Carbon Dioxide Management

Carbon dioxide concentrations are growing rapidly and accelerating. The observed concentration rise is through multiple lines of evidence directly attributable to the use of gas, oil and coal. Of any emitted carbon dioxide, about 40% remains semi-permanent in the atmosphere. According to a 2007 report by the Intergovernmental Panel on Climate Change, "About 50% of a CO₂ increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years."

Three longer term processes are recognized to redistribute and eventually dissipate currently emitted carbon dioxide. The first will be ocean invasion (300 years), which can only reduce concentration by a factor of ~4, because of the establishment of a new equilibrium. The second will be a new equilibrium with carbon carbonate, which can reduce the concentration by a factor of ~3 over a 5,000 year timescale. The third stage is eventual reaction with igneous rock with a time-constant of 400,000 years. These processes are so slow, that practically zero-emissions are at some point unavoidable in order to not exceed any practical carbon dioxide concentration limit.

To avoid a global warming of 2.1°C, it is estimated that a concentration of less than 450 ppm needs to be maintained if other gasses were to return to pre-industrial levels. Currently a global warming of 0.7°C is measured, with another 0.6°C increase expected even without any further increased concentrations because the oceans are still being warmed along with the atmosphere. At the current accelerated growth rate, exponentially extrapolating the Keeling curve, this concentration will be reached in 22 years. Even with constant concentration growth, with the current 2.2 ppm/yr, this concentration will be reached in (450-390 ppm)/(2.2 ppm/yr)=27 years. These timescales are so short with respect to the timescale of the evolution such there is little doubt these concentrations will be reached soon barring any drastic behavior changes. Indeed, the lifetime of for instance power plants can be 40 to 60 years. To avoid these concentrations, an immediate reduction of the concentration growth of 3.5% per year rather than a growth of the concentration growth of 1.7% per year needs to be achieved for the foreseeable future. Reducing the concentration growth can be done by restricting emissions or with carbon sequestration. The concentration growth is dominantly affected by the net human emissions.

The current increase to 386 ppm from 280 ppm causes a radiative forcing of 1.66 W/m^2, and 1.34 W/m^2 from increases in other gases, totaling 3.00 W/m^2. The current concentration of greenhouse gases already have a heating power equaling that of a concentration of (386−280)×3.00/1.66 + 280 = 472 ppm C02-eq (carbon dioxide equivalent). Therefore, the current concentrations are high enough for over a 2 degrees Celsius temperature rise.

To be able to reduce carbon dioxide concentration with Carbon sequestration back to pre-industrial levels, (390−280 ppm)/390ppm/(50%/100) = 70% of all the existing air needs to be scrubbed off any carbon dioxide, where 50% is the percentage of carbon dioxide residing in the atmosphere (and not in the oceans), removing about (390−280 ppm)/(50%/100) = 0.03% of the air, an immense task.