Including regions classified as 'probable' and 'possible' adopters, which have pledged to reduce emissions, more than one-third of the U.S. population lives in such areas, say co-authors Brendan Fisher and Robert Costanza of the University of Vermont.
Together, these regions contribute up to half of the US gross domestic product, equivalent of 16.9% of global GDP, a slightly larger share than Japan, the world's second largest economy.
Although the numbers look promising, Fisher and Costanza caution that "compliance will be a challenge even for current adopters, who have on average increased their carbon dioxide emissions by 14% since 1990." There are no mechanisms to enforce such initiatives, they add.
However, the local nature of these initiatives could make it possible to develop adaptable, site-specific plans for reducing greenhouse-gas emissions.
The United States produces 24% of worldwide greenhouse-gas emissions.