SW,

CO2 levels now are ~380 PPM.

There are multiple, independent ice-core studies which show that over 800,000 plus years (2.1M years in one case) there has never been CO2 levels above about 280 PPM outside our current (quite recent on these time scales) run up.

So I don't know where you got your 1/5000 number. But either you think you know better than the guys doing the historical research, or you agree with me that we are at a 1/1,000,000 event right now. Which is it?
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The charm of fishing is that it is the pursuit of what is elusive but attainable, a perpetual series of occasions for hope. -John Buchan