I’ve written at length in the past about the relationship between decadal-scale climate variability and our rapidly changing human societies. The basic argument is that the sort of climate change that matters happens when a human society becomes accustomed to one climate regime, and then it changes. This is the reason I think greenhouse climate change is worth paying attention to. But it’s also the reason I think the climate’s natural variability is important – whatever the cause, if you’re not alert as a society on decadal scales, you’re screwed.

Here in the desert southwest, for example, population exploded during the relatively wet period that lasted from the 1970s in the 1990s. Some sort of a fundamental modal shift in climate seems to have set in the late 1990s, and now all those people, who built all those houses etc. during wet times, are having to learn how to manage with a lot less precipitation.

Some of the more thoughtful analysis I’ve been reading suggests a similar thing may have happened in Florida. A bunch of folks built a bunch of stuff during a period of relatively few hurricanes, and now there’s been a modal shift. Here’s Timothy Appleby in the Globe and Mail:

Thus, from the early 1940s to the late 1960s, Atlantic tropical storms and hurricanes were relatively commonplace. Then came a period of relative tranquillity, (which was when much of Florida’s coastal population took up residence).

The climate’s clearly a slow-moving, unruly beast. We’re clearly tampering with it, in ways we do not yet fully understand. But even without our “help,” it can be a bugger if we don’t pay attention on time scales rather longer than seems to have been our habit these last few decades.