Big Trouble Ahead? Why the Forecasts for Food Production Could Be Entirely Wrong
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If the mechanism proposed by another paper is correct, it is not just extremes of heat that are likely to rise(17). I’ve explained this before, but I think it’s worth repeating. The jet stream is a current of air travelling eastwards around the upper northern hemisphere. It separates the cold wet weather to the north from the warmer, drier weather to the south. Wobbling along this ribbon are huge meanders called Rossby waves. As the Arctic heats up, the meanders slow down and become steeper. The weather gets stuck.
Stuck weather is another way of saying extreme weather. If the jet stream is jammed to the north of where you are, the weather stays hot and dry, and the temperature builds up – and up. If it’s lodged to the south of you, the rain keeps falling, the ground becomes saturated and the rivers burst their banks. This summer the UK and the US seem to have found themselves on opposite sides of stuck meanders, and harvests in both countries were savaged by opposing extremes of weather.
This is where we stand with just 0.8 degrees of global warming and a 30% loss of summer sea ice. Picture a world with 2, 4 or 6 degrees of warming and a pole without ice, and you get some idea of what could be coming.
Farmers in the rich nations can adapt to a change in averaged conditions. It is hard to see how they can adapt to extreme events, especially if those events are different every year. Last winter, for example, I spent days drought-proofing my apple trees, as the previous spring had been so dry that – a few weeks after pollination – most of the fruit shrivelled up and died. This spring was so wet that the pollinators scarcely emerged at all: it was the unfertilised blossom that withered and died. I thanked my stars that I don’t make my living this way.
Perhaps there is no normal any more. Perhaps the smooth average warming trends the climate models predict – simultaneously terrifying and oddly reassuring – mask wild extremes for which no farmer can plan and to which no farmer can respond. Where does that leave a world which must either keep raising production or starve?
7. Martin Parry, Cynthia Rosenzweig and Matthew Livermore, 2005. Climate change, global food supply and risk of hunger. Philosophical Transactions of the Royal Society – B, vol 360, pp 2125–2138. doi:10.1098/rstb.2005.1751 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1569580/
8. Eg Jerry Knox, Tim Hess, Andre Daccache and Tim Wheeler, 2012. Climate change impacts on crop productivity in Africa and South Asia. Environmental Research Letters 7. 034032. doi:10.1088/1748-9326/7/3/034032
9. Christoph Müller et al, 2012. Climate change risks for African agriculture. Proceedings of the National Academy of Sciences Early Edition. www.pnas.org/cgi/doi/10.1073/pnas.1015078108
10. P. Krishnan et al, 2011. High temperature effects on rice growth, yield, and grain quality. Advances in Agronomy. Vol 111, pp87-205.
11. Jan Beck, 2012. Predicting climate change effects on agriculture from ecological niche modeling: who profits, who loses? Climatic Change – published online.
12. Tom Osborne, Gillian Rose and Tim Wheeler, 2012 (in press). Variation in the global-scale impacts of climate change on crop productivity due to climate model uncertainty and adaptation. Agricultural and Forest Meteorology. http://dx.doi.org/10.1016/j.agrformet.2012.07.006
13. Kyungsuk Cho et al, 2012. Winter wheat yields in the UK: uncertainties in
climate and management impacts. Climate Research. Vol. 54, pp49–68.