Systematic climate model biases in the large-scale pattern of recent
sea-surface temperature and sea-level pressure change
Abstract
Observed surface temperature trends over recent decades are
characterized by (i) intensified warming in the Indo-Pacific Warm Pool
and slight cooling in the eastern equatorial Pacific, consistent with
strengthening of the Walker circulation, and (ii) cooling in the
Southern Ocean. In contrast, state-of-the-art coupled climate models
generally project Walker circulation weakening, enhanced warming in the
eastern equatorial Pacific, and warming in the Southern Ocean. Here we
investigate the ability of 16 climate model large ensembles to reproduce
observed sea-surface temperature and sea-level pressure trends over
1979-2020 through a combination of externally forced climate change and
internal variability. We find large-scale differences between observed
and modeled trends that are very unlikely (<5% probability)
to occur due to internal variability as represented in models. Disparate
trends are found even in regions with weak multi-decadal variability,
suggesting that model biases in the transient response to anthropogenic
forcing constitute part of the discrepancy.