I think there is still too much debate in scientific circles to know for sure what's causing the current upward trend in temps. We know that it's cyclical, and we know that this region has seen significanly warmer temps in the past. How much warmer, and how far back I can't say, but I've seen the fossils that suggest it.

I found a really informative site, if you have the time and inclination to read up on the topic. It seems to be purely scientific in nature, although I didn't read anything but the article I'm linking to and the main page to make sure it wasn't an environmental wacko site.

The bottom line is it's too complex a system to know for sure what's causing it, but there IS data that supports the claim that levels of greenhouse gases (CO^2, in this case) in Antarctica are higher now than at any time in the last 400k years. In fact, they are considerably higher now than the upper limits observed during all but the most recent up/down cycle during that time. It's still rising, too.

They go on to suggest that it's possible (based on current data) that we could not only increase the speed of global warming artificially, but we might actually cancel a period of cooling and subsequent glacial advance (which is where we should be right now, historically speaking) and create a completely new climate regime. Pretty sobering thought.


http://www.aip.org/history/climate/cycles.htm