Reply #3: Here's info about the worst "global warming" ever on Earth...

[FormerRepublican]

"The end of the Paleocene (55.5/54.8 Ma) was marked by one of the most significant periods of global change during the Cenozoic, a sudden global climate change, the Paleocene-Eocene Thermal Maximum (PETM), which upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and on land, a major turnover in mammals.

In an event marking the start of the Eocene, the planet heated up in one of the most rapid and extreme global warming events recorded in geologic history, currently being identified as the 'Paleocene-Eocene Thermal Maximum' or the 'Initial Eocene Thermal Maximum' (PETM or IETM). Sea surface temperatures rose between 5 and 8°C over a period of a few thousand years. In 1990, marine scientists James Kennett and Lowell Stott, both then at the University of California, Santa Barbara, reported analysis of marine sediments showing that, not only had the surface of the Antarctic ocean heated up about 10 degrees at the beginning of the Eocene, but that the entire depth of the ocean had warmed, and its chemistry changed disastrously. There was severely reduced oxygen in deep sea waters, and 30 to 40% of deep sea foraminifera suddenly went extinct. Geologist Jim Zachos of the University of California, Santa Cruz has connected the Eocene heat wave to drastic changes in ocean chemistry that caused the massive worldwide die-off. More recently a synchronous drop in carbon isotope ratios has been identified in many terrestrial environments.

What unleashed the PETM is unclear. Most fingers of blame point to 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.

Tracking the ratio of carbon isotopes in marine calcium carbonate sediments, Kennett and Stott found a sharp decrease in the amount of heavy carbon in 55-million-year-old marine fossils, a decline that caused the relative ratio of 13C to 12C to plunge. A gas with very low amounts of heavy 13C must have literally flooded the atmosphere. In 1995, Gerry Dickens, University of Michigan, argued that only methane gas had enough light carbon to produce the early Eocene plunge. He proposed that a belch of methane escaped from ice in seafloor sediments as the Earth warmed during the latest Paleocene. The methane escaped from submarine clathrates, ice crystals that trap methane hydrate, a form of methane 'ice' that forms in cold bottom water under great pressures and is widely distributed and plentiful in sediments on the outer edges of continental margins. Methane has a global warming potential (GWP) over a 100 year period of 23<1>, meaning per kilogram it is estimated to be 23 times as effective as carbon dioxide as a greenhouse gas. The massive sublimation and release of sedimentary methane hydrates into the ocean-atmosphere reservoir upset the global carbon cycle and led to runaway global warming."

http://en.wikipedia.org/wiki/Paleocene-Eocene_Thermal_Maximum

Worst case scenario - far worse than Earth has ever seen before? Big ocean burp of methane, kills all life on Earth. Regeneration - maybe.

Would global warming this time around be worst case? :shrug:

If we're lucky, it won't get that bad.