However, the magnitude of increase at our site was greater than the global trend determined over the 1950–1993 period (11). The larger increase in temperature observed at the IRRI Farm may reflect the stronger trace-gas-induced warming during the last quarter of the 20th century. No significant trend was observed for mean maximum temperature in the dry season (January to April) although mean maximum temperature in the wet season (June to September) increased slightly (Fig. 1 D and G ). Mean minimum temperature increased by 1.33°C in the dry season and by 0.80°C in the wet season from 1979 to 2003 (Fig. 1 E and H ). Mean radiation also increased during the same period (Fig. 1 C, F, and I ). Radiation had a closer positive correlation with maximum temperature than with minimum temperature. In general, higher solar radiation leads to a higher maximum temperature and a lower minimum temperature because of radiative cooling. Our data suggest that nighttime warming could be greater if radiation remained stable. The temperature rise observed at our site was unlikely caused by the local air pollution, because these warming trends are consistent with temperature increases found elsewhere in the Philippines and globally (11, 15). Increase in night temperature was also observed at the Philippine Rice Research Institute Research Farm (Muñoz, Nueva Ecija, Philippines). Mean minimum temperature during the dry season increased 0.052°C per year at that site.