Climate Change is Already Drastically Altering the World's Climate Zones

posted by Jason Kottke   Nov 02, 2018

In an article published by the Yale School of Forestry & Environmental Studies, Nicola Jones details some of the ways that the Earth's climate zones have shifted in response to our changing climate. Each effect is accompanied by a map, so you can actually see the magnitude. Her first example is that the tropics are getting bigger by 30 miles per decade.

In a paper published in August, Lu and colleagues tracked how and why the Hadley cell is expanding. They found that since satellite records started in the late 1970s, the edges of the tropics have been moving at about 0.2-0.3 degrees of latitude per decade (in both the north and the south) .The change is already dramatic in some areas, Lu says — the average over 30 years is about a degree of latitude, or approximately 70 miles, but in some spots the dry expansion is larger. The result is that the boundary between where it's getting wetter and where it's getting drier is pushing farther north, making even countries as far north as Germany and Britain drier. Meanwhile, already dry Mediterranean countries are really feeling the change: In 2016, for example, the eastern Mediterranean region had its worst drought in 900 years. The last time the tropics expanded northward (from 1568 to 1634, due to natural climate fluctuations), droughts helped to trigger the collapse of the Ottoman Empire.

Two quick things to note here. 1. As Jones states a couple of paragraphs above this one, the "tropics" are actually mostly dry. We think of weather in the tropics as hot and wet, but it's actually hot and dry. The expanding tropics means hotter, drier weather for more of the planet. 2. Re: that bit on the Ottoman empire, I bet there's an interesting book to be written on how climate change (natural and not) is a huge and unacknowledged driver of socioeconomic & political change (the Little Ice Age, the role of climate change in driving the Syrian civil war, the migrant caravan in Mexico may be climate driven, etc.)

Back to the article, some of the other shifts highlighted are:

- Tornado alley in the US has shifted 500 miles east in 30 years.
- Plant hardiness zones are moving north in the US at 13 miles per decade.
- The permafrost line has moved 80 miles north in 50 years in parts of Canada.
- The wheat belt is pushing poleward at up to 160 miles per decade.

Here's the maps showing the shift in tornadic activity:

Tornado Shift

Climates shift and people have to move. Two more decades of this and you're going to see hundreds of millions of climate refugees that the world is not equipped to handle.

Update: I received a couple of responses that consider climate's role in history: Geoffrey Parker's Global Crisis and Climate Change and the Health of Nations by Anthony McMichael. (thx, @ThomasintVeld & jonathan)