Background
The authors note that "China's agriculture has to feed more than one-fifth of the world's population, and, historically, China has been famine prone."  As an example of the latter, they report that "as recently as the late 1950s and early 1960s a great famine claimed about thirty million lives (Ashton et al., 1984; Cambridge History of China, 1987)."

What was done
Investigating how climate in different places affects the value of farmland via the methodology of Mendelsohn et al. (1994), Liu et al. calculated detailed estimates of the economic impact of predicted climate change on agriculture in China, utilizing county-level agricultural, climate, social, economic and edaphic data for 1275 agriculture-dominated counties for the period 1985-1991, together with the outputs of three general circulation models of the atmosphere based on five different scenarios of anthropogenic CO2-induced climate change that yielded a mean countrywide temperature increase of 3.0°C and a mean precipitation increase of 3.9% for the year 2050 relative to the present.

What was learned
In the mean, Liu et al. determined that "all of China would benefit from climate change in most scenarios."  In addition, they state that "the effects of CO2 fertilization should be included, for some studies indicate that this may produce a significant increase in yield," an increase, we would add, that is well established and was not included in their analysis.

What it means
Acting together, the increases in Chinese agricultural productivity estimated to result from the direct effects of increased anthropogenic CO2 emissions plus the changes in temperature and precipitation typically predicted to result from these emissions could well spell the difference between whether China's growing population will or will not be able to adequately feed itself at the midpoint of the current century, which may also spell the difference between whether the world of that day will be peaceful or embroiled in conflict.

References
Ashton, B., Hill, K., Piazza, A. and Zeitz, R.  1984.  Famine in China, 1958-1961.  Population and Development Review 10: 613-615.

Cambridge History of China.  1987.  Volume 14.  Cambridge University Press, Cambridge, UK.

Mendelsohn, R., Nordhaus, W.D. and Shaw, D.  1994.  The impact of global warming on agriculture: A Ricardian analysis.  American Economic Review 84: 753-771.