Sorry, Paul Ehrlich and fellow alarmists.
Theoretical and Applied Climatology
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| Note to Paul Ehrlich: Note the dip in corn yields during the ice age scare of the 1970's |
The impacts of long-term and year-to-year temperature change on corn yield in China
Qi Zhang, Jiquan Zhang, Enliang Guo, Denghua Yan, Zhongyi Sun
Abstract: Impacts of climate change on crop yield can be divided into long-term and year-to-year impacts. The goal of this study is to evaluate whether the long-term and the year-to-year impacts are different using historical datasets. Data on corn yields for 1961–2005 in Jilin and Anhui, located in northeastern and Mideastern China, respectively, are combined with datasets on temperature to build the statistical regression models for evaluation of the impacts of long-term and year-to-year temperature change on corn yield. Over half of the yield trends result from non-climatic factors, such as management and technology. Corn yields could increase threefold (measured by method 1) or twofold (method 2) as long-term temperature increased per degree centigrade. And agriculture in northeastern China has benefitted from climate warming. But the year-to-year temperature change could only result in 12 % yield increase, almost 20 times less than the impacts of long-term temperature change. We conclude that the impacts of long-term and year-to-year temperature change on crop yield are quite different. So, the models derived from year-to-year variations cannot be applied to assess the impacts of long-term climate change.
Qi Zhang, Jiquan Zhang, Enliang Guo, Denghua Yan, Zhongyi Sun
Abstract: Impacts of climate change on crop yield can be divided into long-term and year-to-year impacts. The goal of this study is to evaluate whether the long-term and the year-to-year impacts are different using historical datasets. Data on corn yields for 1961–2005 in Jilin and Anhui, located in northeastern and Mideastern China, respectively, are combined with datasets on temperature to build the statistical regression models for evaluation of the impacts of long-term and year-to-year temperature change on corn yield. Over half of the yield trends result from non-climatic factors, such as management and technology. Corn yields could increase threefold (measured by method 1) or twofold (method 2) as long-term temperature increased per degree centigrade. And agriculture in northeastern China has benefitted from climate warming. But the year-to-year temperature change could only result in 12 % yield increase, almost 20 times less than the impacts of long-term temperature change. We conclude that the impacts of long-term and year-to-year temperature change on crop yield are quite different. So, the models derived from year-to-year variations cannot be applied to assess the impacts of long-term climate change.
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