The Society based this projection on numerical models of the climate system that went into the 2007 IPCC report. The Society's advice, based on this conclusion, is a bit of an understatement: "...Emitting further large amounts of CO2 into the atmosphere over time is likely to be unwise, uncomfortable though that fact may be."

In a stellar summary of past climates, the Society builds a very convincing argument that the climate troubles we face today do not appear in isolation in Earth's history. Although the cause of CO2 levels today - namely human-induced emissions - is a uniquely modern day phenomenon, the Earth has experience tumultuous climate swings in the past.

Based on comparisons of CO2 concentrations with past eras, we may be headed for the "55 million year event," in which global temperatures shot up by 9-10.8 degrees F quite suddenly.

The so-called Paleocene-Eocene Thermal Maximum involved the release of 1,500-2,000 billion tons or more of carbon into the ocean and atmosphere, possibly from a breakdown in methane hydrates under the deep sea floor because of volcanic activity, says the Society statement.

The result was higher ocean temperatures that were more acidic and less oxygenated, and as can be imagined, the loss of many species. In this climate event and other similar ones - namely from 120 and 183 million years ago - it took 100,000 years for the climate to rebound. "...A CO2 release of such magnitude may affect the Earth's climate for that length of time," the authors say.

Other possible similarities to draw from the past:

Warming heats the ocean, causing water to expand and sea level to rise. Relatively small increases in global temperatures - just 5-9 degrees F - have caused the seas to rise by 13-39 feet.

Sudden changes, on the order of decades, can happen with the Earth's climate.

Feedbacks can accentuate the climate change already underway. It's a bit different nowadays, but the recent geologic pattern of glacial and interglacial periods over the past 800,000 years may be launched by slight tilts in the Earth's axis, which then caused CO2 releases from the oceans that reinforce the temperature increases already underway. Similarly, today's temperature increases can be magnified by methane releases in permafrost and peat bogs.

The difference between those times and now - for humans at least - is that in some ways we're even more vulnerable to dramatic climate swings. Despite modern technology and predictive ability of advanced science, the impacts of climate change, like sea level rise, are going to hit hard on a human population of 6.7 billion people (and rising).

"With the current and growing global population, much of which is concentrated in coastal cities, such a rise in sea level would have a drastic effect on our complex society, especially if the climate were to change as suddenly as it has at times in the past," the authors write.

A 100,000 year recovery - while short on the geologic timescale - is longer than any of us can imagine enduring.

As a side note, I was happy to see that a British company, Red Redemption Games, is bringing climate change to the gaming world. It's nice to see something other than the glorification of gun battles. Fate of the World "features a dramatic set of scenarios based on the latest science covering the next 200 years." You can be the "leader" who can pick a crisis and try and expertly try and solve it. Way to get people to start acting - at least virtually so.

Tens of thousands of years needed for Earth to recover from mass carbon releases
It's easy to come up with ways that carbon is released into the atmosphere - an erupting volcano, a massive wildfire, or in today's world, millions of fossil fuel burning cars and power plants. But how does carbon eventually get put back into the earth?

A paper published in Nature Geoscience scientists at Purdue University and the University of California at Santa Cruz examined the Palaeocene-Eocene Thermal Maximum, a 170,000 year period of global warming that took place 56 million years ago. It was caused by a single event that released the equivalent of burning the entire reserve of present day fossil fuels.

Obviously in the 56 million years since then, the carbon has settled out. But how long that took is a question that has puzzled scientists and has obvious relevance to climate change concerns today.

The good news, according to the study in Geoscience, is that the rate of recovery is much more rapid than expected when you take into account the absorptive abilities of the biosphere and Earth's crust. Don't get too excited. They're talking 30,000 to 40,000 years - long past the future generations within our sight.

What made the difference was the regrowth of vegetation and living organisms after the catastrophe, which do a great job of storing carbon, and ocean removal of atmospheric CO2. The oceans would have become supersaturated with carbon compounds, resulting in much of it settling onto the seafloor as carbonate deposits, which have been observed in seafloor records.

What's still not known is what triggered the onset of carbon sequestration. And, of course, tens of thousands of years is a long time to wait for that to happen, no matter how rapid that is on a geologic timescale.

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