A study of the relationship between temperature and yields of various rice varieties, based on 50 years of weather and rice-yield data from farms in the Philippines, suggests that warming temperatures negatively affect rice yields.
Recent varieties of rice, bred for environmental stresses like heat, showed better yields than both traditional rice varieties and modern varieties of rice that were not specifically bred to withstand warmer temperatures. But the study found that warming adversely affected crop yields even for those varieties best suited to the heat. Overall, the advantage of varieties bred to withstand increased heat was too small to be statistically significant.