O futuro clima do Brasil

Eventos climáticos extremos recentes, como as enchentes na Bacia do Rio Madeira em 2014 e as secas atuais no Nordeste e no Sudeste do Brasil, e os seus impactos na segurança energética, hídrica e alimentar mostram que o Brasil é vulnerável aos extremos da variabilidade de clima. Como esses extremos são associados à variabilidade natural do clima, existem evidências de que eles seriam mais intensos e frequentes num futuro clima mais quente, e de que as atividades antrópicas podem também ter uma participação significativa no processo de aquecimento global.Recent extreme climate events such as the Rio Madeira flooding in 2014 and the current drought in Northeastern and in Southeastern Brazil, and their impacts on energy, food and water security, show that Brazil is vulnerable to extremes in climate variability. As these extremes are associated with natural climate variability, there are evidences that they would be more intense and frequent in a warmer future climate, and that human activities can also have a significant role in this process of global warming

Late Pleistocene-Holocene History of Chaco-Pampa Sediments in Argentina and Paraguay

Eine erheblich verbesserte Rekonstruktion der spätpleistozänen/holozänen morphologischen und geologischen Geschichte des paraguayischen Chaco und der argentinischen Pampa Ebene wird vorgestellt. Wegen der großen Ausdehnung des Gebietes waren Satellitenbilder der Schlüssel, um frühere und neue interdisziplinäre geowissenschaftliche Ergebnisse zu einem verlässlicheren Bild zusammenzuführen. Für diesen synoptischen Überblick wurde die Interpretation von Fernerkundungsdaten durch Geländeuntersuchungen und physikalische Altersbestimmungen ergänzt. Viele Lumineszenzalter (75 IRSL und 12 TL) von Löß, lößähnlichen Sedimenten und Sanden wurden bestimmt, die bei der Rekonstruktion der Klimageschichte des Untersuchungsgebiets im Marinen Isotopen Stadium 3 bis 1 (MIS 3–1) beitragen. Lößablagerungen überwiegen in der Zeit vor MIS 2. Die numerische Alter von lakustrinen und alluvialen Sedimenten, im Löß zwischengelagert, belegen wechselnde feuchte und trockene Perioden in der Chaco/Pampa-Ebene im MIS 2 und MIS 1. Überwiegend trockene Bedingungen herrschten von 8.5 bis 3.5 ka BP (mittleres MIS 1), als Sande in Form von Dünen oder in Paläoflussbetten abgelagert wurden. Zeitlich begrenzte Phasen extrem verstärkter Paläoflussaktivität im Mittelholozän wurden auf sporadische Starkregenereignisse in den Anden zurückgeführt. Die Ursprungsgebiete des Löß, der lößartigen Sedimente und der sandigen Ablagerungen wurden in der südwestlichen Pampa, den benachbarten Andenabhängen und im Altiplano lokalisiert. Diese Sedimente wurden von dort nach Osten und später nach Nordosten transportiert, wie sich aus den morphologischen Mustern als Zeugnisse früherer äolischer Aktivität rekonstruieren ließ.researc

Onset and End of the Rainy Season in South America in Observations and the ECHAM 4.5 Atmospheric General Circulation Model

Rainfall in South America as simulated by a 24-ensemble member of the ECHAM 4.5 atmospheric general circulation model is compared and contrasted with observations (in areas in which data are available) for the period 1976–2001. Emphasis is placed on determining the onset and end of the rainy season, from which its length and rain rate are determined. It is shown that over large parts of the domain the onset and ending dates are well simulated by the model, with biases of less than 10 days. There is a tendency for model onset to occur early and ending to occur late, resulting in a simulated rainy season that is on average too long in many areas. The model wet season rain rate also tends to be larger than observed. To estimate the relative importance of errors in wet season length and rain rate in determining biases in the annual total, adjusted totals are computed by substituting both the observed climatological wet season length and rate for those of the model. Problems in the rain rate generally are more important than problems in the length. The wet season length and rain rate also contribute substantially to interannual variations in the annual total. These quantities are almost independent, and it is argued that they are each associated with different mechanisms. The observed onset dates almost always lie within the range of onset of the ensemble members, even in the areas with a large model onset bias. In some areas, though, the model does not perform well. In southern Brazil the model ensemble average onset always occurs in summer, whereas the observations show that winter is often the wettest period. Individual members, however, do occasionally show a winter rainfall peak. In southern Northeast Brazil the model has a more distinct rainy season than is observed. In the northwest Amazon the model annual cycle is shifted relative to that observed, resulting in a model bias. No interannual relationship between model and observed onset dates is expected unless onset in the model and observations has a mutual relationship with SST anomalies. In part of the near-equatorial Amazon, there does exist an interannual relationship between onset dates. Previous studies have shown that in this area there is a relationship between SST anomalies and variations in seasonal total rainfall

Remote Sensing as a Tool for Agricultural Drought Alert Over the South Region of Brazil

