What was done
The authors derived trends in the frequencies of warm days and nights, cool days and nights, and hot days and frost days for the whole of China for the period 1951-1999, based on daily surface air temperature data obtained from approximately 200 weather observation stations scattered across the country.

What was learned
Over the period of record, and especially throughout the 1980s and 90s, there were increases in the numbers of warm days and nights, while there were decreases in the numbers of cool days and nights, consistent with an overall increase in mean daily temperature.  At the extreme hot end of the temperature spectrum, however, the authors report that "the number of days with daily maximum temperature above 35°C showed a slightly decreasing trend for China as a whole."  But at the extreme cold end of the spectrum, the number of frost days with daily minimum temperature below 0°C declined at the remarkable rate of 2.4 days per decade.

What it means
There has been a significant amelioration of temperature extremes in China over the past half-century, with a slight decrease in the number of hot days and a large decrease in the number of frost days.  In terms of human health, these changes are extremely beneficial; for as is made abundantly clear in the many scientific journal articles we have reviewed in the Health Effects (Temperature) section of our Subject Index, extreme cold is by far a greater cause of death in humans than is extreme heat.  And it is extreme cold weather that has been reduced in China, without any concomitant increase in extreme hot weather.  Clearly, global warming has been good for the health of the people of China.