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Mapped Atmosphere-Plant-Soil System Study
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP). The goal of the IPCC is to conduct assessments at regional to global scales of the potential impacts of global warming and their possible feedbacks to climate change. The IPCC consists of three working groups composed of researchers from around the globe that assess information on the climate system and climate change (Working Group I); the effects of climate change on ecological systems, socioeconomic sectors, and human health (Working Group II); and the effects of mitigation of climate change on these areas (Working Group III).
The IPCC has made extensive use of MAPSS model output in regional and global assessments of climate change impacts on vegetation. The IPCC is commissioned to produce assessments every 5 years, the second of which was produced in 1995 (Climate Change 1995: Impacts, adaptations and mitigation of climate change: scientific-technical analyses. Watson, R.T.; Zinyowera, M.C.; Moss, R.H., eds. Cambridge, UK: Cambridge University Press. 878 p.). MAPSS output was used in the analysis of impacts on the forest sector (Volume II, Impacts, Adaptations, and Mitigation of Climate Change) and in the analysis of biosphere-atmosphere feedbacks (Volume I, The Science of Climate Change).
The IPCC produced a special report to assist in the recent Kyoto negotiations of the FCCC on controlling emissions of CO2. The new report (The Regional Impacts of Climate Change. Watson, R.; Zinyowera, M.; Moss, R., eds. 1998. Cambridge University Press.) focused on multisector assessments within 10 large regions of the globe, one of which was North America North of Mexico. MAPSS team leader, Ron Neilson, was appointed by the Office of Science and Technology Policy of the White House as the lead author of the forest sector for this region. Dr. Neilson produced new MAPSS simulations for the special report, based on the latest future climate projections. Assessment products were provided for all 10 regions for the overall assessment of vegetation and water resources and were presented in a special annex to the report.
MAPSS Vegetation Distribution (Current Climate)
Under future global warming, forest boundaries that are limited by cold temperature will shift toward the poles and upward in elevation. However, boundaries that are limited by water, for example, transitions between closed forest and open savanna, could shift toward either drier or wetter conditions, depending on several factors. Increased temperatures will tend to cause drought-induced declines; regional increases in precipitation could mitigate the negative effects of increased temperatures, and elevated CO2 concentration could increase the water-use efficiency of trees and also mitigate the negative impacts of elevated temperatures.
In the early stages of global warming, benefits from elevated CO2 concentrations could dominate the negative effects of increased temperatures, resulting in a broad-scale increase in productivity and density of most forests worldwide. However, the benefits from elevated CO2 could possibly plateau within a few decades while temperatures continue to rise. Eventually, perhaps toward the end of the 21st century, the negative effects from elevated temperature would become dominant, and forests could begin a very large-scale drought-induced decline, thus negating the earlier gains.
Temperate conifer forests in the Northwest will expand in importance in Alaska and in southwest Canada. Tundra and taiga/tundra regions of Alaska will be much reduced in area with expansions of both boreal and temperate conifer forests into those regions. Forests in Washington and Oregon could initially expand in area and density over the next few decades. However, if warming continues, early gains could be more than offset by later losses in both area and density of forests. Drier forest types, such as those in the Klamath region, could expand further north in the coast range, and fires could become more prevalent west of the Cascades over the mid to latter parts of the 21st century.
East of the Cascades, fires could increase whether the region gets greener or drier. If the region initially gets greener, more fine fuels would accumulate, potentially exacerbating the current high fuel conditions, resulting in more and larger fires under periodic short-term droughts. Under drying conditions, later in the 21st century, high fuel loads would become dry and larger fires could again become likely.
If forests in the Northwest initially respond with increased productivity and density, they would sequester more carbon, acting as a negative feedback to further global warming. However, increased forest densities would result in more water use by trees, and less water could become available for irrigation and domestic uses. Under continued warming, if forests begin to decline, they would use less water and, in combination with less snow formation and earlier melt, could result in increased winter flows with possible flooding.
MAPSS Vegetation Distribution (Current Climate)
The Third Assessment Report is scheduled for completion in 2001.
Neilson, R.; Prentice, I.; Smith, B.; Kittel, T.; Viner, D. 1998. Simulated changes in vegetation distribution under global warming. In: Watson, R.; Zinyowera, M.; Moss, R.; Dokken, D., eds. The regional impacts of climate change: an assessment of vulnerability. Cambridge, UK: Cambridge University Press: 439-456.
Shriner, D.; Street, R.; Ball, R.; D'Amours, D.; Duncan, K.; Kaiser, D.; Maarouf, A.; Mortsch, L.; Mulholland, P.; Nelson, R.; Patz, J.; Scheraga, J.; Titus, J.; Vaughan, H.; Weltz, M., et al. 1998. North America. In: Watson, R.; Zinyowera, M.; Moss, R.; Dokken, D., eds. The regional impacts of climate change: an assessment of vulnerability. Cambridge, UK: Cambridge University Press: 255-330.
US Forest Service - Pacific Northwest Research Station, Mapped
Atmosphere-Plant-Soil System Study