Earth has been habitable for billions of years — simulations show it was ‘just luck’

It took evolution 3 or 4 billion years to produce Homo sapiens. If the climate had completely failed just once in that time then evolution would have come to a crashing halt and we would not be here now. So to understand how we came to exist on planet Earth, we’ll need to know how Earth managed to stay fit for life for billions of years. This is not a trivial problem. Current global warming shows us that the climate can change considerably over the course of even a few centuries. Over geological timescales, it is even easier to change…

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