Paper by William Gray and Barry Schwartz: water vapor feedback is negative


Global warming scenarios from CO2 increases are envisioned to bring about rainfall enhancement and resulting upper tropospheric water vapor rise. This initial water vapor enhancement has been hypothesized and programmed in climate models to develop yet additional rainfall and water vapor increase. This causes an extra blockage of IR energy to space (a positive feedback warming mechanism). This additional rainfall and IR blockage is modeled to be approximately twice as large as the additional rainfall needed to balance the increased CO2 by itself. The reality of this additional warming and extra IR blockage has been questioned by many of us. This study analyzes a wide variety of infrared (IR) radiation differences which are associated with rainfall differences on different space and time scales. Our goal is to determine the extent to which the positive rainfall feedbacks as are included in the climate model simulations are realistic.  …

This analysis shows they are not realistic.  …


The albedo increase occurring over the top of strong precipitation and cloudy regions rises at a greater rate than does the rate of decrease of IR within these rainy and cloudy areas. Rainy and cloudy areas are local places of enhanced net radiation to space (Tables 1 and 2 and in idealized form in Figure 3). We have many other areas of rain differences which give similar results. In almost all rain and cloud areas we find that albedo energy flux rises at a greater rate than IR energy flux is reduced.  …


The above measurements are at odds with the Global Climate Model (GCM) simulations of precipitation increase associated with rising CO2 amounts. Models show large tropical upper tropospheric temperature and water vapor increases to be associated with increased rates of precipitation (due to CO2 increases) that are similar to increased rates of precipitation that this study measures. We do not observe such upper tropospheric temperature and moisture increases for rainfall enhancements as do the modelers.  …

The climate modelers have assumed that as CO2 increases it will cause a progressive blockage of IR energy to space and, in addition, a further blockage of IR energy to space will occur from the original increase in upper-level water vapor. Increased IR blockage brings about a gradual increase in global temperature.  …

Our observations do not agree with these GCM scenarios. Our observations indicate that tropical RH [relative humidity] and moisture (q) rather than rising with enhanced precipitation do the opposite and actually go down as precipitation rates increase.  …

We find that there is not a positive water vapor feedback as the modelers have assumed. In fact we see the opposite. As rainfall increases upper-level water vapor contents are weakly reduced.  …


We find that as rainfall increases that there is not a reduction of global net radiation to space as most of the climate models have assumed. There is a weak enhancement of radiation to space with increased rainfall. We find no positive water vapor feedback.  …

A reduction of upper level RH of about 4 percent to go along with a lowering of the emission level of 7 mb would allow a doubling of CO2 to proceed with no warming (Figure 20). We estimate the extra precipitation from a doubling of CO2 to cause a negative (not positive) temperature feedback of about minus 0.6oC.”  “THE ASSOCIATION OF OUTGOING RADIATION WITH VARIATIONS OF PRECIPITATION – IMPLICATIONS FOR GLOBAL WARMING”  h/t Climate Realists


One Response to “Paper by William Gray and Barry Schwartz: water vapor feedback is negative”

  1. goodspkr Says:

    The importance of this cannot be overstated. It is in fact the key to the AGW theory and the disasterous consequences they foretell.

    Rather than seeing a increase in temperature of from 3 to 4 degrees C due to a doubling of CO2, this paper suggests that this number is actually .6 degrees C.

    It also suggests that the climate is stable

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