A recent study by two researchers showcases just how dangerous unchecked warming could be (in the interest of disclosure, I took a class from one of these researchers, Dr. Rosamond Naylor, in college). Using the “middle of the road” estimate of CO2 increases in the atmosphere, the researchers ran 23 climate models to estimate the average summer temperature around the world 100 years from now.
The results are particularly troubling for the tropics and subtropics, a band around the equator that reaches from the Carolinas and the Mediterranean in the north to the tip of Africa in the south — a distance of over 5,000 miles. If we continue to warm the planet with heat-trapping greenhouse gases, we can expect that the majority of the tropics and subtropics will exhibit warmer *average* summer temperatures than the highest previously recorded high temperature. Just to be clear, this means that, on average, the temperature during the summer months will exceed the highest temperature ever recorded. Yikes.
This warming will likely mean decreased crop yields during the growing season: for every degree increase in average summer temperature, crop yields can be expected to decline between 2.5 and 16%. And if you think you’re sitting pretty in your temperate hamlet somewhere in North America, well, sorry. Things will get warmer for you, too, although your statistical risk is lower — only a 10-70% chance of extreme warming, versus the greater than 90% chance in the tropics and subtropics.
Sure, warming also means longer growing seasons in the far North, and we can take some comfort about a decline in cold-weather events that wreak havoc on agriculture and people. The facts, though, are not at all rosy. By polluting the atmosphere with greenhouse gases, we are ensuring that the majority of the world’s poor — those 3 billion that currently reside in the tropics and subtropics — will experience summer temperatures that are greater than any previously recorded.