Downpours and heatwaves caused by climate change could disrupt food supplies from the fields to the supermarkets, raising the risk of more price spikes such as this year's leap triggered by drought in the United States. Food security experts working on a chapter in a U.N. overview of global warming due in 2014 said governments should take more account of how extremes of heat, droughts or floods could affect food supplies from seeds to consumers' plates. "It has not been properly recognised yet that we are dealing with a food system here. There is a whole chain that is also going to be affected by climate change," Professor Dr John Porter of the University of Copenhagen said. "It is more than just the fact that there are droughts in the United States that will reduce yields," he said. Like the other experts, he said was giving personal opinions, not those of the U.N. panel.