Broad Consistency Between Observed and Simulated Trends in Sea Surface Temperature Patterns

Abstract

Using seven single-model ensembles and the two multimodel ensembles CMIP5 and CMIP6, we show that observed and simulated trends in sea surface temperature (SST) patterns are globally consistent when accounting for internal variability. Some individual ensemble members simulate trends in large-scale SST patterns that closely resemble the observed ones. Observed regional trends that lie at the outer edge of the models' internal variability range allow two nonexclusive interpretations: (a) Observed trends are unusual realizations of the Earth's possible behavior and/or (b) the models are systematically biased but large internal variability leads to some good matches with the observations. The existing range of multidecadal SST trends is influenced more strongly by large internal variability than by differences in the model formulation or the observational data sets.Plain Language Summary Climate model simulations agree well with the observed evolution of the global mean sea surface temperature, but their ability to realistically represent changes in the patterns of sea surface temperatures has been questioned. We show with an unprecedented number of simulations from different models and different initial conditions that the observed and simulated changes in SST patterns are consistent in most regions of the ocean. For each model, a few individual simulations recreate the observed patterns. In some regions, the observed changes may be an extreme realization of the Earth's possible behavior. Alternatively, structural model errors may be hidden by the large range of possible realizations. Key Points:• Observed and simulated SST trends are consistent in at least 90% of the global ocean area since the midtwentieth century • This consistency is obtained over larger areas in CMIP6 models than in CMIP5 models • Observed regional trends that lie at the edge of the simulated distribution of internal variability are hard to interpret Supporting Information:• Supporting Information S1 • Text S1

The Peculiar Trajectory of Global Warming

“…For reference, trends in the equatorial Pacific SST gradient (discussed below) are about an order of magnitude larger. Thus, errors in the trends of Δ conv and SST # in the observational record may be possible even if the large-scale spatial patterns of SST trends are, as argued by Olonscheck et al (2020) for the ERSSTv2, COBE2 and HadISST2 SST reconstructions, broadly consistent with the range covered by internal variability of coupled atmosphere-ocean GCMs. The verification of trends in Δ conv from observations independent of SSTs is difficult.…”

“…The question whether the trend in the equatorial Pacific East‐West SST gradient seen in the observational SST reconstructions over recent decades is consistent with results from coupled atmosphere‐ocean GCMs has in itself received much attention (e.g. Coats & Karnauskas, 2017; Olonscheck et al., 2020; Watanabe et al., 2021). The recent analysis by Watanabe et al.…”

Large ensemble climate model simulations: introduction, overview, and future prospects for utilising multiple types of large ensemble

“…By combining the GCM, RCM, and nat-GCM SMILEs we can further investigate the response of both SAT and precipitation to large volcanic eruptions over Europe. To investigate the response to volcanoes previous studies have shown that many ensemble members are needed to tease out the forced response (Maher et al, 2015;Pausata et al, 2015;Bittner et al, 2016;Milinski et al, 2020), meaning that SMILEs are an ideal tool to investigate this question.…”

Winter Precipitation Changes in California Under Global Warming: Contributions of CO2, Uniform SST Warming, and SST Change Patterns

“…In sum, we argue that the El Niño‐like SST change pattern constitutes a factor that should be taken into account in examining the jet extension. However, as there is a large spread in the El Niño versus La Niña‐like SST warming pattern over the tropical Pacific among the CMIP5 coupled climate models (e.g., Li et al., 2016; Olonscheck et al., 2020; Seager et al., 2019), the effect of SST change pattern contributes to the large inter‐model spread in the jet extension and total precipitation change over California under global warming projected by the coupled models.…”

“…In addition, the SST change with El Niño‐like warming pattern has a secondary but also positive contribution to the jet extension via the tropical teleconnection to the North Pacific. However, this effect has a large spread among the CMIP5 coupled models as there is uncertainty in the tropical SST warming pattern between El Niño‐versus La Niña‐like warming over the tropical Pacific (e.g., Li et al., 2016; Olonscheck et al., 2020; Seager et al., 2019). Relative to the SST forcing, the direct CO 2 radiative forcing on the wetting California is negligible.…”