|Abstracts on Global Climate Change|
Analysis of the conflict between omission and commission in low spatial resolution dichotomic thematic products: The Pareto Boundary
Boschetti, L Flasse, SP Brivio, PA
REMOTE SENSING OF ENVIRONMENT 91:3-4 280-292
During the last few years, the remote sensing community has been trying to address the need for global synthesis to support policy makers on issues such as deforestation or global climate change. Several global thematic products have been derived from large datasets of low-resolution remotely sensed data, the latter providing the best trade-off between spatial resolution, temporal resolution and cost. However, a standard procedure for the validation of such products has not been developed yet. This paper proposes a methodology, based on statistical indices derived from the widely used Error Matrix, to deal with the specific issue of the influence of the low spatial resolution of the dataset on the accuracy of the end-product, obtained with hard classification approaches. In order to analyse quantitatively the trade-off between omission and commission errors, we suggest the use of the ‘Pareto Boundary’, a method rooted in economics theory applied to decisions with multiple conflicting objectives. Starting from a high-resolution reference dataset, it is possible to determine the maximum user and producer’s accuracy values (i.e. minimum omission and commission errors) that could be attained jointly by a low-resolution map. The method has been developed for the specific case of diebotomic classifications and it has been adopted in the evaluation of burned area maps derived from SPOT-VGT with Landsat ETM+ reference data. The use of the Pareto Boundary can help to understand whether the limited accuracy of a low spatial resolution map is given by poor performance of the classification algorithm or by the low resolution of the remotely sensed data, which had been classified. (C) 2004 Elsevier Inc. All rights reserved.
Simulating the spatio-temporal variability of streamflow response to climate change scenarios in a mesoscale basin
Drogue, G Pfister, L Leviandier, T El Idrissi, A Iffly, JF Matgen, P Humbert, J Hoffmann, L
JOURNAL OF HYDROLOGY 293:1-4 255-269
A continuous rainfall-runoff simulation was performed to assess the potential effect of climate changes on the streamflow regimes and water resources of tributaries of the Alzette river basin extending over 1176 km(2), mainly in the Grand Duchy of Luxembourg. characterized by various hydrological patterns. Global climate change scenarios for the 2050 horizon, based on GCM projections from the KNMI and UKHI synoptic runs, were disaggregated into mesoscale daily PET and rainfall series. Seasonal expected PET changes were proportionally applied to present daily values, whereas future hyetographs were empirically constructed according to observed trends in rainfall time series for the study area. The various ways of applying the mesoscale rainfall scenarios exert a significant influence on the magnitude and spatial distribution of streamflow responses. The comparison of future and present hydrographs also shows that the impact of mesoscale climate change is extremely variable with regard to the considered hydrological variable. The spatial variability of streamflow responses is largely conditioned by climatic and physiographical characteristics of the sub-basins. The winter period is most affected by altered climate conditions and some sub-re ions appear to be particularly sensitive in terms of changes in low or high flows. (C) 2004 Elsevier B.V. All rights reserved.
Decadal-scale climate drivers for glacial dynamics in Glacier National Park, Montana, USA
Pederson, GT Fagre, DB Gray, ST Graumlich, LJ
GEOPHYSICAL RESEARCH LETTERS 31:12 -
Little Ice Age (14th-19th centuries A. D.) glacial maxima and 20th century retreat have been well documented in Glacier National Park, Montana, USA. However, the influence of regional and Pacific Basin driven climate variability on these events is poorly understood. We use tree-ring reconstructions of North Pacific surface temperature anomalies and summer drought as proxies for winter glacial accumulation and summer ablation, respectively, over the past three centuries. These records show that the 1850’s glacial maximum was likely produced by similar to70 yrs of cool/wet summers coupled with high snowpack. Post 1850, glacial retreat coincides with an extended period (>50 yr) of summer drought and low snowpack culminating in the exceptional events of 1917 to 1941 when retreat rates for some glaciers exceeded 100 m/yr. This research highlights potential local and ocean-based drivers of glacial dynamics, and difficulties in separating the effects of global climate change from regional expressions of decadal-scale climate variability.
Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204
Trehu, AM Long, PE Torres, ME Bohrmann, G Rack, FR Collett, TS Goldberg, DS Milkov, AV Riedel, M Schultheiss, P Bangs, NL Barr, SR Borowski, WS Claypool, GE Delwiche, ME Dickens, GR Gracia, E Guerin, G Holland, M Johnson, JE Lee, YJ Liu, CS Su, X Teichert, B Tomaru, H Vanneste, M Watanabe, M Weinberger, JL
EARTH AND PLANETARY SCIENCE LETTERS 222:3-4 845-862
Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base in contrasting geological settings defined by a 3D seismic survey. By integrating results from different methods, including several new techniques developed for Leg 204, we overcome the problem of spatial under-sampling inherent in robust methods traditionally used for estimating the hydrate content of cores and obtain a high-resolution, quantitative estimate of the total amount and spatial variability of gas hydrate in this structural system. We conclude that high gas hydrate content (30-40% of pore space or 20-26% of total volume) is restricted to the upper tens of meters below the seafloor near the summit of the structure, where vigorous fluid venting occurs. Elsewhere, the average gas hydrate content of the sediments in the gas hydrate stability zone is generally < 2% of the pore space, although this estimate may increase by a factor of 2 when patchy zones of locally higher gas hydrate content are included in the calculation. These patchy zones are structurally and stratigraphically controlled, contain up to 20% hydrate in the pore space when averaged over zones similar to 10 m thick, and may occur in up to similar to 20% of the region imaged by 3D seismic data. This heterogeneous gas hydrate distribution is an important constraint on models of gas hydrate formation in marine sediments and the response of the sediments to tectonic and environmental change. Published by Elsevier B.V.
Soil carbon sequestration impacts on global climate change and food security
SCIENCE 304:5677 1623-1627
The carbon sink capacity of the world’s agricultural and degraded soils is 50 to 66% of the historic carbon loss of 42 to 78 gigatons of carbon. The rate of soil organic carbon sequestration with adoption of recommended technologies depends on soil texture and structure, rainfall, temperature, farming system, and soil management. Strategies to increase the soil carbon pool include soil restoration and woodland regeneration, no-till farming, cover crops, nutrient management, manuring and sludge application, improved grazing, water conservation and harvesting, efficient irrigation, agroforestry practices, and growing energy crops on spare lands. An increase of 1 ton of soil carbon pool of degraded cropland soils may increase crop yield by 20 to 40 kilograms per hectare (kg/ha) for wheat, 10 to 20 kg/ha for maize, and 0.5 to 1 kg/ha for cowpeas. As well as enhancing food security, carbon sequestration has the potential to offset fossil-fuel emissions by 0.4 to 1.2 gigatons of carbon per year, or 5 to 15% of the global fossil-fuel emissions.
Release of methane from a volcanic basin as a mechanism for initial Eocene global warming
Svensen, H Planke, S Malthe-Sorenssen, A Jamtveit, B Myklebust, R Eidem, TR Rey, SS
NATURE 429:6991 542-545
A 200,000-yr interval of extreme global warming marked the start of the Eocene epoch about 55 million years ago. Negative carbon-and oxygen-isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid (similar to10,000 yr) input of isotopically depleted carbon(1,2). It has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source(3,4) and has caused the global climate change. Large-scale hydrate melting, however, requires a hitherto unknown triggering mechanism. Here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the Voring and More basins in the Norwegian Sea. We propose that intrusion of voluminous mantle-derived melts in carbon-rich sedimentary strata in the northeast Atlantic may have caused an explosive release of methane-transported to the ocean or atmosphere through the vent complexes-close to the Palaeocene/Eocene boundary. Similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the Siberian Traps (similar to250 million years ago) and the Karoo Igneous Province (similar to183 million years ago).
