What are the implications of the PETM for us today and the future?

First of all, this abrupt geological event seems analogous to the present day ‘Anthropocene’ in terms of its rapid release of a large amount of CO₂. The atmospheric and surface ocean response during the PETM has shown great similarity to the recent observed changes in response to anthropogenic release of CO₂ today. During the PETM, ~2000 x 10⁹ metric tons of carbon was released in less than 10,000 years. This might seem rapid, but compare with the anthropogenic emissions, this is far too modest.  Over 297 billion metric tonnes of carbon has been released from mankind in 250 years only since the Industrial revolution in AD1750. Although Ruddiman (2003) argued that the anthropogenic greenhouse gas emission has begun 8000 years ago, it is still a much shorter timespan than that of the PETM. Therefore, many scientists have projected a similar or even worse catastrophic marine mass extinction than the PETM due to the rapid rate of current warming and acidification of the ocean. According to a recent model simulation by Ridgwell and Schmidt (2010), a much more severe deep ocean carbonate undersaturation and rapid environmental changes than that of the PETM are projected by the end of the century, which puts further challenges to marine calcifiers, including surface water phytoplankton.

Secondly, based on the recovery phase of the PETM, it seems that the natural buffer system of the ocean - CaCO₃ deposition via calcareous phytoplankton and the weathering of silicate rocks to restore the carbonate ion level in the deep ocean, might give us signs of hope to save the ocean from this acid test challenge. However, don’t forget that this recovery from the PETM took more than 100,000 years to complete! With the rate of anthropogenic CO₂ increase within 250-300 years only, it is certainly incommensurable with the PETM. The natural oceanic system is simply too slow to react to compensate for what we’ve done.

Although the Paleocene-Ecocene Thermal Maximum event might not be big and dramatic enough to be the current analogue of today’s Anthropogenic Era, it has certainly enhanced our knowledge and understanding of the resilience of our ocean’s natural buffer system. It is important to make use of this past event to produce accurate models for future predictions and subsequent geoengineering solution to mitigate the current situation.