In the March issue of The Walrus, Alanna Mitchell talks about the impact of abrupt climate change, focusing on a historic precedent.

Fifty-five million years ago, there was a period called the Paleocene-Eocene Thermal Maximum (PETM). "Scientists considerd the remains of the PETM, which were first discovered 15 years ago, to be the Rosetta Stone of global climate change, the nearest prallel in the fossil record to what is happening to the planet right now," she writes.

What is particularly scary about this is that "the PETM indicates that the catastrophic effects on the planet's biosphere of a massive rise in carbon levels could come into play in our lifetimes -- long before any major steps can be taken to avert the problem."

Her article was apparently finished before the fourth assessment of the Intergovernmental Panel on Climate Change was released (here's a CTV.ca backgrounder).

Mitchell made the point that some scientists fear they have undersold their findings. "The changes are taking place at the more severe end of the spectrum, and they are happening more quickly than many had expected. Global climate change is shaping up to be both intense and abrupt."

She mentions the 2003 Pentagon report on the spectre of abrupt climate change and the implications for U.S. national security.

Greenpeace has archived the document here. Here are some excerpts:

Ocean, land, and atmosphere scientists at some of the world’s most prestigious organizations have uncovered new evidence over the past decade suggesting that the plausibility of severe and rapid climate change is higher than most of the scientific community and perhaps all of the political community is prepared for. If it occurs, this phenomenon will disrupt current gradual global warming trends, adding to climate complexity and lack of predictability. And paleoclimatic evidence suggests that such an abrupt climate change could begin in the near future. ...

Abrupt climate change is likely to stretch carrying capacity well beyond its already precarious limits. And there’s a natural tendency or need for carrying capacity to become realigned. As abrupt climate change lowers the world’s carrying capacity aggressive wars are likely to be fought over food, water, and energy. Deaths from war as well as starvation and disease will decrease population size, which overtime, will re-balance with carrying capacity.

According to this article, extreme climate change could start to hit within the 15 to 45 years, according to the scientists Mitchell spoke with.And most of the life forms currently on the planet, including humans, are adapted to the relatively cool conditions we see now.

I hope that scenario is wrong, and that we're not really into a period of abrupt climate change. We should all hope that.