Climate scientists vigorously debate about how bad global warming will get, how quickly, and how to combat it. One fight involves how much effort to put into stopping leaks of methane gas into the atmosphere. Some academics complain that President Obama's plan to make greater use of natural gas, which consists mostly of methane, will lock America into a supposed solution to climate change that will be worse than burning coal. Is that claim plausible? The basic scientific facts are clear. The most important greenhouse gas that humans are spewing into the atmosphere is carbon dioxide, which comes from burning fossil fuels. The second most important is methane, which is released when coal is mined; it escapes when wells are drilled for oil; and it leaks from pipes that distribute natural gas. Methane is a far more potent greenhouse gas than carbon dioxide. But in stark contrast to CO2, methane breaks down quickly in the atmosphere. Scientists say, "Methane is like a hangover that you can get over it if you stop drinking," said Dr. Pierrehumbert. "CO2 is more like lead poisoning—it sticks around, you don't get rid of it, and it causes irreversible harm." So what has all this got to do with the President's climate plan? Mr. Obama's administration intends to cut carbon dioxide emissions from power plants by 30 percent, from 2005 levels, by 2030. That will push states toward much greater use of natural gas to generate electricity—a shift that is seen as combating global warming because, in a power plant, burning natural gas emits roughly half the carbon dioxide as burning coal. Experts say that it is critical to keep carbon dioxide out of the atmosphere now, even if that requires burning more gas. If only a limited amount of money is going to be available to tackle global warming, that would weigh in favor of Dr. Pierrehumbert's argument for ignoring methane leaks for the time being. Dr. Shindell, a NASA climate scientist, agrees that methane control should not be pursued at the expense of CO2 control. There might be a way out of this conundrum. The idea would be to promise far more aggressive methane control to slow global warming for the benefit of people alive today, along with aggressive CO2 control for the benefit of future generations.