Decreasing atmospheric moisture content is more indicative of moisture shifting to the poles as ice.
The lower moisture content certainly means that temperatures will be more extreme as the specific heat of dry air is is substantially lower than that of moist air. The same amount of heating from the surface will make the air warmer and, if the air is in contact with colder air or surfaces, it will cool more quickly and further, never having gained the heat that it would have were it moist.
Of course, being drier also means that the reduced water vapour has a lower potential for the air to cool if it doesn't get in contact with colder air or surfaces. But it does cool more rapidly over water surfaces as the drier air more readily accepts water vapour; so the evaporation cools the air further, somewhat reducing the air's capacity to carry water vapour. There are positive and negative feedbacks in even that part of the climate system.
The first few links on that page actually use C instead of Anomalous C.
One of the charts shows most of the worlds dew points seemingly climbing which would say that the humidity is increasing not decreasing wouldn't it?
I am still suggesting plotting all the data. Creating a world humidity anomaly is harder than the temperature anomaly. I keep trying to express my concern with averages. I keep failing to express it in a way that Warmists understand. Averages are an awesome tool. Be very wary of averages because they will bite you.
How in the world did David Robinson (Basket Ball Center at > 7' tall) get into the Nuclear Navy? Apparently he was a good student, but practically, I could barely get around the engine room at 6' 3".