Valérie Trouet - Academia.edu (original) (raw)
Papers by Valérie Trouet
Assessing the impact of future climate change on North Atlantic tropical cyclone (TC) activity is... more Assessing the impact of future climate change on North Atlantic
tropical cyclone (TC) activity is of crucial societal importance, but the limited quantity and quality of observational records interferes with the skill of future TC projections. In particular, North Atlantic TC response to radiative forcing is poorly understood and creates the dominant source of uncertainty for twenty-first-century projections. Here, we study TC variability in the Caribbean during the Maunder Minimum (MM; 1645–1715 CE), a period defined by the most severe reduction in solar irradiance in documented history (1610–present). For this purpose, we combine a documentary time series of Spanish shipwrecks in the Caribbean (1495–1825 CE) with a tree-growth suppression chronology from the Florida Keys (1707–2009 CE). We find a 75% reduction in decadal-scale Caribbean TC activity during the MM, which suggests modulation of the influence of reduced solar irradiance by the cumulative effect of cool North Atlantic sea surface temperatures, El Niño–like conditions, and a negative phase of the North Atlantic Oscillation. Our results emphasize the need to enhance our understanding of the response of these oceanic and atmospheric circulation patterns to radiative forcing and climate change to improve the skill of future TC projections.
Climate Research, 2003
This paper describes the development of socio-economic scenarios, in both qualitative and quantit... more This paper describes the development of socio-economic scenarios, in both qualitative and quantitative terms, for use in integrated assessment modelling of the impacts of climate change in 2 contrasting English regions: East Anglia and the North West. The need for socio-economic scenarios is discussed, and the 'mediating' role that they play between intellectual debate and policy deliberation is analysed. Four scenarios are constructed for each region: regional enterprise, global sustainability, regional stewardship and global markets, and we provide the rationale for the socioeconomic and policy changes we propose under each scenario. Spatial mapping of 2 of the scenarios in each region is then conducted for 3 illustrative issues (built development, biodiversity and coastal zone), and a sample of non-spatial agricultural variables is inferred. A major focus of the paper is an examination of the experience of engaging stakeholders in the development of the socio-economic scenarios. We explore, in particular, how stakeholders reconciled a given long-term scenario framework with their shorter-term and particular policy-driven requirements.
We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally... more We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally dry miombo woodland in south central Africa. Between 9 and 34 stem discs were collected from three dry and two wet miombo sites. All samples showed distinct growth rings, which were marked by terminal parenchyma bands. Site chronologies varied in length between 43 and 149 years. An increase in the number of growth ring anomalies in older trees, however, resulted in an increase in dating error and a decrease in between-tree correlations with increase in the chronology length. Annual precipitation variability accounted for some 28% of the common variance in the BrSp chronologies and we found no difference in climate sensitivity between wet and dry miombo sites. The influence of climate, and of precipitation in particular, on tree growth was strongest at the core of the rainy season (December-February). This is also the time of the year when ENSO peaks in amplitude and ENSO effects on precipitation variability in southern Africa are the strongest. We found a negative response of tree growth to ENSO throughout most of the growth year, suggesting that the development of longer chronologies from the miombo region would allow for the investigation of temporal ENSO variability. A spatial extension of the miombo tree-ring network should therefore focus on regions where ENSO effects are the strongest (e.g., southeastern Africa).
We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally... more We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally dry miombo woodland in south central Africa. Between 9 and 34 stem discs were collected from three dry and two wet miombo sites. All samples showed distinct growth rings, which were marked by terminal parenchyma bands. Site chronologies varied in length between 43 and 149 years. An increase in the number of growth ring anomalies in older trees, however, resulted in an increase in dating error and a decrease in between-tree correlations with increase in the chronology length. Annual precipitation variability accounted for some 28% of the common variance in the BrSp chronologies and we found no difference in climate sensitivity between wet and dry miombo sites. The influence of climate, and of precipitation in particular, on tree growth was strongest at the core of the rainy season (December-February). This is also the time of the year when ENSO peaks in amplitude and ENSO effects on precipitation variability in southern Africa are the strongest. We found a negative response of tree growth to ENSO throughout most of the growth year, suggesting that the development of longer chronologies from the miombo region would allow for the investigation of temporal ENSO variability. A spatial extension of the miombo tree-ring network should therefore focus on regions where ENSO effects are the strongest (e.g., southeastern Africa).