Changing global climate: Historical carbon and nitrogen budgets and projected responses of Ohio’s cropland ecosystems
Evrendilek, F Wali, MK
ECOSYSTEMS 7:4 381-392
As the evidence of global climate change continues to mount, its consequences for cropland productivity assume particular significance. Against the backdrop of past agricultural practices, simulation models offer a glimpse into the future, showing the effect of temperature changes on crop production. In this study, we first quantified the carbon (C) and nitrogen (N) budgets of Ohio’s cropland ecosystems using inventory yield data of corn for grain, oat, and all wheat for the period 1866-1996 and soybean for the period 1924-96. Then we explored the responses of Ohio’s continuous soybean croplands to changes in temperature, carbon dioxide (CO2) concentration, initial soil organic C and N (SOC-N) pools, soil texture, and management practices by developing a simple cropland ecosystem model (CEM) and performing a long-term sensitivity analysis. Finally, CEM simulations were evaluated against independent observations of SOC values (0-19 cm) averaged over 470 northwest Ohio sites between 1954 and 1987 under conventional tillage and rotations of corn-soybean-winter wheat by using the historical yield data (r(2) = 0.8). The C contents per hectare of crop harvests increased by 178% for oats, 300% for corn for grain, and 652% for all wheat between 1866 and 1996 and by 305% for soybean between 1924 and 1996. Ohio croplands acted as C-N sources, releasing average net ecosystem emissions (NEE), including the removal of harvested C-N, of 4,598 kg CO2 ha(-1) and 141 kg N ha(-1) in 1886 and 205 kg CO2 ha(-1) (except for the corn-for-grain cropland) and 39 kg N ha(-1) in 1996. The continuous corn croplands continued to become a C sink, sequestering 255 kg C ha(-1) in 1996. Results of the sensitivity analysis for Ohio’s continuous soybean croplands revealed that the SOC pool increased by 6.9% and decreased by 7.5% in response to a doubled CO2 concentration and a temperature increase of 2.8degreesC over 100 years, respectively. The sequestration potential of the SOC pool increased by 6.5% at a rate of 24.6 kg C ha(-1) y(-1) for the same period with finer soil texture (loam to silty clay loam). The shift from conventional to conservation residue practice led to an 11% increase in the steady-state SOC storage at a rate of 42 kg C ha(-1) y(-1) for 100 years.
Ecological issues and risk assessment in China
Fu, BJ Liu, GH Wang, XK Ouyang, ZY
INTERNATIONAL JOURNAL OF SUSTAINABLE DEVELOPMENT AND WORLD ECOLOGY 11:2 143-149
As a result of economic development and population explosion, global ecological environments have been severely disturbed and markedly changed. An ecological crisis involving desertification, soil erosion, degradation of land quality, loss of biodiversity and global climate change has been brought about all over the world. In order to manage ecosystems efficiently, it is necessary to assess ecological risk at multiple scales. Ecological risk is the probability that a region and/or site will experience defined ecological or environmental problems. In this paper, the ecological risks of soil erosion, desertification, and acid deposition have been assessed on a national scale according to natural and human factors, such as topography, soil, vegetation and climate. This assessment has provided very useful information for ecological environmental management in China.
Effects of global climate change on geographic distributions of vertebrates in North Queensland
ECOLOGICAL MODELLING 174:4 347-357
This paper assesses potential changes in the distributions of 12 endemic rainforest vertebrates of the Wet Tropics of Northeastern Australia in response to global warming predictions. It is based on projecting models of current geographic distribution to modelled future conditions taken from regional climate models. In comparing vertebrate species with different mobility, adaptation potential and distribution, consequences of global warming for elements of the regional biodiversity were investigated. The bioclimatic program. BIOCLIM, was used to determine the current climatic ranges and the potential changes in the distributions of the 12 species Linder four climate change scenarios for the year 2100. Results suggest that even species with currently wide climatic ranges may become vulnerable. Species distribution area decreased by more than 50% on average. Furthermore, the remaining predicted range decreased from an average of 90% under a conservative scenario, to about 40% under a less conservative scenario. These results show how sensitively some species could react to climate change and emphasise the need for rapid action on global warming for biodiversity conservation. (C) 2003 Published by Elsevier B.V.
Water scarcity under scenarios for global climate change and regional development in semiarid northeastern Brazil
de Araujo, JC Doll, D Guntner, A Krol, M Abreu, CBR Hauschild, M Mendiondo, EM
WATER INTERNATIONAL 29:2 209-220
The state of Ceara, located in semiarid northeastern Brazil, suffers under irregularly recurring droughts that go along with water scarcity. Structural policies to control and reduce water scarcity, as water supply and demand management, should be seen as long-term planning, and thus must consider climate change and regional development. To this end, the present research proposes a model-based global change scenario. Water stress is assessed for 184 municipalities in Ceara between 2001 and 2025. For this purpose, four global change scenarios are developed, considering both global climate change and the effects of development policies. Climatic, hydrological, and water use models are applied and a proposed index computed for identification of long-term water stress. Application of the methodology in the focus area shows that, if no effective intervention measures are taken, up to almost 60 percent of the municipalities of the state may suffer under long-term water scarcity by 2025. On average, municipalities in the state of Ceara have a water shortage probability for the next 25 years ranging from 9 percent to 20 percent annually, depending on the scenario. The 10 percent most stressed municipalities have a probability of over 80 percent annually of facing water scarcity in the scenario period (25 years). Results also show that a decentralized development policy can compensate for the possible severe effects of climatic trends on future water availability over the scenario period.
