What was done
Based on what is known about the effects of rising temperatures and atmospheric CO2 concentrations on plant growth and development, as well as what might be expected to occur in terms of future technological innovations, the authors estimated the impacts of these three phenomena on the yields of maize (Zea mays) and common beans (Phaseolus vulgaris) in Brazil, where the degree of global warming they investigated is that which is projected for the years 2050 and 2080 by the HadCM3 climate model when it is driven by the greenhouse gas concentration increases that are specified in the A2 scenario of the IPCC's Special Report on Emissions Scenarios.

What was learned
Costa et al. report that the warming conditions associated with increased greenhouse gases "lead to reductions in the potential productivity of maize and beans for the years 2050 and 2080 by up to 30%." However, they say that the CO2 fertilization effect is expected to overcome the negative response to warming and lead to a net increase in the productivity of common beans. In the case of maize, on the other hand, they find that "the CO2 fertilization feedback is much weaker and cannot cancel out the thermal effect." But when they include ever-evolving technology in the mix, they find that "appropriate soil and technological management as well as genetic improvements may very likely induce an increase in bean and maize yield despite the unfavorable future climate conditions."

What it means
Once again, human ingenuity -- aided by just one of the many positive biological effects of the ongoing rise in the air's CO2 content -- would appear to be capable of enabling the agricultural enterprise to continue to meet the world's food needs, even in the face of the unrealistically high temperature increases predicted by the IPCC to occur over the next several decades.