ORCID Profile
0000-0002-2479-8665
Current Organisation
University of Oxford
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Publisher: Copernicus GmbH
Date: 11-03-2021
DOI: 10.5194/NHESS-21-941-2021
Abstract: Abstract. Disastrous bushfires during the last months of 2019 and January 2020 affected Australia, raising the question to what extent the risk of these fires was exacerbated by anthropogenic climate change. To answer the question for southeastern Australia, where fires were particularly severe, affecting people and ecosystems, we use a physically based index of fire weather, the Fire Weather Index long-term observations of heat and drought and 11 large ensembles of state-of-the-art climate models. We find large trends in the Fire Weather Index in the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Reanalysis (ERA5) since 1979 and a smaller but significant increase by at least 30 % in the models. Therefore, we find that climate change has induced a higher weather-induced risk of such an extreme fire season. This trend is mainly driven by the increase of temperature extremes. In agreement with previous analyses we find that heat extremes have become more likely by at least a factor of 2 due to the long-term warming trend. However, current climate models overestimate variability and tend to underestimate the long-term trend in these extremes, so the true change in the likelihood of extreme heat could be larger, suggesting that the attribution of the increased fire weather risk is a conservative estimate. We do not find an attributable trend in either extreme annual drought or the driest month of the fire season, September–February. The observations, however, show a weak drying trend in the annual mean. For the 2019/20 season more than half of the July–December drought was driven by record excursions of the Indian Ocean Dipole and Southern Annular Mode, factors which are included in the analysis here. The study reveals the complexity of the 2019/20 bushfire event, with some but not all drivers showing an imprint of anthropogenic climate change. Finally, the study concludes with a qualitative review of various vulnerability and exposure factors that each play a role, along with the hazard in increasing or decreasing the overall impact of the bushfires.
Publisher: IOP Publishing
Date: 30-09-2019
Abstract: The El Niño Southern Oscillation (ENSO) is a major driver of seasonal and interannual climatic variability across the tropics. The 2015/16 El Niño event was one of the strongest El Niño events of the past century. Here we characterize the meteorological impacts of the 2015/16 El Niño event upon the terrestrial tropics, and place the severity of this event into context of previous strong events in 1982/83 and 1997/98. Strong drought-inducing meteorological anomalies (≥2 s.d.) occurred across vast regions (20%) of the terrestrial tropics, where the wet tropics (≥1200 mm yr −1 ) were more severely affected (33%) than the drier tropics (6%). Central and eastern Amazonia experienced the most sustained and spatially extensive drought inducing anomalies, while parts of the Congo basin and Insular Southeast Asia also experienced severe drought. Surprisingly, some regions of the tropics (e.g. the Guiana Shield) with well known ENSO teleconnections were only briefly affected by the 2015/16 El Niño event. 2015/16 El Niño soil water drought impacts affected 29% of the terrestrial tropics, compared to 16% and 18% in 1982/83 and 1997/98, respectively. Maximum temperatures were particularly exacerbated compared to previous strong El Niños because they were lified by the warming trend due to anthropogenic climate change. This also intensified positive anomalies of atmospheric vapor pressure deficit (the atmospheric demand for moisture), which had strongly negative consequences for vegetation productivity in the tropics. Even if El Niño events do not increase in intensity over coming decades, the pervasive long-term warming trend means that the atmospheric drought impact of each strong El Niño is becoming more severe, and many parts of the tropics will experience novel climate (temperature and VPD) conditions with each new strong El Niño event.
Publisher: Copernicus GmbH
Date: 11-03-2020
Abstract: Abstract. Disastrous bushfires during the last months of 2019 and January 2020 affected Australia, raising the question to what extent the risk of these fires was exacerbated by anthropogenic climate change. To answer the question for southeastern Australia, where fires were particularly severe, affecting people and ecosystems, we use a physically-based index of fire weather, the Fire Weather Index, long-term observations of heat and drought, and eleven large ensembles of state-of-the-art climate models. In agreement with previous analyses we find that heat extremes have become more likely by at least a factor two due to the long-term warming trend. However, current climate models overestimate variability and tend to underestimate the long-term trend in these extremes, so the true change in the likelihood of extreme heat could be larger. We do not find an attributable trend in either extreme annual drought or the driest month of the fire season September–February. The observations, however, show a weak drying trend in the annual mean. Finally, we find large trends in the Fire Weather Index in the ERA5 reanalysis, and a smaller but significant increase by at least 30 % in the models. The trend is mainly driven by the increase of temperature extremes and hence also likely underestimated. For the 2019/20 season more than half of the July–December drought was driven by record excursions of the Indian Ocean dipole and Southern Annular Mode. These factors are included in the analysis. The study reveals the complexity of the 2019/20 bushfire event, with some, but not all drivers showing an imprint of anthropogenic climate change.
Publisher: Wiley
Date: 02-08-2021
DOI: 10.1002/CLI2.11
Abstract: This study aims to investigate local‐scale meteorological conditions associated with large fires in Brazil during recent decades. We assess whether there are large fire types with preceding predictors. Our results show that large fires, defined with a threshold of a daily burned area th percentile of the historical record, mainly occur in August and September in Brazil, and Amazônia and Cerrado experience much higher numbers of large fires than the other biomes. There are two large fire types that have robust meteorological signatures: (1) a wind driven type, characterized by peak wind speed on the day of the fire, and anomalously high wind speed a few (∼3) days before and after the fire and (2) a Hot‐Drought driven type, characterized by anomalously high temperature, low relative humidity, and consistent drought conditions indicated by anomalously high fuel aridity starting as far back as 5 months prior to the fires. A third one is characterized by no anomalous meteorological conditions. The wind driven type most frequently occurs in southern and southeastern Amazônia, Pantanal, and western and northern‐to‐central Cerrado, with some occurrences over the western Caatinga region bordering Cerrado, southern Cerrado, and southern Mata Atlântica whereas the Hot‐Drought driven type most frequently occurs in southern and southeastern Amazônia, Pantanal and western and northern‐to‐central Cerrado, with some occurrences over the western Caatinga region bordering Cerrado, southern Cerrado, central‐to‐southern Mata Atlântica, and a few occurrences over Northern Brazil where the Amazônia meets Roraima. Southern and southeastern Amazônia, Pantanal and western and northern‐to‐central Cerrado are the major large fire prone regions. Our results highlight that understanding the temporal and spatial variability of the meteorological conditions associated with large fires is essential for developing spatially explicit forecasting, and future projections of large fire hazards under climate change in Brazil, in particular the Hot‐Drought driven type.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Sihan Li.