London, March 17 (IANS): Global warming of only 2oC will harm crops in many parts of the world, reducing yields from the 2030s onwards - much sooner than predicted earlier.

A study, published in the latest issue of journal 'Nature Climate Change', contends that the impact of climate change on crops will vary both from year-to-year and geographically, with the variability becoming greater as the weather becomes more and more erratic.

However, crops in the temperate and tropical regions of the world are expected to bear the brunt of climate change.

Said Andy Challinor of the School of Earth and Environment at the University of Leeds and lead author of the study: "Our research shows that crop yields will be negatively affected by climate change much earlier than expected."

The study feeds directly into the Working Group II report of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, to be published at the end this month.

For the study, the researchers created a new data set by combining and comparing results from 1,700 published assessments of the response that climate change will have on the yields of rice, maize and wheat.

In the earlier, Fourth Assessment Report, scientists had contended that temperate climates such as Europe and most of North America could withstand a couple of degrees of warming without a noticeable effect on harvests.

"As more data have become available, we've seen a shift in consensus, telling us that the impact of climate change in temperate regions will happen sooner rather than later," said Challinor.

The researchers state that we will see, on average, an increasingly negative impact of climate change on crop yields from the 2030s onwards. The impact will be greatest in the second half of the century, when decreases of over 25 percent will become increasingly common.

Thus, later in the century, greater agricultural transformations and innovations will be needed in order to safeguard crop yields for future generations.

"Climate change means a less predictable harvest, with different countries winning and losing in different years. The overall picture remains negative, and we are now starting to see how research can support adaptation by avoiding the worse impacts," said Challinor.