Crops yields, especially in temperate climates such as North America and Europe, will be affected by climate change much earlier than predicted and with only a slight change in temperatures, according to a new international study.

The  study, led by Andy Challinor at the University of Leeds in England, says global warming of only 2 C will be detrimental to crops in temperate and tropical climates starting around the 2030s.

“Our research shows that crop yields will be negatively affected by climate change much earlier than expected,” writes Challinor in the journal Nature Climate Change.

"The impact of climate change on crops will vary both from year to year and from place to place – with the variability becoming greater as the weather becomes increasingly erratic.”

Previous predictions had forecast that temperate climates could withstand a couple of degrees of warming without a noticeable effect on crops.

This new study refutes that.

“We’ve seen a shift in consensus,telling us that the impacts of climate change in temperate regions will happen sooner rather than later,” noted Challinor.

According to the study, the greatest impact will be in the second half of the century, when decreases of more than 25 per cent will become increasingly common. 

Researchers from Australia, Colombia, the United States and the United Kingdom combined and compared results from 1,700 published reports of how climate change has affected yields of corn, wheat and rice.

The researchers says their analyses comes from the largest data set to date on crop responses.

In conclusion, the researchers said there is a need for greater innovations soon to safeguard crops for future generations.

"Climate change means a less predictable harvest, with different countries winning and losing in different years. The overall picture remains negative," they wrote.