Ensemble Climate Scenarios for
Vietnam
Dr Carol McSweeney, Met Office Hadley Centre
Scenario Dissemination Workshop, IMHEN, Hanoi
Monday 20th February 2012
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Ensemble Climate Scenarios
for Vietnam
Table of Contents
• Generating scenarios that account for model
uncertainty
• What do the projections indicate?
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Addressing Policy Needs in the Provision of
Climate Scenarios
Needs:
• Need to account for projections from more than one model
• Need projections to be High-Resolution (downscaled) for policyrelevant impacts assessments
Constraints:
• Downscaling is resource intensive
• Restriction on ability to use an RCM to downscale GCMs from different
modelling centres
Solution:
• Downscale models from HadCM3Q family
• Sampling of an ensemble to give a sub-set of 4-6 models that represent
the range of outcomes from a larger ensemble for downscaling
•
Reference: McSweeney et al (Submitted to Journal of Climate) ‘Selecting ensemble members
to provide regional climate change information’.
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Sampling from a GCM Ensemble
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•
Sample uncertainty
caused by range of
magnitudes of climate
change in the different
GCMs (changes by 2080s
under SRES A1B)
•
Sample based on multiple
climate variables, and
sub-regions
•
Q0-16 are members of
the Hadley centre’s own
ensemble
Reference: McSweeney et al (Submitted to Journal of Climate) ‘Selecting
ensemble members to provide regional climate change information’.
Regional Model Domain
• 25km resolution
• Extends considerably
further North of Vietnam
to include Red River
basin
• Outputs available at
daily resolution
• Model run 1950-2050
• Driven at the
boundaries by 5 different
Global Models
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How do the new scenarios
Improve on earlier scenarios?
Model
uncertainty?
Emissions
Uncertainty?
Model Realism
over Vietnam?
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Old Scenarios
New Scenarios


only ECHAM4
5 models from
HadCM3Q0-16


A2 and B2
A1B
ECHAM4 suffers
from significant
shortcomings in
south-east Asia
HadCM3Q family of
models assessed
before downscaling
– all significantly
better
Why model uncertainty but not
emissions uncertainty?
• There are large differences in spatial patterns of rainfall change
in different models which can cause large uncertainty for some
regions.
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Why model uncertainty but not
emissions uncertainty?
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•
On timescales of
interest for planning
(i.e up to 2050), there
is little difference
between the emission
scenarios
•
The range of
uncertainty across
different models, are
much larger than the
uncertainties cause by
emissions scenarios.
How do HadCM3 scenarios improve
on ECHAM4?
Problems with the old scenarios
inherited from the Driving GCM
ECHAM4
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ECHAM4 based scenarios
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Future Climate for Vietnam
Initial Results
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Daily maximum
temperature
change
2020-2050
compared with
1970-2000
(JJA)
• Range of responses
across different ensemble
members
• Also a range of spatial
patterns in those changes.
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Summary of Projected Changes
in Temperature for Vietnam
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Rainfall change
2020-2050
compared with
1970-2000
(JJA)
• Range of responses across
different ensemble members
• Also a range of spatial
patterns in those changes.
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Summary of Projected Changes in
Rainfall for Vietnam
For most
regions the
projections
include both
increases and
decreases in
total rainfall
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Derived
Outputs:
Extremes
Indices
• Change in the number of
days with ‘heavy rainfall’
(higher than 95%ile)
• Increases in heavy
rainfall in more regions
than average rainfall
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Derived Outputs: Storm tracks
• Initial results on the number of storm tracks
passing through each model grid-box
• Still work to on the verification of the storm
tracks and the projected changes.
• Range of responses across the 5 models
indicates importance of multi-model approach.
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Questions and answers
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Eliminate model that are particularly
unrealistic
In this region, no need to
eliminate any models
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Climate Model Uncertainties
Structural Uncertainty
(IPCC CMIP3 multi-model ensemble)
Parameter
Uncertainty
(QUMP perturbed
physics
ensemble)
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