for Arctic melt and sea level rise, some things closer to home get less attention. Take food supply: new modelling studies show that there are climate tipping points here too, beyond which crop yields will collapse.
Using a model of future climate change the researchers found that the number of degree-days above 29 °C in a growing season could rise to 413 by the end of the century if we do not cut greenhouse gas emissions. This would cause maize yields to fall by 82 per cent. Even if we reduce emissions by 50 per cent by 2050 relative to 1991 levels - a target which governments are struggling to agree on - yields could still fall by between 30 and 46 per cent.
"If US yields go down a lot, it could drive up prices of staple food commodities all around the world", say the researchers. "Almost surely the poor would suffer far more that the US would."
David Pimentel at Cornell University in Ithaca, New York, argues that curbing biofuel production would tackle starvation and high food prices far quicker than curbing greenhouse gas emissions. "Some 66 per cent of the world population malnourished, yet the US turns 33 per cent of its corn crops into biofuels," he says.
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