Paper Reviewed
Attavanich, W. and McCarl, B.A. 2014. How is CO2 affecting yields and technological progress? A statistical analysis. Climatic Change 124: 747-762.

In an intriguing study published in Climatic Change, Attavanich and McCarl (2014) describe how they analyzed the impacts of climate, crop production technology and atmospheric carbon dioxide (CO2) enrichment on current and future crop yields, which they did with the help of "an econometric model estimated over pooled historical data for 1950-2009 and data from free-air CO2 enrichment experiments."

Their primary econometric findings, to quote the two researchers, were that (1) "yields of C3 crops (soybeans, cotton and wheat) directly respond to the elevated CO2, while yields of C4 crops (corn and sorghum) do not, but they are found to indirectly benefit from elevated CO2 in times and places of drought stress," that (2) "ignoring atmospheric CO2 in an econometric model of crop yield likely leads to overestimates of the pure effects of technological progress on crop yields," in light of the fact that "CO2 contributes about 51, 15, 17, 9 and 1% of yield growth of cotton, soybeans, wheat, corn and sorghum, respectively," and that (3) in terms of projections, "the effect of CO2 fertilization generally outweighs the effect of climate change on mean crop yields in many regions, resulting in an increase of 7-22, 4-47, 5-26, 65-96 and 3-35% for yields of corn, sorghum, soybeans, cotton and wheat, respectively."

Consequently, and in light of the likelihood that the human population of the planet will reach nine billion by 2050, and that the demand for food is likely to more than double over this time period (Muldowney et al., 2013), it would seem to be the better part of prudence to not strive so adamantly to curtail anthropogenic CO2 emissions, as they may actually be needed to prevent an unimaginable holocaust of starvation somewhere on the temporal path of getting from here to there.

Reference
Muldowney, J., Mounsey, J. and Kinsella, L. 2013. Agriculture in the climate change negotiations; ensuring that food production is not threatened. Animal 7:s2: 206-211.