Global warming 55 million years ago
Thursday, January 5, 2006 9:03:09 AM
What caused the PETM is unclear. Maybe volcanic eruptions that disgorged gigatonnes of carbon dioxide, or coastal reservoirs of methane gas, sealed by icy soil, that were breached by warmer temperatures or receding seas. (see my log on Mass Extinctions of Saturday, 3. December 2005 and my log on Methane emissions and oceans of Saturday, 12 November 2005.)
According to a study appearing today in the British journal Nature PETM shows that anthropogenic (man-made) forcing may have lasting effects not only in global climate but in deep-ocean circulation as well.
This is another sign that global warming could slow the Atlantic current that gives western Europe its mild climate (see my log on Global Warming = Climate Change [including Gulf Stream problems] of Thursday, 1 December 2005)
PETM was also a mass extinction event, although not as spectacular as the Permian mass extinction (see my log on Mass Extinctions – end of Permian of Saturday, 3 December 2005)
During the PETM, ocean acidification likely caused a mass extinction of phytoplankton. In September 2005 a team of scientists writing in Nature warned that the same fate could befall modern day marine life. The massive spike in atmospheric greenhouse gases 55 million years ago may have resulted from rapid decomposition of frozen methane hydrate deposits found in the deep ocean near continental margins and in the Arctic. (See my log on Methane emissions and oceans of Saturday, 12 November 2005)
Scientists are concerned that a parallel release of frozen methane deposits today could trigger a similarly catastrophic climate event.
- http://news.mongabay.com/2005/1114-petm.html (“Massive climate change rocked ecosystems, animals 55 million years ago” - mongabay.com - November 14, 2005)