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Assessing climate change impacts on water resources in Chile Reunión profesores Estadounidenses Fulbright Valparaiso, Chile 15 setiembre 2011 Ed Maurer.

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Presentation on theme: "Assessing climate change impacts on water resources in Chile Reunión profesores Estadounidenses Fulbright Valparaiso, Chile 15 setiembre 2011 Ed Maurer."— Presentation transcript:

1 Assessing climate change impacts on water resources in Chile Reunión profesores Estadounidenses Fulbright Valparaiso, Chile 15 setiembre 2011 Ed Maurer Civil Engineering Department

2 Global Climate is Changing Temperatures are increasing globally Most recent warming attributed to human- driven GHG emissions Some impacts already evident and attributable to warming Source: U.S. Global Change Research Program (USGCRP)

3 Observed Changes: High confidence changes in: –rainfall intensity –extreme temperatures –regional drought –glacier melt –early snowmelt –lake warming Changes are consistent with observed warming, if not attributable Source: IPCC Climate Change 2007: Impacts, Adaptation, and Vulnerability -- Summary for Policymakers.

4 Projections of Global Change Range of ‘likely warming’ by end of 21 st century variable By mid-21 st century most differences smaller °3.4°4.0°2.4°2.8°

5 Which pathway are we on? Scenarios trends are averages across all models available for each scenario class. Raupach et al., PNAS, 2007 Global Carbon Project, 2009 Current emissions are tracking above the most intense IPCC emission scenario

6 Looking toward the future: end of 21 st century 21 modeled changes for A1B emissions minus Warming is large-scale, certain Precipitation changes more regional, less confident Regional changes drive regional impacts. Precipitation number of models out of 21 that project increases in precipitation source: IPCC, 2007

7 How do changes in Chile compare to the California Case? 21 modeled changes for A1B emissions minus Warming is large-scale, certain Precipitation changes more regional, less confident Regional changes drive regional impacts.

8 Regional Changes Projected changes non-uniform Impacts also non-uniform Median runoff change, minus Greater water scarcity More wildfires Accelerating invasive species Tourism, recreation impacts Agricultural vulnerability Extreme urban heat events Worsening air quality episodes Ocean fishery migration Increased severe flooding events Source: U.S. Global Change Research Program (USGCRP)

9 Estimating regional impacts 1. GHG Emissions Scenario Adapted from Cayan and Knowles, SCRIPPS/USGS, Global Climate Model 4. Land surface (Hydrology) Model 3.“Downscaling” 5. Operations/impacts Models

10 Availability of GCM Simulations  20 th century through 2100 and beyond  >20 GCMs  Multiple Future Emissions Scenarios

11 Need for Downscaling Dynamic –Better representation of terrain captures local processes and feedbacks –Computationally expensive –Still contain biases Statistical –Assumes stationary transfer function Image: Canadian Climate Change Scenarios Network Images: IPCC

12 Downscaling Downscaling for Impacts Models Raw GCM Output Bias correct and spatially downscale GCM output Run hydrology model with projected climate Precip, Temp Flow, Snow, etc.

13 Multi-Model Ensemble Projections for Feather River Increase Dec-Feb Flows +77% for A2 +55% for B1 Decrease May-Jul -30% for A2 -21% for B1

14 Impact Probabilities for Planning Snow water equivalent on April 1, mm Point at: 120ºW, 38ºN 2/3 chance that loss will be at least 40% by mid century, 70% by end of century Combine many future scenarios, models, since we don’t know which path we’ll follow (22 futures here) Choose appropriate level of risk

15 Translating this approach to Chile Four key basins Ecologically and economically important

16 Series diarias Se rellenan de series incompletas de P y Q Análisis (1) estacional, (2) periodo pluvial y nival, (3) anual Variables hidroclimatológicas e índices representativos Tendencias (Mann-Kendall y Regresión Lineal) Mataquito Basin T med, T max, T min, P Q día

17 Escenarios de Cambio Climático específicos cuenca Mataquito Para un solo escenario (A1b) pero ahora estudiando un poco cambios en variabilidad

18 Snow Cover and Extreme Events P 2 días previos (mm) Caudal Máximo (m 3 /s) T max promedio (°C)13,017,4 Cota estimada línea de nieve (m) * A partir de P’s y T’s en Curicó, adoptando una tasa de lapso de 9 °C/Km Two events: 23 may may , with lower total rain produced greater peak stream flow.

19 Capturing Uncertainties in an Ensemble - Temperature Internal variability (forecast) important first few years Model Uncertainty dominates through mid-21 st century Uncertain emissions pathway most important after that Hawkins & Sutton, BAMS, 2009

20 Does this capture the range of uncertainties? Perturbed physics experiments and theoretical feedback analyses extend tail to right Uncertainty in emissions is on same order if planning horizon includes end of 21 st century or beyond Roe and Baker, 2007

21

22 Caudales (mm/año) Temperatura Media Anual (Celsius) Precipitaciones (mm/año)


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