Are Earth's carbon sinks changing?

NASA's Orbiting Carbon Observatory (OCO) satellites have found that carbon sinks might be changing.

We power our daily lives mainly by burning fossil fuels, and this adds greenhouse gases to the air, warming the planet. That's where trees, the ocean, and soil and grasslands come in. They reduce the amount of carbon dioxide in the air. When something takes carbon away from the air, it's called a sink. But NASA's satellites have found these sinks might be changing. Could it be that our sinks stop removing carbon from the air, and add more instead? Let's take a look.