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Contributions of regional scale climate change research to the management of climate risks were explored at a meeting of researchers, policymakers, and practitioners in June 2007 (convened by the Task Group on Data and Scenario Support for Impact and Climate Analysis of the Intergovernmental Panel on Climate Change). Although existing knowledge is already being used to inform a wide variety of decisions in multiple contexts, there remain significant knowledge gaps that hamper effective climate-risk management, particularly at the interfaces of different spatial and temporal scales of analysis and cross-system interactions. In this Introduction we synthesize discussions of such knowledge gaps, and highlight recommendations for user-oriented research that produces and communicates information that is credible, defensible, and actionable for climate-risk management.

The IPCC and other global environmental assessment processes stress the need for national scientific participation to ensure decision makers’ trust in the associated scientific conclusions and political agendas. The underpinning assumption is that the relationship between scientists and decision makers at the national level is characterized by trust and interpretive synergy. Drawing on ethnographic research in Brazil, this article challenges that assumption through a case study of the policy uptake of divergent scientific interpretations as to whether or not the Amazon is a net carbon sink. It shows that the carbon sink issue became a site for struggles between important Brazilian scientists and decision-makers with central authority over the definition of the country’s official position in international climate negotiations. In a geopolitically charged scientific controversy involving scientific evidence bearing on the Kyoto Protocol, Brazilian decision makers studied revealed critical distance from national scientists advancing evidence that the Amazon is a net carbon sink. As such, the decision-makers’ interpretations were at odds also with dominant framings in the Brazilian media and closer to those of American scientists involved in carbon cycle research in the Amazon. Seeking to explain this disconnect, the paper discusses the divergent policy preferences of key scientists and decision-makers involved, and the correlations of these preferences with interpretations of the available scientific evidence. It identifies the continued impact of a national political tradition of limited participation in decision making and suggests that this tradition-while increasingly challenged by countervailing democratizing trends-is reinforced by key Brazilian decision makers’ constructions of science as a medium through which rich countries maintain political advantage. Reflecting this, key Brazilian decision-makers justified rejecting national scientists’ interpretations of the Amazon as a significant overall carbon sink by suggesting that the scientists’ scientific training and associated foreign interactions bias them in favor of foreign interests, compromising their ability to accurately identify national interests. The paper situates its analysis in terms of theories of the science-policy interface and argues for greater attention to the role of culturally and politically laden understandings of science and the role of science in policy and geopolitics.

Carbon and nitrogen biogeochemical cycles in savannas are strongly regulated by the seasonal distribution of precipitation and pulses of nutrients released during the wetting of the dry soil and are critical to the dynamics of microorganisms and vegetation. The objective of this study was to investigate the spatial and temporal variability of C and N isotope ratios as indicators of the cycling of these elements in a cerrado sensu stricto area, within a protected area in a State Park in the state of São Paulo, Brazil. The foliar δ13C and δ15N values varied from 33.6 to 24.4 and 2.5 to 4.5 , respectively. The δ13C values showed a consistent relationship with canopy height, revealing the importance of structure of the canopy over the C isotopic signature of the vegetation. Carbon isotopic variations associated with the length of the dry season indicated the importance of recent fixed C to the integrated isotopic signature of the leaf organic C. The studied Cerrado species showed a depleted foliar δ15N, but a wide range of foliar Nitrogen with no difference among canopy heights. However, seasonal variability was observed, with foliar δ15N values being higher in the transition period between dry and rainy seasons. The variation of the foliar C and N isotope ratios presented here was consistent with highly diverse vegetation with high energy available but low availability of water and N.

Biome models of the global climate-vegetation relationships indicate that most of the Brazilian Amazon has potential for being covered by tropical forests. From current land-use processes observed in the region, however, substantial deforestation and fire activity have been verified in large portions of the region, particularly along the Arc of Deforestation. In a first attempt to evaluate the long-term potential for tropical-forest degradation due to deforestation and fires in the Brazilian Amazon, we analysed large-scale data on fire activity and climate factors that drive the distribution of tropical forests in the region. The initial analyses and results from this study lead to important details on the relations between these quantities and have important implications for building future parameterizations of the vulnerability of tropical forests in the region.

