"The hardest thing to fix will be the result of Bush reneging on his campaign promise to declare CO₂ from power plants as a pollutant. It is practically impossible to retrieve CO₂ once it has been emitted. Much of it stays in the air more than 1,000 years. Because of his broken promise many coal-fired power plants were built that would not otherwise have been built. Very hard to fix—there's a strong reluctance to bulldoze a new power plant that cost more than a billion dollars. Our great-grandchildren will suffer because of his broken promise."

Read an extended interview with James Hansen about the Bush legacy here.