Earth has stayed habitable for billions of years – exactly how lucky did we get?
(WorldNews Environment)

xtock / shutterstock 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 climate. Calculations show that there is the potential for Earth`s climate to deteriorate to temperatures below freezing or above boiling...