The climate can change fast and it can change hard. One of the great mistakes of modern society (no doubt pre-modern too to the extent they could) is building a huge infrastructure based upon the idea that what I personally see in the climate is normal. That’s a huge problem because normal changes over time. As a historian of the American West, the most obvious example of this is how white Americans divided the water up during the 1880s and 1890s, assuming that was normal. Whoops! That was an unusually wet period. So there’s not enough water in the rivers for all the states to get their legally mandated share. Not to mention the thousands of abandoned farms one can see driving through the western Plains, monuments to a different idea of the environment. In any case, we are in for some big problems, perhaps not so differently from the early 14th century European famine:
One of the most important insights of recent studies is that, when the climate changes, it can do so swiftly and relentlessly. It is possible, in a human lifetime, to see sea levels rise and ice shelves break away, and, when they do, nothing about what happens next can be taken for granted. The climate record is full of sudden disasters. Studies have also clarified some of the mechanisms of the relationship between climate and shorter-term weather; a 2010 report on the M.W.P., published in the journal Climate Dynamics, looked at the connections between the rain in Europe, the temperature of the Indo-Pacific warm pool, and the flood levels of the Nile. The Great Famine looks like a fourteenth-century example of what we now call extreme weather. We are also learning how, in our own time, changing ocean temperatures can cause shifts in El Niño, the name given to a collection of weather patterns that originate in the Pacific and stretch across the globe; a “Godzilla El Niño” is credited for the oddly warm weather in the Northeast this winter. We have built cities and economies on assumptions about the seasons that may prove unstable. The best models we have now project that, as a consequence of climate change, the frequency of extreme-weather events, from superstorms to droughts, will increase sharply.