Friday, November 14, 2014

Geoengineering the Anthropocene


                                        Rice Paddies produce methane.....a powerful Greenhouse gas

Earth Scientists are considering changing the name of the most recent period of Earth History.  The period since the end of the ice age, covering the last 10,000 years, is currently known as the Holocene.  The term is a composite of two Greek words, meaning something like "entirely new" or "wholly new."  The name refers to the fact that after the last Ice Age ended, earth's climate warmed and changed to something new ----a period during which more temperate conditions prevailed over much of the planet.  

But now it seems there is something even more "entirely new" then the Holocene, and thats the Anthropocene, coming from the root word "anthropos" or human.   Proponents of the Anthropocene note that humans are busily covering huge areas of the earth in rocks (i.e. concrete) and modifying much of the rest by cutting trees and farming.  Human's are also drilling oil wells, strip mining coal beds, and creating huge open pit mines to get at mineral deposits that took many many millennia to form.  But perhaps most importantly, humans are altering the climate by pumping CO2 into the atmosphere, in a kind of massive unwitting Geoengineering project.   Surely all these human-caused geologic changes are important enough to warrant the naming of new geologic period, the Anthropocene!

As usual, the devil is in the details.  Even proponents of the Anthropocene can't agree on when when the Holocene ended and the Anthropocene started.    Maybe the earth will only enter the Anthropocene sometime in the 100 years, when global warming warms the earth beyond recognition? Or maybe we are already in the Anthropocene starting with the invention of the Automobile?  Or with the industrial revolution?  Or with the invention of concrete and the building of roads during the Roman Empire?   

If it was up to me, I'd endorse Bill Ruddiman's "early Anthrogenic Warming hypothesis" and say the Anthropocene started when the Chinese invented rice agriculture, and proceeded to transform huge areas of southeast Asia from mostly dry, arid hillslopes  into made-by-hand terraced wetlands that could support rice.  Ruddiman noted that Rice began to be cultivated ca. 8000 years ago, but more recent work shows that rice may've been initially domesticated 10-12,000 years ago.  Once rice agriculture was invented, it quickly spread through China.  More land in Japan, VietNam, Cambodia, Laos and other parts of Southeast Asia were transformed into rice paddies a bit later.  Taken together, the construction of terraces and rice paddies across SE Asia is the single largest human engineering effort anywhere on the planet. 

And these rice paddies can be considered to be an early planetary geoengineering project.  Each of the paddies produces methane, a greenhouse gas much more powerful than CO2.  The global methane flux jumped significantly at periods in the past when rice agriculture is known to have expanded, producing small increments of global warming thousands of years ago.  






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