"Together, higher CO2 concentrations and warmer temperatures predicted for the end of this century will about double the amount of CH4 emitted per kilogram of rice produced.," explained Professor Chris van Kessel of the University of California in Davis and co-author of the study.

https://www.treehugger.com/climate-change/rice-growing-more-methane-climate-warms.html

Source:  https://www.sciencedaily.com/releases/2012/10/121021154455.htm

Regarding crop yield declines for rice, previously research on rice grown in Asia has shown that for every 1°C increase in minimum nighttime temperatures crop yields declined 10%.

https://www.treehugger.com/climate-change/rice-growing-more-methane-climate-warms.html