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The mathematical models used to simulate the present climate and project future climate when forced by greenhouse gases and aerosols are generally referred to as General Circulation Models (GCMs). While they have demonstrated significant skill in the continental and hemispherical scales and incorporate a large proportion of the complexity of the global system, they are inherently unable to present local subgrid scale features and dynamics [Wigley el al., 1991].

Using the PRECIS regional climate modeling system this study analyses the distribution of extremes of temperature and precipitation in South America in the recent past (19611990) and in a future (20712100) climate under the IPCC SRES A2 and B2 emissions scenarios. The results show that for the present climate the model simulates well the spatial distribution of extreme temperature and rainfall events when compared with observations, with temperature the more realistic. The observations over the region are far from comprehensive which compromises the assessment of model quality. In all the future climate scenarios considered all parts of the region would experience significant and often different changes in rainfall and temperature extremes. In the future, the occurrence of warm nights is projected to be more frequent in the entire tropical South America while the occurrence of cold night events is likely to decrease. Significant changes in rainfall extremes and dry spells are also projected. These include increased intensity of extreme precipitation events over most of Southeastern South America and western Amazonia consistent with projected increasing trends in total rainfall in these regions. In Northeast Brazil and eastern Amazonia smaller or no changes are seen in projected rainfall intensity though significant changes are seen in the frequency of consecutive dry days.

Most of tropical South America east of the Andes and south of 23°S experienced a warm 2008, with annual mean temperatures 2° to 3°C warmer than normal. Likewise, warm conditions (1° to 2°C above normal) were observed in northern Venezuela, interior Brazil between Amazonia and Northeast Brazil, and in eastern Peru (Fig. 7.11a). Cooler-than-normal conditions (anomalies of −0.5 to −1°C) were observed in southeast Brazil. From January to April, warm temperature anomalies were detected in eastern Amazonia, Northeast Brazil, southern Paraguay, and northern Argentina. In the interior of Northeast Brazil, mean temperatures reached 32° to 34°C, exceeding the mean by more than 4°C. Negative daily maximum temperature anomalies of 2° to 3°C were reported in Uruguay, southern Brazil, and the Brazilian highlands, associated with the penetration of a cold air mass.

Rainfall and river indices for both the northern and southern Amazon were used to identify and explore long-term climate variability on the region. From a statistical analysis of the hydrometeorological series, it is concluded that no systematic unidirectional long-term trends towards drier or wetter conditions have been identified since the 1920s. The rainfall and river series showing variability at inter-annual scales linked to El Niño Southern Oscillation was detected in rainfall in the northern Amazon. It has a low-frequency variability with a peak at – 30 years identified in both rainfall and river series in the Amazon. The presence of cycles rather than a trend is characteristic of rainfall in the Amazon. These cycles are real indicators of decadal and multi-decadal variations in hydrology for both sides of the basin. Sea-level pressure (SLP) gradients between tropics and sub topics were explored in order to explain variability in the hydrometeorology of the basin. Sea surface temperature (SST) gradients inside the tropical Atlantic and between the tropical Atlantic and the sub-tropical Atlantic have been assessed in the context of changes in rainfall in the Amazon, as compared to northern Argentina. Trends in SSTs in the subtropical Atlantic are linked to changes in rainfall and circulation in northern Argentina, and they seem to be related to multi-decadal variations of rainfall in the Amazon.

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.

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.