Get Started on Reducing Your Carbon Footprint

By: Matt Malinowski

What is a Carbon Footprint?

Climate change is primarily caused by human emissions of carbon dioxide.  To keep the atmosphere in balance and the climate from changing, the 7 billion people on earth must emit less than 2 tCO2e/yr, which can be offset by natural processes. However, to arrest the climate change that is already happening, we need to remove CO2 from the atmosphere by reducing emissions to or below zero (hence the pledges of various governments to do so by 2050). The carbon footprint will help each of us understand where we can reduce and by how much.

A carbon footprint is an estimates the climate impacts of consumption and other activities. You enter information about your household’s utility bills, food habits, travel, and spending in different categories into an online calculator, which multiplies your inputs by CO2 emission rates associated with each activity. For example, commuting by bus will result in lower CO2 than driving alone. The calculator returns both a total as well as breakdown by category, which can help prioritize and focus action.

Below is an illustration of my household’s footprint according to the CoolClimate Household Calculator from the University of Berkeley. It includes all four members of my household, and our direct fossil fuel emissions from work air travel and utilities, as well as more indirect effects such as estimates of what our health insurer or bank does with our monthly payments. It all works out to 12 tons per person per year.  While I work in energy efficiency, am concerned about climate change, and bike and live in a dense, walkable neighborhood, my footprint is more than twice the global average of 5 tons and nowhere near the target.

Once you’ve calculated your footprint, you can start taking actions to reduce it.

There are a number of other calculators available that factor in different aspects of consumption and may use different emission rates. As you can see, there is a broad range of estimates, though I would put more stock in the higher estimates as those calculators tend to be more comprehensive.

Calculator Household Footprint for 4 People (tCO2e) Capabilities
EPA 18 Includes energy use and driving, but not flights; need to convert results from pounds to kg
Carbon Footprint 22 Includes energy, detailed driving, flights and transit, and detailed consumption, including mortgage payments
Conservation International 42 Mid-level car driving/travel customization
FootPrintCalculator.Org   Nice graphical interface, but did not try
Carbon Fund   Assumes 24 t/person
Terrapass 23 Includes energy, detailed driving, flights and transit, abut not consumption   had to extrapolate family from single person breakdown of mobility (x2), food (x4), and home (x1)

To use any of these, it will help to download the past year’s utility bills, tally up any trips or commutes (should be easier to do this year due to the pandemic), and have an categorized list of spending by category from your bank, credit card providers, or a third-party service such as Mint. It helps to enter this into a spreadsheet, as some calculators require monthly totals while others require annual, or some may be per-person versus household.

Categorizing spending by category was the most laborious, but also very rewarding as I was able to get a full view of our spending for the year and compare the different categories, not just from a climate but also a budgetary perspective. However, if you do not have the 1-2 hours right now, most of the calculators accept general inputs (e.g., I found that food & drink was 20% of our total spend, goods like clothes and appliances another 20%, utilities 3%, and services, including the aforementioned health insurance and mortgage 56%).

As a final alternative, there is a smartphone app called Joro that will do this automatically by linking to your online credit card accounts, pulling transaction information, and multiplying it by emission rates for each sector.

Next Steps

Where did your carbon footprint come in? Which portions of your consumption had the biggest impacts versus the lowest? Were you surprised by the result?

Now that you have a sense of your impact on the climate and where it comes from, are you ready to work on reducing it? Next, you can go to the Action Guide for some quick steps that you can take to reduce as well as outline a strategy for the rest of the year.