On May 9, 2013, carbon dioxide levels in the atmosphere reached the level of 400 parts per million (ppm). The last time the Earth experienced this level of carbon dioxide was in the Pliocene about three to five million years ago. Investigate what the temperatures were during this time period and compare them to today. What could explain the changes?
The last time atmospheric CO2 was at 400ppm, humans didn't exist. It was during the ancient Pliocene era, tree million years ago. If we compare the temperatures in that periode with the tempertatures today, we can observe great diferences:
- In the Piocene the global average temperatures were 3 to 4 ºC warmer than today and the polar temperatures were 10ºC warmer too.
- In the Pliocene the Artic was ice free and the sea level was between 5 and 40 meters higher.
However, the most important diference is that in the Pliocene a higher concentration of CO2 would have been entirely down to natural earth processes. Nowadays, the increase of CO2 levels has been happening much more rapidly today than it did during que Pliocene epoch because of the industrialization, the human activities, burning fosil fuels and other process have changed the amount of greenhouse gases emitted into the atmosphere. Therefore we will progressively continue see climate changes over the next years.
Sources:
http://www.esrl.noaa.gov/gmd/ccgg/trends/weekly.html
https://en.wikipedia.org/wiki/Pliocene
https://scripps.ucsd.edu/programs/keelingcurve/2013/12/03/what-does-400-ppm-look-like/
http://www.skepticalscience.com/pliocene-snapshot.html
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