Climate Change Impacts for the Conterminous USA: An Integrated Assessment     

Allison?M.?ThomsonEmail author  Robert?A.?Brown  Norman?J.?Rosenberg  R.?Cesar?Izaurralde  Verel?Benson 《Climatic change》2005,69(1):43-65

Here we simulate dryland agriculture in the United States in order to assess potential future agricultural production under a set of general circulation model (GCM)-based climate change scenarios. The total national production of three major grain crops—corn, soybeans, and winter wheat—and two forage crops—alfalfa and clover hay—is calculated for the actual present day core production area (CPA) of each of these crops. In general, higher global mean temperature (GMT) reduces production and higher atmospheric carbon dioxide concentration ([CO₂]) increases production. Depending on the climatic change scenarios employed overall national production of the crops studied changes by up to plus or minus 25% from present-day levels. Impacts are more significant regionally, with crop production varying by greater than ±50% from baseline levels. Analysis of currently possible production areas (CPPAs) for each crop indicates that the regions most likely to be affected by climate change are those on the margins of the areas in which they are currently grown. Crop yield variability was found to be primarily influenced by local weather and geographic features rather than by large-scale changes in climate patterns and atmospheric composition. Future US agronomic potential will be significantly affected by the changes in climate projected here. The nature of the crop response will depend primarily on to what extent precipitation patterns change and also on the degree of warming experienced.  相似文献   

Climate Change Impacts for the Conterminous USA: An Integrated Assessment Summary     

James?A.?Edmonds  Norman?J.?RosenbergEmail author 《Climatic change》2005,69(1):151-162

This special issue of Climatic Change describes an effort to improve methodology for integrated assessment of impacts and consequences of climatic change. Highlights of the seven foregoing Parts (papers) that constitute this special issue are summarized here. The methodology developed involves construction of scenarios of climate change that are used to drive individual sectoral models for simulating impacts on crop production, irrigation demand, water supply and change in productivity and geography of unmanaged ecosystems. Economic impacts of the changes predicted by integrating the results of the several sectoral simulation models are calculated through an agricultural land-use model. While these analyses were conducted for the conterminous United States alone, their global implications are also considered in this summary as is the need for further improvements in integrated assessment methodology.  相似文献   

Water quality in the Great Barrier Reef region: responses of mangrove, seagrass and macroalgal communities   总被引：1，自引：0，他引：1  

Schaffelke B  Mellors J  Duke NC 《Marine pollution bulletin》2005,51(1-4):279-296

Marine plants colonise several interconnected ecosystems in the Great Barrier Reef region including tidal wetlands, seagrass meadows and coral reefs. Water quality in some coastal areas is declining from human activities. Losses of mangrove and other tidal wetland communities are mostly the result of reclamation for coastal development of estuaries, e.g. for residential use, port infrastructure or marina development, and result in river bank destabilisation, deterioration of water clarity and loss of key coastal marine habitat. Coastal seagrass meadows are characterized by small ephemeral species. They are disturbed by increased turbidity after extreme flood events, but generally recover. There is no evidence of an overall seagrass decline or expansion. High nutrient and substrate availability and low grazing pressure on nearshore reefs have lead to changed benthic communities with high macroalgal abundance. Conservation and management of GBR macrophytes and their ecosystems is hampered by scarce ecological knowledge across macrophyte community types.  相似文献   

Power spectra of the interplanetary magnetic field     

James W. Sari  Norman F. Ness 《Solar physics》1969,8(1):155-165

Power spectra based on Pioneer 6 interplanetary magnetic field data in early 1966 exhibit a frequency dependence of f ^–2 in the range 2.8 × 10^–4 to 1.6 × 10^–2 cps for periods of both quiet and disturbed field conditions. Both the shape and power levels of these spectra are found to be due to the presence of directional discontinuities in the microstructure (< 0.01 AU) of the interplanetary magnetic field. Power spectra at lower frequencies, in the range of 2.3 × 10^–6 to 1.4 × 10^–4 cps, reflect the field macrostructure (> 0.1 AU) and exhibit a frequency dependence roughly between f ^–1 and f ^–3/2. The results are related to theories of galactic cosmic-ray modulation and are found to be consistent with recent observations of the modulation.  相似文献   

Spectrum measurements of the sun near 1 cm wavelength     

Staelin  David H.  Gaut  Norman E.  Law  Sara E.  Sullivan  Woodruff T. 《Solar physics》1968,3(1):26-27

The solar brightness temperature was measured at frequencies of 19.0, 21.0, 22.2, 23.5, and 25.5 GHz on 8 days in February and March, 1966. The observed average brightness temperatures were 10 800, 10 900, 11 000, 10 700, and 9 800°K, respectively. The daily values were close to these averages.Presently at the University of Maryland.  相似文献   

Letters to the editor     

John C. Gower  Norman Gray  M. E. Demina  Basanta K. Sahu 《Mathematical Geology》1973,5(2):203-209

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Geometric selection in two-dimensional crystal aggregates     

