Nonlinear temperature effects indicate severe damages to US crop yields under climate change
Nonlinear temperature effects indicate severe damages to US crop yields under climate change
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DOI：
10.1073/pnas.0906865106
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发表时间：
2009-09-15
影响因子：
11.1
通讯作者：
Roberts, Michael J.
中科院分区：
文献类型：
--
作者：
Schlenker, Wolfram;Roberts, Michael J.
美国生产全球41%的玉米和38%的大豆。这些作物是四种最大的热能来源中的两种，因此对世界粮食供应至关重要。我们将这两种作物的县级产量面板，加上棉花（一种温暖气候的作物），与一个新的精细尺度天气数据集配对，该数据集包含了生长季节每天和所有日子的温度分布。我们发现，玉米的产量随着温度的升高而增加，玉米为29摄氏度，大豆为30摄氏度，棉花为32摄氏度，但温度超过这些阈值是非常有害的。在最佳值以上的下降斜率比在最佳值以下的下降斜率明显更陡。当我们分离温度和产量的时间序列或横截面变化时，也发现了同样的非线性和不对称关系。这表明，历史上种子品种或管理做法对温暖气候的适应有限，因为横截面包括农民对温暖气候的适应，而时间序列则没有。在Hadley III模型中，保持当前种植区域不变，在最慢（B1）变暖情景下，面积加权平均产量预计在世纪结束前下降30-46%，在最快变暖情景下（A1 FI）下降63-82%。
The United States produces 41% of the world's corn and 38% of the world's soybeans. These crops comprise two of the four largest sources of caloric energy produced and are thus critical for world food supply. We pair a panel of county-level yields for these two crops, plus cotton (a warmer-weather crop), with a new fine-scale weather dataset that incorporates the whole distribution of temperatures within each day and across all days in the growing season. We find that yields increase with temperature up to 29 degrees C for corn, 30 degrees C for soybeans, and 32 degrees C for cotton but that temperatures above these thresholds are very harmful. The slope of the decline above the optimum is significantly steeper than the incline below it. The same nonlinear and asymmetric relationship is found when we isolate either time-series or cross-sectional variations in temperatures and yields. This suggests limited historical adaptation of seed varieties or management practices to warmer temperatures because the cross-section includes farmers' adaptations to warmer climates and the time-series does not. Holding current growing regions fixed, area-weighted average yields are predicted to decrease by 30-46% before the end of the century under the slowest (B1) warming scenario and decrease by 63-82% under the most rapid warming scenario (A1FI) under the Hadley III model.