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Cooling the world with crops

08 November 2010

Europe and North America’s massive agricultural plantations could be harnessed to cool the globe in the face of global warming according to Dr Joy Singarayer, speaking at the Royal Society's Discussion Meeting: Geoengineering - taking control of our planet's climate.

Europe and North America’s massive agricultural plantations could be harnessed to cool the globe in the face of global warming according to Dr Joy Singarayer, speaking at the Royal Society's Discussion Meeting: Geoengineering - taking control of our planet's climate.

Planting reflective crops that would send a small percentage of the sun’s light and heat back into space is one suggested form of a suite of potential geoengineering techniques known as Solar Radiation Management (SRM) that could be used to reduce the Earth’s temperature.  Dr Singarayer suggests that this technique could be utilised in European, North American and Southern Asian agricultural policy to counteract global warming at the Royal Society’s Discussion Meeting.

Dr Singarayer, Research Fellow, and Professor Andy Ridgwell, Royal Society University Research Fellow, both at the University of Bristol, have assessed the potential for the use of large-scale planting of crop varieties with increased reflectivity to incoming solar radiation (due to variation in leaf glossiness or canopy structure) and found that it would have a significant cooling effect.  Arable land represents a considerable fraction of global land-use (over 10%), with particularly dense agricultural regions covering Europe, North America and Southern Asia. The scientists’ initial assessment of the potential of crop biogeoengineering used a global climate model (the UK Met Office’s HadCM3) to suggest that an increase of 20% in crop canopy albedo (reflectivity) could provide Europe with an average summertime cooling of over 1°C. This would be one fifth of the total mitigation required to regionally offset a doubling of carbon dioxide, or up to 50% of that required to offset summer warming over Europe in the mid-21st century under a moderate global warming scenario.

In addition, Dr Singarayer is assessing the levels of reflectivity in different varieties of crops such as wheat, both traditional and modern.  Initial results have shown significant variation in reflectivity, suggesting that planting particular crop varieties, which have been found to be highly reflective, could have an even bigger impact on climate than so far predicted.

Dr Singarayer said: “Our current studies on crop reflectivity are at an early stage, but our initial results are really encouraging, as they suggest that simply by choosing to plant specific strains of crops, we could alter the reflectivity of vast tracts of land and significantly reduce regional temperatures.  The concept of using increased reflectivity to manipulate our climate is, in fact, an ancient one - humankind has for centuries painted settlements white to reflect the sun and keep cool.  We could now realise the opportunities to do this on a much bigger scale via our agricultural plantations.”

Professor Andy Ridgwell, Royal Society University Research Fellow and co-organiser of the Discussion Meeting, said: “Although reducing carbon emissions must remain the priority of all nations in order to minimise the potential impacts of climate change, relatively cost-effective and non disruptive proposals such as planting more 'climate friendly' varieties of crops, could provide a helpful step in limiting the degree of climate change.”