Tuesday, August 28, 2012

New evidence that water vapor is a negative feedback

A paper published today in the Journal of Geophysical Research asks the question, "Why does the temperature rise faster in the arid region of northwest China?" The runaway greenhouse theory alleges that warming from greenhouse gases will be amplified by increased evaporation and atmospheric water vapor. According to the theory, wet areas with the most atmospheric water vapor should warm faster than arid areas with less. However, observations from 1960-2010 show that the dry region of China warmed faster than the rest of China and the entire globe. The authors explain this apparent paradox as primarily due to the Siberian High, a natural atmospheric circulation. CO2 is well-mixed in the atmosphere and therefore cannot account for different rates of warming in different regions.

The finding that arid regions warm faster and cool faster than wet regions around the globe was confirmed by physicist Clive Best, who examined 5600 weather stations in the global CRUTEM4 temperature and humidity database, finding that water vapor acts as a strong negative feedback rather than a positive feedback as alleged by the IPCC.
[Clive Best] "the IPCC argues that  feedbacks from increased water evaporation will lead to enhanced warming. This is not observed in those regions most effected by water vapour. In fact the opposite seems to be the case implying negative feedback."

Key Points
  • Faster rise of annual temperature is mainly caused by winter temperature rising
  • The most important factor of winter temperature rising is Siberian High
  • The effect of Siberian High on temperature is greater than greenhouse gas's
Baofu Li
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
Graduate University of Chinese Academy of Sciences, Beijing, China
Yaning Chen
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
Xun Shi
Department of Geography, Dartmouth College, Hanover, New Hampshire, USA
During 1960–2010, the air temperature in the arid region of northwest China had a significant rising trend (P < 0.001), at a rate of 0.343°C/decade, higher than the average of China (0.25°C/decade) and that of the entire globe (0.13°C/decade) for the same period. Based on the analysis of the data from 74 meteorological stations in the region for 1960–2010, we found that among the four seasons the temperature change of winter has been playing the most important role in the yearly change in this region. We also found that the winter temperature in this region has a strong association with the Siberian High (correlation coefficient: R = −0.715) and the greenhouse gas emission (R = 0.51), and between the two the former is stronger. We thus suggest that the weakening of the Siberian High during the 1980s to 1990s on top of the steady increasing of the greenhouse emission is the main reason for the higher rate of the temperature rise in the arid region of the northwest China.

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