Duncan Green cites a new paper that shows that changes to the climate (higher temperatures, changed rainfall, increased CO2 concentration) has meant:
- global food prices have risen by 6.4%
- the world has spent an additional $50bn per year on food
- crops equivalent to one year’s production of maize in Mexico and wheat in France have been lost
Here is the abstract from David Lobell and Wolfram Schlenker’s (2011) paper:
Efforts to anticipate how climate change will affect future food availability can benefit from understanding the impacts of changes to date. Here we show that in the cropping regions and growing seasons of most countries, with the important exception of the United States, temperature trends for 1980-2008 exceeded one standard deviation of historic year-to-year variability. Models that link yields of the four largest commodity crops to weather indicate that global maize and wheat production declined by 3.8% and 5.5%, respectively, compared to a counter-factual without climate trends. For soybeans and rice, winners and losers largely balanced out. Climate trends were large enough in some countries to offset a significant portion of the increases in average yields 16 that arose from technology, CO2 fertilization, and other factors.
These may seem like relatively small numbers so far, but the key driver identified in the study – temperature rises – is projected to increase at significantly faster rates in the coming decades than occurred in the period of this study (global average temperatures have risen by 0.13C per decade since 1950, and are projected to rise by 0.2C per decade over next 2-3 decades, according to IPCC, with higher rises likely in areas of cultivated land – so local impacts in food growing areas will be more extreme, even assuming that there are no tipping points along the way).