This article discusses seasonal and interannual variations of the evapotranspiration (ET) rates in Bananal Island floodplain, Brazil. Measurements included ET and sensible heat flux using the eddy covariance method, atmospheric forcings (net radiation, Rn, vapor pressure deficit, VPD, wind speed and air temperature), soil moisture profiles, groundwater level and flood height, taken from November 2003 to December 2006. For the hydrological years (October-September) of 2003/2004, 2004/2005 and 2005/2006, the accumulated precipitation was 1692, 1471, 1914 mm and the accumulated ET was 1361, 1318 and 1317 mm, respectively. Seasonal analyses indicated that ET decreased in the dry season (average 3.7 mm day1), despite the simultaneous increase in Rn, air temperature and VPD. The increase of ET in the wet season and particularly in the flood period (average 4.1 mm day1) showed that the free water surface evaporation strongly influenced the energy exchange. Soil moisture, which was substantially depleted during the dry season, and adaptative vegetation mechanisms such as leaf senescence contributed to limit the dry season ET. Strong drainage within permeable sandy soils helped to explain the soil moisture depletion. These results suggest that the Bananal flooding area shows a different pattern in relation to the upland Amazon forests, being more similar to the savanna strictu senso areas in central Brazil. For example, seasonal ET variation was not in phase with Rn; the wet season ET was higher than the dry season ET; and the system stored only a tiny memory of the flooding period, being sensitive to extended drought periods.

A precipitação é um dos principais fatores que determina a dinâmica sazonal da vegetação na região de savanas tropicais, como é o caso do cerrado brasileiro. Neste trabalho foram analisadas as relações da precipitação sazonal, com o comportamento sazonal das classes de uso e cobertura da terra (UCT), principalmente as fisionomias de cerrado do Estado de Tocantins. Foi analisada a dinâmica sazonal do cerrado, incluindo áreas florestadas e não florestadas, a partir da análise de imagens do MODIS/TERRA IV (Índices de Vegetação) de janeiro a dezembro de 2004, bem como dados diários de precipitação de 2004 e uma série de precipitação diária do período de 1969 a 2005. Os resultados da análise de precipitação mostram que a área de estudo apresentou uma alta sazonalidade, com estação seca de maio a setembro. As análises dos IV mostram que a dinâmica sazonal das formações de cerrado é similar àquela das áreas convertidas para outros usos. O padrão sazonal das classes de UCT segue os padrões da precipitação, cujos menores valores foram registrados no mês de agosto de 2004, mês este que apresentou os menores valores dos IV. Diferentemente das demais classes de UCT, a formação florestal não se ajustou ao padrão de precipitação, apresentando valores de IV similares ao longo do ano com leve decréscimo no mês de setembro de 2004. ABSTRACT: Precipitation is one of the main factors that determine the seasonal dynamics of the vegetation in tropical savanna areas, as the Brazilian cerrado. In this work the relationship of the seasonal precipitation with the seasonal behavior of the land use and land cover (LULC) types, mainly savannah physiognomies of the Tocantins State, was investigated. We analyzed the savanna seasonal dynamics, including forest and converted areas, with MODIS/TERRA VI (vegetation indexes) satellite measurements from January to December 2004 and daily precipitation of 2004 and daily precipitation series from 1969 to 2005. The results of the precipitation analysis show that the study areas exhibited a high seasonality with a dry season from May to September. The analysis of the VI showed that the seasonal dynamic of the savanna formations and the converted areas were similar. The seasonal pattern of these LULC types follows the precipitation pattern, when the lowest VI values were recorded in August of 2004. Differently of these LULC types, forest formations do not fitted to the precipitation pattern, this LULC type keep similar VI values along year with light decrease in September of 2004.

