What was done
Noting that "responses to elevated CO2 may differ at different temperature levels and that a potential reduction in yield due to high temperatures" is "very relevant," the authors grew well watered and fertilized cotton (Gossypium hirsutum L.) plants from seed to maturity -- one plant to each container of washed sand, with spacing between plants similar to the plant spacing found in typical cotton fields -- within the Georgia Envirotron (located at the University of Georgia Griffin Campus), where they were placed within chambers maintained at all combinations of two day/night air temperatures regimes (25/15°C and 35/25°C) and three atmospheric CO2 concentrations (400, 600 and 800 ppm), during which time, as well as at the end of the study, various plant characteristics were measured.

What was learned
In terms of final yield, Yoon et al. report that at the lower of the two air temperature regimes, "final boll weight at harvest was 1.59 times (at 600 ppm) and 6.3 times (at 800 ppm) higher compared to ambient CO2," and they say that "increasing the temperature increased this difference, as the final boll weight was 34.1 times (at 600 ppm) and 23.3 times (at 800 ppm) higher compared to ambient CO2." In addition, they state that "the response of final lint yield to CO2 was more or less similar to the response of boll weight."

What it means
Both higher air temperatures and higher atmospheric CO2 concentrations -- individually and in combination -- were a great boon to cotton productivity in this well-controlled study, demonstrating that in this experiment not only were the "twin evils" of the radical environmentalist movement not detrimental to cotton growth and development, they were almost unbelievably beneficial.