Key to understanding the discussion around Natural Climate Solutions is understanding the terms commonly-used in scientific studies, policy briefs and other literature. This glossary is compiled from a variety of sources, including government agencies and non-profit organizations, to provide plain-English definitions of these terms. Links to the original sources are provided after each definition. In some cases, terms were edited for clarity.

1 Million Metric Tons of Carbon

1 Million Metric Tons of Carbon — the U.S. Environmental Protection Agency’s Greenhouse Gas Equivalencies Calculator helps define what this measure means in everyday terms. For example, 1 million metric tons of carbon dioxide equivalents is the same amount of greenhouse gases emitted by 217,480 passenger cars in a year. (US EPA)

Acres, Hectares and Square Miles

Acres, Hectares and Square Miles are different units of measurement used to measure the size of a piece of land. The World Land Trust’s website includes an Area Converter tool that can be used to convert one measure to another. 1 hectare = 2.47 acres. 1 square mile = 640 acres.1 acre is approximately the size of 16 tennis courts. (World Land Trust)

Carbon Dioxide Equivalent (CO2e)

Carbon Dioxide Equivalent (CO2e) Is the international standard used to express greenhouse gases (US EPA). Carbon dioxide (CO2) is not the only greenhouse gas. Others, like methane (CH4) have different warming properties and longevity in the atmosphere compared to CO2.  To report all the greenhouse gases in terms of one number, these gases of differing properties are converted to the amount of CO2 that would have the same warming potential.  (USDA Forest Service). As explained by The Guardian, the idea is to express the impact of each different greenhouse gas in terms of the amount of CO2 that would create the same amount of warming. That way, a carbon footprint consisting of lots of different greenhouse gases can be expressed as a single number.


Teragram – one teragram equals 1 million metric tons. (WRI)


Petagrams/Gigatonne – one petagram or one gigatonne equals 1 billion metric tons (NOAA/NASA)