Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

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Wednesday 8 July - 17:30-19:00 UPMC Jussieu - ROOM 207 - Block 24/34

1119 (b) - Extreme hydrological events: deciphering changes in hazard and risk at different time-scales

Parallel Session

Lead Convener(s): H. Kreibich (German Research Centre for Geosciences, Potsdam, Germany)

Convener(s): G. Mahe (Institut de Recherche pour le Développement, Montpellier cedex 5, France), J.M. Martinez (IRD, Toulouse, France), J.E. Paturel (IRD, Abdijan, Ivory Coast), B. Turcq (Institut de Recherche pour le Développement, Lima, Peru)

17:30

Attribution of Hydrological Extreme Events and the Need for National Inventories of Loss and Damage

M. Allen (University of Oxford, Oxford, United Kingdom)

Abstract details
Attribution of Hydrological Extreme Events and the Need for National Inventories of Loss and Damage

M. Allen (1)
(1) University of Oxford, School of geography and the environment, Oxford, United Kingdom

Abstract content

The Report of Working Group I (Physical Science Basis) of the IPCC assessed the evidence for trends in hydro-meteorological extremes and the growing literature on the attribution of extreme weather events, in a probabilistic sense, to anthropogenic drivers. In a very small number of cases, these event attribution studies have been carried through to hydrological impacts, but this remains a new and emerging science.

The Report of Working Group II (Impacts of Climate Change) of the IPCC reported on numerous studies of the hydrological impacts of observed climate change, but because of the paucity of the literature on "end-to-end" attribution, stepped back from making strong statements attributing these impacts to anthropogenic influence. Owing to the multiple uses of the phrase "Climate Change" in the IPCC and UNFCCC, there is considerable scope for confusion on this point, so I will review these issues carefully. The central question is the attribution of harm: how strong is the evidence that past greenhouse gas emissions and other forms of anthropogenic influence on climate have caused actual harm through their impact on hydrological extreme events?

I will argue, perhaps controversially, that these specific issues have evolved in such a way that the IPCC, or any global review process, is no longer the appropriate venue for their assessment: quantifying harm involves value judgments and region-specific contextualising and confounding factors such that it is often impossible to make any useful generalisations. Instead, the role of bodies such as the IPCC should become the assessment and recommendation of methods and standards of evidence, while actual assessments are carried out at a regional or national level.

I will provide a general, non-specialist over-view of the science of Probabilistic Event Attribution, specifically focussing on its application to recent flood and drought events. I will explain how different ways of framing the attribution question can yield different-seeming conclusions even if confronted with the same evidence, requiring the broader community to engage with these issues and not simply rely upon "attribution specialists". 

In the context of extreme hydrological events, I will then ask what kind of extreme event is likely to be most important in determining the overall level of climate change harm: is it those very extreme events that would have been "effectively impossible" (or, more accurately, just very, very unlikely) in the absence of climate change, or is is the much broader range of events that have simply been made somewhat more (or less) likely by climate change. I will argue it is often the second category that is overlooked in national climate impact assessments because the role of climate change is relatively subtle, yet because there are simply so many more of these events, their cumulative impact could be quite profound. 

All this builds up to the conclusion that, if countries are to get serious about quantifying Loss and Damage from climate change -- and it remains very much a matter of debate whether they will -- then they have no option but to work towards national or shared regional attribution services to allow them to quantify the role of anthropogenic climate change in regional hydrology, accounting for location-specific factors. I will discuss what this might involve, and present some ideas on how to go forward.

