What's behind Obama's decision to open U.S. waters to oil drilling—an about-face that's enraging environmentalists? In part, it's a concession to get conservative members of Congress to sign on to a climate-change bill, which would create a cap-and-trade system to limit carbon emissions. But that's only part of the strategy. The wider aim is to counteract growing public skepticism over global warming, fueled by critics who say that climate change isn't real, or that capping emissions will destroy U.S. industry. To get the bill passed, the White House aims to cast it less as a means to save the planet than as a tool to defend U.S. energy security. Allowing offshore drilling is a down payment designed to make that claim credible. There are few things Americans fear more than the specter of foreign states strangling U.S. oil supplies—and boosting domestic supply is one possible answer. Expect Obama to push cap-and-trade in a similar context: capping emissions would lower oil consumption, reducing our reliance on suppliers like Venezuela. That doesn't mean Obama has dropped his commitment to the environment. It means he's willing to do what's necessary to get a bill passed.