As atmospheric carbon dioxide levels rise, scientists look back four million years for answers on what to expect from climate
The Pliocene is the geologic era between five million and three million years ago. Scientists have come to regard it as the most recent period in history when the atmosphere’s heat-trapping ability was as it is now and thus as our guide for things to come.
Recent estimates suggest CO2 levels reached as much as 415 parts per million (ppm) during the Pliocene. With that came global average temperatures that eventually reached 3 or 4 degrees C (5.4-7.2 degrees F) higher than today’s and as much as 10 degrees C (18 degrees F) warmer at the poles. Sea level ranged between five and 40 meters (16 to 131 feet) higher than today.
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