A spate of decisions over the past two years by the Supreme Court has significantly impaired the Environmental Protection Agency’s authority to limit pollution in the air and water, regulate the use of toxic chemicals and reduce the greenhouse gasses that are heating the planet.This term, the court’s conservative supermajority handed down several rulings that chip away at the power of many federal agencies.But the environmental agency has been under particular fire, the result of a series of cases brought since 2022 by conservative activists who say that E.P.A. regulations have driven up costs for industries ranging from electric utilities...