These changes are indicative that sunshine durations, rather than increased greenhouse gases, were the "control knob" which decreased maximum temperatures and decreased daily temperature ranges throughout China, and opposite of the predictions of AGW theory and climate models.
Spatiotemporal change of diurnal temperature range and its relationship with sunshine duration and precipitation in China
Xiangjin Shen et al
We examined the spatiotemporal variation in diurnal temperature range (DTR) and discussed the reasons for the changes of DTR in China based on data from 479 weather stations from 1962 to 2011. Results showed that DTR decreased rapidly (0.291 C/decade) from 1962 to 1989 due to slightly decreased Tmax and significantly increased Tmin, but the decrease in DTR has stopped since 1990 as Tmax and Tmin kept pace with each other. During 1990-2011, DTR remained trendless, with slight increase in the 1990s and slight decrease after 2000. During the whole study period from 1962 to 2011, DTR decreased at a rate of 0.157 C/decade nationally. Spatially, decreases in DTR were greatest in Northeast China and lowest in Southwest China with a transect running from northeast to southwest showing the decreasing trends change from high to low. Seasonally, DTR decreases were greatest in winter and lowest in summer, and the magnitudes of decrease reduced from the north to south of China. The changes in DTR were closely correlated with changes in sunshine duration (SD) in China except the Tibetan Plateau, suggesting that SD decrease is an important contributor to the decrease of DTR through its influence on Tmax. In addition to the contribution of SD decrease, the increasing of precipitation played an important role in DTR decrease in Northwest China, the most arid region of China. It appeared that changes of cloud cover (CC) were not the reasons for DTR changes in the past 50 years as CC has decreased during the study period.
The authors examined 479 weather stations in China from 1962-2011 and find
"Results showed that DTR [daily temperature range] decreased rapidly (0.291 C/decade) from 1962 to 1989 due to slightly decreased Tmax [maximum temperatures] and significantly increased Tmin [minimum temperatures], but the decrease in DTR [daily temperature range] has stopped since 1990 as Tmax [maximum temperatures] and Tmin [minimum temperatures] kept pace with each other. During 1990-2011, DTR [daily temperature range] remained trendless, with slight increase in the 1990s and slight decrease after 2000. During the whole study period from 1962 to 2011, DTR [daily temperature range] decreased at a rate of 0.157 C/decade nationally."
"Seasonally, DTR [daily temperature range] decreases were greatest in winter and lowest in summer, and the magnitudes of decrease reduced from the north to south of China.
"The changes in DTR [daily temperature range] were closely correlated with changes in sunshine duration (SD) in China except the Tibetan Plateau, suggesting that SD [sunshine duration] decrease is an important contributor to the decrease of DTR [daily temperature range] through its influence on Tmax [maximum temperatures]."In addition, the authors find that "the most arid region of China" experienced "increasing of precipitation," the opposite of the debunked CAGW meme of "dry gets drier and wet gets wetter."
"In addition to the contribution of SD [sunshine duration] decrease, the increasing of precipitation played an important role in DTR [daily temperature range] decrease in Northwest China, the most arid region of China."
Similar to the findings of this paper, examination of the raw global temperature data [prior to tampering] shows a significant increase in minimum temperatures over the period 1962-1989, and then leveling off 1989-present. However, over the entire period 1940-present, there is no trend in minimum, maximum, or average global temperature anomalies.
Spatiotemporal change of diurnal temperature range and its relationship with sunshine duration and precipitation in China
Xiangjin Shen et al
We examined the spatiotemporal variation in diurnal temperature range (DTR) and discussed the reasons for the changes of DTR in China based on data from 479 weather stations from 1962 to 2011. Results showed that DTR decreased rapidly (0.291 C/decade) from 1962 to 1989 due to slightly decreased Tmax and significantly increased Tmin, but the decrease in DTR has stopped since 1990 as Tmax and Tmin kept pace with each other. During 1990-2011, DTR remained trendless, with slight increase in the 1990s and slight decrease after 2000. During the whole study period from 1962 to 2011, DTR decreased at a rate of 0.157 C/decade nationally. Spatially, decreases in DTR were greatest in Northeast China and lowest in Southwest China with a transect running from northeast to southwest showing the decreasing trends change from high to low. Seasonally, DTR decreases were greatest in winter and lowest in summer, and the magnitudes of decrease reduced from the north to south of China. The changes in DTR were closely correlated with changes in sunshine duration (SD) in China except the Tibetan Plateau, suggesting that SD decrease is an important contributor to the decrease of DTR through its influence on Tmax. In addition to the contribution of SD decrease, the increasing of precipitation played an important role in DTR decrease in Northwest China, the most arid region of China. It appeared that changes of cloud cover (CC) were not the reasons for DTR changes in the past 50 years as CC has decreased during the study period.
You just keep coming up with interesting papers, which is why I read this blog every day.
ReplyDeleteThanks very much for your kind words and insightful comments!
DeleteCan the decrease in cloud cover be reconciled with the decrease in sunshine duration?
ReplyDeleteWould you not expect a decrease in cloud cover to be accompanied by an INCREASE in sunshine duration? Unless, of course, the decrease in sunshine is due atmospheric pollution.
Yes you are correct, sunshine hours are hours of sunshine above some arbitrary brightness threshold. I suspect that their cloud database thresholds differ from the sunshine hours threshold to account for lack of correlation, but that is just my speculation.
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