Percentage yield change as a function of temperature for the three major crops and for temperate and tropical regions for local mean temperature changes up to 5.5 degrees.  Shaded bands indicate the 95 percent confidence interval of regressions consistent with the data based on 500 bootstrap samples, which indicate use of the full datase (blue) or the subset of data used in AR4 (orange). Graphic: Challinor, et al., 2014 / doi:10.1038/nclimate2153

16 March 2014 (PhysOrg) – A study led by the University of Leeds has shown that global warming of only 2°C will be detrimental to crops in temperate and tropical regions, with reduced yields from the 2030s onwards.

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

"Furthermore, 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."

The study, published today by the journal Nature Climate Change, feeds directly into the Working Group II report of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, which is due to be published at the end of March 2014.

In 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.

Due to increased interest in climate change research, the new study was able to create the largest dataset to date on crop responses, with more than double the number of studies that were available for researchers to analyse for the IPCC Fourth Assessment Report in 2007.

In the Fourth Assessment Report, scientists had reported that regions of the world with temperate climates, such as Europe and most of North America, could withstand a couple of degrees of warming without a noticeable effect on harvests, or possibly even benefit from a bumper crop.

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

"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," concludes Professor Challinor. [more]

Climate change will reduce crop yields sooner than we thought


ABSTRACT: Feeding a growing global population in a changing climate presents a significant challenge to society1, 2. The projected yields of crops under a range of agricultural and climatic scenarios are needed to assess food security prospects. Previous meta-analyses3 have summarized climate change impacts and adaptive potential as a function of temperature, but have not examined uncertainty, the timing of impacts, or the quantitative effectiveness of adaptation. Here we develop a new data set of more than 1,700 published simulations to evaluate yield impacts of climate change and adaptation. Without adaptation, losses in aggregate production are expected for wheat, rice and maize in both temperate and tropical regions by 2 °C of local warming. Crop-level adaptations increase simulated yields by an average of 7–15%, with adaptations more effective for wheat and rice than maize. Yield losses are greater in magnitude for the second half of the century than for the first. Consensus on yield decreases in the second half of the century is stronger in tropical than temperate regions, yet even moderate warming may reduce temperate crop yields in many locations. Although less is known about interannual variability than mean yields, the available data indicate that increases in yield variability are likely.

A meta-analysis of crop yield under climate change and adaptation

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