Four years ago this week, BP's Deepwater Horizon drill platform exploded. Eleven workers died that day. Their bodies were never found. Over the next 87 days, 210 million gallons of oil gushed into the Gulf of Mexico. It fouled fishing grounds, ravaged the coastline, and shut down tourism. The world got an ugly look at some of the terrible hidden costs of fossil fuels. Spill-related health problems plague the people and the wildlife of the Gulf to this very day. I personally hoped that we, as a nation, would quickly learn from this tragedy and move swiftly to prevent a repeat disaster in our most vulnerable coastal environments. So it boggles the mind that Shell Oil is still determined to drill in one of the most fragile and remote ecosystems on Earth: the Arctic Ocean -- the last bastion of America's polar bears, endangered bowhead whales and other rare wildlife.