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The thesis concerns the analysis and interpretation of data from satellite borne radar altimeters over ice covered ocean surfaces. The applications of radar altimetry are described in detail and consider monitoring global climate change, the role that sea ice plays in the climate system, operational applications and the extension of high precision surface elevation measurements into areas of sea ice. The general nature of sea ice cover is discussed and a list of requirements for sea ice monitoring is provided and the capability of different satellite sensors to satisfy needs is examined. The operation of satellite borne altimeter over non-ocean surfaces is discussed in detail. Theories of radar backscatter over sea ice are described and are used to predict the radar altimeter response to different types of sea ice cover. Methods employed for analysis of altimeter data over sea ice are also described. Data from the Seasat altimeter is examined on a regional and global scale and compared with sea ice climatology. Data from the Geosat altimeter is compared with co-incident imagery from the Advanced Very High Resolution Radiometer and also from airborne Synthetic Aperture Radar. Correlations are observed between the altimeter data and imagery for the ice edge position, zones within the ice cover, new ice and leads, vast floes and the fast ice boundary. An analysis of data collected by the Geosat altimeter over a period of more than two years is used to derive seasonal and inter-annual variations in the total Antarctic sea ice extent. In addition the retrieval of high accuracy elevation measurements over sea ice areas is carried out. These data are used to produce improved maps of sea surface topography over icecovered ocean and provide evidence of the ability of the altimeter to determine sea ice freeboard directly. In addition the changing freeboard of two giant Antarctic tabular icebergs, as measured by the Geosat altimeter, is presented. As a summary the achievements are reviewed and suggestions are made towards directions for further work on present data sets and for future data from the ERS-1 satellite.

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nono

This PhD project explores the political influence of four sets of non-governmental actors upon the international politics of global warming. The forms of influence attributable to Working Group 1 of the Intergovernmental Panel on Climate Change (the body set up to advise governments on the science of climate change), the mass media's coverage of global warming, and the political involvement of both the fossil fuel lobbies and environmental groups in the policy debate on climate change, are understood via use of literatures on the dimensions of power appropriate to understanding the significance of non-state actors. The project stems from a widely acknowledged absence of a detailed understanding of the role of non-governmental organisations in international environmental politics, which extends to the international politics of global warming. The influence of each group of actors is conceptualised in different ways, so that the forms of power used to describe the various groups are not compared. Rather, the aim of the thesis is to assess what a less state-centred reading of the international politics of global warming, derived from a discussion of the role of the above actors, has to offer existing explanations. The analysis of these groups of actors sheds light on different aspects of the way the issue of climate change has been addressed at the international level. The conclusions drawn about the influence of these actors are used to critique the popular use of Regime accounts in international environmental politics that focus upon the process of institutional bargaining between states, which are argued to provide an inadequate basis for explanation of the global politics of climate change.

Multiple global climate models suggest that the Canadian Prairies will experience temperature increases due to climate warming. This could influence pasture and grazing production. Three climate scenarios CGCM2 A21, CSIROMk2 B11 and HadCM3 A21 were used to predict daily weather data to 2099 and incorporated into the GrassGro decision support tool to project pastoral production during 30-year increments, 2010 to 2099. Simulations were compared with the World Meterological Organization baseline years, 1961-1990 at two sites (Saskatoon and Melfort) and two soil textures (loam topsoil / loam subsoil and sandy-loam / sandy-clay-loam). Two tame grasses [crested wheatgrass (CWG; <i>Agropyron cristatum</i>) and hybrid bromegrass (HBG; <i>Bromus inermis x Bromus riparius</i>) and a mixed native pasture (<i>Festuca hallii; Elymus lanceolatus; Pascopyrum smithii; Nassella viridula</i>) were studied at each location.<p> Soil moisture was greater for loam/loam than sandy-loam/sandy-clay-loam resulting in more plant available moisture in all climate scenarios at both locations. However, plant available moisture alone was unable to explain changes in pasture dry matter (DM) production. The results projected from CGCM2 A21 were more favorable to plant and livestock production than those of CSIROMk2 B11 and HadCM3 A21. CGCM2 A21 simulated increases in mean DM production of HBG at both locations during spring each 30-yr period (P<0.05) but an overall decline (P<0.05) in mean average daily gain (ADG) of steers at Melfort, whereas at Saskatoon there was an increase in ADG (P<0.05). CWG decreased in DM production at Melfort during summer and increased at Saskatoon with CGCM2 A21 but there was an overall decrease in ADG of steers during each 30-yr period relative to baseline. It was concluded that HBG was better able to stabilize production under various future climatic conditions than CWG. There was a shift in species dominance from <i>Festuca hallii</i> to <i>Elymus lanceolatus</i> in the mixed native pasture at both locations associated with the increase in summer temperatures. This suggests that various grass species may respond differently to climate change.These results indicate that climate change will cause significant changes in soil moisture, productivity and quality of tame pastures, liveweight of grazing cattle and species composition of native pasture.

