How will permafrost affect and be affected by global environmental change?

Permafrost is defined as ground that remains at or below 0°C for at least two consecutive years. Permafrost underlies approximately 25 % of the land area in the northern hemisphere and can be up to 1500 m thick. Under current climate-change scenarios, permafrost degrades from both the top and bottom, increasing the depth of the “active layer”, and the extent of talik formation.

The deepening of the active layer could trigger the massive decomposition of organic matter stored in the first three meters below surface. The most recent estimates put the organic carbon pool in permafrost at 50% of the global soil organic carbon pool. This pool is equivalent to twice the amount of carbon in the atmosphere. The decomposition processes would lead to the emission of vast quantities of greenhouse gases, including methane and carbon dioxide, which could greatly affect the global climate.

Under the sea, permafrost occurs as subsea permafrost. Its presence on Arctic shelves is intrinsically linked to the occurrence of gas hydrates which are released to the atmosphere through “holes” in the permafrost, called gas seeps. Its exact distribution on the shelves of the Arctic has not yet been correctly assessed, which hampers the attempts to correctly depict the mechanisms of gas hydrate occurrence and release.

In alpine areas, permafrost is responsible for the occurrence and the preservation of landforms that could evolve dramatically, resulting in large scale natural hazards for alpine valley settlements. In the Arctic, rapid coastal erosion of permafrost is expected to increase dramatically following the drastic reduction of summer sea ice extent, threatening the existence of Inuit communities.

Permafrost observation and monitoring is probably one of the most important challenges of the twenty-first century

More information on theIPA website

What is the role of land-use change for the present, past, and future evolution of the Earth?

The elements for possible consideration in this question have global dimensions. These elements range from carbon storage, food production, the water cycle, climate (including albedo), human societies, to migration. Answering this question requires full Earth system models that are not yet up to the task, in part because the processes that connect key elements of these models are not well constrained or understood. There are many causes of these deficiencies, including the fact that observing land-use change is difficult on the time and space scales needed for documenting and understanding key processes.

How and why did genuine global changes happen? What were their local and global consequences on the physical environment, the ecosystems and the societies? What thresholds are involved?

Without paleoclimatic information, we would not know that atmospheric CO2 can vary naturally by up to 100 ppm on glacial-interglacial times, that abrupt climatic changes did occur on annual or decadal scales, that ice sheets may disrupt very rapidly, and basically that climate can change at all. These testimonies of how our Earth system is functioning are invaluable, yet still quite sparse and often not so well understood. They will likely deliver numerous further surprises. A great variety of climatic changes occured in the past, with many different amplitudes or consequences, and on many different time scales. When exceeding some thresholds, they were able to induce changes on the environment of past ecosystems and societies. These events should be traced back and quantified, before we can claim that we are in a position to predict future changes and their impacts.

How will the release of Siberian methane affect global warming? Can climate models predict its signature?

Because it’s a complicated process, and we can’t predict how much of the released gas may be re-absorbed by plants and the oceans, how quickly it will be released, or whether the sudden increase in methane will trigger an, as yet, un-predicted event. It is estimated that a Siberian thaw could push 500 billion tonnes of carbon dioxide gas into the atmosphere. The U.N.-sponsored Panel on Climate Change has published its estimate for global warming over the next one hundred years, producing a rise of between 3 and 11 degrees F. The addition of Siberian gas releases could change these predictions to 5 to 15 degrees F.

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 we undo the fossil fuel CO2? (A longer version: what are the most promising and sustainable strategies in carbon management and sequestration?

Given the slowness of transition towards a low-carbon economy, we are bound for a high CO2 world. It is most likely that we will have to sequester CO2 and manage the carbon pools on land and in the ocean to keep the atmospheric CO2 below a dangerous level. The unintended consequences of our ‘geophysical experiment’ (Roger Revelle) will have to be undone by intended actions that are informed by the best science. Earth system research is in a unique position to answer such a question that involves an extremely large number of disciplines and their interaction with the human dimension.

How much does loss of organic matter in soil (due to land degradation) contribute to national CO2 emissions; how much fixation will result from intensification of agriculture and conservation?

Land degradation is a widespread phenomenon in which large quantities of C are involved. Its contribution to national C-balances has not been quantified.
Explicit knowledge of this aspect of land degradation may stimulate government interest in the value of land, which is often one of the main assets of poor farmers.

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.

How to curb carbon emission and related gases released from the industries and vehicles all over the world in next decade?

Emission of carbon related gases is most responsible for global warming and green house effect. Factories, industrial zones and vehicles emit enormous amount of carbon compounds. Due to rapid deforestation such huge amount of carbon remains in the atmosphere instead of being used by the trees for the process of photosynthesis. Global warming is a result of such uncontrolled carbon emission.