Tuesday at a climate summit at the Vatican, Gov. Jerry Brown (D-CA) said warned of extinction when talking about climate change.

Brown said, “We don’t even know how far we’ve gone, or if we’ve gone over the edge. There are tipping points, feedback loops, this is not some linear set of problems that we can predict. We have to take measures against an uncertain future which may well be something no one ever wants. We are talking about extinction. We are talking about climate regimes that have not been seen for tens of millions of years. We’re not there yet, but we’re on our way.”

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