What was done
The authors used the agrometeorological model of Doorenbos and Kassam (1994) "to estimate sugarcane yield in tropical southern Brazil, based on future A1B climatic scenarios presented in the fourth Intergovernmental Panel on Climate Change report," first calculating potential productivity, which considers "the possible impacts caused by changes in temperature, precipitation, sunshine hours and CO2 concentration in the atmosphere, as well as technological advances," and then actual productivity, which additionally accounts for the yield-reducing effects of water stress.

What was learned
Gouvea et al. calculate that "potential productivity will increase by 15% in relation to the present condition in 2020, by 33% in 2050 and by 47% in 2080," and that "actual productivity will increase by 12% in relation to the present condition in 2020, by 32% in 2050 and by 47% in 2080." Of these productivity gains, they further indicate that the portions due to expected technological advances, including the development of new varieties and best management practices, will account for 35% of the yield gains in 2020, 51% in 2050, and 61% in 2080.

What it means
It is intriguing that in spite of all of the doom-and-gloom prognostications that typically emanate from the climate-modeling camp, this modeling exercise suggests "there will be," in the words of the four researchers, "a beneficial effect of forecasted climate changes on sugarcane productivity, due to the expected increases in temperature and CO2 concentration [italics added]."

Although correct, this conclusion seems a bit unusual, especially when it is realized that the crop growth-promoting factors (rising air temperatures and CO2 concentrations) are the abominable twin evils of the climate-alarmist crowd. Then again, it is probably not all that surprising, since the Brazilian scientists who conducted the work state that "in Brazil, the sugarcane industry presents an important opportunity for the replacement of fossil fuels," which is a climate-alarmist-sponsored policy.

Does this mean that the two growth-promoting factors are providing an "important opportunity" for humanity to ultimately weaken their beneficial impacts by enacting policies that actually diminish their strength (i.e., reduce their rates of increase) via an augmented use of biofuels? Things can get complicated, indeed, when the economies of nations are thrown into the mix of already highly politicized and debatable science.

Reference
Doorenbos, J. and Kassam, A.H. 1994. Efeito da agua no rendimento das culturas. Campina Grande: UFPB. Estudos FAO Irrigacao e Drenagem.