The Guardian has an article published today :
Global food crisis will worsen as heatwaves damage crops, research finds.
This shoddy piece of alarmist nonsense rides on the back of a new paper by
MET Office/Reading Uni scentist Ed Hawkins and University of Leeds Earth Sciences professor Andy Challinor et al:
Increasing influence of heat stress on French maize yields from the 1960s to the 2030s
In the Guardian article, Ed Hawkins says:
Our research rings alarm bells for future food security… Over the last 50 years, developments in agriculture, such as fertilisers and irrigation, have increased yields of the world’s staple foods, but we’re starting to see a slowdown in yield increases…. Increasing frequency of hot days across the world could explain some of this slowdown.
Andy Challinor says:
Current advances in agriculture are too slow to offset the expected damage to crops from heat stress in the future… Feeding a growing population as climate changes is a major challenge, especially since the land available for agricultural expansion is limited. Supplies of the major food crops could be at risk unless we plan for future climates.
All of which sounds pretty worrying, but lets take a closer look at the paper before we take the article author’s advice to cut our emissions – thereby crippling ourselves economcally. The paper proceeds with the following methodology:
the effects on historical crop yields of improved technology, precipitation and daily maximum temperatures are modelled empirically, accounting for a non-linear technology trend and interactions between temperature and precipitation.
I asked Ed Hawkins on twitter why the effect of increased co2 wasn’t taken into account and he told me that:
Any CO2 response is in long term trend, & maize uses C4 photosynthesis = less responsive to increasing CO2 than many plants. Some uncertainty over exact numbers, but is small compared to 300% yield increase largely due to other technological factors.
I’ve been aware for some time that the claims made for wonder-fertilisers and super-pesticides are exaggerated by those with commercial interests in selling them for (big) profits. As well as higher co2 fertilisation (which also reduces drought stress) the last 50 years has seen a generally milder climate, increased sunshine hours, longer growing seasons and stable rainfall amounts. Of course, it is in the interests of those who profit from sales of artificial fertilisers, herbicides and pesticides to claim the beneficient natural effects to be the result of their product’s application and downplay the natural factors in improving yields.
And the same is true for Global Doomsters like the alarmist media who can sell papers on the back of public alarm and the scientists getting big research grants to investigate possible (but highly unlikely) scenarios of 4C temperature increases. Ed Hawkins and Andy Challinor concentrate on the negative effect of very hot days and hardly mention the generally beneficient aspect of a warmer climate due to increased sunshine hours or longer growing seasons at all. So I asked for information:
No reply yet, I’ll update if I get one. In the meantime, here’s a figure from the paper and below that, the MET office’s records for UK sunshine hours. Granted the study was on French Maize, but you get the general idea of trends globally from the UK figures, they are similar to Japan too.
According to http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts/climate-change-impacts-by-sector/agriculture :
Many crops show positive responses to elevated carbon dioxide and low levels of warming, but higher levels of warming often negatively affect growth and yields.
Crop responses in a changing climate reflect the interplay among three factors: rising temperatures, changing water resources, and increasing carbon dioxide concentrations. Warming generally causes plants that are below their optimum temperature to grow faster, with obvious benefits. For some plants, such as cereal crops, however, faster growth means there is less time for the grain itself to grow and mature, reducing yields. Higher temperatures will mean a longer growing season for crops that do well in the heat, such as melon, okra, and sweet potato, but a shorter growing season for crops more suited to cooler conditions, such as potato, lettuce, broccoli, and spinach.
Hatfield, J., K. Boote, P. Fay, L. Hahn, C. Izaurralde, B.A. Kimball, T. Mader, J. Morgan, D. Ort, W. Polley, A. Thomson, and D. Wolfe, 2008: Agriculture. In: The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States
My interim conclusion is that while it might be the case than some very hot days might have a negative impact on drought stressed crops, this may be more than offset by the beneficient aspects of generally increased sunshine hours and longer growing seasons, not to mention extra co2, which is known to reduce drought stress and increase grain and fruit size. We would be able to make better assessments if sunshine hours figures were available for the specific locations in France where the data was gathered.
My own experience as an organic vegetable grower over the last 20 years is that sensible husbandry can ensure good yields over a variety of conditions from year to year, despite the fact that natural interannual variation is far larger than longer term trends. Given that it is estimated that a 1C change in average temperature would move the climatology around 140km on the ground, I see no cause for alarm in the rates of change we have seen, or are likely to see, in average surface temperature. Any increase in ‘very hot days’ will be relative to the location, and easily coped with through chioices of crops to grow, provision of shade, improvement of irrigation etc. Adaption in this case is much easier and cheaper than mitigation of ‘global warming’ through co2 emission reduction (as if that would change the temperature).
The real cause of ‘the food crisis’ is the corn to ethanol hare brained schemes of Al Gore and his ilk. And the commoditisation of staple foodstuffs, ensuring a deliberate move towards ‘just in time’ food production and the short term glut/famine scares it brings. It’s all about the politics and economics of scarcity, and screwing more money out of ordinary people.