One of the things that temperature affects is how much water can be in the atmosphere. The hotter it is, the more water vapor you can have in the air before it starts to form a cloud. So one very simple expectation that we could have on climate is that warmer = more humid (absolute humidity that is). Since there's more than temperature to climate, we don't really expect it'll work out that simply everywhere, all the time. But it tells us one line of research to take -- look to see what has been happening to atmospheric moisture content.
Jeff Masters has written this up at his blog on the Weather Underground, and I'm relying partly on his notes in my write up.
The research has been done, and you can find a summary of it in chapter 3 of the 4th IPCC report; section 3.4.2.1 is the one you want. As usual, I prefer and recommend going to the scientific papers that are cited, rather than to rely only on the summary. One of the papers to look up is Trenberth, K.E., J. Fasullo, and L. Smith, 2005: Trends and variability in column integrated atmospheric water vapor. Clim. Dyn., 24, 741−758. The conclusion being that atmospheric water vapor has increased about 5% over the past century, and 4% since 1970.
In other words, what we expected from a warmer earth is what is observed. Score (another) one for our understanding of the climate system.
In looking at weather, we also tend to look at water vapor as a severe weather sign. It takes a lot of energy to evaporate water. Conversely, if you get it to condense, you release a lot of energy. The main place the energy can go is to make the air warmer. Warmer air rises (giving us motion*). It also makes more water condense. It is this process that powers hurricanes, or, less dramatically, thunderstorms. A second expectation we have had is more water vapor = stronger storms. This was documented for rainfall in Karl, T.R., and R.W. Knight, 1998: Secular Trends of Precipitation Amount, Frequency, and Intensity in the United States. Bull. Amer. Meteor. Soc., 79, 231–241.
*The upwards motion of air in a storm has to be balanced by inwards motion at the bottom -- the air that is going up has to come from somewhere.
So, score a second point for our understanding of the climate system.
It wasn't just rain that was expected to show this kind of tendency. Snow comes from a similar meteorological setup -- rising air condensing moisture and dropping it as precipitation. But snow is much more variable. 1 inch* of water equivalent (namely, take the snow and melt it, then see how deep it is) snow can be anything from 3 inches snow (an incredibly heavy/thick snow) to 20 (a very dry, powdery snow). We normally guess 10:1. But one thing this means is that 30 inches of snow in one year may not be the same as 30 inches in another year. This gives even more variability to the numbers than you'd otherwise see.
* replace inch with cm, or meters, if you like. These are matters of proportion, so it doesn't matter what unit you use.
Nevertheless, people have been researching it since at least the 1990s (
Karl, T.R., P.Y. Groisman, R.W. Knight, and R.R. Heim, 1993: Recent Variations of Snow Cover and Snowfall in North America and Their Relation to Precipitation and Temperature Variations. J. Climate, 6, 1327–1344), but at that time without finding a statistically significant result. The statistically significant result was documented in Changnon, S.A., D. Changnon, and T.R. Karl, 2006: Temporal and Spatial Characteristics of Snowstorms in the Contiguous United States. J. Appl. Meteor. Climatol., 45, 1141–1155.
Score a third for our understanding of the climate system.
The thing is, warmer climate does not necessarily mean nicer. Nor does it necessarily mean worse. You have to do some thinking about the system, preferably combined with observing it, to discover what the nature of the changes will be. And then decide whether those changes are nice or not.
The current blizzard (NWS has issued a blizzard warning for my area), and the weekend's major snow, are indeed things expected for this area from climate change. The power failures, loss of cable tv, people trapped at home while in need of medication, and so on, that are occurring are all, also, expected things for climate. It being more common is expected from our understanding of climate change.
