883 resultados para Changing Permafrost in the Arctic and its Global Effects in the 21st Century


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Compte-rendu / Review

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La preocupación por el cambio climático y por cómo afecta a nuestras comunidades, ecosistemas y vidas, ha aumentado mucho durante los últimos años del siglo XX y principios del siglo XXI. Este libro analiza la situación tanto desde aspectos científicos como sociales y nos facilita una descripción de los problemas y de lo que se puede hacer para contrarrestarlos local y globalmente. Los autores explican diferentes formas de estudiar el cambio climático con métodos interdisciplinarios para medir y preveer sus efectos futuros y adaptar nuestra sociedad, y analizan las conexiones entre el cambio climático y la salud de diferentes ecosistemas, el crecimiento económico y social, y el discurso global sobre el desarrollo sostenible.

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El debate sobre el modelo civilizatorio de la modernidad de Occidente, consu economía concentradora y excluyente, y su matriz económico energética petrolera y extractivista no sustentable, ha reavivado en los escenarios políticos y académicos de la salud la discusión de la propuesta del buen vivir inscrita en las nuevas constituciones de Bolivia y Ecuador. Ante la crisis social, sanitaria y ambiental producida por la imposición de una economía de la muerte, y la consiguiente multiplicación de modos de vivir malsanos, se discuten aquí las tesis de Bolívar Echeverría sobre la base material de la vida y la cultura, como una herramienta para evaluar históricamente los desempeños de los gobiernos de las izquierdas realmente existentes, y trabajar un modelo de transición histórica y el indispensable remozamiento de la conciencia crítica desde una visión radicalmente renovadora, pero que mire la realidad sin dogmatismo, sin estridencias míticas y con un sentido de profunda autocrítica.

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Twenty first century challenges facing agriculture include climate change, threats to food security for a growing population and downward economic pressures on rural livelihoods. Addressing these challenges will require innovation in extension theory, policy and education, at a time when the dominance of the state in the provision of knowledge and information services to farmers and rural entrepreneurs continues to decline. This paper suggests that extension theory is catching up with and helping us to understand innovative extension practice, and therefore provides a platform for improving rural development policies and strategies. Innovation is now less likely to be spoken of as something to be passed on to farmers, than as a continuing process of creativity and adaptation that can be nurtured and sustained. Innovation systems and innovation platforms are concepts that recognise the multiple factors that lead to farmers’ developing, adapting and applying new ideas and the importance of linking all actors in the value chain to ensure producers can access appropriate information and advice for decision making at all stages in the production process. Concepts of social learning, group development and solidarity, social capital, collective action and empowerment all help to explain and therefore to apply more effectively group extension approaches in building confidence and sustaining innovation. A challenge facing educators is to ensure the curricula for aspiring extension professionals in our higher education institutions are regularly reviewed and keep up with current and future developments in theory, policy and practice.

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To inspire new ideas in research on pollination ecology, we list the most important unanswered questions in the field. This list was drawn up by contacting 170 scientists from different areas of pollination ecology and asking them to contribute their opinion on the greatest knowledge gaps that need to be addressed. Almost 40% of them took part in our email poll and we received more than 650 questions and comments, which we classified into different categories representing various aspects of pollination research. The original questions were merged and synthesised, and a final vote and ranking led to the resultant list. The categories cover plant sexual reproduction, pollen and stigma biology, abiotic pollination, evolution of animal-mediated pollination, interactions of pollinators and floral antagonists, pollinator behaviour, taxonomy, plant-pollinator assemblages, geographical trends in diversity, drivers of pollinator loss, ecosystem services, management of pollination, and conservation issues such as the implementation of pollinator conservation. We focused on questions that were of a broad scope rather than case-specific; thus, addressing some questions may not be feasible within single research projects but constitute a general guide for future directions. With this compilation we hope to raise awareness of pollination-related topics not only among researchers but also among non-specialists including policy makers, funding agencies and the public at large.

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Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of CMIP3 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We suggest that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.

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The Third Western Hemisphere Transportation Ministerial meeting was held in New Orleans, Lousiana, United States, from 14 to 16 December 1998, under the theme Transportation in the 21st Century: A Vision for Integration. The meeting was attended by Ministers and heads of delegations from 33 countries of the Americas, representatives of various international organizations and business sector of the Continent. The current issue of the Bulletin provides the complete text of the Ministerial Declaration. For additional information, contact José María Rubiato: e-mail jrubiato@eclac.cl

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"It is particularly critical to assess the impact, given the empirical data available, on institutions in California, Texas, Florida and Washington which anti-affirmative action laws and court orders have been passed/handed down."

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The Community Climate System Model version 3 is used to analyse changes in water mass subduction rates in the South Atlantic Ocean over the 21st century. The model results are first compared to observations over 1950-2000, and shown to be rather good. The subduction rates do not change significantly over the 21st century, but the densities at which water masses form become significantly lighter. The strong westerly winds in this region do not change much, which suggests small changes to the rate at which the Atlantic sector of the Southern Ocean takes up heat and carbon dioxide over the 21st century.