What was done
The authors assessed the rice yield impacts of climate-model-predicted CO2-induced climate changes in China's chief rice-producing regions based on the IPCC's B2 scenario of CO2 emissions growth and the CERES-rice model of crop productivity operating within the context of the predicted CO2 and climate changes over the course of the 21st century.

What was learned
In the summary section of their paper, Yao et al. report that "at most stations in the main rice areas of China, [the] B2 climate change scenario could bring negative effect[s] on rice yield," with "the simulated results indicat[ing] that not only mean rice yield would decrease, but also the probability [of] low yield and the variance of yield would increase." Likewise, they say the predicted "high probability in low yields also indicates an increasing frequency for continuous year[s] of low yield." Hence, they conclude "that B2 climate change would pose a threat in mean rice yield over decades, and bring a high risk and increased instability for inter-annual yield," which all sounds pretty depressing. However - and this is a huge however - in the results and discussion section of their paper, they let it be known that with the "CO2 direct effect on rice yield, rice yield increases in all selected stations [our italics]."

What it means
This study of China's future ability to produce its most important agricultural crop clearly indicates that, although speculative climate-change predictions of what may occur in the future are bleak indeed in terms of their negative impact on rice production, the tried-and-true effects of the anticipated future increase in the air's CO2 content on rice productivity are able to more than compensate for the negative impact of the predicted climate change, and to do so essentially everywhere throughout the country.