Stratospheric water vapor increase at Colorado site
Water vapor in the atmosphere is responsible for a significant portion of the greenhouse effect, and even small changes in the upper troposphere or lower stratosphere can have a large effect on climate. A new analysis of balloon-borne water vapor measurements using frost point hygrometers over Boulder, Colorado, shows that stratospheric water vapor has increased over the past 30 years. Hurst et al. break the long measurement record into four discrete time periods and determined the water vapor trends in each period for five 2-kilometer-thick stratospheric layers 16 km to 26 km above the ground.
They find that, on average, stratospheric water vapor increased by about 1 part per million by volume (27 percent) over the past 30 years, though there were many shorter-term variations in the record. Water vapor levels increased during 1980 to 1989 and 1990 to 2000, decreased from 2001 to 2005, and then increased again after 2005. The authors find that, at most, 30 percent of the observed water vapor increases can be attributed to greater amounts of methane oxidation in the stratosphere. The 2001 to 2005 decrease in midlatitude water vapor has been linked to observations of anomalously low tropopause temperatures in the tropics, but, to date, no connection between the observed water vapor increases and tropical tropopause temperatures has been found despite ongoing efforts.
Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD015065, 2011
Title: Stratospheric water vapor trends over Boulder, Colorado: Analysis of the 30 year Boulder record
A few points:
1. Boulder is not the entire world (though some there think it is), this is a single point of measurment.
2. The amount of increase is tiny, in the range of 0.04 to 0.09 parts per million per year
3. I have located a slide show from NOAA ESRL, outlining the findings in a graphically rich presentation, which you can view here (PDF)