Can marginal seas account for the missing CO2 and is the marginal sea sink affected by human activities on land?

Current estimate of CO2 uptake by the oceans by and large ignored marginal seas and continental shelves. Preliminary investigations indicate that these areas are a larger sink of CO2 than open oceans on the per area basis. If proven, this sink may be as large as 25% of the oceanic sink. Human activities on land are affecting this sink via construction of dams, increasing nutrient discharge into the continental shelves, etc. Global synthesis, however, is nonexistent because of insufficient data.

Where is the missing atmospheric carbon dioxide?

About 25 to 35% of the carbon dioxide released to the atmosphere is missing according to the 2007 IPCC Report.

Understanding the mechanisms that are removing this missing carbon dioxide from the atmosphere will improve predictions of future carbon dioxide levels, estimates of future global warming, and be useful for evaluation atmospheric carbon dioxide mitigation strategies.

The search for the “missing sink” has been going on for decades. Broecker et al. (1979) identified this problem. A paper written by Tans et al. (1990) launched a major research effort to find the missing sink.

After three decades of research, scientists still do not have a full understanding of the “missing sink.” This is the most important question facing Earth System researchers at present.

References

Broecker, WS, T. Takahashi, HJ Simpson & TH Peng. 1979. “Fate of Fossil Fuel Carbon Dioxide and the Global Carbon Budget.” Science, 206, 409-418.
DOI: 10.1126/science.206.4417.409

IPCC, 2007. www.ipcc.ch

Tans, PP, IY Fung, T Takahashi. 1990. “Observational Constraints on the Global Atmospheric CO2 Budget.” Science, Vol. 247, pp. 1431-1438.
DOI: 10.1126/science.247.4949.1431

How can the earth’s vegetation and biota be used to help offset already high atmospheric CO2 levels in order to minimize or mitigate the effects of climate change on the biosphere?

Because Earth’s climate is already changing, and regardless of how policy changes human inputs of CO2, we are going to lose biodiversity if we do not start to understand how we can used biodiversity to mitigate high atmospheric CO2. We already have examples of the use of forests and tree planting to bank carbon. However, a large component of biota occurs in grasslands and earlier successional systems which are not being promoted as potential carbon banks. If we procede to approach the climate change issue with just planting trees we will end up losing those biota that cannot live in forests.

Is there a critical global temperature rise at which the biosphere will switch from being a net sink of CO2 to being a net source?

Current plans to mitigate climate change assume that reducing anthropogenic emissions of CO2 will eventually stop the increase in atmospheric concentrations. There is concern, however, that rising temperatures could trigger changes in the biosphere such that the biosphere becomes a net source. If such a critical temperature exists, exceding it would have catastrophic consequences.

What do Amazonian Dark Earths or terra preta have to do with the Global Climate and what lessons can they teach us about sustainable development and human/environment interaction?

We currently know little about Amazonian Dark Earths. They are ubiquitous prehistoric human-made soils that store significant amounts of carbon and are thus a global carbon sink. The soils are exceptionally fertile and resilient, standing out from the predominantly infertile Amazonian soils. Some scientists have already suggested that we could create terra preta and develop more productive and sustainable agriculture in the tropics. Most importantly, prehistoric native Amazonians practiced a more sustainable, environmentally-friendly form of food production that once supported dense populations and complex societies in the Amazon Rainforest.

How will natural and human controls on the atmospheric CO2 concentration operate under the influence of changing climate and changing society in the next 100 years?

We can budget the sources and sinks for carbon for the past 30 years, with increasing confidence over time (Global Carbon Project, 2009). However, we do not have a solid understanding of the mechanisms responsible for variability and change in the natural sinks; nor for potentially dramatic releases of CO2 from permafrost or methane clathrates. We have even less understanding of the societal controls on the CO2 source (beyond a basic need for energy), and thus we do not have a good basis to predict or to control emissions.