The impacts of human activities on the water-land environment of the Shiyang River basin, an arid region in northwest China
Kang, SZ Su, XL Tong, L Shi, PZ Yang, XY Abe, YK Du, TS Shen, QL Zhang, JH
HYDROLOGICAL SCIENCES JOURNAL-JOURNAL DES SCIENCES HYDROLOGIQUES 49:3 413-427
The Shiyang River basin is a typical interior river basin that faces water shortage and environmental deterioration in the and northwest of China. Due to its arid climate, limited water resources and some inappropriate water-related human activities, the area has developed serious loss of vegetation, and gradual soil salinization and desertification, which have greatly impeded the sustainable development of agriculture and life in this region. In this paper, the impacts of human activities on the water-soil environment in Shiyang River basin are analysed in terms of precipitation, runoff in branches of the river, inflow into lower reaches, water conveyance efficiency of the canal system and irrigation water use efficiency in the field, replenishment and exploitation of groundwater resources, soil salinization, vegetation cover and the speed of desertification. The results show that human activities and global climate change have no significant influence on the precipitation, but the total annual runoff in eight branch rivers showed a significant decrease over the years. The proportion of water use in the upper and middle reaches compared to the lower reach was increased from 1:0.57 in the 1960s, to 1:0.27 in the 1970s and 1:0.09 in the 1990s. A reduction of about 74% in the river inflow to the lower reaches and a 15-m drop in the groundwater table have occurred during the last four decades. Strategies for improving the water-soil environment of the basin, such as the protection of the water resources of the Qilian Mountains, sustainable use of water resources, maintenance of the balance between land and water resources, development of water-saving agriculture, diverting of water from other rivers and control of soil desertification, are proposed. The objective of this paper is to provide guidelines for reconstruction of the sustainable water management and development of agriculture in this region.
Growth responses to ultraviolet-B radiation of two Carex species dominating an Argentinian fen ecosystem
Zaller, JG Searles, PS Caldwell, MM Flint, SD Scopel, AL Sala, OE
BASIC AND APPLIED ECOLOGY 5:2 153-162
Solar ultraviolet-B radiation (UV-B, 280-315 nm) in the Southern Hemisphere has been increasing over the last few decades due to seasonal stratospheric ozone depletion associated with the ‘ozone hole’ and a more general erosion of the stratospheric ozone layer. We studied the effect of UV-B radiation on growth responses of Carex curta and C. decidua, the two most dominant sedges in a fen ecosystem in Tierra del Fuego (Argentina) in field plots and growth chambers where U-V-B radiation was manipulated using different transparent plastic films that either transmitted or attenuated UV-B radiation. In the field, leaf and spike elongation of both species was unaffected by UV-B treatments in all four seasons studied (1997/98 through 2000/2001). Specific leaf areas (SLA) were only measured in the last two seasons and remained unaffected by UV-B for both species in the third field season. However, SLA decreased for C. curta in the fourth season but increased for C. decidua under near-ambient UV-B. Ecosystem specific root length was unaffected by UV-B. Although UV-B did not have a statistically significant effect on biomass production, there was a trend for a 15% higher production under near-ambient UV-B in the fourth year (P = 0.064). In the growth chambers, simulated ambient UV-B approximately equivalent to ambient UV-B in Tierra del Fuego stimulated seedling emergence of C. curta but reduced emergence of C. decidua; leaf elongation remained unaffected in both species. While plant morphology of C. curta remained unaffected by UV-B radiation, C. decid-ua had fewer tillers per plant, however tillers had more leaves and biomass under simulated ambient UV-B than under reduced UV-B radiation. The SLA of C. curta was unaffected by UV-B treatments; however, it was significantly lower for C. decidua under simulated ambient UV-B. Root morphology remained unaffected by UV-B for C. curta but roots of C. decidua were significantly thicker under simulated ambient UV-B. Taken collectively, our findings demonstrate that even moderate changes in UV-B radiation (e.g., corresponding to those expected with current stratospheric ozone depletion) may influence growth, morphology and biomass allocation in a species-specific manner for these native sedges in growth chambers and might also affect competitive relationships of these species in the field.