We here present a reconstruction of the winter Pacific North American (PNA) pattern based on thre... more We here present a reconstruction of the winter Pacific North American (PNA) pattern based on three winter climate sensitive tree ring records from the western USA. Positive PNA phases in our record are associated with warm phases of ENSO and PDO and the reorganization of the PNA pattern towards a positive mode is strongest when ENSO and PDO are in phase. Regime shifts in our PNA record correspond to climatic shifts in other proxies of Pacific climate variability, including two well-documented shifts in the instrumental period (1976 and 1923). The correspondence breaks down in the early 19th century, when our record shows a prolonged period of positive PNA, with a peak in 1800-1820. This period corresponds to a period of low solar activity (Dalton Minimum), suggesting a 'positive PNA like' response to decreased solar irradiance. The distinct 30-year periodicity that dominates the PNA reconstruction in the 18th century and again from 1875 onwards is disrupted during this period.
Climate Research
Considerable progress has been made in assessing European climate variations of the last millenni... more Considerable progress has been made in assessing European climate variations of the last millennium, but little is known about the Mediterranean region and particularly its eastern part including the Balkan Peninsula. This area, however, will be particularly vulnerable to a predicted temperature increase and precipitation decrease, likely resulting in amplified drought extremes and episodes. Here we present a well-replicated composite tree-ring width chronology of millennial length from Albania, Balkan Peninsula. The Pinus heldreichii Christ dataset contains 302 series from 217 living and dead trees from 3 high-elevation sites, and spans the years 968-2008. Signal strength and growth-climate relationships were investigated using subsets according to location, age class, and growth level, as well as differently detrended chronology versions. Growth comparisons amongst the 3 sites' chronologies, between age classes and between growth-rate groups reveal an overall strong common signal. Growth-climate relationships over the last 100 yr, however, indicate that tree-ring formation does not depend on one single dominant factor, but rather on various combinations of summer precipitation and temperature resulting in temporally varying drought sensitivity. Our results emphasize a mixed and variable climate signal, corresponding with findings from other P. heldreichii sites across the Balkan Peninsula and Southern Italy.
Aim The goal of this study was to understand better the role of interannual and interdecadal clim... more Aim The goal of this study was to understand better the role of interannual and interdecadal climatic variation on local pre-EuroAmerican settlement fire regimes in fire-prone Jeffrey pine (Pinus jeffreyi Grev. & Balf.) dominated forests in the northern Sierra Nevada Mountains.
![Research paper thumbnail of tree-ring based comparison of Terminalia superba climate–growth relationships in West and Central Africa [2013]](https://attachments.academia-assets.com/45624653/thumbnails/1.jpg)
](Tropical lowland forests are characterized by humid climate conditions with interannual variation... more Tropical lowland forests are characterized by humid climate conditions with interannual variations in amount of precipitation, length of dry season, and relative humidity. The African tree species, Terminalia superba Engl. & Diels has a large distribution area and potentially incorporates these variations in its tree rings. Tree ring analysis was performed on 60 plantation trees (increment cores) and 41 natural trees (stem disks) from Ivory Coast and the Congolese Mayombe Forest. Natural forests and old plantations (50-55 years) showed similar growth patterns. Regional chronologies were developed for the two sample regions and showed a long-distance relationship for the period 1959-2008. Growth in the Mayombe was associated with early rainy season precipitation, but no relation was found between tree growth and precipitation in Ivory Coast. Congolese trees possibly show a higher climate-sensitivity than Ivorian trees, because precipitation in the Mayombe is more limiting, and Congolese T. superba trees are found closer to the margins of their distribution. Likewise, tree growth in the Mayombe was also influenced by the SSTs of the Gulf of Guinea and the South Atlantic Ocean during the early rainy season. However, tree growth was influenced by ENSO in both regions. In the Mayombe, La Niña years were associated with stronger tree growth whereas in Ivory Coast, El Niño years corresponded with stronger tree growth. The presented relation between ENSO, precipitation and tree growth is original for equatorial African forests, suggesting an influence of global climate variability on tree growth.
