The carbon sink has been present since the formation of the atmosphere and is responsible for reducing the detrimental effects of global warming on Earth.

This past Friday, Stephen W. Pacala, the Director of the Princeton Environmental Institute, gave a lecture about the vital role of the carbon sink in preventing CO2 concentration from reaching a dangerous level in the atmosphere. The carbon sink also known as carbon sequestration, refers to the intake and storage of the element carbon. The most common example of this process in nature occurs during the photosynthesis process of trees and plants, when these organisms store carbon as they absorb carbon dioxide (CO2) during growth. Because they take in carbon that would otherwise rise up and trap heat in the atmosphere, trees and plants are important players in efforts to stave off global warming.

Since the Industrial revolution, the concentration of CO2 in the Earth’s atmosphere has substantially increased.  As shown in Figure 1,the atmospheric level of carbon dioxide reached 390 ppm in 2010. Pacala noted that in 2012, this number has grown to 400 ppm. This means that the Earth’s atmosphere has reached a point at which it is technologically impossible for humans to stop the increase of atmospheric level of CO2.

atmospheric-co2

Figure 1: Atmospheric levels of carbon dioxide have grown to about 390 ppm compared to preindustrial levels of around 270-280 ppm. (Climate Central)

Pacala also stated that an acceleration of the production of CO2 in the atmosphere has been observed, which is analogous to the acceleration of ice-loss in the artic. He claimed that the acceleration of ice loss is -17 ± 8 Gt/yr2. Pacala suggested that this magnitude of acceleration could be very dangerous for coastal cities and that “goverments have to do something before we face extinction.”  Pascala claimed that the failure of US climate legislation to control the rise of atmospheric carbon to this point has condemned all of us to 10 years of additional delay. 500 ppm is the closest feasible target, a double of the pre-industrial CO2 concentration before we can stop completely the riseof atmospheric CO2.

Given Pascala’s perspective that it is technologically impossible to stop the increment of atmospheric CO2, he and other scientists are starting to look for other natural alternatives. One of these alternatives is the modeling of forests that would “sink” as much carbon possible. Plants use wood as a mean to compete with other trees. Wood enables them to fill as much space as possible and, consequently, to obtain more light to carry out photosynthesis. Wood is one of the most carbon-rich compounds that exist, and it is therefore necessary to maximize it in forests. It is also necessary to have a “Nash Equilibrium” and vary the population with plants that are not focused on creating wood, but rather on creating fine leaves, roots and nutrients. This way, important nutrients like Nitrogen and Phosphorus will be available to create more wood. Nitrogen and Phosphorus are limiting reactants in the production of wood and should therefore be considered when maximizing wood.

According to Pacala, increasing concentrations of CO2 in the Earth’s atmosphere pose a serious threat to the carbon sink.  Plants eventually reach a point at which they cannot incorporate more carbon, and the sink ceases to function.  This inefficiency makes global warming even more dangerous. Fortunately, the main reason why these models work is because it is a model that maximizes the carbon sink and therefore reduces the atmospheric concentration of CO2. But Pacala states that these processes are not enough. Pacala argued that it is necessary for the government to replace coal with natural gas, tighten national efficiency standards and make agreements with the largest carbon emitters (Europe, Japan and China).

“The survival of the human race depends on the carbon sink” Pacala concluded.

References

1. Climate Central.Atmospheric CO2 vs Time Graph. Digital image.The Washington Post. N.p., 28 Nov. 2011. Web. 27 Oct. 2012. <http://www.washingtonpost.com/blogs/capital-weather-gang/post/most-dire-global-warming-forecasts-unlikely-study-finds/2011/11/27/gIQAz2er4N_blog.html>.

2. Roger Sedjo and Brent Sohngen (2012).“Carbon Sequestration in Forests and Soils”.Annual Review of Resource Economics(Annual Reviews)4: 127-144.