What to do with long-term proxy data?

· Learn how to graph time series data

· Learn how to plot on two y-axes

· What conclusions can be drawn from graphed data

Introduction:

Today we will be graphing different types of time controlled data. This activity will be helpful when plotting data in the paleoclimatology lab later in the semester. Keep the directions and graphs to help you through that activity. For this activity we will be generating a graph in Microsoft Excel version 2010 or later. We will be using tree ring and precipitation data from central Florida to make our graphs

As you may know, tree growth is controlled by the conditions in which the tree is growing. A tree growing on a rocky mountain side is not going to grow as quickly as a tree growing near a lake. Likewise, a tree growing in the shade will not do as well as a tree in full sun. Trees are a type of proxy that record their environment in their annual growth. They record anything that limits their growth (ex. precipitation, temperature, light availability, etc.). When relationships with one variable are particularly strong, we can examine the growth of a proxy and the variations in recorded climate, we can determine how climate affects the organism’s ability to grow (ring width in this activity), and eventually reconstruct prehistoric climate data. However, there are portions of growth that are limited by other factors.

Graph: 5 pts

Step 1: Opening the data:

· Save the data file “graphing exercise data.xlsx” from Blackboard to a folder where you can find it later. It would be good to have one for this class.

· Open Microsoft Excel on your computer. The menus may be slightly different in Macintosh systems so you may need to explore a little bit more than others.

· Go to “File Open” and select the “graphing exercise data.xlsx” file from the location you saved it in previously.

· In the first tab you will find the year, ring width (RW), and precipitation (PPT) data from 1940 to 2003.

Step 2: Plotting:

For this exercise we will be comparing precipitation to ring growth on the same graph. This will be a visual comparison so it will be important to compare the same data along the same x-axis.

· Click away from the data to avoid plotting everything on one graph.

· Insert new Scatter (XY with smooth line) plot

· This should insert a new black white box

· Now we will need to select the data we want to graph.

· Click on the blank area of the graph and in the “Design” tab of the menu, choose “Select data.”

· Under the Legend Entries menu, click the “Add” button.

· You can add more than one plot to the graph by using this add button more than once.

· A menu for editing a series pops up and allows you to change a series’ name and what the x and y values are going to be.

· Click the add data button (box on the right of x and y value boxes.

· Select x-values from the “Year column” and y-values from the “RW” column.

· You should now have a plot with ring width on the y and years on the x axis.

· Because we are interested in the relationship between precipitation and ring width, we need to plot precipitation on the same graph.

· Now it is time to add the measurements of precipitation (PPT).

· Select the graph by clicking in any of the white area on the graph. Navigate to the design tab of the task ribbon and open the “Select Data” menu again.

· On the left hand side of the menu select the “Add” button.

· In the “Edit Series” window enter “PPT” in the “Series Name” menu.

· Click on the select data button for the x-axis and select the years like in the first plot.

· Then add the y-data as the ring width measurements and hit ok and ok.

· Your graph should now have two lines at two different magnitudes; one with large variation and one with small amounts of variation resembling the one below.

· Here comes the cool part. In order to put the two time series at similar scales, we need to put the data on two y-axes.

· To do this select the PPT line and right click on it.

· In the drop down menu, select the “Format Data Series” option

· On the right had side of this menu, select “Series Options” and plot the series on a “Secondary Axis.”

· Notice how excel has automatically placed the new axis on the right had side of the graph. Make sure that the ring width axis is on the left, the precipitation axis is on the right, and each is properly labeled so the reader knows what they are looking at.

· Now that the data has been properly plotted, answer the following questions using the graph as your guide.

Questions: 5 pts

1) When peaks and troughs align, does this mean the data is more or less similar?

2) If the data have similar patterns, what does this mean for the relationship between precipitation and ring growth?

3) What conclusion can we draw about ring growth when growth and precipitation graphs act differently from one another?

4) If it is possible to develop 400 years of ring width data, what benefits might this have for reconstructing climate?

5) Hypothesis Question: Suppose water resource managers in Phoenix, Arizona have access to 400 years of precipitation data developed from tree rings. How might this knowledge help them manage the city’s water consumption?