Global Climate Model GCM Scenarios for Climate Change Impacts Research

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Global Climate Model (GCM) Scenarios forClimate
Change Impacts Research

• Trevor Murdock, M.Sc. tmurdock_at_uvic.ca
• Canadian Institute for Climate Studies
  www.cics.uvic.ca
• 14 Sep 2004

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Outline

• Context definitions
• Global Climate Models (GCMs)
• Scenarios
• Uncertainty
• Emissions
• Vegetation
• Applying scenarios to impacts studies
• Downscaling RCMs other approaches
• Climate normals
• Scenarios for BC
• Summary

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Context and definitions

• Identify Vulnerabilities - what aspects of
  climate change is a community / region
  susceptible to?
• Study potential Impacts of climate change
  projections of future climate are required use a
  range of Scenarios from Global Climate Models
  (GCMs) to deal with uncertainty
• Adaptation strategies involve managing for
  current and potential future climate (change and
  variability) impacts

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What are Global Climate Models?

• GCMs compute global weather patterns several
  times per day projected over the next century
• GCMs are the
• only credible tools currently available for
  simulating the physical processes that determine
  global climate... IPCC

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Sources of Uncertainty
Source Hadley Centre for Climate Prediction
and Research, UK Met. Office
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Emissions Scenarios

• Emissions scenarios based on different
  assumptions abouthow the globaleconomy will
  evolve and emitfossil fuels overthe next
  century
• SRES recommended
• IS92a gg ga also available
• Naming convention also denotes members of
  ensembles with numbers and ensemble averages with
  x (i.e. CGCM2 A11, A12, A13, A1x)

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Emissions Concentrations
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GCMsEach GCM has different parameterizations of
physics of the Atmosphere, Ocean, Cryosphere
Biosphere
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Vegetation in GCMs

• GCMs typically ignore climate/vegetation
  feedbacks
• CCCMa (Canada)
• CGCM2 - no vegetation
• CGCM3 - simple CLASS scheme
• CGCM4 - will include more sophisticated
  vegetation and biophysical processes
• Hadley Center (UK)
• HadCM3 includes representation of freezing and
  melting of soil moisture and evaporation includes
  the stomatal resistance on temperature, vapour
  pressure, and CO2 concentration (Cox et al.,
  1998)

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Applying Scenarios Downscaling

• GCM scenarios coarse resolution (100s of kms /
  monthly)
• Dynamic methods
• retain internal physical consistency
• high resolution AGCMs, Regional Climate Models
  (RCMs)
• Statistical methods
• less costly/less complicated
• Weather generators LARS-WG, Multiple linear
  regression - SDSM
• Best solution often not to downscale at all
• interpolate (introduces false geographical
  precision)
• apply change fields from larger spatial scale to
  working scale

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Regional Climate Models

• Account for sub-grid scale forcings such as
  topography and land cover in a physically-based
  way
• Note more physics can mean more uncertainty

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Applying Scenarios Climate Normals

• Baseline Climates
• Usually 1961-1990
• Good baseline data needed for 2 reasons
• GCM scenario differences need to be applied to an
  observed baseline (to remove model bias).
• Impacts assessment should include analysis of
  recent climate
• Types of observational baselines
• Individual station data (raw, homogenized)
• Gridded station data (interpolated)
• Gridded satellite data
• Gridded reanalysis data (statistical/dynamical/mod
  eling)
• PRISM 4km x 4km ( or resampled to 2km x 2 km )
  grid Temperature, Rainfall, Snowfall

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CCIS Custom Regions

• http//www.cics.uvic.ca/scenarios/data/select.cgi
  
• Predefined regions or create by clicking on map
• Control panel interface (rather than steps)
• Dynamic map creation allows for user
  customization of many features (legend, decimal
  places, grid, etc.)
• Meta-information about full map and region (min,
  max, median, area-weighted mean, stddev)

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• http//www.cics.uvic.ca/scenarios/data/select.cgi
  

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Summary

• Impacts work most effective in the context of
  Vulnerability, Impacts, and Adaptation
• GCM based scenarios used to represent range of
  plausible future climates for impacts studies
• Vegetation beginning to be included explicitly in
  GCMs
• Downscaling may be used to overcome differences
  in scale between GCMs and impacts analysis
• GCM change fields are applied to climate normals
• Scenarios for BC see www.cics.uvic.ca/scenarios
  for more tools, scenarios, and data