We like to think about risks with simple arrows. If A, then B. If wildfires break out, some people may lose their homes. If an oil pipeline leaks, it can pollute the soil. But if you put a wildfire and an oil pipeline leak together in the same place at the same time, the whole becomes a lot nastier than sum of its parts.

The world’s oceans face three different major risks from the carbon that we put in the air. That extra carbon (9.2 billion tons in 2009 alone) is acidifying the ocean, warming it, and possibly even stripping it of oxygen. I’ve written about all three of carbon’s impacts in recent years, but I’ve chosen to write