Paper finds a decrease of IR radiation from greenhouse gases over past 14 years, contradicts expected increase

A paper published in the Journal of Climate finds from 800,000 observations a significant decrease in longwave infrared radiation from increasing greenhouse gases over the 14 year period 1996-2010 in the US Great Plains. CO2 levels increased ~7% over this period and according to AGW theory, downwelling IR should have instead increased over this period. 

According to the authors, 

"The AERI data record demonstrates that the downwelling infrared radiance is decreasing over this 14-yr period in the winter, summer, and autumn seasons but it is increasing in the spring; these trends are statistically significant and are primarily due to long-term change in the cloudiness above the site."

The findings contradict the main tenet of AGW theory which states increasing greenhouse gases including the primary greenhouse gas water vapor and clouds will cause an increase of downwelling longwave infrared "back-radiation." 

The paper also finds a negative trend in precipitable water vapor, as do other global datasets, again the opposite of predictions of AGW theory that warming allegedly from CO2 will increase precipitable water vapor in the atmosphere to allegedly amplify warming by 3-5 times. Is the unexpected decrease in water vapor the cause of the decrease in downwelling IR?

Global datasets also show an increase of outgoing longwave IR radiation to space from greenhouse gases over the past 62 years, again in contradiction to the predictions of AGW theory. 

Gero, P. Jonathan, David D. Turner, 2011: Long-Term Trends in Downwelling Spectral Infrared Radiance over the U.S. Southern Great Plains. J. Climate, 24, 4831–4843.

doi: http://dx.doi.org/10.1175/2011JCLI4210.1

Long-Term Trends in Downwelling Spectral Infrared Radiance over the U.S. Southern Great Plains

P. Jonathan Gero

Space Science and Engineering Center, University of Wisconsin—Madison, Madison, Wisconsin

David D. Turner

NOAA/National Severe Storms Laboratory, Norman, Oklahoma, and Department of Atmospheric and Oceanic Sciences, University of Wisconsin—Madison, Madison, Wisconsin

Abstract

A trend analysis was applied to a 14-yr time series of downwelling spectral infrared radiance observations from the Atmospheric Emitted Radiance Interferometer (AERI) located at the Atmospheric Radiation Measurement Program (ARM) site in the U.S. Southern Great Plains. The highly accurate calibration of the AERI instrument, performed every 10 min, ensures that any statistically significant trend in the observed data over this time can be attributed to changes in the atmospheric properties and composition, and not to changes in the sensitivity or responsivity of the instrument. The measured infrared spectra, numbering more than 800 000, were classified as clear-sky, thin cloud, and thick cloud scenes using a neural network method. The AERI data record demonstrates that the downwelling infrared radiance is decreasing over this 14-yr period in the winter, summer, and autumn seasons but it is increasing in the spring; these trends are statistically significant and are primarily due to long-term change in the cloudiness above the site. The AERI data also show many statistically significant trends on annual, seasonal, and diurnal time scales, with different trend signatures identified in the separate scene classifications. Given the decadal time span of the dataset, effects from natural variability should be considered in drawing broader conclusions. Nevertheless, this dataset has high value owing to the ability to infer possible mechanisms for any trends from the observations themselves and to test the performance of climate models.