A man in a tractor prepares a field before sowing winter wheat near the village of Moskovskoye, north of Stavropol in southern Russia,. REUTERS/Eduard Korniyenko

Every degree of rise in local temperature could result in around 40 million tonnes of global yield reduction in wheat, amounting to a loss of a quarter of current global wheat production.

An international research consortium has calculated that the global wheat harvest is likely to be reduced by 6% per each degree Celsius of local temperature increase if no adaptation takes place.

Adaptation, such as cultivating more heat-tolerant wheat cultivars could substantially reduce climate change induced risks, the study concludes.

The research to which the Natural Resources Institute Finland also contributed has been published online in the journal Nature Climate Change.

The wheat grain yield declines are predicted for most regions in the world.

The researchers tested 30 different wheat crop models with field experiments where mean temperatures in the growing season ranged from 15 °C to 26 °C.

The temperature impact varied widely across field test conditions and year-to-year variability. Greater yield reductions were seen in warmer years and lesser reductions in cooler years.

Discrepancies between observation and simulation varied among individual models, whereby deviations increased with increasing growing season temperature.

Most reliable estimates of observed yields over the range of temperature regimes were achieved by using the multi-model ensemble median estimate.

"Increased yield variability is critical economically as it could weaken regional and global stability in wheat grain supply and food security, amplifying market and price fluctuations, as experienced during recent years," says Reimund Rötter from the Natural Resources Institute Finland.

Apart from Finland, scientists from Germany, France, Denmark, the Netherlands, Spain, UK, Columbia, Mexico, India, China, Australia, Canada and the US participated in the global study.

Earlier studies on crop yields
Research from the International Institute for Applied Systems Analysis has warned that increased temperature and changing precipitation levels, along with the increased CO2 atmospheric concentration could lead to between an 18% decline in global caloric production from cropland to as much as a 3% increase by 2050.

Risk of a major slowdown in crop production over the next 20 years has also been indicated in studies done by researchers from Stanford University and the National Center for Atmospheric Research.

A reduction in corn and wheat production will be 20 times higher than they would be without human-induced global warming.

Earlier last year, the UN's climate panel IPCC had issued a report saying that climate change had already begun to cut into the global food supply.

The rate of increase in crop yields is slowing, especially in wheat, and changes in temperature and rainfall patterns could lead to food price rise between 3% and 84% by 2050, the report said.

The fifth assessment report from the IPCC projects that the global mean temperature can rise up to 5 °Celsius by the end of this century.

Fossil fuel use and cement production contributed majorly to the 35.3 billion tonnes of carbon dioxide sent into the atmosphere during 2013, said the report "Trends in global CO2 emissions", released by PBL Netherlands Environmental Assessment Agency and the Joint Research Centre of the European Commission.