17:50

Future changes in extreme streamflow over the Amazonian sub-basins

M. Guimberteau (LSCE, CEA, CNRS, UVSQ, Gif-sur-Yvette, France), J. Ronchail (LOCEAN and Université Paris Diderot, Paris, France), J. C. Espinoza (Instituto Geofisico del Peru, Lima, Peru), M. Lengaigne (LOCEAN, Paris, France), B. Sultan (IRD, Paris, France), J. Polcher (CNRS, Paris, France), G. Drapeau (LOCEAN, Université Paris Diderot and PRODIG, Paris, France), J.-L. Guyot (IRD, Brasilia, Brazil), A. Ducharne (Sorbonne Universités, UPMC, CNRS, EPHE, UMR 7619 METIS, Paris, France), P. Ciais (LSCE, CEA, CNRS, UVSQ, Gif-sur-Yvette, France)

Abstract details
Future changes in extreme streamflow over the Amazonian sub-basins

M. Guimberteau (1) ; J. Ronchail (2) ; JC. Espinoza (3) ; M. Lengaigne (4) ; B. Sultan (5) ; J. Polcher (6) ; G. Drapeau (7) ; JL. Guyot (8) ; A. Ducharne (9) ; P. Ciais (1)
(1) LSCE, CEA, CNRS, UVSQ, Gif-sur-Yvette, France; (2) LOCEAN and Université Paris Diderot, Paris, France; (3) Instituto Geofisico del Peru, Lima, Peru; (4) LOCEAN, Paris, France; (5) IRD, LOCEAN, Paris, France; (6) CNRS, Lmd, Paris, France; (7) LOCEAN, Université Paris Diderot and PRODIG, Paris, France; (8) IRD, Brasilia, Brazil; (9) Sorbonne Universités, UPMC, CNRS, EPHE, UMR 7619 METIS, Paris, France

Abstract content

The Amazon basin plays an important role in regulating the local and global climate since the discharge at its outlet contributes nearly 20% of global freshwater inputs (Callède et al., 2010). Streamflow changes have been characterized by more severe extreme values on the main stream for about forty years. At Óbidos, the last gauging station before the outlet, the high flows significantly increase by 13% over 1903-2011 and exceed 250,000 m³/s almost every year since the late 60s (updated from Callède et al., 2004). The low flows are stable over the period 1903-2011 but significantly decrease by 16% over the last twenty years. The resulting increase in the annual amplitude of discharge during the last two decades is marked by severe droughts (2005 and 2010) and floods (2002, 2009, 2012 and 2014), mainly attributed to large-scale oceanic and atmospheric circulation changes (Espinoza et al., 2012, 2013, 2014). The populations living near the rivers whose activity is regulated by the present annual cycle of waters are particularly sensitive to these extreme streamflow events. During high floods, boat trips are dangerous and the mobility of the populations is reduced. Severe low flows make the boat trips longer and increase fish mortality. Thus, food prices increase and directly impact the local economy. Given these facts, it is crucial to estimate the future of the hydrological extremes in the Amazon basin in a future warmer climate (between +1.5 and +5.0°C by 2100). The model ORCHIDEE (ORganising Carbon and Hydrology In Dynamic EcosystEms), the land component of the IPSL global climate model (GCM), is able to accurately simulate the present-time streamflow in many stations over the Amazon basin (Guimberteau et al, 2012). ORCHIDEE is therefore used to provide discharge projections at sub-basin scale under future climate. Climate change scenarios over the Amazon basin were built with the delta downscaling method approach from up to eight AR4 GCMs based on three emission scenarios for two periods of the 21st century. For the middle of the century under a medium-emission scenario, no change is found in high flow on the main stem of the Amazon River, but the low flows decrease by 10%. Contrasting discharge variations are pointed out depending on the location in the basin. In the western upper part of the basin, which undergoes an annual persistent increase in precipitation (P), more flooding events are expected (high flows increase by 7%). By contrast, simulated P decreases during the dry seasons over the southern, eastern and northern parts of the basin lead to significant low-flow decrease, especially in the Xingu River, where it reaches -50%. In the north, the low-flow decrease becomes higher toward the east. Finally, the southern sub-basins, that have low runoff coefficients, will become more responsive to P change (increase in streamflow elasticity to P by up to 35%) than the western sub-basins, experiencing high runoff coefficient and no change in streamflow elasticity to P.