Ecophysiological response to severe drought in Pinus halepensis Mill. trees of two provenances
Atzmon, N Moshe, Y Schiller, G
PLANT ECOLOGY 171:1-2 15-22
As a result of predicted regional climatic changes the need to select for the more drought-tolerant genotypes (ecotypes) among Mediterranean conifers has become clear. Aleppo pine (Pinus halepensis Mill.) seems to be one of the most drought-tolerant pine species. Nevertheless, the existence of geographical trends in their genetic differentiation indicates potentially large differences in drought-tolerance among provenances. This assumption was verified by the finding of large variation among provenances in their internal water relations. Hence, the aim of this stud), was to compare the ecophysiological behaviour of several Aleppo pine provenances under contrasting climatic conditions. Growth parameters (height and diameter) and survival rate were measured in two provenance trials, one planted under sub-desertic conditions at the northern edge of the Negev desert, and the second under thermo-Mediterranean climatic conditions in the central coastal plains, Israel. Ecophysiological parameters such as: predawn needle water potential, sap flow in the xylem (i.e. transpiration), photosynthesis and water-use efficiency were measured in trees of selected provenances. The results suggest that it is not possible to predict provenance performance under harsh conditions from their performance under more favourable ones. Therefore, selection must be carried out under the exact conditions in which the trees from the resultant selection will be planted. The present study clearly emphasises the need for broad selection programs of P. halepensis.
Long-term tillage and crop rotation effects on microbial biomass and C and N mineralization in a Brazilian Oxisol
Balota, EL Colozzi, A Andrade, DS Dick, RP
SOIL & TILLAGE RESEARCH 77:2 137-145
Crop rotation and tillage impact microbial C dynamics, which are important for sequestering C to offset global climate change and to promote sustainable crop production. Little information is available for these processes in tropical/subtropical agroecosystems, which cover vast areas of terrestrial ecosystems. Consequently, a study of crop rotation in combination with no tillage (NT) and conventional tillage (CT) systems was conducted on an Oxisol (Typic Haplorthox) in an experiment established in 1976 at Londrina, Brazil. Soil samples were taken at 0-50, 50-100 and 100-200 mm depths in August 1997 and 1998 and evaluated for microbial biomass carbon (MBC) and mineralizable C and N. There were few differences due to crop rotation, however there were significant differences due to tillage. No tillage systems increased total C by 45%, microbial biomass by 83% and MBC:total C ratio by 23% at 0-50 mm depth over CT. C and N mineralization increased 74% with NT compared to CT systems for the 0-200 mm depth. Under NT, the metabolic quotient (CO2 evolved per unit of MBC) decreased by 32% averaged across soil depths, which suggests CT produced a microbial pool that was more metabolically active than under NT systems. These soil microbial properties were shown to be sensitive indicators of long-term tillage management under tropical conditions. (C) 2003 Elsevier B.V. All rights reserved.
Prepared for the GHG steamroller?
Kolwey, N Shepard, M
POWER 148:5 26-+
Global climate change is shaping up as a dominant environmental, business, and regulatory issue for the 21st century. Many utilities are formulating a strategy for reducing their greenhouse gas emissions-a handful have even inventoried and begun to cut them voluntarily-but quite a few remain in denial. The early birds are seeking a double competitive edge: reduced risk of not being ready to meet expected mandatory carbon caps and a “green” reputation in the marketplace.
Verification of magnetostratigraphic scales of miocene core section from Lake Baikal
Horiuchi, K Gol’dberg, EL Matsuzaki, H Kobayashi, K Shibata, Y
GEOLOGIYA I GEOFIZIKA 45:3 408-412
The dynamics of cosmogenic Be-10 contents in the BDP-96-1 (100 to 200 m) and BDP-98-2 (200 to 600 m) cores was used to test published magnetostratigraphic scales for the Miocene section and to time the core base. Only one of three alternative scales for the BDP-98 core tested against the Be-10 decay of T-1/2 = 1.5 myr showed a perfect consistency with the decay law. The basal age of the 600 m BDP-98 section was estimated at 8.4 myr.