New and harder evidence on climate change, hunger and food prices

May 18, 2011 1 By admin

New research published in Science magazine  shows climate change is already hitting food production, but the harvest picjournos reporting it seem to have got themselves in a tangle. The Guardian reported it as saying that prices would be pushed up by ‘as much as 20%’, while the Economist put the figure at about 5%. It pains me to say it, but the Guardian got it wrong.

The origin of the discrepancy appears to be that the Guardian article glosses over the research’s finding that the fertiliser effect of higher CO2 concentrations (CO2 is the basic input for photosynthesis, so more CO2 means more plant activity) works in the opposite direction to other aspects of climate change, increasing yields and bringing down the 20% figure for the reduction from climate change impacts on the weather to something more like 5%.

The numbers on food prices are actually: 18.9% gross impact of higher temperatures (and precipitation trends, though these are far less significant than the temperature effects) from 1980 to 2008, and 6.4% net impact of higher temperatures plus estimated benefits of the fertilisation effect.

The study points out that this approximately 5% increase in food prices is equivalent to around $50bn per year of additional spending on food (out of the total of around $1 trillion the world spends annually).
So… we have a study which (for the first time, I think) quantifies the impacts of climate change on today’s yields and prices, due to changes in temperature and rainfall – both of which are projected to become more severe as a result of increased levels of CO2 in the atmosphere (note that higher temperatures are shown to be much more significant than rainfall patterns over the period of this study). It finds a 4% decline in maize and 2-3% decline in wheat yields (i.e. around 4% less maize and 2-3% less wheat was produced globally than would have been the case without global warming.) In real terms, these percentages are equivalent to the annual production of maize in Mexico, and of wheat in France.
Putting some of these elements together, the study shows that changes to the climate (higher temperatures, changed rainfall, increased CO2 concentration) has meant that:
– 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
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).

All clear? [h/t Tim Gore]