WORD WATCH

Al Gore may be kicking himself for helping to popularize the term “carbon footprint.” Even conservative think tanks have incorporated the phrase into their arsenals, using it last week to criticize the former vice president for his Tennessee mansion’s Texas-sized electric bills.

Before Gore became a crusader against global warming, there were no “carbon footprints,” according to a Nexis search of all news sources from 1980 to 2000. From 2000 to the beginning of 2006, there were 217 uses of the phrase, starting with a quote in the Seattle Times in November 2000 and gaining frequency the following spring, when the World Resources Institute posted an online carbon footprint calculator. Then in 2006, the year of the documentary “An Inconvenient Truth,” which featured Gore, and with the growing popularity of trading carbon credits to reduce one’s footprint, there were more than 1,000 mentions. In the first two months of this year, the term’s frequency was up to nearly 2,000.

A footprint, literally, is the impression of a foot. Metaphorically, according to Dictionary.com, it can apply to tire tracks, especially on wet pavement; the area affected by an increase in sound, as from an airplane; a satellite’s reach on Earth; and the predicted impact point for Earth-bound spacecraft and associated debris.

Although “carbon footprint” -- the amount of greenhouse gases, measured in units of carbon dioxide, that human activities produce -- hasn’t achieved dictionary status, it has gained political cachet, as

Gov. Arnold Schwarzenegger, among others, knows. Last week, the jet-setter governor was trying to reduce his oversized “carbon footprint” by buying trees for planting.

-- SWATI PANDEY