# Step-by-Step

In this Section

## Step-by-Step

A worksheet is available to guide the student and to record results and respond to discussion questions.  Students can begin to add their notes and ideas to this worksheet during the introduction described in the teacher notes.  The procedure here begins after these introductory concepts have been explained.

## Part 1 - Reducing Carbon Emissions and the CO2 Concentration

Open the spreadsheet labeled "Student Spreadsheet" and view the worksheet labeled “Wedges.” You will notice there are two sets of data for emissions and carbon dioxide concentrations (rows 12-22). The first is for projected “Business as Past” emissions (A1G) to compare to future emissions. The second set is a dynamic data range for emissions and concentrations under the selected mitigation strategy. These values change when students enter in a number of wedges (multiple of 5 from 0 to 25) they would like to consider.

1. Define an emission strategy:
1. Enter a number of wedges (which also must be a multiple of 5) in the yellow box (Cell C7)
2. Calculate the required emissions in 2061 (50 years into the future( (enter equation in cell C8).  The projected 2061 BAP emissions are 25.85 GtC/y.  By noting that each of the wedges helps by reducing the global total emissions by 1 GtC/y, we can see that the 2061 BAP emissions – number of wedges = required 2061 emissions.
2. The carbon emissions and CO2 concentration graphs are automatically updated to provide some understanding of how successful the mitigation strategy (# wedges) was.
3. The emissions and concentration graph are automatically updated.  Review these graphs (rows 24-39) to provide a visual sense of how well your mitigation strategy worked.
4. Evaluate if the emissions and concentration goals were met:
1. For the 80x50 emission reduction goal: Enter an equation in cell J8 to calculate the percent reduction in emissions. The 1990 value is constant and provided in cell J5, and the value for the year 2050 is automatically included in cell J6. Enter the % reduction calculation in cell J8.

As an excel equation, this can be written as =100*(J5-J6)/J5

2. For the 350 ppm concentration target in 50 years (2061), review information automatically generated in cells J10 and L10.

## Part 2 - Analyze the effectiveness of the mitigation strategy to meet the 2°C goal

Since the modeling program EdGCM takes a very long time to run, it cannot be implemented in the classroom. Thus, graphs and maps of results of EdGCM modeling are provided in a separate document for the different scenarios (numbers of wedges).

1. Open the document containing results for all wedge scenarios. This file is setup so that the user can easily access the specific results for their desired number of wedges. The “Business as Past” map is provided with each scenario to provide a comparison.
2. The maps with results data provide temperature anomaly data. This is calculated using the following process:
1. The average annual surface air temperature is averaged over the years 1980-1999, spatially over the whole globe.
2. This data is then subtracted spatially from the average annual temperature data for each year modeled in the wedge scenario to acquire the anomaly data.

The temperature anomaly is used because, according to the National Oceanic and Atmospheric Association (NOAA), “Anomalies more accurately describe climate variability over larger areas than absolute temperatures do, and they give a frame of reference that allows more meaningful comparisons between locations and more accurate calculations of temperature trends.”7

3. Several questions are prepared for the student to answer. One can view all the maps at the same time; however, it is important to stick with the chosen number of wedges throughout the exercise.

## Part 3 - Selecting mitigation wedges

By this point in the unit, students should realize that 25 wedges (or more!) are necessary to meet both the 350 ppm and the 2 °C criteria. One important concept is that no scenario meets the 80x50 policy. There is simply no way to reduce emissions on a global scale that quickly.

This part of the unit will show the students the type of actions that are required to effectively mitigate carbon dioxide emissions. Wedges that can be considered are provided in a Powerpoint file.

1. Follow directions in Part 3 of the student worksheet to select and record the specific wedges. To make the activity more realistic relative to the current sources of GHG emissions, there is a limit on the amount of different categories one can choose.
2. It is acceptable to use most wedges more than once, as long as it makes logical sense. The wedges labeled with a blue star can only be used once
3. After selecting 25 wedges, students should add up the total cost to implement their wedges. The class can then compare which wedges were used, ion what combinations, and what the “best” choices are.