December to March climatologies of precipitation and vertically integrated water vapor transport were analyzed and compared in order to find the main paths by which moisture is fed to high rainfall regions in the southern hemisphere in this season. The southern tropics (20°S to 0°) exhibit high rainfall and receive ample moisture from the northern trades, except in the eastern Pacific and the Atlantic Oceans. This inter-hemispheric flow is particularly important for Amazonian rainfall, establishing the North Atlantic as the main source of moisture for the forest during its main rainy season. In the subtropics the rainfall distribution is very heterogeneous. The meridional average of precipitation between 35°S to 25°S is well modulated by the meridional water vapor transport through the 25°S latitude circle, being greater where this transport is from the north and smaller where it is from the south. In South America, to the east of the Andes, the moisture that fuels precipitation between 20°S and 30°S comes both from the South and from the North Tropical Atlantic Oceans whereas between 30°S and 40°S it comes mostly from the North Atlantic after passing over the Amazonian rainforest. The meridional transport (across 25°S) curve exhibits a double peak over South America and the adjacent Atlantic, which is closely reproduced in the mean rainfall curve. This corresponds to two local maxima in the two dimensional field of meridional transport: the moisture corridor from Amazonia into the continental subtropics and the moisture flow coming from the southern tropical Atlantic into the subtropical portion of the South Atlantic Convergence Zone. These two narrow pathways of intense moisture flow could be suitably called aerial rivers. Their longitudinal positions are well defined. The yearly deviations from climatology for moisture flow and rainfall correlate well (0.75) for the continental peak but not for the oceanic peak (0.23). The structure of two maxima is produced by the effect of transients in the time scale of days.

By using differential equations, evolutionary game theory shows that most of the games of competition for resources have equilibrium strategies named Evolutionary Stable. Although this approach can deduce these points, it is not possible to say how or whether a population will reach such equilibrium. We present an evolutionary agent-based model where individuals compete for space using mixed strategies. Agents belong to spatial locations that settle with whom they can interact, but they can freely move to contiguous partitions according to a definition of satisfiability. The simulation results show that, although the agents do not have any knowledge about equilibrium points, the populations mean strategy always converges to a stable state, close and above to the analytic equilibrium. Moreover, it is reached independently of the initial population.

By using differential equations, evolutionary game theory shows that most of the games of competition for resources have equilibrium strategies named Evolutionary Stable. Although this approach can deduce these points, it is not possible to say how or whether a population will reach such equilibrium. We present an evolutionary agent-based model where individuals compete for space using mixed strategies. Agents belong to spatial locations that settle with whom they can interact, but they can freely move to contiguous partitions according to a definition of satisfiability. The simulation results show that, although the agents do not have any knowledge about equilibrium points, the populations mean strategy always converges to a stable state, close and above to the analytic equilibrium. Moreover, it is reached independently of the initial population.

Current studies show that reservoirs are responsible for emissions of greenhouse gases (St. Louis et al. 2000, Duchemin et al. 2002, Soumis et al. 2004, Abril et al. 2005, Lima et al. 2008). Surface waters of aquatic ecosystems exhibit supersaturated dissolved CO2 (Cole 1999, Richey et al. 2002) because respiration based on both autochthonous and allocthonous organic carbon usually exceeds primary production (del Giorgio et al. 1997, Cole 1999, Jonsson et al. 2003). Dissolved organic carbon transported to the aquatic ecosystem from the drainage basin usually remains biologically refractory. Upon exposure to sunlight in a relatively well-lit aquatic environment, however, terrigenous organic carbon might undergo photolytic degradation and become more labile (Cole 1999). In spite of photomineralization, carbon dioxide effluxes may also result from methanotrophic activities (Frenzel et al. 1990, Abe et al. 2005, Lima 2005) associated with diel oxygen production via photosynthesis (King 1990, Lima et al. 2005a). Moreover, diel changes in sunlight may also affect dissolved gas solubility and, in particular, surface water density, leading to convection during cooling events (MacIntyre et al. 2001). We evaluated possible roles of sunlight on the daily variability of CH4 and CO2 diffusive fluxes from Corumba reser- ´ voir in Brazil. Our results support that CO2 and CH4 emissions in Corumba are substantially influenced by sunlight- ´ induced processes, although we cannot precisely identify the primary variables inducing diel changes