Climate data can help predict some crop failures several months before harvest, according to a new study from an international team, including scientists from the University of Leeds and US Space Agency NASA.

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Scientists at NASA's Goddard Space Centre found that in about one-third of global cropland, temperature and soil moisture have strong relationships to the yield of wheat and rice at harvest. For those two key crops, a computer model could predict crop failures three months in advance for about 20 percent of global cropland.

The scientists who made the discovery published their findings this month in the journal Nature Climate Change. Molly Brown, one of the researchers, explained, "You can estimate ultimate yields according to the climatic condition several months before. From the spring conditions, the preexisting conditions, the pattern is set."

If the reliability and timeliness of crop failure forecasts could be demonstrated, the researchers said they could be used to help governments, insurers and others to plan accordingly.

Testing the forecasting

To test this, a research team led by Toshichika Iizumi of the National Institute for Agro-Environmental Sciences in Tsukuba, Japan used modelling from 1983 to 2006, and factored in satellite observations, temperature and precipitation forecasts to examine the reliability of their forecasts. They did this by measuring how well their data predicted the crop yield or crop failure that actually occurred at the end of each season. So, by looking at the temperature and soil moisture in June of a given year, they hoped to accurately predict the success of a corn harvest in August and September.

The team studied four crops (corn, soybeans, wheat and rice), and found their model predicted wheat and rice yields most accurately. They found that, with these crops, the model could also be used to forecast relatively minor yield changes, not just devastating crop failures brought about by severe droughts or other weather extremes.

Leeds Univeristy's Andy Challinor said, "The impact of climate extremes – the kind of events that have a large impact on global production – is more predictable than smaller variations in climate, but even variations of 5 percent in yield were correctly simulated in the study for many parts of the globe."

Professor Challinor said the research could potentially encourage communities and governments to invest in the infrastructure needed to take advantage of favourable years. If satellite data and climate models forecast a good season for rice before seeds are even planted, farmers or communities could get loans to invest in technologies to benefit from such conditions, while insurers could keep insurance premiums low.

On the other hand, if the forecast predicts a poor growing season, the loans would be smaller and insurance premiums larger. The researchers hope it could work as both a social safety net for agricultural communities, as well as encouraging communities and governments to invest in the infrastructure needed to take advantage of those good years.

Which has the more significant effect on yields: Climate or economics?

NASA's Dr Brown qualified that, while climate's role in crop yields and failures may seem intuitive, it's difficult to demonstrate how large a role it plays, partly because of the overwhelming influence of social and economic factors.

She explained factors such as available agricultural technology, fertiliser, seeds and irrigation infrastructure, are key to determining how much a farmer can grow. She used the example of farmers in the United States, who can grow around 10 times more corn per acre than farmers in Zimbabwe, but said that although economics is currently believed to 'set the bar', other factors – including climate – can still cause variations that lead to good years and bad, and that climate could play a larger role everywhere in years to come.

Dr Brown said part of the research using the forecasting model would also go to determine just how much of an effect the weather has on yield. She elaborated, "We're trying to bound how much the weather matters. For particular crops in particular places it makes a huge difference, especially with wheat yield."

Dr Brown added that she hopes the research will form "an initial step" in a much larger effort to allow farmers in poorer countries to reap better harvests in years with good growing conditions, and build resiliency for the other years. "We can make a new framework that would allow much greater exploitation of satellite data and climate prediction models; if you knew you were going to have a good year, you could plan, you could give out loans, you could do other things to boost food production to be prepared for bad years," she said.