In 2012-2013, 701 million tons of wheat were harvested all over the world. Climate change can cut that number, however, by 42 million tons for every degree Celsius the temperature goes up, says a study published in the journal Nature Climate Change.

According to their findings, researchers found that wheat yields will drop by 6 percent each year every time temperatures increase by a degree if extreme fluctuations in weather are not addressed. This kind of drop in production is equivalent to a quarter of the world's wheat trade, a dramatic reduction considering the world actually needs to increase its food supply to feed billions.

Researchers tested 30 models of wheat crops systematically for the study, comparing them to field experiments conducted in areas where growing seasons have an average temperature range between 15 and 32 degrees Celsius. Taking into account planting dates and rates, temperatures and other factors for crop management, the models gave researchers an idea as to how temperature changes affect wheat, allowing them to make production predictions based on these changes.

It's alarming that climate change's effects are being felt sooner but researchers pointed out that global warming is not just the problem. More aptly, attention must be placed on extreme temperatures, which will also mean the cold.

"Simply looking at the average temperature doesn't really show us anything because it's the extremities that are more detrimental to crops," explained Vara Prasad, USAID Feed the Future Sustainable Intensification Innovation Lab director and one of the authors for the study.

Researchers also saw that increases in temperature leads to shorter time for wheat plants to mature properly and produce full heads to be harvested, resulting in each plant producing less grain.

Prasad uses filling a glass of water as an analogy. Say, having ideal conditions is akin to having a minute to fill the glass with water. Challenges presented by climate change will be like just having 40 seconds to fill the glass with water, with water supply running low.

The kind of research Prasad and colleagues do will help in refining crop models to produce more accurate predictions about wheat yield. This will also aid farmers in choosing wheat varieties better suited given challenges and production goals to be met as well as determining best planting dates to minimize the effects of extreme weather during growing season.

In the United States, Kansas produces the most wheat, growing more than 9 million acres of the grain in 2014.

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