Climate Change Event Horizon: Over the Falls?

Against my better judgment (why don't I listen to my 'better judgment' more often?), I've engaged in yet another online debate about "global warming". This one's at Onward Oregon with an OSU chemist who claims that "climate change" is a scam unsupported by science. My entry in the debate is post 7 in this thread.


I intend to continue that discussion ...
... but I think I'll eventually start a new thread in that forum
containing the phrase "event horizons".

That phrase - event horizons - relates to a metaphor for climate change that I've been wanting to explore. Imagine that you're in a boat floating mindlessly down a gently flowing river on a wonderfully warm summer day, picnic basket just a reach away, passing some substantive clear cuts, but still lined in places with older forests.

The only problem is, you've floated into an unexplored portion of the river for which there is no map. Suddenly, the river narrows, & thus, the water flows more quickly. A few rapids appear. You secure the picnic basket. You notice that the banks have turned into steep canyon walls. Even if you could navigate the current to the edge, it's unlikely you can get out of the water with your gear.

Then, ominously, you hear a waterfall ahead. The roar is barely perceptible at first, but becoming progressively more deafening as you flow onwards. You realize too late that you have already passed the metaphorical boating equivalent of an event horizon, & that you are going to go over the falls regardless of how hard you paddle back upstream. (Oh, I forgot to mention: the boat has no functional motor because fuel prices are too high.)

How would we know if we had already passed that event horizon for climate change? What evidence would one seek to evaluate that hypothesis? I discuss the nature of that evidence in my "Beyond the Tipping Point" lecture, the basis of the Climate Change 1 & 2 weekend workshops.

And - just in case - do you know where your life vest is?
This is sounding like a really large PETM-like waterfall ...