At the end of his first year in office, President Obama flew to Copenhagen and made a big promise: that the United States would cut its greenhouse gas emissions substantially by 2020 — a bold and risky pledge that hinged on a balky Congress to make it possible. His efforts became bogged down within months, and Mr. Obama’s pledge to the rest of the world soon looked like a pipe dream. On Monday, Mr. Obama is planning to bypass Congress and take one of the biggest steps any American president has ever taken on climate change, proposing new rules to cut emissions at power plants. Yet, by itself, the president’s plan will barely nudge the global emissions that scientists say are threatening the welfare of future generations. “Is it enough to stop climate change? No,” said Ted Nordhaus, chairman of the Breakthrough Institute, an environmental think tank in Oakland, […]