Published online 30 September 2009 | Nature | doi:10.1038/news.2009.963


Climate change will hit developing world harvests hardest

Report quantifies link between global warming and food security.

Drought struck wheat fieldsBy 2050, yields of wheat could drop by a third or more in some areas.Punchstock

Developing countries could see large drops in crop yields by 2050 if climate change is left unchecked, according to a US report, potentially leaving as many as 25 million more children malnourished compared to a world without global warming.

The study by the International Food Policy Research Institute in Washington DC is one of the most comprehensive to look at the links between climate change and food security. The results are being released today at the international climate-change meeting taking place in Bangkok, Thailand.

The report forecasts the effects on crop yields and agricultural supply and demand under the A2 scenario of the fourth report from the International Panel on Climate Change (IPCC) — that is that by 2100 the temperature will rise between 2.0 °C and 5.4 °C and sea levels will ascend by between 26 cm and 59 cm compared to 1990 levels. It uses two climate models to forecast these effects: one developed by the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, and one by the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Clayton, Australia.

"This report brings together for first time a detailed modelling of crop growth under climate change with insights from the crop market," says Gerald Nelson, the study's lead author.

Asian impact

Some of the biggest effects could be felt on irrigated wheat and rice yields, the study finds. If left unchecked, climate change will reduce wheat yields from irrigated fields by 20-35% by 2050 compared with the potential yields for these crops under a no-climate-change scenario.

"The developing countries will probably be the hardest hit by climate change and will face bigger reductions in crop yields than industrialized countries," says Nelson.

The results show that southern Asia will be hit particularly hard by climate change, with some of the largest losses in crop production. In a worst-case scenario, the models show that farmers in this region could see a nearly 50% drop in wheat production by 2050 compared with potential production with no climate change.

Nelson says that the biological effects of climate change on crops will "work their way through the agricultural market", reducing production and increasing food prices. As a result, he says, consumption and calorie intake will fall, leading to more malnutrition. The report calls for additional investments of at least US$7 billion per year for research, to increase agricultural productivity, and help farmers adapt to climate change.

Extreme scenario

"This report links climate change to food security," Keith Goulding, says a soil scientist at Rothamsted Research in Hertfordshire — Britain's largest agricultural research centre. "This is important as one of the problems we face is narrowly focused policies that address one issue without considering others."


Goulding supports the main conclusions of the report but notes that the IPCC climate scenario used in the study predicts "quite extreme conditions".

And some of the results, such as climate change effects on crop production by regions, and on world prices for livestock products and major grain, don't take into account gains in crop yields and production from a possible carbon fertilization effect — increased carbon dioxide levels in the atmosphere may be beneficial to some crops, he says. "Taking carbon fertilization into account could give a more optimistic outcome," he says.

But Goulding adds that the models also do not include loss of land to bioenergy crops — and that could further increase the risk to food security. 


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  • #60098

    CO2 absorbs infrared light. Air is mostly blue (it absorbs non-blue light), but it is also complement-of-infrared, in the sense that the CO2 in the air absorbs infrared.The Earth surface radiates 390 W/m2 of infrared, while the top of the atmosphere radiates 240 W/m2. The difference is the infrared energy absorbed by the atmosphere (around 150 W/m2). I think the industrial age has brought up the concentration of CO2 concentration by 30%, from 280 parts per million to 390 parts per million. We burned roughly 500 billion metric tons of carbon in 150 years.

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