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Extreme Low-Temperature Events During Northeast China's Warm Season
Fengjin, X. and Lianchun, S. 2011. Analysis of extreme low-temperature events during the warm season in Northeast China. Natural Hazards 58: 1333-1344.

The authors write that "the damage from extreme low temperature events during the warm season in Northeast China is one of the major disasters that affect agriculture in China," noting that "rice, sorghum, corn, soybeans, and other major crops are all vulnerable to low-temperature damage."

What was done
Fengjin and Lianchun computed temporal trends in the frequency of occurrence of extreme minimum temperatures during Northeast China's warm season (May to September) over the period 1956-2005, while concurrently calculating trends in the region's annual average near-surface air temperature, after which they compared the former dependent trend with the latter independent trend.

What was learned
The two Beijing Climate Center researchers report that for the entire 1956-2005 period, the overall rate of increase in the annual average temperature was 0.32°C per decade; but they report that from 1970 to 2005 it was 0.49°C per decade, and that "from 1990, the increasing trend in the annual average temperature has become much more significant." Somewhat similarly, they found that "the average number of extreme minimum temperature days during the warm season in the 1950s was 15.8 days; in the 1960s, the average was 16.5 days; in the 1970s, the average increased to 17.3 days, and this was similar in the 1980s." However, they state that in the 1990s, the average "decreased sharply to 13.3 days," and they report that since 2000, the number of extreme minimum temperature days has been "decreasing constantly with an average of 11.4 days." Consequently, as warming has accelerated across Northeast China over the latter part of the past half-century, there has been a concomitant decrease in the number of extreme minimum temperature events during that region's warm season. And they say that a "decreased frequency of extreme low temperatures over the past few decades has also been reported in other regions, e.g., Australia and New Zealand (Salinger et al., 2000; Stone et al., 1996)."

What it means
With ever fewer extreme minimum temperature events occurring in response to the warmer temperatures of the past few decades, farmers in Northeast China have been able to harvest greater amounts of rice, sorghum, corn, soybeans and other major crops than would otherwise have been possible, thanks to the warming experienced in that particular part of the world.

Salinger, M.J., Stigter, C.J. and Das, H.P. 2000. Agrometeorological adaptation strategies to increasing climate variability and climate change. Agricultural and Forest Meteorology 103: 167-184.

Stone, R., Nicholls, N. and Hammer, G. 1996. Frost in NE Australia: trends and influence phases of Southern Oscillation. Journal of Climate 9: 1896-1909.

Reviewed 7 December 2011