CO2 is a naturally occurring odorless and colorless gas in the earth’s atmosphere. Together with other greenhouse gases (like methane and nitrous oxide), CO2 contributes to climate change by absorbing the sun’s natural radiation and reflecting it back to the earth’s surface. Although CO2 occurs naturally through processes like photosynthesis, human-caused CO2 emissions have increased dramatically since the Industrial Revolution. The burning of fossil fuels, industrial manufacturing, and other everyday acts all contribute to carbon dioxide levels, in turn contributing to climate change.

The total amount of greenhouse gases (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride) emitted over the full life cycle of a product, service, organization, or individual. Carbon footprints in the era of global warming are to be avoided, however to know an exact footprint is challenging as calculations vary wildly, but the most commonly accepted standard is the GHG Protocol developed by the World Resources Institute and the World Business Council for Sustainable Development. Simplified calculators to aid self-awareness are available from Climate Crisis and the Environmental Protection Agency, but more rigorous methodologies like the GHG Protocol should be used for organizational reporting and decision-making.

The state of balancing one’s carbon emissions with an equivalent in carbon offsets. The term is misleading, however, as it implies that one’s greenhouse gas emissions can be rendered harmless by investing in an equivalent amount of offset units (see carbon offsetting), and is often used to directly imply that a product or organization emits no greenhouse gases at all. Re-nourish discourages the use of the term on marketing materials or in messaging claims.

The act of investing in projects that reduce greenhouse gas production through the purchase of carbon offset units. A single carbon offset unit is equivalent to one metric ton of carbon dioxide (or its equivalent in other greenhouse gases). Individuals and organizations can purchase carbon offsets as a way of mitigating the carbon dioxide emissions resulting from everyday practices like travel, energy use, and waste disposal.

Typically the money from carbon offsetting goes toward funding renewable energy, energy efficiency projects, or GHG sequestration. The U.S. government regulates certain corporate carbon offsets through cap and trade agreements, while the voluntary offset market is growing.

There is much debate about the efficacy of carbon offsetting; proponents argue that it can help drive awareness by placing a monetary value on carbon emissions, while opponents argue that voluntary offset programs may actually increase carbon emissions by providing an excuse to consume more. Essentially it can allow one company to buy the rights to pollute more from another and not actually decreasing, in the end, any carbon in the atmosphere.