The crops, spread across North America and Europe, would send a small percentage of the sun's light and heat back into space.
Different strains of crops such as wheat have different levels of reflectivity, or albedo, say scientists. Selecting those that reflect the most could make summers in Europe more than 1 per cent cooler, they claim.
Lead researcher Dr Joy Singarayer, from the University of Bristol, said: "The concept of using reflectivity to manipulate our climate is an ancient one - humankind has for centuries painted settlements white to reflect the sun and keep cool.
"We could now do this on a much bigger scale via our agricultural plantations."
The findings will be outlined in London today at the Royal Society discussion meeting entitled Geoengineering - Taking Control of our Planet's Climate.