Maura Brennan and Elizabeth Dell co-lead what they say is the largest Michigan chapter of the Citizens Climate Lobby, a national group sharply focused on a very specific goal: Convincing Congress to enact a carbon tax on coal, oil, and natural gas and distribute the money to all American households. The market-based logic is simple: Raising fossil fuel prices will push the country toward ever-cheaper, renewable, clean power sources such as wind, solar, and energy efficiency, cutting the greenhouse gas emissions warming our planet.