Disclaimer: I think global warming is a big scary problem and carbon pricing mechanisms of some form should have been set up like a decade ago.
If your acquaintance was referring to a http://en.wikipedia.org/wiki/Clathrate_gun_hypothesis style event, then you probably shouldn’t be overly worried. My understanding of the current science is that methane’s low atmospheric lifetime means that clathrate-gun style events are extremely unlikely to be immense problems. There’s some scientific discussion on the issue of large-scale methane releases, with a small group of researchers who are moderately to very convinced that it’s a potential extinction-level event (I think Shakhova is in this camp, not sure about any others) and the majority of climate researchers thinking it’s slightly scary but not any worse than continued exponential CO2 emissions on their own (i.e., unpleasant but not extinction-level unless we’re idiots and burn all the coal forever, even after it’s not economic).
RealClimate, a blog run by some of the climate scientists who do a lot of IPCC work (Gavin Schmidt, Michael Mann, Stefan Rahmstorf, etc.) have looked at methane releases before, see for example http://www.realclimate.org/index.php/archives/2012/01/much-ado-about-methane/ and http://www.realclimate.org/index.php/archives/2012/01/an-arctic-methane-worst-case-scenario/ . They mostly conclude that the sensible worst-case scenarios are about as bad as continuing CO2 emissions, i.e. there’s not really a danger of utterly catastrophic methane release.
About the only other extinction-level event I can see from climate change is if climate sensitivity is on the order 6c per doubling of CO2 and we don’t release until maybe one-and-a-half doublings. After about a 6c increase in global average surface temperature, average temperature in some places on Earth is high enough that humans living there can’t maintain homeostasis, IIRC. But about 90% of climate sensitivity probability mass is in the range 1.5c-4c, and the remaining 10% is mostly in the range 4-5. 6c climate sensitivity is extremely unlikely. Earth system sensitivity might be that high, but that’s only relevant on longer-than-a-century timescales.
Spencer Weart’s Discovery of Global Warming is a pretty good reference to basically everything in climate science. Realclimate doesn’t update often and tends to be aimed more at people already in the know, but is occasionally quite interesting. SkepticalScience is a bit propaganda-y, but its list of global-warming-skeptic arguments and rebuttals is an excellent resource, roughly comparable to talk.origin’s index to creationist claims. Tamino is a professional statistician who has done some climate research, his blog is pretty snarky but usually quite good at explaining the statistics behind some result. His explanation about the ‘pause’ in global warming is one of the best ones I’ve seen. Wood for Trees provides an interactive climate-data-graphing tool that isn’t perfect but is occasionally useful.
The IPCC reports are probably the best place to go for information on global warming, but they are pretty dense and difficult to interpret.