Carbon Accounting and Policy in Copenhagen

The challenge for policy makers at the upcoming (Dec 7 - Dec 18) UN Climate Change Conference in Copenhagen can be seen from some simple carbon accounting and one equation (as discussed today in the Global Warming Debate).

The Figure above (from IPCC 2007 WG1 Ch. 7 Fig. 7.3) displays the estimated carbon cycle for the 1990's. What's important to notice is the equilibrium flows (up- and down-arrows). The black arrows indicate pre-industrial "natural" fluxes and the red arrows indicate "anthropogenic" (man-made) fluxes. The question here is how much carbon will the biosphere and the oceans absorb relative to how much is emitted. If you add together all the net fluxes for Weathering, Respiration, Land, and Oceans you get 4.4 GtC/yr of carbon absorbed by the biosphere and the oceans. Of course, notice the 6.4 GtC/yr unbalanced emission from fossil fuels.

To say it another way, the biosphere and the oceans are capable of absorbing about 4.4 GtC/yr (+/- 20%). The figure above shows the actual world carbon emissions from 1950 to 2010. In 2008, we emitted 8.59 GtC/yr which is about twice the absorptive capacity of the biosphere and oceans. In other words, sometime in the 1970's or early 1980's the world's carbon cycle went out of equilibrium. Ultimately, that equilibrium has to be restored.

The "Emissions Equations" shows our policy choices:

CO2 = (N) x (Q/N) x (E/Q) x (CO2/E)

(CO2 Emissions) = (Population) x (Output per capita) x (Energy Production per capita) x (Carbon Intensity)

(CO2 Emissions) = (Population) x (Output per capita) x (Energy Intensity) x (Carbon Intensity)

If we want to control CO2 emissions we can (1) reduce population growth, (2) reduce output per capita, (3) reduce energy intensity or (4) reduce carbon intensity. Since reducing population growth is off the table (only China has tried population control) and since reducing output per capita (economic growth) is off the table, we are left with the technical challenges of reducing energy intensity (heavily insulated buildings, electric cars, mass transit, etc.) and reducing carbon intensity using renewable energy sources (solar, wind, geothermal, etc.)

If only it was a "simple" as totally changing out our existing energy systems. The figure above shows a plot of the World's Ecological Footprint (EF), a measure of human demand on all the Earth's ecosystems. The figure above is calculated as a ratio of the number of Earths needed to support human demand over the number of earths actually available (one Earth). Interestingly enough, we exceeded the Earth's ability to meet human demands at about the same time in the 1970's that we exceeded the ability of the biosphere and the oceans to absorb our carbon emissions.

There is no immediate, quick fix technical solution (heavily insulated buildings, electric cars, etc.) for the EF problem. However, both the EF and the carbon cycle have to be brought back into equilibrium. To be successful in Copenhagen, policy makers will have to find a way to take us back the the 1970's in terms of our carbon emissions and our demands on the Earth's ecosystems. With population growth and economic growth taken off the table, they don't have a chance.