Analyzing Surface Temperature Data

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Analyzing Surface Temperature Data
Objective – to use surface temperature grid data to create a visualization and calculate a global mean
temperature.
Directions – Open the Excel file called Observational Surface Temperature Data (2010) and use the file to
complete the following tasks.
Task 1 – Creating a Visualization
What you should see when you open the file is a rather large set of numbers that represent average surface
temperatures (in °C) for an area of the globe. These numbers are generated by computer programs but are of
little use to any human since there is no way to understand what it actually means. To address this problem,
scientists use an additional computer program to create a visualization that helps a person make sense of all
those numbers. You will create a simple visualization that will help you better understand this data.
1. Start by clicking and dragging to select ALL the numbers in this data set.
It is 144 columns wide and 74 columns long.
2. In the toolbar at the top of your screen, click on Conditional Formatting,
then Color Scale, then Red-Yellow-Blue Color Scale.
3. You have now told the program to assign a color to each cell based on the
number that is inside that cell. You should notice that negative values are
cold (blue) and high positive values are hot (red). This is the same
process scientist use to create the maps and animations you will look at
later on.
4. To get an even better picture, zoom out so that you can see the entire data set. In the lower left of your
screen there is a zoom slider bar. Click and drag that all the way to the left (12%).
5. What you are looking at is a color map of the globe based on temperature. Take a moment to make sure
you understand what you are looking at. See if you can figure out where the continents and oceans are
and try to come up with an explanation for the places where the temperature is lower than the
surrounding area.
6. Finally, click on this link World Temperature Map and see how closely your visualization matches with
a more sophisticated one. You should be able to easily identify places like the west coast of South
America, the Himalayas, and Africa.
Task 2 – Calculating a Mean Global Temperature
The second thing scientists can do from a data set like this is to calculate an average (mean) global temperature.
This task is meant to make you understand how that process works. Follow the steps below to use this data to
calculate a global temperature.
1. First you must realize that the number in each
cell is a point (Example: points A and B in
the picture to the right) with latitude and
longitude coordinates that is representative of
an area of the globe.
2. The temperature at each point is calculated
basically by taking an “average” of all the
weather station data available area around
that point. This is OBSERVATIONAL
DATA!
3. Since the Earth is a sphere, the area at each
point is not the same. For example, compare
the size of the four boxes around point A to
the four boxes around point B.
4. To account for this, each point is assigned a
weight based on its latitude and the weighted
average of all the points is taken to calculate
the global mean temperature.
5. The following formula is designed to tell
Excel to perform a weighted average for the
entire globe and calculate a Global Mean
Temperature.
6. Copy and paste this formula
=SUMPRODUCT(A4:EN76*$A$131:$A$203)/SUMPRODUCT(144*$A$131:$A$203) into cell A2.
7. This gives you the global mean temperature in degrees C for the year 2010. If you would like to
convert to Fahrenheit, multiply by 1.8 and add 32.
8. This process is repeated for each year to help examine the trend over a period of time. However most
global temperature graphs are presented as temperature anomalies. This means the global mean
temperatures are averaged over a period of about 30 years and then individual temperatures are
compared to this to see if they are above or below the average.
Task 3 – Summarize what you learned
Type or write a summary that explains what was done in this activity, what you learned from it, and why it is
important to your understanding of global climate science.