Today’s letter, once again, will be turning attention away from the warming effect of water vapor while placing a more general focus on whatever may be cause of any particular warm anomaly. There is a fine example waiting for us in the eastern half of Asia, where an exceptionally broad area is being warmed by 10C or more. We’ll mainly be looking at everything within a wide circle that includes the Himalaya range in the south up to the coast of the Arctic Ocean. One small area of very cold anomaly is noteworthy as an odd exception to everything else.
There is a map called Sea Ice / Snow Cover that I seldom display, maybe not ever before because of a special interest in the snow cover feature. It would be great to see what this map may have looked like on any average day at this time of year during the base period, some thirty years ago. I would wager that almost everything within the circle of high current warming would have had a much higher percentage of snow cover showing. When snow is missing that can only mean more solar energy is being absorbed by the ground and vegetation instead of just being reflected away in the original shortwave form of entry. By contrast, whatever amount of energy is absorbed wastes little time before being released, but has first been converted into the longwave form of radiation that the greenhouse gases can capture and briefly hold, giving a boost to air temperatures while doing so. The comparative results are reflected in the anomalies of today.
I think water vapor still accounts for a considerable amount of the warming in this region, which the next map will help us understand, but the missing snow cover could well be of rivaling importance—sorry, but I have no good way to calculate or closely estimate the actual relative numbers. This same map is useful for one more purpose, altogether outside of the snow and ice zones, because of the color coding it offers for showing elevation everywhere. This is a handy thing to have available when analyzing anomalies. Higher elevation, as everyone knows, consistently implies reduced air temperatures. It also means that fewer molecules of greenhouse gas with the ability to trap radiation will be available due to overall thinness in the air above—which goes a long way toward providing an explanation for the steady reduction of temperatures wherever elevation rises by a significant amount.
Now we’ll open today’s Precipitable Water map to see what it can tell us. Almost everything in the zone of warm anomaly is shaded in either gray or black, which is generally always true for the coolest parts of the planet. This mode of shading and the high leverage behind each of the low numbers creates complications for doing analysis when cool places are warming. As observed in Antarctica, for example, any PWat reading of “1kg” is almost useless because we need to know the number in grams. Fractions never count at any level, and on top of that when we do want to know an actual kg number we typically need to use magnification in order to pick out the right shade of gray, usually with difficulty. As for the small area that is very cold on today’s anomaly map, the one with an arrow shape, we can see in closeup that it has an actual reading of 1kg or less, compared with other readings in nearby areas ranging up to 4 or 5. That amount of relative dryness is a reality and by itself fully accounts for a temperature differential of more than 20C before checking on snow cover.
Carl