Over the past 100 years, levels of carbon in the atmosphere have risen 30%—to 393 parts per million. One thing that has kept global warming in check is that the oceans absorb a third of that carbon dioxide. Until recently the process of oceans soaking up our excess CO2 was considered beneficial. But the 22 million tons per day of carbon dioxide that the oceans are taking up is beginning to wreak havoc on ocean ecosystems. Scientists are discovering that all this carbon dioxide is causing the ocean to rapidly acidify, changing ocean ecosystems in profound ways.