Sustainability, Energy and Environment Community

University of Colorado Boulder

Supporting data & links

Supporting data - Gathered below are data used in calculations elsewhere on the website. These calculations answer questions like: "How many miles do you need to drive to emit the same amount of CO2 as eating a 1/4 pound burger?" Answer: About 8 miles (for details, see the Food section below as well as our note on carbon percentages & terminology).

Percentages of greenhouse gas emissions

Percentages listed in one place on this website can seem to contradict numbers listed elsewhere. But there isn't any contradiction and the percentages aren't wrong. Instead, the numbers come from studies that aren't directly comparable because of different categories, different assumptions etc. For example, the pie chart on our Science page is based on emissions from five U.S. economic categories: electricity, transportation, industry, commercial+residential, and agriculture (EPA calcuation). Those percentages cannot be directly compared to the ones we show on the home page for a similar, but different set of U.S. categories: energy, transport, products, and food (UCS calculation). In other cases, we discuss global average percentages, which can vary substantially from corresponding U.S. values.

Terminology for greenhouse gases

Greenhouse gases come in many forms such as carbon dioxide (CO2), methane, and nitrous oxide. CO2 is the largest overall contributor to climate change. But less common gasses like methane have a much more powerful effect per pound of gas than CO2. In order to have comparable numbers, we convert all the greenhouse gases into a “CO2 equivalent” for this website. For example, when we state the CO2 emissions for beef, the number includes the methane produced by the cow converted into an equivalent amount of CO2.

Supporting links - Also gathered below are links to particularly relevant websites. Many of these links also appear in the "Learn more" sections of many pages.

U.S. focus - Most of the data on this website pertain to the United States. Exceptions are noted on the corresponding webpages. Many other countries emit less CO2 per capita and have a different mix of emission sources. For example, the proportion of greenhouse gases from transportation tends to be higher in the U.S. than most countries. Note: Some videos on this website may not be available outside the U.S.


EPA Greenhouse Gas Equivalencies Calculator - Want a tool to translate abstract energy or emissions measurements into concrete terms you can understand, such as the annual emissions from cars, households, or power plants? EPA has a handy online calculator for this. As an example, we took the average American emissions of 36,000 pounds of CO2 (see Home section above) and entered it in the calculator. It returned 18 equivalencies including (1) driving an average passenger vehicle 40,023 miles and (2) using up 668 propane cylinders for home barbeques.

EPA Equivalencies Calculator