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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 - PowerPoint PPT Presentation
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Assessing climate change impacts on water resources in Chile
Assessing climate change impacts on water resources in Chile
Reunión profesores Estadounidenses FulbrightValparaiso, Chile
15 setiembre 2011
Ed MaurerCivil Engineering Department
Global Climate is ChangingGlobal 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)
Observed Changes: 1970-2004Observed 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.
Projections of Global ChangeProjections of Global Change
• Range of ‘likely warming’ by end of 21st century variable
• By mid-21st century most differences smaller
2010
1.8° 3.4° 4.0°2.4° 2.8°
Which pathway are we on?Which pathway are we on?
• Scenarios trends are averages across all models available for each scenario class.
Raupach et al., PNAS, 2007Global Carbon Project, 2009
• Current emissions are tracking above the most intense IPCC emission scenario
1990 1995 2000 2005 2010 2015
Fo
ssil
Fu
el E
mis
sio
n (
GtC
y-1)
5
6
7
8
9
10
A1B
A1FI
A1T
A2
B1
B2
Carbon Dioxide Information Analysis Center
International Energy Agency
Looking toward the future: end of 21st century
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
Figure 11.12Figure 11.12number of models out of 21 that project increases in precipitationsource: IPCC, 2007
How do changes in Chile compare to the California
Case?
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
.
Regional ChangesRegional Changes
• Projected changes non-uniform
• Impacts also non-uniform
Median runoff change, 2041-2060 minus 1901-1970
Greater water scarcityMore wildfiresAccelerating invasive speciesTourism, recreation impactsAgricultural vulnerability
Extreme urban heat eventsWorsening air quality episodes
Ocean fishery migrationIncreased severe flooding events
Source: U.S. Global Change Research Program (USGCRP)
Estimating regional impactsEstimating regional impacts
1. GHG Emissions Scenario
Adapted from Cayan and Knowles, SCRIPPS/USGS, 2003
2. Global Climate Model4. Land surface
(Hydrology) Model
3. “Downscaling”
5. Operations/impac
ts Models
Availability of GCM SimulationsAvailability of GCM Simulations
20th century through 2100 and beyond >20 GCMs Multiple Future Emissions Scenarios
Need for DownscalingNeed 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
Downscaling
Downscaling for Impacts ModelsDownscaling for Impacts Models
Raw GCM
Output
• Bias correct and spatially downscale GCM output
• Run hydrology model with projected climateP
reci
p,
Tem
p
Flow, Snow, etc.
Multi-Model Ensemble Projections for Feather River
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
Impact Probabilities for PlanningImpact Probabilities for Planning
Sn
ow
wa
ter
eq
uiv
ale
nt
on
Ap
ril
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
Translating this approach to ChileTranslating this approach to Chile
Four key basins
Ecologically and economically important
• 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
Tmed, Tmax, Tmin, P
Qdía
Escenarios de Cambio Climático específicos cuenca Mataquito
Para un solo escenario (A1b) pero ahora estudiando un poco cambios en variabilidad
Snow Cover and Extreme Events
Snow Cover and Extreme Events
2002 2008
P 2 días previos (mm) 103.6 83.9
Caudal Máximo (m3/s) 931 2690
Tmax promedio (°C) 13,0 17,4
Cota estimada línea de nieve (m) 1700 2200
* A partir de P’s y T’s en Curicó, adoptando una tasa de lapso de 9 °C/Km
• Two events: 23 may 200827 may 2002
2002 2008
2008, with lower total rain produced greater peak stream flow.
Capturing Uncertainties in an Ensemble - Temperature
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
Does this capture the range of uncertainties?
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
Caudales(mm/año)
Temperatura Media Anual(Celsius)
Precipitaciones(mm/año)