# Part 4—Compare Two Stations and Examine Global Patterns of Temperature

## Step 1 – Compare the GSOD data for Key West, FL with Barrow, AK for the year 1948

1. Create a graph to compare the average daily temperatures for Key West, Florida to the daily temperatures for Barrow, Alaska. This is most effective if you put the both datasets on the same Excel worksheet and graph them on one set of axes.
2. The graph of the mean daily temperature in Barrow and Key West for 1948 looks like this:

3. Notice that the shapes of the graphs are quite different. Barrow has greater seasonal variation in temperature than does Key West. What reasons can you think of that might account for this?
• Key West is nearer the equator and so does not have freezing temperatures.
• The ocean surrounds Key West and moderates the hot temperatures in the summer.
• Barrow is 330 miles north of the Arctic Circle, so there are days when the sun never rises during the winter, and days when the sun never sets during the summer.
• Are these two stations similar in any way?
• Choose another station in the U.S. and look at a typical year of its temperature data from the GSOD archive.
• If you have trouble importing data into Excel or creating the worksheet pages and graphs, then download and use the KeyWest-GSOD.xls ( 4.4MB Jan17 11) file.

## Step 2 – Using GHCN data for Key West, FL and Barrow, AK Compare the Annual Average Temperatures from 1948 to 2011

Monthly average GHCN temperature data for Key West is freely available from the NCDC portal, and can be downloaded in the same manner as the Barrow GHCN data. In the interest of time, the KeyWest_GHCN_1.xls (Excel 82kB Nov7 12) file is provided here for your convenience. Repeat the process used in Part 3 for Barrow, Alaska to graph the average annual temperature for Key West from 1948 to 2011, in degrees Fahrenheit.
1. Launch Excel and import the GHCN data for Key West, Florida.
2. Compute the annual average temperature for 1948-2011.
3. Convert the monthly average temperatures from degrees C to degrees F (see Part 3, Step1).
4. Compare the annual average temperatures for Barrow to those for Key West over this time period. Is the trend for Key West temperatures similar to the trend in Barrow?
5. Follow the procedure in Part 3, Steps 2 and 3 to graph the annual average temperatures for Key West for 1948-2011 and fit a trendline to the data. What does the slope of the line represent?

6. How much has the average temperature increased in Key West?

If you have trouble creating the worksheet pages, annual_average temperatures or graphs, then download and use the Key_WestGHCN_Part4_final.xls (Excel 151kB Nov7 12) file to complete the above graphing steps.

## Step 3 – Consider Global Changes in Temperature

Scientists have looked at past global temperature trends and have modeled global processes to predict average temperature trends projected 100 years into the future. In most parts of the U.S., average surface temperatures are increasing. Even the Southeast, which shows a slight decrease in average temperature over the past 100 years, would show an increase if you looked at the last 25 years.

The map below shows the general trend that average surface temperatures are increasing faster in colder areas than in warmer areas. In the future, this could mean less land- and sea-ice in polar regions and less mountain snow, which becomes water for reservoirs in dry areas like Colorado and southern California. Predicted consequences of long-term climate change include the likelihood that plants that need a seasonal change will need to migrate to colder latitudes, or to higher elevations where there are mountains to "climb." In addition, scientists are concerned about the ocean becoming less salty with the melt of polar ice and that change this could affect ocean circulation, fish and other marine life. There is also concern about global sea level rise due to melting land ice.

Scientists have modeled what the next hundred years of climate change may entail, and while it is generally characterized by rising temperatures, human behavior may influence how dramatic the changes may be. Assumptions based on population growth, emissions of carbon dioxide from automobiles and power plants, and many other factors contribute to what the IPCC calls "scenarios." A range of predictions result from scenarios that limit carbon dioxide emissions to current levels, to those that assume emissions increasing as they were in the year 2000. The two scenarios are identified below as "low growth" and "high growth." In either case, dramatic temperature increases are projected.