NOAA 2001-107
Contact: Pat Viets

Data Shows Effect of Climate Conditions on Corn and Soybean Yield
and Residential Energy Needs

The Commerce Department's National Oceanic and Atmospheric Administration today unveiled two new indices that evaluate the effect of climate conditions on corn and soybean yield and on residential energy needs. The development of the indices is part of NOAA's "Environomics" program, an effort to better understand the impact of weather and climate on socioeconomic sectors of the nation.

The indices were developed by NOAA's National Climatic Data Center in Asheville, N.C., which maintains the world's largest weather database.

Anecdotal statements about the weather are often used to explain variations in economic activity, and these statements are often based on perceptions about the weather that may or may not be valid. Through NOAA's Environomics program, relationships between the nation's climate and vital economic sectors of the nation are clearly defined using climate indices, which enhance the understanding of how year-to-year variations and trends in weather and climate affect associated sectors.

Thomas Karl, director of NOAA's National Climatic Data Center, said, "Climate indices developed through the Environomics program provide quantitative information regarding climate's influence while providing historical perspective on how weather and climate conditions affecting our economy and society today compare with conditions of the past."

The period of high energy demand and prices of the late 1970's coincided with extremely cold winters that contributed to higher residential energy usage. The Residential Energy Demand Temperature Index (REDTI), which provides information related to climate sensitive residential energy demand, reflects this increased demand through historically high index values and can be used in part to explain the cause of the historically high energy demand of that time. By providing continuing updates to the index, a clearer understanding of future fluctuations in energy demand will be possible.

The REDTI tracks both unusually hot and unusually cold conditions. It varies from year to year due to variability and trends in temperature, and it responds most strongly to temperature conditions in heavily populated regions. REDTI values range from 0 to 100. Values greater than 90 indicate a much above average temperature-related energy demand and values less than 10 reflect much below average conditions.

The REDTI for the 2001 April-September season was 34, indicative of slightly below average residential energy demand for cooling and heating. Based on the 107 year record, the population-weighted REDTI value of 34 ranks as the 19th lowest value.

The nation's warm season (April-September) 2001 ranked as the fourth warmest such period since 1895, the first year of complete climate records. The preliminary national average temperature was 67.4 F (19.7 C), which was 1.6 F (0.9 C) above the long-term mean. Although the area-weighted national temperature gave the season a rank of fourth warmest on record, the persistence of average to cooler than average temperatures in some of the most heavily populated regions of the U.S. contributed to a REDTI that was below average. Energy usage statistics for 2001 will be available from the Department of Energy's Energy Information Administration in 2002.

While the REDTI provides information on the impacts of temperature on energy demand, the Crop Moisture Stress Index, was developed to quantify the effect of soil moisture conditions on crop yield. It provides historical perspective on conditions such as moisture stress, that are closely associated with corn and soybean yields and is a source of information for explaining the cause of lower national yields.

The CMSI ranges from zero to 100 and specifically measures the proportion of the nation's corn or soybeans affected by severe to catastrophic drought or catastrophic wetness. Values near zero indicate that few productive corn or soybean growing areas were affected by severe drought or catastrophic wetness. This index reflects conditions during July and August and is weighted by the mean (1991-2000) annual crop productivity within 344 climate divisions in the contiguous U.S. Although a number of factors affect the success of a single crop growing season, drought or excessive wetness during critical phases of crop growth have a significant impact on the nation's corn and soybean yield.

Although warmer than average temperatures coincided with drought in some parts of the country during the warm season months of 2001, conditions in the heart of the major corn and soybean crop growing regions were generally normal to wetter than normal. The corn CMSI for the 2001 crop growing season was eight, and the soybeans CMSI was seven. This means that severe to catastrophic drought or catastrophic wetness affected only 8 percent and 7 percent of the nation's corn and soybeans, respectively. Both index values were below average and reflect favorable soil moisture throughout a large part of the crop growing regions during July and August (the reproductive season).

The CMSI for corn exceeded 40 during the drought-plagued growing seasons of 1983 and 1988 and 30 during the catastrophically wet summer of 1993, years in which corn yields were less than 75 percent of the 2000 yield. The 2001 growing season (May-September) followed several years in which national corn and soybean yields were generally high, according to the U.S. Department of Agriculture. The low values of this year's corn and soybean CMSI indicate that conditions associated with this index were again favorable for good corn and soybean yields. National crop yields for 2001 will be available from the department of agriculture following the harvest season.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation's coastal and marine resources.

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Note to Editors: Additional data for the September and April-September season are online at

More information about the calculation of NOAA's Environomics indices and the most recent values are available at