Atmospheric CO2 at 405.6 ppm – level not seen in 15 million yrs

Categories: Analysis
Published on: February 7, 2016 / 05 February 2016

annual-mean-co2-growth-rateEver since 1990, the world has experienced atmospheric CO2 levels in a range that hasn’t been seen since the Pliocene geological epoch. A period of time 2.6 – 5.3 million years ago hosting carbon dioxide levels ranging from 350 to 405 parts per million and global average temperatures that were 2-3 degrees Celsius hotter than 1880s levels. Overall, global sea levels towered about 80 feet higher than those humankind has grown accustomed to.

If global atmospheric CO2 levels had stabilized in this range, it’s likely that we would have eventually seen climates, temperatures, and sea levels that became more and more like those experienced 2-5 million years ago. A process that would have likely taken centuries to reach a final, far warmer climate state. One in which little to no ice remained upon Greenland or West Antarctica, and one hosting a substantial retreat of coastlines.

From 1990 through 2015, that was our climate context. The new world that was steadily settling into place. One that would eventually assert itself unless atmospheric CO2 levels were somehow drawn down to below 350 parts per million. It was kind of a big deal. Unfortunately, few experts really talked about it.

But starting in 2015 and continuing on into 2016 the fossil fuel burning time machine again cranked us back toward hotter, more dangerous times. For during the past two years we began to exceed the maximum CO2 threshold of the Pliocene and we started to enter CO2 ranges that were more typical to those of the Middle Miocene climate epoch of 15 to 17 million years ago.