According to a study conducted by David Lobell, researcher of the Lawrence Livermore National Laboratory in the US, from 1981-2002 fields of wheat, corn and barley throughout the world have produced a combined 40 million tonnes less per year because of increasing temperatures caused by human activities.
Though the impacts are relatively small compared to the technological yield-gains over the same period, the results demonstrate that negative impact of climate trends on crop yields at the global scale are already occurring.
Most experts believe that adaptation by farmers to climate change would lag several years behind climate trends, because of the difficultly in distinguishing climate trends from natural variability.
A key to move forward is to study how well cropping systems can adapt to a warmer
world. Investments in this area could potentially save billions of dollars and millions of lives.
The importance of this study was that it demonstrated a clear and simple relationship at the global scale, with yields dropping by approximately 3-5 per cent for a 1 degree Fahrenheit increase.
This is the first study to estimate how much global food production already has been affected by climate change. Annual global temperatures increased by about 0.7 degrees Fahrenheit between 1980 and 2002, with even larger changes observed in several regions.
Climate effects on the six most widely grown crops in the world - wheat, rice, maize (corn), soybeans, barley and sorghum (a genus of about 30 species of grasses raised for grain) - were studied.
Production of these crops accounts for more than 40 per cent of global cropland area, 55 per cent of non-meat calories and more than 70 per cent of animal feed.