Climate change involves more than straightfoward warming, it also affects the patterns of weather and the seasons, as John Parker discovers in an excellent feature — What’s happened to the seasons? — in the Spring issue of The Economist’s Intelligent Life magazine. Parker’s done his homework, and his article is the best overview of recent changes in seasonal weather around the world, and the knock on impacts on agriculture and ecosystems that I’ve read. Here’s a sample:
Some seasons have vanished altogether. In Kashmir there used to be a brief rainy season between winter and spring, called tsonth -– three or four weeks of torrential downpours, bright sunshine and snow on the ground. But, says Rais Akhtar of the University of Kashmir, the state has not seen a tsonth for ten years. The first rainy season seems to have dried up in Uganda. In Ntchenachena, in northern Malawi, villagers used to describe four episodes of rain, each with their proper name and association with particular farming events. Since 2001, they say, the pattern can no longer be discerned.
Parker points to increasing unpredictability in “traditional” seasons posing a challenge to agriculture as well as dislocations in ecosystem linkages. We may even have seen an example of that in the last year in New Zealand. 2009 was a remarkable switchback between hot and cold weather. May was very cold, but August was the warmest in the 155 year record. And temperatures then flatlined through until the end of October, which was the coldest for 64 years. Check out the NIWA summary of the year, or MetService Weather Ambassador Bob McDavitt’s round up at Sciblogs. Perhaps global warming really is turning out to be global weirding.