Callède J., Guyot J., Ronchail J., L'Hôte Y., Niel H. & de Oliveira E. Evolution du débit de l'Amazone à Obidos de 1903 à 1999, Hydrol. Sci. J., 2004, 49, 85-98

Callède J., Cochonneau G., Ronchail J., Alves V., Guyot J., Guimaraes V. & De Oliveira E. Les apports en eau de l'Amazone à l'Océan Atlantique, Rev. Sci. Eau, 2010, 23, 247-273

Espinoza J. C., Ronchail J., Guyot J. L., Junquas C., Drapeau G., Martinez J. M., Santini W., Vauchel P., Lavado W., Ordoñez J. & Espinoza R. From drought to flooding: understanding the abrupt 2010-11 hydrological annual cycle in the Amazonas River and tributaries, Environ. Res. Lett., 2012, 7, 024008

Espinoza J. C., Ronchail J., Frappart F., Lavado W., Santini W. & Guyot J. L. The Major Floods in the Amazonas River and Tributaries (Western Amazon Basin) during the 1970-2012 Period: A Focus on the 2012 Flood, J. Hydrometeorol., 2013, 14, 1000-1008

Espinoza J. C., Marengo J. A., Ronchail J., Carpio J. M., Flores L. N. & Guyot J. L. The extreme 2014 flood in south-western Amazon basin: the role of tropical-subtropical South Atlantic SST gradient, Environ. Res. Lett., 2014, 9, 124007

Guimberteau M., Drapeau G., Ronchail J., Sultan B., Polcher J., Martinez J., Prigent C., Guyot J., Cochonneau G., Espinoza J., Filizola N., Fraizy P., Lavado W., De Oliveira E., Pombosa R., Noriega L. & Vauchel P. Discharge simulation in the sub-basins of the Amazon using ORCHIDEE forced by new datasets, Hydrol. Earth Syst. Sc., 2012, 16, 911-935

18:03

Fires in Amazon: Comparison between land use and palaeoclimatic changes

R. C. Cordeiro (Universidade Federal Fluminense, Niteroi, Brazil), B. Turcq (Institut de Recherche pour le Développement, Lima, Peru), P. Moreira-Turcq (Institut de Recherche pour le Développement, Lima, Peru), L. Silva Moreira (Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil), A. Sifeddine (Institut de Recherche pour le Développement - IRD, Paris, France), R. De Aragão Ribeiro Rodrigues (Embrapa, Sinop, Brazil), F. F. L. Simões Filho (CNEN, Rio de Janeiro, Brazil), G. S. Martins (Universidade Federal Fluminense, Niteroi, Brazil), A. B. Santos (Universidade Federal Fluminense, Niteroi, Brazil), M. Barbosa (Vale, Rio de Janeiro, Brazil), M. C. Guilles Da Conceição (Universidade Federal Fluminense, Niteroi, Brazil), J. C. S. Seoane (Univesidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil), H. Evangelista (Universidade do estado Rio de Janeiro, Rio de Janeiro, Brazil)

Abstract details
Fires in Amazon: Comparison between land use and palaeoclimatic changes

