Carbon Dioxide and Agricultural Yield: An Assemblage and Analysis of 430 Prior Observations1

Abstract The probable effect of the increasing global atmospheric CO 2 concentration on agricultural yields was evaluated. More than 430 observations of the yield of 37 species grown with CO 2 enrichment were extracted from more than 70 reports published during the past 64 years. Most of the studies were performed in greenhouses or growth chambers. Open fields might respond less than greenhouses or growth chambers to increased CO 2 because nutrient levels in general world‐wide agriculture are lower than those in the indoor studies, or open fields might respond more because light levels are generally higher outside. The data also were dominated by high value crops, but results should be applicable to the three‐fourths of the world agriculture represented by the C 3 crops and possibly to the remaining C 4 crops as well. Keeping these limitations of the data in mind, the analysis showed that yields probably will increase by 33% (with a 99.9% confidence interval from 24 to 43%) with a doubling of atmospheric CO 2 concentration.