Though not endorsed by the Sierra Club, Mark Warner has demonstrated some action on clean energy and environmental issues. As Virginia's governor, he was able to drastically reduce emissions from Virginia coal plants and he fought against suburban sprawl to protect open spaces.

He was also dedicated to protecting the Chesapeake Bay by regulating wastewater treatment plant discharges and helped clean up 260 bodies of water so that they could be removed from the EPA's list of "impaired" waters. Warner promises to encourage the development of renewable energy sources as a measure against global warming; unfortunately he does support "clean coal" technology, some oil drilling, and nuclear power.