Dr. Jeff Masters, best known as a hurricane watcher for Wunderblog, is respected enough across the political spectrum such that it is possible -- not likely, but possible -- that his warning about the dangers of replicating the PETM will be taken seriously. So it's worth a look.
Since the beginning of the Industrial Revolution, humans have pumped
about 500 gigatons of carbon into the atmosphere. There are about 5,000
gigatons in the planet's coal reserves, while oil and traditional
natural gas deposits are hundreds of gigatons each (Rogner, 1997).
Given that humans are now adding about 10 gigatons of carbon to the
atmosphere each year (Global Carbon Project, 2007),
we will surpass the 1,000 gigaton mark 50 years from now at current
emission rates. This is at the lower end of the 1,000 - 2,000 gigatons
of carbon that are estimated to have been added to the atmosphere
during the PETM--the most extreme natural global warming event of the
past 65 million years. Though our view of events so long ago is very
fuzzy, the PETM should serve as a cautionary tale. We cannot rule out
the possibility that continuation of our current rates of fossil fuel
burning will lead to an extreme climatic warming event like the PETM.
In particular, we need to keep a careful eye on the huge reservoirs of
methane hydrate stored in marine sediments (500 - 10,000 gigatons of
carbon) and stored in permafrost (7.5 - 400 gigatons). Continued
warming of the planet could trigger substantial releases of these
massive reservoirs of greenhouse gases, leading to a repeat of the PETM
event. However, a 2008 study by the U.S. Climate Change Science Program
(CCSP, 2008) concludes that there is currently no evidence that a
sudden catastrophic release of methane stored in ocean sediments or in
permafrost will happen over the next century. It should take at least a
century for global warming to penetrate the deep oceans and permafrost
regions containing these significant reservoirs of methane hydrates.
The study concludes, "Catastrophic release of methane to the atmosphere
appears very unlikely in the near term (e.g., this century)...Although
the prospect of a catastrophic release of methane to the atmosphere as
a result of anthropogenic climate change over the next century appears
very unlikely based on current knowledge, many of the processes
involved are still poorly understood, and developing a better
predictive capability requires further work. On a longer time scale,
methane release from hydrate reservoir is likely to be a major
influence in global warming over the next 1,000 to 100,000 years". So,
the bottom line is: don't expect global warming to be able to cause
huge releases of methane hydrates in the coming century, such as may
have occurred during PETM. But it is wise to ponder that a release of
greenhouse gases similar in magnitude to what we are doing now
coincided with the most extreme global warming event of the last 65
million years. We should not be surprised if our human greenhouse gas
emissions cause a similar massive climate perturbation over the next
1,000 years, leading the dawn of a new geological era--the Anthropocene.
Masters notes that the PETM was an extinction event, but mostly for plankton species. However:
The PETM did not cause mass extinctions
on land of plants and animals, but a major turnover in mammalian life
occurred at that time. Many of today's major mammalian orders emerged
in the wake of the PETM. The new geological era it ushered in, the
Eocene, is named for the Greek goddess of the dawn (Eos), since this was the dawn of the era of large mammals.
Maybe we should try to avoid another extinction event, even if our species might survive?
Just wondering...
