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Assessing climate change impacts on water resources in Chile

Assessing climate change impacts on water resources in Chile. Ed Maurer Civil Engineering Department. Reunión profesores Estadounidenses Fulbright Valparaiso, Chile 15 setiembre 2011. Global Climate is Changing. Temperatures are increasing globally

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Assessing climate change impacts on water resources in Chile

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

  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: 1970-2004 • 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. 2010 Projections of Global Change • Range of ‘likely warming’ by end of 21st century variable • By mid-21st century most differences smaller 1.8° 2.4° 2.8° 3.4° 4.0°

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

  6. Looking toward the future: end of 21st century 21 modeled changes for A1B emissions 2080-2099 minus 1980-1999 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 2080-2099 minus 1980-1999 Warming is large-scale, certain Precipitation changes more regional, less confident Regional changes drive regional impacts .

  8. Extreme urban heat events Worsening air quality episodes Ocean fishery migration Increased severe flooding events Greater water scarcity More wildfires Accelerating invasive species Tourism, recreation impacts Agricultural vulnerability Regional Changes • Projected changes non-uniform • Impacts also non-uniform Median runoff change, 2041-2060 minus 1901-1970 Source: U.S. Global Change Research Program (USGCRP)

  9. Estimating regional impacts 2. Global Climate Model 4. Land surface (Hydrology) Model 1. GHG Emissions Scenario 5. Operations/impacts Models • “Downscaling” Adapted from Cayan and Knowles, SCRIPPS/USGS, 2003

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

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

  12. Downscaling for Impacts Models • Bias correct and spatially downscale GCM output • Run hydrology model with projected climate Raw GCM Output Downscaling 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. 2/3 chance that loss will be at least 40% by mid century, 70% by end of century Point at: 120ºW, 38ºN Impact Probabilities for Planning Snow water equivalent on April 1, mm • 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. Mataquito Basin Tmed, Tmax, Tmin, P Qdía • 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)

  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 • Two events: • 23 may 2008 • 27 may 2002 • * A partir de P’s y T’s en Curicó, adoptando una tasa de lapso de 9 °C/Km Mataquitocuenca con nieve a 1700m Mataquitocuenca con nieve a 2200m 2002 2008 2008, 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-21st 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 21st century or beyond Roe and Baker, 2007

  21. Thanks!

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

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