Public concern over global warming has presented companies of all sizes with a mandate to account for, and reduce, their greenhouse gas emissions. Still emerging, however, are the legal and fiscal implications of carbon emissions caused by corporations.

Mayor NickelsMany of the largest cities in the United States are competing to be the "greenest" city in the country. While the implementation of many of these efforts remains in development, the race never would have started without the leadership of Seattle Mayor Greg Nickels, who forged the way for the first cities to ratify the Kyoto Protocol in the face of federal indifference.

John BoeselLofty goals for emissions reductions will mean nothing if significant advances in clean transportation technology don't emerge soon. Luckily, WESTSTART/CALSTART exists to encourage those breakthroughs.

Brad SorensenExperts and investors alike agree that wind power is currently the most viable form of renewable energy available for mass production. Yet despite recent improvements in efficiency and cost, wind power has a long way to go.

Michelle WymanA global organization comprised of local governments on every continent, International Council for Local Environmental Initiatives (ICLEI) is well-equiped to fight climate change on all its diverse fronts.

William McDonoughArchitect William McDonough's list of accomplishments is long and distinguished: author of Cradle to Cradle, Time Magazine "Hero" for the environment, founder of William McDonough+Partners.

Prof. Harry AtwaterProfessor Harry Atwater of Caltech in Pasadena, California , gives a detailed explanation of his research into thin-film photovoltaics.