Medieval Climate Anomaly (MCA) terrestrial proxy records (speleothem, NW Scotland; tree rings, Mo... more Medieval Climate Anomaly (MCA) terrestrial proxy records (speleothem, NW Scotland; tree rings, Morocco) from close to the centres of action of the winter North Atlantic Oscillation (NAO) indicate that the MCA was characterized by a pervasive positive phase of the NAO(1). Spatial gradients across Europe in this MCA synoptic climatological interpretation were analyzed using the Proxy Surrogate Reconstruction approach based
Assessing the impact of future climate change on North Atlantic tropical cyclone (TC) activity is... more Assessing the impact of future climate change on North Atlantic
tropical cyclone (TC) activity is of crucial societal importance, but the limited quantity and quality of observational records interferes with the skill of future TC projections. In particular, North Atlantic TC response to radiative forcing is poorly understood and creates the dominant source of uncertainty for twenty-first-century projections. Here, we study TC variability in the Caribbean during the Maunder Minimum (MM; 1645–1715 CE), a period defined by the most severe reduction in solar irradiance in documented history (1610–present). For this purpose, we combine a documentary time series of Spanish shipwrecks in the Caribbean (1495–1825 CE) with a tree-growth suppression chronology from the Florida Keys (1707–2009 CE). We find a 75% reduction in decadal-scale Caribbean TC activity during the MM, which suggests modulation of the influence of reduced solar irradiance by the cumulative effect of cool North Atlantic sea surface temperatures, El Niño–like conditions, and a negative phase of the North Atlantic Oscillation. Our results emphasize the need to enhance our understanding of the response of these oceanic and atmospheric circulation patterns to radiative forcing and climate change to improve the skill of future TC projections.
Climate Research, 2003
This paper describes the development of socio-economic scenarios, in both qualitative and quantit... more This paper describes the development of socio-economic scenarios, in both qualitative and quantitative terms, for use in integrated assessment modelling of the impacts of climate change in 2 contrasting English regions: East Anglia and the North West. The need for socio-economic scenarios is discussed, and the 'mediating' role that they play between intellectual debate and policy deliberation is analysed. Four scenarios are constructed for each region: regional enterprise, global sustainability, regional stewardship and global markets, and we provide the rationale for the socioeconomic and policy changes we propose under each scenario. Spatial mapping of 2 of the scenarios in each region is then conducted for 3 illustrative issues (built development, biodiversity and coastal zone), and a sample of non-spatial agricultural variables is inferred. A major focus of the paper is an examination of the experience of engaging stakeholders in the development of the socio-economic scenarios. We explore, in particular, how stakeholders reconciled a given long-term scenario framework with their shorter-term and particular policy-driven requirements.
We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally... more We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally dry miombo woodland in south central Africa. Between 9 and 34 stem discs were collected from three dry and two wet miombo sites. All samples showed distinct growth rings, which were marked by terminal parenchyma bands. Site chronologies varied in length between 43 and 149 years. An increase in the number of growth ring anomalies in older trees, however, resulted in an increase in dating error and a decrease in between-tree correlations with increase in the chronology length. Annual precipitation variability accounted for some 28% of the common variance in the BrSp chronologies and we found no difference in climate sensitivity between wet and dry miombo sites. The influence of climate, and of precipitation in particular, on tree growth was strongest at the core of the rainy season (December-February). This is also the time of the year when ENSO peaks in amplitude and ENSO effects on precipitation variability in southern Africa are the strongest. We found a negative response of tree growth to ENSO throughout most of the growth year, suggesting that the development of longer chronologies from the miombo region would allow for the investigation of temporal ENSO variability. A spatial extension of the miombo tree-ring network should therefore focus on regions where ENSO effects are the strongest (e.g., southeastern Africa).
We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally... more We present five Brachystegia spiciformis Benth. (BrSp) tree-ring chronologies from the seasonally dry miombo woodland in south central Africa. Between 9 and 34 stem discs were collected from three dry and two wet miombo sites. All samples showed distinct growth rings, which were marked by terminal parenchyma bands. Site chronologies varied in length between 43 and 149 years. An increase in the number of growth ring anomalies in older trees, however, resulted in an increase in dating error and a decrease in between-tree correlations with increase in the chronology length. Annual precipitation variability accounted for some 28% of the common variance in the BrSp chronologies and we found no difference in climate sensitivity between wet and dry miombo sites. The influence of climate, and of precipitation in particular, on tree growth was strongest at the core of the rainy season (December-February). This is also the time of the year when ENSO peaks in amplitude and ENSO effects on precipitation variability in southern Africa are the strongest. We found a negative response of tree growth to ENSO throughout most of the growth year, suggesting that the development of longer chronologies from the miombo region would allow for the investigation of temporal ENSO variability. A spatial extension of the miombo tree-ring network should therefore focus on regions where ENSO effects are the strongest (e.g., southeastern Africa).
