Abstract
Regional climate projections are challenging because of large uncertainty particularly stemming from unpredictable, internal variability of the climate system. Here, we examine the internal variability-induced uncertainty in precipitation and surface air temperature (SAT) trends during 2005–2055 over East Asia based on 40 member ensemble projections of the Community Climate System Model Version 3 (CCSM3). The model ensembles are generated from a suite of different atmospheric initial conditions using the same SRES A1B greenhouse gas scenario. We find that projected precipitation trends are subject to considerably larger internal uncertainty and hence have lower confidence, compared to the projected SAT trends in both the boreal winter and summer. Projected SAT trends in winter have relatively higher uncertainty than those in summer. Besides, the lower-level atmospheric circulation has larger uncertainty than that in the mid-level. Based on k-means cluster analysis, we demonstrate that a substantial portion of internally-induced precipitation and SAT trends arises from internal large-scale atmospheric circulation variability. These results highlight the importance of internal climate variability in affecting regional climate projections on multi-decadal timescales.
Highlights
Changes in regional climate are relevant for effective decision-making on how to manage adaptation and mitigation, and how to cope with potential losses and damages at the regional scale in a future warmer climate [1]
Based on k-means cluster analysis, we demonstrate that a substantial portion of internally-induced precipitation and surface air temperature (SAT) trends arises from internal large-scale atmospheric circulation variability
The Community Climate System Model Version 3 (CCSM3) is a comprehensive coupled atmosphere-ocean-sea ice-land general circulation model, which consists of Community Atmospheric Model Version 3 at 2.8° horizontal resolution (T42 spectral truncation) and 26 levels in the vertical, Parallel Ocean Program at 1° horizontal resolution with increased resolution to 0.32° at the equator and 40 levels in the vertical, Community Sea Ice Model Version 5 with plastic-elastic-viscous dynamics, and Community Land Model described in Collins, Bitz [16], to which readers are referred for details
Summary
Changes in regional climate are relevant for effective decision-making on how to manage adaptation and mitigation, and how to cope with potential losses and damages at the regional scale in a future warmer climate [1]. Projections of regional climate change are characterized by considerable uncertainty, which has emerged as a pressing challenge in climate science [2]. Uncertainty in regional climate projections mostly comes from three distinct sources [3,4,5,6,7]. The first source is model-response uncertainty: each global climate model may produce different future responses to the same prescribed external radiative forcing due to different physics, dynamical cores and resolutions, as well as model biases [8]. The second is emission-scenario uncertainty, which arises from the uncertainties in future trajectory of external radiative forcing, including time-dependent emissions of greenhouse gases and particles, PLOS ONE | DOI:10.1371/journal.pone.0149968. The second is emission-scenario uncertainty, which arises from the uncertainties in future trajectory of external radiative forcing, including time-dependent emissions of greenhouse gases and particles, PLOS ONE | DOI:10.1371/journal.pone.0149968 March 1, 2016
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