Climate Model Intercomparison of Regional Temperature Projections for Southeast Asia
DOI:
https://doi.org/10.5281/zenodo.22807617Keywords:
CMIP6, Southeast Asia, regional temperature projection, CORDEX-SEA, inter-model spread, dynamical downscaling, bias correction, SSP scenarios, Maritime Continent, IndochinaAbstract
Southeast Asia's temperature response to future greenhouse gas forcing is projected with markedly less agreement
across global climate models than in many mid-latitude regions, owing to the interplay of land-sea contrast,
monsoon circulation and a maritime continent whose small islands and narrow straits are poorly resolved at typical
global model grid spacing. We compared historical performance and future projections from 13 CMIP6 global
climate models and a six-member CORDEX-Southeast Asia regional climate model ensemble, evaluating
1995-2014 simulated near-surface air temperature against a station-based gridded observational dataset for four
sub-regions (Indochina, Myanmar, the Philippines and the Maritime Continent) before examining projected warming
under SSP2-4.5 and SSP5-8.5 for the mid-century (2041-2060) and end-century (2081-2100) periods. The raw
global model ensemble showed a domain-mean cold bias of 0.6 degrees C relative to observations, largest over the
Maritime Continent (-1.1 degrees C) where island and coastline geometry is most poorly resolved, and inter-model
spread in historical mean temperature exceeded 2.0 degrees C across the ensemble even before considering future
forcing. Dynamical downscaling through the CORDEX-SEA regional models reduced the domain-mean bias to 0.2
degrees C and narrowed the inter-model range by roughly one third, with the largest correction again concentrated
over the Maritime Continent. Projected end-century warming relative to 1995-2014 ranged from 1.6 to 2.3 degrees
C across sub-regions under SSP2-4.5 and from 3.1 to 4.2 degrees C under SSP5-8.5, with Indochina warming most
and the Maritime Continent least in both scenarios and across nearly every individual model, a spatial pattern that
was far more consistent across the ensemble than the projections' absolute magnitude. Four models identified as
carrying an implausibly high equilibrium climate sensitivity accounted for a disproportionate share of the upper end
of the projected warming range. These results indicate that while the sign and relative spatial pattern of Southeast
Asian warming is robust across the current model generation, absolute projected magnitudes remain sensitive to
model selection, downscaling method and climate sensitivity screening choices that should be made explicit in
regional impact assessments.
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