carbon footprint

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The amount of carbon-containing greenhouse gases released into the environment by an activity, process, individual, or group, expressed usually as the equivalent in kilograms of carbon dioxide.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A measure of the amount of carbon dioxide produced by a person, organization or state in a given time