Emily Cunningham

Over the last few years, there has been a heavy emphasis on climate research studying impacts between 1.5C and 2C—mostly in anticipation of the IPCC report on that subject, which was published last October.

Up until a year or two ago, there was hardly any coverage in the mainstream press on climate scenarios north of 2C—a level scientists of the world consider catastrophic, and island nations call "genocide."

But 2C isn't a "likely" scenario—it's a tremendously optimistic scenario. Today we are on track for more than 4C by the end of the century—after which, warming could continue.

Over the last 30 years, the world as a whole has done little to nothing to bend those curves downward. In fact, last year we added carbon to the atmosphere at an unprecedented rate. Every year is worse than the last.

The upper-end of the UN's bell curve of possibilities puts the planet at 8C warmer by the end of the century—a worst-case outcome of a do-nothing carbon trajectory.

4C may seem unthinkable, with such horrifying impacts we would like to believe the chances are vanishingly slim we get there. But while I think we will avoid that amount of warming, it is far from a worst case.

That we often think of it that way is a reflection of just how tilted toward best-case and even beyond-bast-case most scientific research has been over the last few decades, when we did little in response.