The students in my Harvard University class and I went through an exercise last fall to help them understand how the world might address the climate crisis and keep the average global temperature increase below two degrees Celsius. The students were led by John Sterman, a management professor at the Massachusetts Institute of Technology. Sterman co-developed En-ROADS, a computer simulation of the effects of climate policies, and they were able to see the consequences of their proposals on the average global temperature.

The exercise gave both good and bad news. The good news is that it's going to be difficult to keep the temperature under 1.5 degrees C. If we implement a large portfolio of solutions, the most important of which are eliminating fossil-fuel subsidies and putting a stiff price on carbon, the challenge can be met.