We are, like it or not, already "intervening" in the form of diplomatic pressure and as part of a UN-inspired, though probably doomed, "peace initiative".
The current strategy seems to be to put pressure on the Russian government to stop supporting Assad: were it not for them he'd probably have gone by now, and while that in itself wouldn't solve everything it would help.
No one is talking about military intervention - that would be ridiculous. Sending an army in to do what exactly? But while I was never a great fan of Tony Blair, he brought it home to us all that the modern world is now interconnected on a scale never seen before, through ease of travel and communication. You can't, whatever else you do, ignore events such as those in Syria AND naively suppose that it will not affect us to an extent. It will.