The carbon buildup of 2000 to 7000 gigatons over perhaps as long as 20,000 years equates to approximately 0.1 to 0.35 gigatons a year, however there have been studies pointing to perhaps as short a build up as 3,000 years,(1)Appy Sluijs et al. (2007) “Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary” Nature, Volume 450, Number 7173, Pages 1218–21 which would explain why the biosphere didn’t adapt fast enough to deal with the increasing carbon. At 3,000 years the annual buildup would be around 0.7 to 2.3 gigatons a year. Currently human activity on the planet is believed to be causing 29 gigatons of carbon annually, however this is a fairly recent occurrence. Between 1750 and 1900, only around 12 gigatons of carbon were released as carbon-dioxide into the atmosphere from burning fossil fuels, equating to 0.08 gigatons a year. In the twentieth century the release of carbon into the atmosphere shot up to 260 gigatons, equating to 2.6 gigatons a year. In the first decade of the twentieth century the carbon output shot-up even further to 83 gigatons, equating to 8.3 gigatons a year.(2)Carbon-dioxide Information Analysis Center 31-Jul-2013 Dataset
This last rapid increase was after the world recognized the importance of reducing the carbon output, and almost all nations signed the Kyoto Protocol in 1997. The Kyoto protocol is an agreement to reduce global output of carbon that placed specific requirements on most of the worlds industrial powers of the time, but no requirements of developing nations. China was classified as a developing nation, and subsequently most of the planet’s non-essential industry has been relocated to China, causing China’s carbon output to increase from 0.9 gigatons in 1997 to 2.3 gigatons by 2010. This has not just led to massive industrialization in China, but massive health issues and an expected life expectancy drop of 5.5 years across northern China.(3)Edward Wong (July 8, 2013) “Pollution Leads to Drop in Life Span in Northern China, Research Finds” New York Times The researchers projected that the 500 million Chinese who live north of the Huai River will lose a combined 2.5 billion years of life expectancy because of outdoor air pollution. They did not examine the effects of the pollution on the animals or plants in the area, however it is difficult to not predict the effects. The Kyoto Protocol was ratified by most technologically advanced nations, however the United States refused to ratify it believing it would simply move the problem from industrialized nations to developing nations, and thereafter Canada withdrew entirely, meaning that North America is an effective exception to the Protocol, and continues to the world’s largest carbon source per-capita.
The PETM does look a great deal like our modern era, except for one obvious reversal. Currently we are producing massive and unsustainable amounts of carbon-dioxide, and perhaps someone was doing the same back then, however, we are 12,000 years into an extinction event, whereas the PETM marked a point of rapid new species appearance. While the rapid buildup of carbon-dioxide could be accounted for as a sign of industry, the emergence of new species indicates that the likelihood of a civilization is low, at least a civilization anything like our own. Several possibilities present themselves:
It could have been a random convergence of natural phenomena we have yet to account for.
It could have been a civilization that did not have much presence on the surface of the planet, perhaps a subterranean or off-world civilization. Theoretically the carbon build-up could have been an attempt to alter the planet’s biosphere back to the cretaceous period’s biosphere. Perhaps some Dinosauroids did survive underground or on the Moon or Mars, and they were attempting to fix their ancestor’s mistake. The new mammalian species could have been genetically modified organisms designed as food sources, or perhaps simply designed as creatures that would survive better on the new colder Earth.
It could have been an colonial attempt by a presumably mammalian species from another star system.
The PETM was followed by several hyper-thermals similar to the PETM during the first 3 million years of the Eocene Epoch. Between 52 and 55 million years ago there were a series of short-term changes of carbon isotope composition in the ocean(4)Simone Galeotti et al. (2010) “Orbital chronology of Early Eocene hyper-thermals from the Contessa Road section, central Italy.” Earth and Planetary Science Letters, Volume 290, Pages 192-200 that led to a temperature increase of 4 to 8°C (7 to 14°F) at the surface of the ocean. As with the PETM they are not fully understood, or explained. They were likely caused by the same cause.
References [ + ]
|1.||⇑||Appy Sluijs et al. (2007) “Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary” Nature, Volume 450, Number 7173, Pages 1218–21|
|2.||⇑||Carbon-dioxide Information Analysis Center 31-Jul-2013 Dataset|
|3.||⇑||Edward Wong (July 8, 2013) “Pollution Leads to Drop in Life Span in Northern China, Research Finds” New York Times|
|4.||⇑||Simone Galeotti et al. (2010) “Orbital chronology of Early Eocene hyper-thermals from the Contessa Road section, central Italy.” Earth and Planetary Science Letters, Volume 290, Pages 192-200|