Thursday, January 08, 2015

Climate Change, Natural and Un

Climate change is natural and constantly occurring.

That statement, or something like it, is frequently heard from the mouths of various proponents of the drill-baby-drill school. It has the merit of being at least partially true. It may also create the illusion that climate change, being natural, is relatively harmless.

Humans first occupied the land that is now England at least 800,000 years ago. More than once since then, climate change has completely scoured that country of humans. Such catastrophes were common and widespread during the Pleistocene. The last 12,000 years or so, the Holocene, has been much more beneficent, with a great moderation of the rapid and drastic changes that dominated the early days of our species.

It's quite plausible that it was this moderation which permitted the development of agriculture and civilization. The Holocene, until recently, has been characterized by relative stability in the second most important regulator (after insolation) of climate, the CO2 content of the atmosphere. At the end of the Pleistocene, the atmospheric CO2 rose from about 200 ppm to 280 ppm and stayed close to that until the industrial revolution and widespread fossil fuel burning started increasing it. That increase was slow at first, reaching 300 ppm about 80 years ago, but has accelerated, and now has breached the 400 ppm level.

Current CO2 levels have not been seen in several million years - a time when the climate was much different than today - and, at present rates, seem likely to have doubled the Holocene levels by mid-century.