Two global changes that directly alter crop productivity are rising carbon dioxide concentration ([CO₂]) and rising tropospheric ozone concentration ([O₃]).  While elevated [CO₂] directly stimulates productivity in C₃ crops, rising tropospheric [O₃] negatively impacts photosynthesis and subsequent growth and production.  Free Air Concentration Enrichment (FACE) provides a means to fumigate large plots of vegetation (~200-350 m²) with enriched concentrations of CO₂ and O₃, without disturbing the soil-plant-atmosphere continuum.  The size of FACE plots enables a broad range of experiments, from gene expression studies to yield trials.  Major food crops including maize (Zea mays), sorghum (Sorghum bicolor), rice (Oryza sativa), wheat (Triticum aestivum) and soybean (Glycine max), have been grown at elevated CO₂ concentrations anticipated for the middle of this century (~500-600 ppm) in FACE experiments.  We used meta-analysis to quantitatively review the responses of crops to elevated [CO₂].  Both C₃ and C₄ crops had reduced stomatal conductance to water vapor at elevated [CO₂]; however, there was little evidence that this response is caused by decreased stomatal density.  Light saturated photosynthesis was stimulated by 13% in C₃ crops grown at elevated [CO₂], and was unaffected by [CO₂] in C₄ crops.  These changes in carbon gain fed forward to biomass and yield, which were both modestly higher in C₃ crops grown at elevated [CO₂] and unaffected in C₄ crops.  While meta-analyses allow mean responses to be distilled from diverse studies, they are limited by available data. FACE studies of major food crops have only been done in a handful of locations around the globe.  Further, rising carbon dioxide is only one element of global climate change.  Crops will also be challenged with rising tropospheric [O₃], warmer temperatures, altered precipitation patterns and changes in pests and pathogens.  One of the future challenges for FACE experiments is to include other aspects of global change.