[cjohnson (OP)]

Global warming theories suggest that tempuratures are on the rise, and the ice caps are melting, which will free more water, causing sea level rise.  As temperature rises, the atmosphere is able to hold more water as vapor.  Could this act as a buffer system to absorb some of the impact?  As I understand it, the ice caps have melted many times in the earth's history (non present during most of the mesazoic era).  If they completely melted, how much devestation could we expect to see?

[frethack]

As temperature rises, the atmosphere is able to hold more water as vapor.  Could this act as a buffer system to absorb some of the impact?

 
 
Qualitatively, yes.  The atmosphere would hold some of the melted glacial water.  Quantitatively, the amount will be small compared to the amount of water released to the oceans, so it likely will produce little buffering.

As I understand it, the ice caps have melted many times in the earth's history (non present during most of the mesazoic era).

Actually, the planet has been without ice caps throughout the vast majority of geologic time.  The problem is that we evolved and our population has expanded during an ice age (though we are currently in an interglacial).  As sea levels rise, which they inevitably will, densely populated coastal regions will be inundated, though the magnitude of inundation cannot be reliably predicted.  The climate is generally fickle, and "climate stability" is a bit of a misnomer.  Even a geologically short period of cooling (say, a hundred years or so) can return the climate system to a period similar to the little ice age.  By the time the next full glacial period rears its head we had better have our climate system figured out...the land lost to glaciation will dwarf the land lost to sea level rise. 

If they completely melted, how much devestation could we expect to see?

If they completely melted, we may be looking at another N American intercontinental seaway, but that is a very unlikely scenario.  We have had polar ice in E Antarctica since the Eocene/Oligocene boundary (~34 million years), so as long as Drakes Passage is open and there is a land mass at the south pole, we will have ice.  Greenland glaciation is relatively new, and it is feasible that there could be a large amount of melting.  Just under a thousand years ago, people thrived in the coastal regions.  There were grassy plains and fertile soil, but the climate took a turn for the worse.  Now where there are burial grounds and evidence of grasslands, the land is permafrost.  Again...climate is fickle.

[einfopedia]

Climate is a fundamental driver of the water cycle. It determines how much water is available supply and how much water we need demand in the short and long term.

[CZARCAR]

do fossil fuels power volcanoes?

[damocles]

do fossil fuels power volcanoes?

No, but they do power geysers  []

http://www.geyser.co.uk/ (no implied endorsement)