Today’s letter will forcus on the power of water vapor to affect air temperatures due to the properties it holds while serving as a greenhouse gas. Many observations have led me to believe that if all other factors affecting temperatures remain equal, then any change in the total volume of water vapor in the air overhead will cause changes in air temperature to occur in a regular way, based on a logarithmic scale. Results generally show that any doubling of water vapor content, no matter what the base number may be, will cause an increase of 10C degrees in air temperature. Of course Nature seldom allows all other factors to remain perfectly unchanged while water vapor and temperature comparisons are being made, but sometimes the differences are clearly limited or can be reasonably adjusted. Today we have such an opportunity, so we’ll start with the anomaly map for North America:
Just by looking at the way the situation is set up in the 48 US states and much of Canada we can see that major temperature differences exist in many places that have exactly the same latitude and not too many differences in topography or other geographical features. Will precipitable water provide the key to explaining this peculiar mix?
The reason behind the sharp divide between the eastern and western halves of the US is immediately apparent. For still more clarity I want to zero in on three specific locations having about the same latitude where we can easily match their anomaly readings to vapor volume readings and draw comparisons. The three I have chosen, using anomalies as the guide, are all Canadian. From the top map, they include the lukewarm anomaly in western Alberta, the cold one in southeastern Saskatchewan and the larger area in the east that displays maximum warming. The respective anomaly readings that I obtain are +2C, -10C and +18C. Moving over to the PWat map I get 12kg, 4kg and 27kg in correspondence. I’ll let you do the math, but all three are in the ballpark for realizing 10C per each double of kg. The best example, from 4 to 27 kg, implies two full doubles and nearly a third, realizing a measured temperature differential of 28C.
“All other factors” were by no means completely equal in these comparisons. In particular, the Alberta temperature was most likely penalized by a degree or two because of undergoing clouds and snowfall while the other two had clear skies. The latitude of its anomaly area is also somewhat higher than the others. This next map is helpful with respect to the former:
Carl