Just as my night time reading is all about drought (I’ll tell you about that another day), I find this fascinating paper in this weeks Science:
Battisti, David S. and Rosamond L. Naylor, Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat, Science (2009)
The bottom line is that heat waves may be more important than droughts for some food production. They give the example of a major perturbation on wheat production and consequential world wheat prices arising from the hot, dry 1972 summer in the Ukraine and Russia. They then point out that while that summer ranked in the top ten percent of temperature anomalies between 1900 and 2006 (with temperatures 2-4C above the long term mean), one third of the summers in the observation period were drier!
They then use observational data and simulations from 23 global climate models to show a high probability (>90%) that growing season temperatures in the tropics and subtropics by the end of the 21st century will exceed the most extreme seasonal temperatures recorded from 1900 to 2006. The consequences for food production are extreme!
A couple of choice quotes:
... regional disruptions can easily become global in character. Countries often respond to production and price volatility by restricting trade or pursuing large grain purchases in international markets?both of which can have destabilizing effects on world prices and global food security. In the future, heat stress on crops and livestock will occur in an environment of steadily rising demand for food and animal feed worldwide, making markets more vulnerable to sharp price swings.
... with growing season temperatures in excess of the hottest years on record for many countries, the stress on crops and livestock will become global in character. It will be extremely difficult to balance food deficits in one part of the world with food surpluses in another, unless major adaptation investments are made soon to develop crop varieties that are tolerant to heat and heat-induced water stress and irrigation systems suitable for diverse agroecosystems. The genetics, genomics, breeding, management, and engineering capacity for such adaptation can be developed globally but will be costly and will require political prioritization ...