Global Warming And Precipitation – Does Warmer = Wetter?

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I love a good blargument. Yesterday, me and another blogger were having a good back and forth about the the current blizzards in relation to Anthropogenic Global Warming. My friend argues that AGW will cause more blizzards such as this one, and therefore, Time magazine is right concerning the article they put out this week. My blogfriend says this:

Global warming theory postulates conditions that make storms like the recent one more likely, and stronger – by increasing the amount of moisture in the air, and also increasing the heat that drives storm intensity. That is why, if these storms are held up as some kind of evidence to confirm or refute alternative theories, then they do NOT refute global warming theory at all – they are, in fact, completely consistent with the type of events that the models say are more likely to happen.

This is not complicated. If it is 50 degrees, then X amount of water evaporates into the air, and will eventually fall back to earth as precipitation. If it is 51 degrees, then X plus a little more water will evaporate. And the air will be able to hold that extra water. You end up with more precipitation.

He later provides a link to the EPA to show that the U. S. has indeed had an increase in precipitation over the last one hundred years. I love info like that, even though it supports my debate opponent. Facts are cool. And the nice thing about new information is that you can take that and start asking other questions related to it. Something dawned on me during this exchange. When Steve McIntyre found an error in the North American temperature records that moved the warmest year on record from 1998 to 1932, the Y2K error, my fellow skeptics were rightly reminded that North America is only 7% of the globe and the adjustment doesn’t affect the global temps.

They were right of course. But doesn’t that follow for weather events too? And then I wondered – what is the precipitation levels for the world as a whole? From the EPA:

Precipitation has generally increased over land north of 30°N from 1900-2005, but has mostly declined over the tropics since the 1970s. Globally there has been no statistically significant overall trend in precipitation over the past century, although trends have varied widely by region and over time.

That would be a global redistribution of precipitation, not an increase, which should be the case in a warmer world. So, if you say this:

This is not complicated. If it is 50 degrees, then X amount of water evaporates into the air, and will eventually fall back to earth as precipitation. If it is 51 degrees, then X plus a little more water will evaporate. And the air will be able to hold that extra water. You end up with more precipitation.”

Then how is it we don’t have a wetter world? I know that is simplistic, and it doesn’t disprove AGW. But it does make you think, doesn’t it.