If extreme weather becomes the norm, starvation awaits

I believe we might have made a mistake: a mistake whose consequences, if I am right, would be hard to overstate. I think the forecasts for world food production could be entirely wrong. Food prices are rising again, partly because of the damage done to crops in the northern hemisphere by ferocious weather. In the US, Russia and Ukraine, grain crops were clobbered by remarkable droughts. In parts of northern Europe, such as the UK, they were pummelled by endless rain.

Even so, this is not, as a report in the Guardian claimed last week, "one of the worst global harvests in years". It's one of the best. World grain production last year was the highest on record; this year's crop is just 2.6% smaller. The problem is that, thanks to the combination of a rising population and the immoral diversion of so much grain into animal feed and biofuels, a new record must be set every year. Though 2012's is the third biggest global harvest in history (after 2011 and 2008), this is also a year of food deficit, in which we will consume 28m tonnes more grain than farmers produced. If 2013's harvest does not establish a new world record, the poor are in serious trouble.

So the question of how climate change might alter food production could not be more significant. It is also extremely hard to resolve, and relies on such daunting instruments as "multinomial endogenous switching regression models". The problem is that there are so many factors involved. Will extra rainfall be cancelled out by extra evaporation? Will the fertilising effect of carbon dioxide be more powerful than the heat damage it causes? To what extent will farmers be able to adapt? Will new varieties of crops keep up with the changing weather?

But, to put it very broadly, the consensus is that climate change will hurt farmers in the tropics and help farmers in temperate countries. A famous paper published in 2005 concluded that if we follow the most extreme trajectory for greenhouse gas production (the one we happen to be on at the moment), global warming would raise harvests in the rich nations by 3% by the 2080s, and reduce them in the poor nations by 7%. This gives an overall reduction in the world's food supply (by comparison to what would have happened without manmade climate change) of 5%.

http://www.guardian.co.uk/commentisfree/2012/oct/15/extreme-weather-starvation-food-production?commentpage=all#start-of-comments