RC. Cordeiro (1) ; B. Turcq (2) ; P. Moreira-Turcq (3) ; L. Silva Moreira (4) ; A. Sifeddine (5) ; R. De Aragão Ribeiro Rodrigues (6) ; FFL. Simões Filho (7) ; GS. Martins (1) ; AB. Santos (1) ; M. Barbosa (8) ; MC. Guilles Da Conceição (9) ; JCS. Seoane (10) ; H. Evangelista (11)
(1) Universidade Federal Fluminense, Departamento de geoquimica, Niteroi, Brazil; (2) Institut de Recherche pour le Développement, LOCEAN, Lima, Peru; (3) Institut de Recherche pour le Développement, GET, Lima, Peru; (4) Universidade Federal Fluminense, Departamento de geoquimica, Niterói, Rio de Janeiro, Brazil; (5) Institut de Recherche pour le Développement - IRD, Umr locean (ird/upmc/cnrs/mnhn), Paris, France; (6) Embrapa, Embrapa agrossilvipastoril, Sinop, Brazil; (7) CNEN, Institute of nuclear engineering, Rio de Janeiro, Brazil; (8) Vale, Rio de Janeiro, Brazil; (9) Universidade Federal Fluminense, Departamento de geoquímica, Niteroi, Brazil; (10) Univesidade Federal do Rio de Janeiro, Geologia, Rio de Janeiro, Brazil; (11) Universidade do estado Rio de Janeiro, Laramg, Rio de Janeiro, Brazil

Abstract content

Interpreting the geological record of Amazon biomass combustion requires comparing charcoal accumulation rates in various biomes at different time scales. Charcoal accumulation rates, a proxy for palaeofire records, were obtained in sediment cores from Amazon lakes surrounded by several vegetation types and froma reservoir in an intense land use change region. The records presented in this studywere obtained in the following areas i) a reservoir in Alta Floresta region (northern Mato Grosso State); ii) Lago do Saci (southern Pará State), a lake close to Alta Floresta and located at the southern border of Pará State; iii) a bog in an ecotone area in the Humaitá region (southern Amazonas State); iv) lakes in lateritic iron crust of the Carajás Hills (southeastern Pará State); v) Lago Comprido, a floodplain lake close to the Amazon River and surrounded by tropical rain forest (Monte Alegre, Pará State; vi) Lagoa da Pata in the Morro dos Seis Lagos alkaline complex (São Gabriel da Cachoeira, Amazonas State) and vii) Lago Caracaranã, a secluded lake in the northern Amazon cerrado (Roraima State). The highest charcoal accumulation rates were observed for modern records related to an intense change in land use at Alta Floresta, which had no precedent during the Holocene history of the Amazon. High charcoal accumulation rates that were observed in the Carajás region during low lake level phases in the Amazon in the mid-Holocene were comparable to those at the onset of the human settlement in Alta Floresta region. An increase in charcoal accumulation rate was observed in the late Holocene when the lake level was high, suggesting an interaction between climates and human presence. Low charcoal accumulation rates are typical of modern high rainfall environments, as observed in Lagoa da Pata where the environment is not susceptible to occurrences of wildfires even during relatively drier climatic phases. Low charcoal accumulation rates also exist in the relatively dry cerrado (savanna type) biome even during relatively dry phases in the Caracaranã region where the savanna-type vegetation biomass is lower and thus generates less charcoal particles than forest ecosystems. The timing of fires correlated well with the mid-Holocene dry climate phase in Brazil.  These events may be related to changes in the high-resolution record of CO2 in ice cores from the last 11,000 years. These records indicate an increase in CO2 concentration of 25 p.p.m.v. that occurred between 7000 and 1000 years BP. Anomalies of 5 ppm in the CO2 concentration in the atmosphere identified at the Taylor Dome station may similarly be related to the high variability in forest fire occurrence in the Amazon region recorded by the high charcoal accumulation rates that can be associated principally with human activity during the late Holocene, especially considering from higher lake levels that indicate a wetter climate compared to the mid Holocene.

18:16

Intense storm activity during the Little Ice Age on the French Mediterranean coast

L. Dezileau (Université Montpellier II, GeoSciences, Montpellier, France), P. Blanchemanche (CNRS, Lattes, France)

Abstract details
Intense storm activity during the Little Ice Age on the French Mediterranean coast

L. Dezileau (1) ; P. Blanchemanche (2)
(1) Université Montpellier II, GeoSciences, Sciences de la terre de l'eau et de l'environnement, Montpellier, France; (2) CNRS, Université montpellier 3, Lattes, France

Abstract content

Understanding long-term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution. Understanding this variability is also important for predicting present and future community vulnerability and economic loss. Our ability to make these assessments has been limited by the short (less than 50 years) instrument record of storm activity. Storm- induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales. In this study, we present a record of these extreme climatic events that have occurred in the French Mediterrannean coast over the past 1500 years. The identification of these extreme events is based on the analysis of sediment cores from Gulf of Aigues-Mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms.

Overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century A.D. The apparent increase in intense storms around 250 years ago occurs during the latter half of the Little Ice Age, a time of lower continental surface temperatures. Comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics. The apparent increase of the superstorm activity during the latter half of the Little Ice Age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large Central Atlantic/European domain and leading to a modification of the occurrence of extreme wind events along the French Mediterranean coast. A complete understanding of the relationship between climate fluctuations, storm activity, and the coastal response will be crucial to predicting the impacts of future climate change. 

 

18:29

Characterization of drought and soil moisture in context of climate change : results and operational applications of ClimSec project in France

J.-M. Soubeyroux (Météo-France, Toulouse, France), P. Josse (Météo France, Toulouse, France), J.-P. Vidal (IRSTEA, Lyon, France), E. Martin (Météo France, Toulouse, France), C. Pagé (CERFACS, Toulouse, France), F. Habets (CNRS, Paris, France)

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Characterization of drought and soil moisture in context of climate change : results and operational applications of ClimSec project in France

JM. Soubeyroux (1) ; P. Josse (2) ; JP. Vidal (3) ; E. Martin (4) ; C. Pagé (5) ; F. Habets (6)
(1) Météo-France, Dclim, Toulouse, France; (2) Météo France, Direction de la Climatologie et des Services Climatiques, Toulouse, France; (3) IRSTEA, Lyon, France; (4) Météo France, Cnrm-game, Toulouse, France; (5) CERFACS, Toulouse, France; (6) CNRS, UMR 7619 Metis, université Pierre et Marie Curie, Paris, France

Abstract content

Evolution of water resource is one of the main stakes of climate change in France. The ClimSec project (2008-2011) focused on the impact of the climate change on drought and soil moisture over France by using a high resolution climatological reanalysis since 1958 based from a Soil Vegetation Atmosphere Transfer model, the Safran/Isba/Modcou suite.

The high-resolution 1958–2008 Safran atmospheric reanalysis was used to force the Isba land surface scheme and the hydrogeological model Modcou. Meteorological droughts are characterized with the Standardized Precipitation Index (SPI) at time scales varying from 1 to 24 months. Similar standardizing methods were applied to soil moisture and streamflow for identifying multiscale agricultural droughts – through the Standardized Soil Wetness Index (SSWI) – and multiscale hydrological droughts, through the Standardized Flow Index (SFI). Based on a common threshold level for all indices, drought event statistics over the 50-yr period – number of events, duration, severity and magnitude – have been derived locally in order to highlight regional differences at multiple time scales and at multiple levels of the hydrological cycle (precipitation, soil moisture, streamflow). Results show a substantial variety of temporal drought patterns over the country that are highly dependent on both the variable and time scale considered. Independent spatio-temporal drought events have then been identified and described by combining local characteristics with the evolution of area under drought have finally been used to compare past severe drought events, from multi-year precipitation deficits (1989–1990) to short hot and dry periods (2003). Results show that the ranking of drought events depends highly on both the time scale and the variable considered. This multilevel and multiscale drought climatology served as a basis for assessing the impacts of climate change on droughts in France.

At the end of the project, the new drought indices were adapted for the operational hydrological monitoring and used for the qualification of drought event in real time, namely for the 2011 spring drought.

These indices were also calculated in future climate from the various regionalized climatic projections available over France. Three particular experiences in socioeconomic scenarios, climatic models and downscaling methods have been run to estimate the relative importance different uncertainties for drought evolution.

