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Beyond Green: Three numbers to know for safe levels of CO2 concentration  

There are three numbers that any environmentally informed citizen should know about: 275, 350 and 392. No, they don't make up a winning lottery number or a password to some treasure account: They refer to the concentration of carbon dioxide in the atmosphere, in parts per million (ppm).

Carbon dioxide is one of the greenhouse gases that helps trap heat in the atmosphere, preventing the earth from having temperature swings similar to the moon - a clearly inhospitable environment. So some CO2 is very useful. In fact, for most of the last several million years, up until the late 1800s, our atmosphere had a concentration between 180 and 275 ppm CO2, and life as we know it flourished. Out of the growing research and evidence around global warming over the past decades, many scientists, climate experts and progressive national governments have determined that the safe upper limit to ppm concentration of CO2 is 350.

The last number, 392, is the ppm concentration of CO2 in the atmosphere today, well beyond the upper safe limit.

Recent reports from NASA's key indicators regarding global climate change include the decline of Arctic sea ice at a rate of 11.5 percent per decade relative to the 1979-2000 average (www.climate.nasa.gov); loss of land ice at the rate of 24 cubic miles per year since 2002; and an increase in the rise of sea level since 1993 to 3.17 mm per year. These and other indicators describe the trend toward increasing climate instability and likelihood of abrupt climate changes because we have exceeded a safe concentration of CO2 in the atmosphere.

Think of flipping a light switch at night. Increased pressure on the switch eventually makes the room go from dark to light or vice versa. The change is instantaneous and dramatic, even though relatively slow in coming.

Multiple strategies will be necessary to return atmospheric concentrations below 350 ppm CO2, including dramatically reducing the amount of fossil fuels burned and supporting reforestation and other ways to recapture atmospheric carbon and store it in carbon sinks. Similar to the strategy to re-balance a national budget, this is called carbon sequestration, for it is also about creating a more sustainable carbon budget by removing carbon from the atmosphere and depositing it in a reservoir.

The difference between the two is that sequestering carbon to stabilize the climate is a mutually enhancing activity that benefits all people and the entire living community.

Emerging forests sequester carbon each growing season, as do soils and peat bogs - and all three serve as important carbon storage "sinks."

Perhaps one of the most promising of all carbon sequestration strategies is the process of converting biomass to charcoal or biochar through the process of pyrolysis. Pyrolysis, or gasification, involves heating a biomass in the absence - or near absence - of oxygen, thereby storing more than 50 percent of the carbon in the material. This resulting carbon resists degradation and can be held in the soil for hundreds to thousands of years. At the same time, it can greatly enhance the soil and generate heat energy.

It has been estimated that this relatively simple technology - possible at industrial and backyard scales - could be used to store 2.2 gigatons of carbon annually by 2050, about twothirds of what is presently accumulating in the atmosphere each year.

Combined with energy conservation, efficiency and converting to clean, renewable energy sources, pursuing the development of biochar production could be part of an effective strategy to return to below that critical 350 ppm CO2.

When asked to list three important points, local resident and five-year biochar enthusiast Doug Clayton noted soil benefits due to the high adsorption property that stabilizes nutrients and water and permanent sequestration of carbon due to thermal alteration that makes it indigestible to microorganisms; thirdly, he said, "(It's) not a silver bullet, (as) biochar systems have to work with all the other changes to our relationship with the earth."

For more information, visit www.biochar-international.org, terrapreta.

bioenergylists.org and www.biocharnortheast.org.

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