Corn yields in the United States and sea surface temperature anomalies in the equatorial pacific ocean during the period 1868–1982

Abstract The yearly variation of corn yield above or below the trend in the United States is shown to be closely associated with the occurrence of warm sea-surface temperature anomalies in the equatorial Pacific Ocean. Data for the past 115 years indicate that warmer than normal sea-surface temperatures in the equatorial Pacific Ocean are likely to coincide with above average corn yields in the United States. In the period 1868–1982 there have been fifty warm sea-surface temperature years as identified by Quinn et al. (1978). Examination of the yields on a state-by-state basis shows that Illinois has the strongest association and Iowa is second. For the 115-year record, Illinois and Iowa show a statistical level of significance in a chi square test at the 0.1% level. The adjacent states are at a much lower level. For the total U.S. corn yield which includes a much larger region the results are still significant at the 1.0% level. The results of this paper suggest that during the onset of a warm sea-surface temperature event there is a southerly displacement of the storm tracks during the growing season which modifies the climate so as to produce above average growth of the corn crop. It should be emphasized that these two climate anomalies occur concurrently. In fact, the maximum deviation from normal of the sea-surface temperatures occurs in the winter season after the corn crop has grown. Therefore, these results represent a correlation. The timing of the events suggests that the cause lies elsewhere.