The landmark Paris Agreement of 2015 gave the world a shared target for halting climate change: that global warming should stop well short of 2 degrees Celsius. But how did that target come about, and what exactly does it mean?

Today, companies are storing millions of tons of carbon dioxide underground every year to prevent this climate pollution from warming the planet. In the future it might be billions of tons. But is it dangerous to pump so much liquefied carbon below our feet?