Multiple global climate models suggest that the Canadian Prairies will experience temperature increases due to climate warming. This could influence pasture and grazing production. Three climate scenarios CGCM2 A21, CSIROMk2 B11 and HadCM3 A21 were used to predict daily weather data to 2099 and incorporated into the GrassGro decision support tool to project pastoral production during 30-year increments, 2010 to 2099. Simulations were compared with the World Meterological Organization baseline years, 1961-1990 at two sites (Saskatoon and Melfort) and two soil textures (loam topsoil / loam subsoil and sandy-loam / sandy-clay-loam). Two tame grasses [crested wheatgrass (CWG; <i>Agropyron cristatum</i>) and hybrid bromegrass (HBG; <i>Bromus inermis x Bromus riparius</i>) and a mixed native pasture (<i>Festuca hallii; Elymus lanceolatus; Pascopyrum smithii; Nassella viridula</i>) were studied at each location.<p> Soil moisture was greater for loam/loam than sandy-loam/sandy-clay-loam resulting in more plant available moisture in all climate scenarios at both locations. However, plant available moisture alone was unable to explain changes in pasture dry matter (DM) production. The results projected from CGCM2 A21 were more favorable to plant and livestock production than those of CSIROMk2 B11 and HadCM3 A21. CGCM2 A21 simulated increases in mean DM production of HBG at both locations during spring each 30-yr period (P<0.05) but an overall decline (P<0.05) in mean average daily gain (ADG) of steers at Melfort, whereas at Saskatoon there was an increase in ADG (P<0.05). CWG decreased in DM production at Melfort during summer and increased at Saskatoon with CGCM2 A21 but there was an overall decrease in ADG of steers during each 30-yr period relative to baseline. It was concluded that HBG was better able to stabilize production under various future climatic conditions than CWG. There was a shift in species dominance from <i>Festuca hallii</i> to <i>Elymus lanceolatus</i> in the mixed native pasture at both locations associated with the increase in summer temperatures. This suggests that various grass species may respond differently to climate change.These results indicate that climate change will cause significant changes in soil moisture, productivity and quality of tame pastures, liveweight of grazing cattle and species composition of native pasture.

Orientador: Raquel Ghini / Banca: Flávia Rodrigues Alves Patrício / Banca: Antônio Carlos Maringoni / Resumo: Os níveis de concentração de CO2 atmosférico estão se elevando nas últimas décadas devido principalmente à queima de combustíveis fósseis. Essa alteração atmosférica, além de intensificar o fenômeno do efeito estufa, pode afetar o comportamento de algumas plantas e microrganismos de interesse agrícola. O CO2, por ser um componente básico da fotossíntese, em alta concentração, pode causar alterações na morfologia e nos processos fisiológicos das plantas, assim como na interação destas com fitopatógenos. Sendo assim, o presente estudo teve por objetivo avaliar o efeito da alta concentração de CO2 atmosférico na severidade do oídio, causado por Microsphaera diffusa, e da ferrugem asiática, causado por Phakopsora pachyrhizi, na soja e também em alguns fatores relacionados ao desenvolvimento da planta que podem exercer influência na doença, como o crescimento, peso da matéria seca e nodulação. Foram realizados três ensaios em estufas de topo aberto com (E+CO2) ou sem (E) injeção de CO2 e sem estufa (T), correspondendo às concentrações de, aproximadamente, 647 ppm, 474 ppm e 453 ppm, respectivamente. No primeiro ensaio, foram avaliadas características de desenvolvimento da planta; no segundo, a severidade da ferrugem asiática, que ocorreu de forma espontânea; e no terceiro, a severidade do oídio em quatro cultivares com diferentes níveis de resistência. As cultivares foram: FT-Estrela, altamente suscetível (AS); Embrapa 48, suscetível (S); FT-Cometa, moderadamente resistente (MR) e FT-5 (Formosa), resistente (R). Nos resultados obtidos, foi verificado um aumento significativo na severidade do oídio, no tratamento com injeção de CO2,em folhas primárias e na planta inteira das cultivares analisadas em conjunto, mas não houve alteração na expressão de resistência das cultivares. Para a ferrugem asiática, houve redução da severidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The concentration of atmospheric CO2 is increasing in recent decades, mainly due to burning of fossil fuels. This atmospheric change can intensify the phenomenon of the greenhouse effect, and can affect the behavior of important agricultural plants and microorganisms. The CO2, as a basic component of photosynthesis, in high concentrations, can cause changes in morphological and physiological processes of plants, as well as interaction with plant pathogens. Therefore, this study aimed to assess the effect of high concentrations of atmospheric CO2 on the severity of powdery mildew in soybean, caused by Microsphaera diffusa, and also in some characteristics related to the development of the plant that may influence the disease, such as growth, weight of dry matter and nodulation. Three trials were developed under open-top chambers with (E+CO2) or without (E) injection of CO2 and without greenhouse (T), with the approximate concentrations of 647 ppm, 474 ppm, and 453 ppm, respectively. On the first trial, growth characteristics were evaluated, on the second, the severity of rust, caused by Phakopsora pachyrhizi, which occurred spontaneously; on the third, the severity of powdery mildew on four cultivars with different levels of resistance: FT-Estrela, highly susceptible (AS); Embrapa 48, ...(Complete abstract click electronic access below) / Mestre