Posted on Tumblr 9/20/2013 to infovis658:
The Nature Conservancy features a Carbon Footprint Calculator that asks the user a series of questions about their energy use with regard to home, travel, diet and waste. Each answer translates to an estimated carbon usage, which are added up and compared to the U.S. average.
As I was answering the questions, I was looking critically at the figures they use for each potential use. In particular, I was interested in their choice of pie and bar charts to compare personal energy consumption to a national average.
The Results tab displays a pie chart of my household carbon use next to the U.S. Average. According to the calculator, my carbon footprint at 22 Tons of carbon per year is much lower than the U.S. Average and in fact matches the world average for a household of four people. This might be expected since I live in an apartment in a city with a functioning and expansive commuter transit system. But I wasn’t sure it was telling the full story.
The charts break down carbon use by categories for home, travel, diet and waste, indicating that the greatest usage (52.1%) in my household is for Home energy, followed by Diet (22.7%), Travel (12.9%) and Waste (12.3%). This makes sense as I use public transportation, eat a mostly vegetarian diet, recycle a lot and have limited control over the energy use in my building (I have no real way to adjust the heat). Putting my usage chart next to another pie chart indicating the U.S. average can be somewhat misleading, as at first glance it appears that I am using a larger amount of energy than the U.S. average in certain categories such as Home and Diet, when it is really a greater proportion. The bar chart at right shows the relationship a bit more clearly, since it shows total usage. One complaint is that the bar chart seem to be using a different color for Recyling & Waste than the pie chart. Also, it is difficult to tell if the light blue area for the World Average represents a specific category or total carbon usage.
A level of granularity in energy use is not reflected in the questions, which assigns a predetermined amount of carbon to each action under a suggested usage modification. These include an estimated decrease from the U.S. average, if you are doing something to reduce carbon use in that area; zero change, if you note that you are only doing a little or rarely; or an increase in carbon if you are not implementing the suggested change.
Example: “We’ve taken steps to heat and cool our home efficiently. “
Impact in Tons of C02:
Wherever possible: -1.5
In some areas: 0.0
Very little: 1.3
For example, my apartment building is a 100 year old building that uses oil heat. The co-op board’s plan has been to convert slowly to oil with a lower carbon concentration and will eventually switch to natural gas, the higher concentration of carbon is currently not avoidable. I may be doing all I can within my own apartment to reduce the carbon footprint in my living space, but it may still be higher than someone at a more efficient building who is doing less.
The chart provides a few helpful calls to action next to the results. One is a rather clever way to use the results to help users offset their guilt or rather “Offset Your Carbon Footprint Now.” This may ultimately be the goal of the visualization, but it appears to be flawed from a non-profit development viewpoint. Each Metric Ton of carbon use per year is multiplied by a $15 donation to indicate how much your household should contribute to the Nature Conservancy. It says I should give $300. But doesn’t this mean that the more someone cares about the issue and the more someone tries to reduce their carbon footprint, the lower the donation estimate would be?
I would take it a step further. Non-profit solicitations usually offer a range of suggested donations. Why not use that figure as a baseline for a minimum donation? Then, compare it to the US average again and ask the user if they would like to up their donation to offset additional carbon use.