In Google type (or cut and paste):

site:www.habitablezone.com/currentevents

And then the word(s) you want to search. For example

site:www.habitablezone.com/currentevents wmd

site:www.habitablezone.com/currentevents "terri schiavo"

And so on. You'll get every page Google has indexed, which might not be that many. This can also prove useful if you want to find posts by particular people, rather than particular topics e.g.

site:www.habitablezone.com/currentevents brosz cripes

site:www.habitablezone.com/currentevents davin yeti

But please use it for good, not evil. ;-)

Oh, the same principle works for every board e.g.

site:www.habitablezone.com/space nuclear

It's far from comprehensive, but I hope this helps.