Norman H. Gray 《Mathematical Geology》1984,16(1):91-100

The simultaneous growth of randomly oriented crystals nucleated at a surface rapidly produces a coarsely crystalline radial or columnar aggregate possessing a strong preferred shape and lattice orientation. Such textures are common in natural crystalline aggregates and are considered to arise because those crystals having their fastest growth direction normal to the initial substrate outdistance and eventually eliminate their less favorably oriented neighbors. In its simplest form the process of elimination is a purely geometric phenomenon. Detailed analysis and computer simulation of textural changes accompanying geometric selection in random two dimensional needlelike crystal aggregates demonstrate that selection initially proceeds exceedingly rapidly but slows drastically once roughly 90 percent of the crystals originally present are eliminated. Subsequent decrease in crystal density is inversely proportional to the square root of the distance from the initial substrate. Increases in crystal size larger than one or two orders of magnitude are thus unlikely to arise in natural crystalline aggregates in which only simple geometric selection is involved.  相似文献   

PCB-containing paint and plaster caused extreme PCB-concentrations in biota from the Sørfjord (Western Norway)--a case study     

Ruus A  Green NW  Maage A  Skei J 《Marine pollution bulletin》2006,52(1):100-103

The Sørfjord (Western Norway) has a long history of industry and pollution, and has been monitored for several decades. The environmental monitoring has comprised analyses of different contaminants in sea water, mussel, fish, seaweed and sediments. Measurements of polychlorinated biphenyls (PCBs) in blue mussels (Mytilus edulis) some 17 years ago indicated a local source. In 2001 severe concentrations were measured in blue mussels and further investigations disclosed the primary source of PCBs in the Sørfjord. In 2002, extreme PCB-concentrations were found in cod (Gadus morhua) from the same area. However, no induction of EROD activity was detected, indicating the limitations of this assay as marker for PCB contamination. A future scientific challenge will be to understand the specific mechanisms and effects of such PCB accumulation in fish.  相似文献   

Participatory modeling in dairy farm systems: a method for building consensual environmental sustainability using seasonal climate forecasts     

Victor E. Cabrera  Norman E. Breuer  Peter E. Hildebrand 《Climatic change》2008,89(3-4):395-409

Dairy farmers face increasing pressure to decrease environmental impact while remaining economically viable. Adaptation of farm management practices in response to seasonal climate forecasts may be one means of achieving these objectives. This paper describes the interactive and iterative process by which farmers, researchers, extension agents, regulatory agencies, and other stakeholders collaborated to create, calibrate, and validate the Dynamic North Florida Dairy Farm model (DyNoFlo), a whole-farm decision support system to decrease nitrogen leaching while maintaining profitability under variable climate conditions. Participatory modeling may enhance the creation of adoptable and adaptable user-friendly models that include environmental, economic and biophysical components. By providing farmers, policy makers, and other stakeholders with a more holistic view of current practices, common ground among them was more easily identified and collaboration was fostered. Farmer values included willingness to be good environmental stewards when they are profitable. The participatory research and development process enhanced understanding of and potential adaptation to seasonal climate variability conditioned to the El Niño Southern Oscillation (ENSO) phases in light of increasing environmental regulations and economic challenges. Adoption of the collaboratively-developed DyNoFlo is expected to be higher than usual because stakeholders feel greater ownership of the final product.  相似文献   

Magnetic zones of Mars: Deformation‐controlled origin of magnetic anomalies     

Gunther KLETETSCHKA  Robert J. LILLIS  Norman F. NESS  Mario H. ACUÑA  Jack E. P. CONNERNEY  Peter J. WASILEWSKI 《Meteoritics & planetary science》2009,44(1):131-140

Abstract— Intense magnetic anomalies over Martian surface suggest preservation of large volumes of very old crust (>3 Gyr) that formed in the presence of a global magnetic field. The global distribution of the magnetic intensities observed above the Martian crust suggests a division into three zones. Zone 1 is where the magnetic signature is negligible or of relatively low intensity at Mars Global Surveyor (MGS) satellite mapping altitude (400 km). Zone 2 is the region of intermediate crustal magnetic amplitudes and zone 3 is where the highest magnetic intensities are measured. Crater demagnetization near zone 3 reveals the presence of rocks with both high magnetic intensity and coercivity. Magnetic analyses of terrestrial rocks show that compositional banding in orogenic zones significantly enhances both magnetic coercivity and thermal remanent magnetization (TRM) efficiency. Such enhancement offers a novel explanation for the anomalously large intensities inferred of magnetic sources on Mars. We propose that both large magnetic coercivity and intensity near the South Pole is indicative of the presence of a large degree of deformation. Associated compositional zoning creates conditions for large scale magnetic anisotropy allowing magnetic minerals to acquire magnetization more efficiently, thereby causing the distinct magnetic signatures in zone 3, expressed by intense magnetic anomalies. We use a simple model to verify the magnetic enhancement. We hypothesize that magnetically enhanced zone would reside over the down welling plume at the time of magnetization acquisition.  相似文献