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“You would have grasslands, which didn’t really exist that much in the Eocene.”

In addition to these two impacts, existing evidence suggests three smaller asteroids also hit Earth during this time -- the late Eocene epoch -- pointing to a disturbance in our solar system's asteroid belt.

Indeed, from the larger perspective of Earth’s planetary history, Antarctica was green for a large chunk of time, specifically during the period prior to the Eocene Epoch 56 million years ago.

All but the most specialist sea plankton moved to higher latitudes during the Early Eocene Climatic Optimum, an interval of sustained high global temperatures equivalent to worst case global warming scenarios.

Washington in the Eocene looked different from today, with a coastline well east of where Seattle sits today and a chain of volcanic islands dotting the horizon offshore.