To have a chance of meeting either of those targets, there is one thing every single country must do: Stop drilling and digging for new oil, gas and coal — right now. That’s the conclusion of a recent analysis from the think tank Oil Change International. Using investment-grade data from a Norwegian firm that tracks fossil-fuel reserves, OCI calculated two global “carbon budgets” — in other words, two scenarios that show how much of our fossil-fuel reserves we can tap into before the resulting greenhouse-gas emissions cause catastrophic warming. One scenario gives us a “likely,” or 66 percent, chance of keeping overall warming below 2 degrees C, and the other provides a 50-percent likelihood of staying below 1.5 degrees.