We here present a reconstruction of the winter Pacific North American (PNA) pattern based on thre... more We here present a reconstruction of the winter Pacific North American (PNA) pattern based on three winter climate sensitive tree ring records from the western USA. Positive PNA phases in our record are associated with warm phases of ENSO and PDO and the reorganization of the PNA pattern towards a positive mode is strongest when ENSO and PDO are in phase. Regime shifts in our PNA record correspond to climatic shifts in other proxies of Pacific climate variability, including two well-documented shifts in the instrumental period (1976 and 1923). The correspondence breaks down in the early 19th century, when our record shows a prolonged period of positive PNA, with a peak in 1800-1820. This period corresponds to a period of low solar activity (Dalton Minimum), suggesting a 'positive PNA like' response to decreased solar irradiance. The distinct 30-year periodicity that dominates the PNA reconstruction in the 18th century and again from 1875 onwards is disrupted during this period.
Climate Research
Considerable progress has been made in assessing European climate variations of the last millenni... more Considerable progress has been made in assessing European climate variations of the last millennium, but little is known about the Mediterranean region and particularly its eastern part including the Balkan Peninsula. This area, however, will be particularly vulnerable to a predicted temperature increase and precipitation decrease, likely resulting in amplified drought extremes and episodes. Here we present a well-replicated composite tree-ring width chronology of millennial length from Albania, Balkan Peninsula. The Pinus heldreichii Christ dataset contains 302 series from 217 living and dead trees from 3 high-elevation sites, and spans the years 968-2008. Signal strength and growth-climate relationships were investigated using subsets according to location, age class, and growth level, as well as differently detrended chronology versions. Growth comparisons amongst the 3 sites' chronologies, between age classes and between growth-rate groups reveal an overall strong common signal. Growth-climate relationships over the last 100 yr, however, indicate that tree-ring formation does not depend on one single dominant factor, but rather on various combinations of summer precipitation and temperature resulting in temporally varying drought sensitivity. Our results emphasize a mixed and variable climate signal, corresponding with findings from other P. heldreichii sites across the Balkan Peninsula and Southern Italy.
Aim The goal of this study was to understand better the role of interannual and interdecadal clim... more Aim The goal of this study was to understand better the role of interannual and interdecadal climatic variation on local pre-EuroAmerican settlement fire regimes in fire-prone Jeffrey pine (Pinus jeffreyi Grev. & Balf.) dominated forests in the northern Sierra Nevada Mountains.
Tropical lowland forests are characterized by humid climate conditions with interannual variation... more Tropical lowland forests are characterized by humid climate conditions with interannual variations in amount of precipitation, length of dry season, and relative humidity. The African tree species, Terminalia superba Engl. & Diels has a large distribution area and potentially incorporates these variations in its tree rings. Tree ring analysis was performed on 60 plantation trees (increment cores) and 41 natural trees (stem disks) from Ivory Coast and the Congolese Mayombe Forest. Natural forests and old plantations (50-55 years) showed similar growth patterns. Regional chronologies were developed for the two sample regions and showed a long-distance relationship for the period 1959-2008. Growth in the Mayombe was associated with early rainy season precipitation, but no relation was found between tree growth and precipitation in Ivory Coast. Congolese trees possibly show a higher climate-sensitivity than Ivorian trees, because precipitation in the Mayombe is more limiting, and Congolese T. superba trees are found closer to the margins of their distribution. Likewise, tree growth in the Mayombe was also influenced by the SSTs of the Gulf of Guinea and the South Atlantic Ocean during the early rainy season. However, tree growth was influenced by ENSO in both regions. In the Mayombe, La Niña years were associated with stronger tree growth whereas in Ivory Coast, El Niño years corresponded with stronger tree growth. The presented relation between ENSO, precipitation and tree growth is original for equatorial African forests, suggesting an influence of global climate variability on tree growth.
Medieval Climate Anomaly (MCA) terrestrial proxy records (speleothem, NW Scotland; tree rings, Mo... more Medieval Climate Anomaly (MCA) terrestrial proxy records (speleothem, NW Scotland; tree rings, Morocco) from close to the centres of action of the winter North Atlantic Oscillation (NAO) indicate that the MCA was characterized by a pervasive positive phase of the NAO(1). Spatial gradients across Europe in this MCA synoptic climatological interpretation were analyzed using the Proxy Surrogate Reconstruction approach based