How large are the actual yield increases due to [CO2]? showed from an exhaustive survey of over 1000 chamber studies that elevation of [CO2] to 660 μmol mol−1 caused an average 33% increase in yields for C3 crops, with 99% confidence limits of 24–43%. This review will consider the effect of elevation to the estimated 2050 [CO2] of ca 560 μmol mol−1, which approximates the level used in large-scale FACE experiments with food crops. The 33% increase observed at 660 μmol mol−1 equates to 23% at 560 μmol mol−1 assuming a linear response, or 25% if a more realistic hyperbolic response with saturation of yield response at 2000 μmol mol−1 is assumed (table 1)