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9 - Carbon Emissions from Land-Use Change: Model Estimates Using Three Different Data Sets
- Edited by Daniel G. Brown, University of Michigan, Ann Arbor, Derek T. Robinson, University of Waterloo, Ontario, Nancy H. F. French, Michigan Technological University, Bradley C. Reed, United States Geological Survey, California
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- Book:
- Land Use and the Carbon Cycle
- Published online:
- 05 February 2013
- Print publication:
- 28 January 2013, pp 241-258
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Summary
Introduction
Land-use and land-cover change (LUCC) are an important contributor to emissions of direct (e.g., carbon dioxide [CO2], methane [CH4], and nitrous oxide[N2O]) and indirect (e.g., carbon monoxide [CO], nitrogen oxide [NOx], and nonmethane hydrocarbons) greenhouse gases to the atmosphere. The future projections for atmospheric composition and climate, as well as the associated potential for mitigating emissions and climate change, critically depend on these gases. LUCC has the potential to alter regional and global climate through changes in the biophysical characteristics of the Earth's surface (e.g., albedo and surface roughness) and changes in the biogeochemical cycles of the terrestrial ecosystems (e.g., global carbon [C] and nitrogen [N] cycles). Because of these strong links between LUCC and climate change, historical reconstruction and future projections of LUCC are necessary to better understand climate change.
Estimating the impact of historical LUCC activities on C storage from regional to global scales critically depends on understanding the disturbance history of land. This consists of knowing the current land-cover type, the process used in changing the land to its current land-cover type, and its preconversion land-cover type. Additionally, information about the age of forests, which indicates the maturity, and successional stage of the land are required. Furthermore, the biogeochemical processes and feedbacks adopted to estimate emissions are critically important. For example, it is essential for terrestrial C cycle models to consider the interactions between the terrestrial C and N cycle processes, which are altered not only by changes in LUCC activities but also climate, N inputs, and atmospheric CO2 concentrations (Jain et al. 2009). The uncertainties arising because of these factors hinder our ability to make accurate predictions of changes in the global C cycle and regional and global climate change. This is reflected by the fact that even estimates of the amount of CO2 released to the atmosphere or absorbed by the terrestrial ecosystems for years immediately following LUCC activities have been published with relatively large differences in results (Hurtt et al. 2006; Jain and Yang 2005; Yang, Richardson, and Jain 2010). For example, according to the latest Intergovernmental Panel on Climate Change (IPCC) AR4, CO2 emissions due to LUCC for the 1990s could vary between 0.5 and 2.7 Pg C·yr−1 (median value of 1.6 Pg C·yr−1) (Denman et al. 2007).
5 - The potential response of historical terrestrial carbon storage to changes in land use, atmospheric CO2, and climate
- from Part I - Climate system science
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- By Atul K. Jain, Department of Atmospheric Science, University of Illinois
- Edited by Michael E. Schlesinger, University of Illinois, Urbana-Champaign, Haroon S. Kheshgi, Joel Smith, Francisco C. de la Chesnaye, John M. Reilly, Massachusetts Institute of Technology, Tom Wilson, Charles Kolstad, University of California, Santa Barbara
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- Book:
- Human-Induced Climate Change
- Published online:
- 06 December 2010
- Print publication:
- 11 October 2007, pp 62-71
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Summary
Introduction
Modeling and measurement studies indicate that ocean and land ecosystems are currently absorbing slightly more than 50% of the human CO2 fossil emissions (Prentice et al., 2001). However, a significant question remains regarding the sources and sinks of carbon over land governed by changes in land covers and physiological processes that determine the magnitude of the carbon exchanges between the atmosphere and terrestrial ecosystems. Most of these processes are sensitive to climate factors, in particular temperature and available soil water (Post et al., 1997). It is also likely that these processes are sensitive to changes in atmospheric CO2. Moreover, the climate variation is not uniformly distributed throughout the Earth's surface or within ecosystem types. Therefore, simulations of terrestrial carbon storage must take into account the spatial variations in climate as well as non-climate factors that influence carbon storage, such as land-cover type and soil water holding capacity, that interact with climate. Estimates should also account for land-cover changes with time. Because the changes in land cover, mainly from forest to croplands or forest to pasturelands, shorten the turnover of carbon above and below ground, they act to reduce the sink capacity of the biosphere.
Historical changes in biospheric carbon storage and exchange with the atmosphere are commonly simulated with globally aggregated biospheric models (Jain et al., 1996; Kheshgi and Jain, 2003), mostly in response to changes in atmospheric CO2 and climate, or changes in land-cover types (Houghton and Hackler, 2001; Houghton, 2003).
1 - Concerns about Climate Change and Global Warming
- Edited by Robert G. Watts, Tulane University, Louisiana
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- Book:
- Innovative Energy Strategies for CO2 Stabilization
- Published online:
- 22 October 2009
- Print publication:
- 11 July 2002, pp 1-26
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Summary
Introduction
Climate is defined as the typical behavior of the atmosphere, the aggregation of the weather, and is generally expressed in terms of averages and variances of temperature, precipitation and other physical properties. The greenhouse effect, the ability of certain gases like carbon dioxide and water vapor to effectively trap some of the reemission of solar energy by the planet, is a necessary component to life on Earth; without the greenhouse effect the planet would be too cold to support life. However, human activities are increasing the concentration of carbon dioxide and several other greenhouse gases, resulting in concerns about warming of the Earth by 1–5°C over the next century (IPCC, 1996a). Recent increases in global averaged temperature over the last decade already appear to be outside the normal variability of temperature changes for the last thousand years. A number of different analyses strongly suggest that this temperature increase is resulting from the increasing atmospheric concentrations of greenhouse gases, thus lending credence to the concerns about much larger changes in climate being predicted for the coming decades. It is this evidence that led the international scientific community through the Intergovernmental Panel on Climate Change (IPCC, 1996a) to conclude, after a discussion of remaining uncertainties, “Nonetheless, the balance of the evidence suggests a human influence on global climate”. More recent findings have further strengthened this conclusion.