Earth's
surface) since the 1980s. Do note that satellite data are not included here.
In this lab, your team will analyze the global surface temperature record from 1880 to the present. You
will evaluate long-term trends and shorter-term fluctuations, and you will look for evidence of climate
forcings and mechanisms of natural variability on the global surface temperature. The goal is to give you
a sense of the complexity encountered when extrapolating recent temperature trends into the future, and
the need for models to make reasoned predictions of temperature change.
II. Instructions
Type up brief answers to the questions asked in Tasks 1 through 3. Include graphs, tables,
and calculations as needed, and explain the reasoning behind your answers.
A. Fluctuations of the global climate
Open the Global Average Temperature
file in Excel. The data are saved in columns, with the year in
column A, and global mean annual temperature in column B.
Task 1
(25 points)
:
Choose 10 non-successive years at random, and compare the average annual
temperature in each year to that of the following year (e.g., if 1871 and 1925 are two of your ten years,
compare 1871 to 1872, 1925 to 1926, and so on).
Example
Year set
Average Temp (C)
Yearly change
1883
13.76
1884
13.7
-0.06
1
Laboratory Exercise #1: Global Average Temperatures
Year set
Average Temp (C)
Yearly change
What is the typical magnitude (i.e., ignoring the sign) of the year-to-year global average
temperature changes?
Of your 10 years, how many times did the temperature increase/decrease in the following year?
Increase: ________ times
Decrease: ________ times
Does it seem possible to predict whether next year is going to be warmer than this year globally?
2
Laboratory Exercise #1: Global Average Temperatures
B. Decadal-to-century variability and trends
Task 2
(25 points)
:
Make a chart of annual temperature vs. time for the years
1880-2022
and calculate its
slope using a trendline.
(Paste the chart here.)
How would you describe the general appearance of the
1880-2022
curve? Describe the major
features of the global temperature time series.
How much warming has occurred over the entire time series?
What are the 5 warmest years in the record? The 5 coldest?
Have we come anywhere close to having one of the coldest years in the record during your team’s
lifetime?
Now make a chart of annual temperature vs. time for only the years
1975-2022
.
(Paste the chart here.)
How does the
1975-2022
slope compare to the
1880-2022
slope, and what does this indicate?
3
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Laboratory Exercise #1: Global Average Temperatures
As you have seen in class, carbon dioxide has been increasing in concentration over the 20
th
century. Discuss how this is related to the temperature time series you are examining.
Is CO
2
a perfect global temperature predictor? Why or why not?
How long a record do you think is needed to see clear evidence of global warming? Explain.
C. Interannual Variability (Choose one
of the following tasks.)
Choice 1 - Task 3
(50 points)
:
Following is a list of major volcanic eruptions since 1880 and the year that
each occurred:
1883
Krakatau
1890
Unidentified
1902
Soufriere/Pelee
1902
Santa Maria
1964
Agung
1982
El Chichon
1991
Pinatubo
2006
Tungurahua
For any four of the above eruptions, note the average annual global temperature for the year in
which the eruption occurred, the year before the eruption, and list temperatures for three to five
years after the eruption.
Eruption 1 (Year:
)
Eruption 2 (Year:
)
Temperature (°C)
Temperature (°C)
Eruption year
Year prior
3-5 yrs after
Eruption year
Year prior
3-5 yrs after
Yr 1
Yr 2
Yr 3
Yr 4
Yr 5
Yr 1
Yr 2
Yr 3
Yr 4
Yr 5
Eruption 3 (Year:
)
Eruption 4 (Year:
)
Temperature (°C)
Temperature (°C)
Eruption year
Year prior
3-5 yrs after
Eruption year
Year prior
3-5 yrs after
4
Laboratory Exercise #1: Global Average Temperatures
Yr 1
Yr 2
Yr 3
Yr 4
Yr 5
Yr 1
Yr 2
Yr 3
Yr 4
Yr 5
What is the typical magnitude and sign (warming or cooling) of the effect that large volcanic
eruptions have on global climate?
How long does it take for the climate to return to “normal” after a major eruption?
Comparing what you know about global temperature trends and the overall impact of aerosols
(both natural and anthropogenic) on current climate, do you think it would be wise to invest in
stratospheric aerosol injection to attempt to modulate atmospheric temperatures over the near to
mid-term? Weigh some basic pros and cons of this approach, and look back on the slides in the
Earth’s Energy Balance & Radiative Forcing
discussion if necessary.
5
Laboratory Exercise #1: Global Average Temperatures
1991 Pinatubo eruption
https://pubs.usgs.gov/fs/1997/fs113-97/
Choice 2 - Task 3
(50 points)
:
El Niño and La Niña are the warm and cool phases, respectively, of a
recurring climate pattern across the tropical Pacific: the El Niño-Southern Oscillation, or ENSO. Below is
a graphical representation of ENSO years in recent times. As you can see, the pattern can shift back and
forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature,
precipitation, and winds. These changes disrupt the large-scale air movements in the tropics, triggering a
cascade of global side effects.
Oceanic Niño Index (ONI)
Selecting the strongest El Niño (red) and La Niña (blue) events (marked by
month/year) will give you the best chance of identifying a temperature signal in the dataset.
Before making the final selection of the ENSO years your team will analyze, look at both of the following
datasets:
6
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Laboratory Exercise #1: Global Average Temperatures
NOAA’s National Weather Service Climate Prediction Center
for three-month running averages
of above (red) and below (blue) normal sea surface temperatures (SSTs). Temperature anomalies
beyond the +/-0.5˚C threshold for the Oceanic Niño Index (and for a minimum of 5 consecutive
overlapping seasons) are shown in color.
Larger temperature anomalies indicate stronger events.
NOAA’s Physical Sciences Laboratory
for the top 24 ranked strongest El Niño and La Niña
event years by season. These tables show similar data as the above link, but rank the strongest
ENSO years by season rather than showing the magnitude of seasonal temperature anomalies
year by year.
Choose
two El Niño events
and
two La Niña events
(but not ones that occurred during the year of a
major volcanic eruption; see above). Note the average annual global temperature for the ENSO year, for
two years before the event, and for two years after the event.
El Niño event 1
El Niño event 2
Temperature (°C)
Temperature (°C)
Two
years
prior
One
year
prior
ENSO
year
One
year
after
Two
years
after
Two
years
prior
One
year
prior
ENSO
year
One
year
after
Two
years
after
La Niña event 1
La Niña event 2
Temperature (°C)
Temperature (°C)
Two
years
prior
One
year
prior
ENSO
year
One
year
after
Two
years
after
Two
years
prior
One
year
prior
ENSO
year
One
year
after
Two
years
after
Can ENSO be detected in the global temperature even though it is basically a tropical
phenomenon?
7
Laboratory Exercise #1: Global Average Temperatures
By how much and in which direction (warming or cooling)?
Discuss your data for El Ni
ñ
o and
La Ni
ñ
a events separately.
How do you think ENSO may respond to continued climate change (atmospheric and oceanic
warming) and what may be the resultant associated climate impacts?
Upload the lab assignment as a doc, docx, xls, xlsx, or pdf via
UNM Canvas
by the end of
class. I am unable to open pages or numbers files
.
8
2015
2016
2019
2015