Oceans are a great passion of mine and something I elevated as a global priority at the U.S. State Department. Why? Because all life depends on the oceans. Circulation in the North Atlantic has slowed to the lowest level in centuries, which scientists fear will devastate fisheries and lead to rising sea levels. Meanwhile, billions of pounds of plastic end up in the oceans every year, endangering wildlife and risking our health as the debris enters the food chain. We need an international agreement, modeled on the Paris Agreement, to bind countries to reduce plastic use. We could get there with leadership.