That reduction is equivalent to seasonally offsetting about 20 percent of regional warming due to the concentrations of carbon dioxide in the atmosphere expected by the end of this century.

The researchers emphasized that such a plan could be achieved without disrupting food production, either in terms of yield or the types of crops grown.

" We propose choosing between different varieties of strains of the same crop species in order to maximize solar reflectivity rather than changing crop type, although the latter could also produce climatic benefits," said Andy Ridgwell of the University of Bristol.

"We see this as akin to the choices that are regularly made for other properties of a crop, such as choosing wheat varieties more suited for bread and biscuit making rather than pastry and cakes, for instance."

Society has so far remained unwilling to make the drastic reductions in fossil fuel use needed to cut carbon dioxide emissions, Ridgwell explained. Therefore, scientists are looking for alternatives that might help avert "dangerous" climate change.

One set of strategies, called "geoengineering," envisages the creation of novel technological devices that will act as artificial trees to extract carbon dioxide from the air and planetary-scale engineering schemes to manipulate the earth's energy budget-for instance, injecting reflective aerosols into the atmosphere or constructing a sunshade in space.

"Such schemes would generally be fantastically expensive and require a close cooperation and agreement globally that continued for decades," Ridgwell said.

His team suggests their "bio-geoengineering" approach as a more immediately practical option. Indeed, global agriculture already produces a cooling of climate because crop plants tend to reflect more sunlight back out to space than the natural vegetation they have replaced.

By specifically selecting crop varieties with even higher reflectivity, a property known as albedo, that effect might be increased enough to lower the air temperature even further.

They say the climate control strategy could help reduce the severity of agricultural and health impacts of heat waves as well as droughts in some regions of the world, and at very little cost.

Ultimately, further regional cooling of climate could be achieved through selective breeding of plants with even greater reflective properties than those now available or by genetically modifying crop plants to optimize their albedo.

"The continuing lack of international agreement in substantially limiting or curbing carbon dioxide emissions is driving the state of the climate system closer to suspected points of catastrophic, or at least extremely costly, changes, including sea-level rise and ecosystem disruption," Ridgwell said.

"Our proposal cannot provide a full solution to climate change, but it can reduce the severity of agricultural and health impacts of heat waves as well as droughts in much of central North America and mid-latitude Eurasia.

"Thus, while it is not a substitute for carbon dioxide emissions reductions, considering its relatively low cost, albedo bio-geoengineering could be employed as a temporary measure for helping reduce climate change impacts."

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