In the same time, a diagnosis on drought evolution can be established with a schedule much shorter and more intense for the agricultural drought linked to the deficit of soil wetness than for meteorological drought in relation with the precipitation. The climatic projections suggest that France could know at the end of the XXIth century a quasi-continuous drought with a strong intensity, totally unknown in the present climate.

18:42

Analysis hydrometeorological events of floods in the watershed Mono shared Benin-Togo (West Africa)

E. Amoussou (University of Parakou, Parakou, Benin), Y. Tramblay (Université de Montpellier 2, Montpellier, France), S. H. Totin Vodounon (University of Parakou, Parakou, Benin), G. Mahe (Université de Montpellier 2, Montpellier, France), J.-E. Paturel (IRD, Abdijan, Ivory Coast), P. Ribstein (Université Pierre et Marie Curie, Paris, France), L. Descroix (UMR PALOC, Dakar-Hann, Senegal), M. Boko (University of Abomey-Calavi, Abomey-Calavi, Benin)

Abstract details
Analysis hydrometeorological events of floods in the watershed Mono shared Benin-Togo (West Africa)

E. Amoussou (1) ; Y. Tramblay (2) ; SH. Totin Vodounon (3) ; G. Mahe (2) ; JE. Paturel (4) ; P. Ribstein (5) ; L. Descroix (6) ; M. Boko (7)
(1) University of Parakou, Geograaphy, Parakou, Benin; (2) Université de Montpellier 2, Ird, laboratoire hydrosciences montpellier, Montpellier, France; (3) University of Parakou, Geography, Parakou, Benin; (4) IRD, HydroSciences Montpellier, Abdijan, Ivory Coast; (5) Université Pierre et Marie Curie, Laboratoire sisyphe, Paris, France; (6) UMR PALOC, Lmi pateo, campus international de recherches ucad/ird de hann, Dakar-Hann, Senegal; (7) University of Abomey-Calavi, Geography, Abomey-Calavi, Benin

Abstract content

The recurrence of extreme anomalies of precipitations involving of the floods or the droughts is a normal component of the natural variability of the climate. The harmful effects of the floods these last have strong incidences socio-economic and ecological and involved human losses of life and property damages. The vulnerability with these natural risks is high in West Africa and basin of Mono in particular, where the populations tend to occupy the most exposed zones more and more. The objective is to model the distribution of the risings entering to the dam Nangbeto thanks to hydrological model GR4J with the step of daily time to assess the risks of flood in the low valley of the river.

The data used cover the period 1961 to 2010. They is the daily outputs (m3.s-1), the evapotranspiration (mm/jour, calculated according to method FAO) and average precipitations on the basin (mm/day). The various methods of space interpolation of the rains were tested (linear, cubic, Thiessen, simple average). Model GR4J was useful with modeling of the risings upstream and the stopping of 1988 to 2010 to appreciate the effects of the dam.

The results show a marked variation in rainfall by increasing annual maximum daily followed by an increase in ETP. The rates recorded in output Nangbéto dam are equivalent to those recorded input, especially during floods, showing the weak regulatory role of the dam and the very limited capacity of the reservoir. The annual maximum incoming flow at the dam can be modeled by an extreme value distribution (GEV) Fréchet-type, while those measured at the outlet of the dam after a GEV law Weibull (bounded). The dominant runoff generation mechanism in the basin is the gradual rising waters associated with increased saturation of the soil, rather than isolated episodes of rainfall. The analysis of flood flows between 1988 and 2010 showed no increase in flood magnitude during this period. Finally the effectiveness of the model to reproduce GR4J flood flows has been tested showing that the observed floods are simulated during calibration. However, validation tests over several periods with different climatic characteristics show a degradation of performance criteria and the model as one moves away from the calibration period, showing the instability of the model parameters in the time. Under these conditions, the use of such a model to assess future risks future flooding is risky and it is necessary to consider alternative approaches.