In this study the estimative of the Combined Drought Index (CDI) to identify agricultural drought over Southern Brazil is introduced. This combined drought index is based on a combination of three indicators: Standardized Precipitation Index (SPI), Soil Moisture Anomalies (SMA) and Vegetation Health Index (VHI). The proposed CDI has four levels, watch, warning, alert I and alert II, thus benefiting an increasing degrees of severity. This CDI was applied during the first 6 months of 2020 to different study sites over Southern Brasil, representative of the crop areas. The performance of the CDI levels was assessed by comparison with risk areas. Observations show a good match between these areas and the CDI. Important crop drought events in 2020 were correctly predicted by the proposed CDI in all areas

Perspectivas de pesquisas na relação entre clima e o funcionamento da Floresta Amazônica

Pesquisas recentes do programa LBA (Programa de\ud Grande Escala da Biosfera‑Atmosfera na Amazônia)\ud demonstram ligações entre o clima e o uso da terra\ud na Amazônia e o funcionamento do bioma (1). A\ud vegetação tem uma estreita relação com a atmosfera,\ud controlando uma série de processos físico‑químicos que influenciam\ud a taxa de formação de nuvens, quantidade de núcleos de condensação\ud de nuvens, quantidade de vapor de água, balanço de radiação, emissão\ud de gases biogênicos e de efeito estufa entre tantas outras propriedades.\ud A Amazônia, por sua localização tropical e grande área (Figura 1), é\ud uma importante fonte de vapor de água para nosso planeta. Ela também\ud contém o maior reservatório de carbono entre os ecossistemas\ud terrestres, e tem um papel fundamental na mitigação das mudanças\ud climáticas em curso. A mobilização de pequena fração do carbono\ud acumulado na biomassa da floresta pode perturbar o ciclo de carbono\ud global. A Amazônia também é parte do mais intenso ciclo hidrológico\ud de nosso planeta, com um sofisticado processamento e reciclagem de\ud vapor de água, que alimenta a maior bacia hidrológica. Estes aspectos\ud fazem da região amazônica uma questão central em pesquisas de clima\ud e nas mudanças globais. Desde seu início, o programa LBA focou no\ud relacionamento entre clima, ciclos biogeoquímicos e o papel da mudança\ud de uso do solo em curso, alterando o funcionamento do bioma

Assessing the role of compound drought and heatwave events on unprecedented 2020 wildfires in the Pantanal

The year 2020 had the most catastrophic fire season over the last two decades in the Pantanal, which led to outstanding environmental impacts. Indeed, much of the Pantanal has been affected by severe dry conditions since 2019, with evidence of the 2020's drought being the most extreme and widespread ever recorded in the last 70 years. Although it is unquestionable that this mega-drought contributed significantly to the increase of fire risk, so far, the 2020's fire season has been analyzed at the univariate level of a single climate event, not considering the co-occurrence of extreme and persistent temperatures with soil dryness conditions. Here, we show that similarly to other areas of the globe, the influence of land-atmosphere feedbacks contributed decisively to the simultaneous occurrence of dry and hot spells (HPs), exacerbating fire risk. The ideal synoptic conditions for strong atmospheric heating and large evaporation rates were present, in particular during the HPs, when the maximum temperature was, on average, 6 °C above the normal. The short span of the period during those compound drought-heatwave (CDHW) events accounted for 55% of the burned area of 2020. The vulnerability in the northern forested areas was higher than in the other areas, revealing a synergistic effect between fuel availability and weather-hydrological conditions. Accordingly, where fuel is not a limiting factor, fire activity tends to be more modelled by CDHW events. Our work advances beyond an isolated event-level basis towards a compound and cascading natural hazards approach, simultaneously estimating the contribution of drought and heatwaves to fuelling extreme fire outbreaks in the Pantanal such as those in 2020. Thus, these findings are relevant within a broader context, as the driving mechanisms apply across other ecosystems, implying higher flammability conditions and further efforts for monitoring and predicting such extreme events

Understanding Brazil’s catastrophic fires : causes, consequences and policy needed to prevent future tragedies

Brazil has experienced unprecedented wildfires in the last decade. Images ofimmense burnt areas or dead animals that failed to escape the 2020 wildfires have shocked the world. To prevent or minimize further similardisasters wemustunderstandthe factors thathave ledto these catastrophic events. The causes and consequences of wildfires entail complex interactions between the biophysical and sociocultural spheres, and suitable management decisions require a sound scientific base. We present the recent panorama of increasing fire outbreaks in the Brazilian biomes, and discuss the causes that have contributed to such fires, their impacts on the environment and overall consequences for human well-being, based on reviewing the extensive specialist literature, on authors’ expert knowledge and information provided by environmental managers, researchers and politicians during a workshop organized to debate the wildfire issue in Brazil. Our up-to-date review is aimed at the academic public, environmental managers and decision- and policy-makers. First, we present evidence on the contrasting effects of fire on different ecosystems. Second, we outline the historic perceptions and policies related to fire use and management in Brazil since its colonization to the present date. Third, we propose means to advance fire prevention and develop successful management strategies. Finally, we answer frequently asked questions to clarify and/or demystify some fire-related issues not always properly addressed in the media