Hi O'Tink,
I had already watched Ivar Giaever's video when I was poking around YouTube after you posted Freeman Dyson's talk...and I watched it again just now...
Here is (part of) what seems to me unconvincing; a kind of unspoken message Dyson and Giaver and others give...because learning about Bell's Theorem the other day, I ran across this (fallacious) analogy: All crows are black (barring the occasional mutation). Therefore, if it is a black bird, it MUST be a crow.
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The unspoken climate change discredit message seems to me, "If there is no catastrophic global warming, that means there is no reason to worry about polluting the Earth, we can continue at will to foul our nest without consequences"...i.e., a form of if it is a black bird, that proves it is a crow.
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So, here is my own personal reasoning about catastrophic climate change, it goes kinda in reverse:
By my own processes of discernment, I have no doubt we are able to degrade the Earth so much that we humankind can no longer survive here.
So my view admits catastrophic climate change a possibility - maybe even a probability - but our prevailing scientific method is quite primitive, and I am unsure it is even capable of discerning this kind of answer accurately (sensitive dependence on initial conditions).
However imo the issue global warming, in and of itself, does not ultimately even matter, there is still an urgency for us to work to protect our lifeline.