The overriding environmental issue of these times is the warming of the planet. The Democratic hopefuls in the 2008 campaign are fully engaged, calling for large — if still unquantified — national sacrifices and for a transformation in the way the country produces and uses energy. The Republicans do not go much further than conceding that climate change could be a problem and, with the notable exception of John McCain, offer no comprehensive solutions. In 2000, when Al Gore could have made warming a signature issue in his presidential campaign, his advisers persuaded him that it was too complicated and...