Causes of climate change over the historical record

Hegerl, Gabriele C.; Brönnimann, Stefan; Cowan, Tim; Friedman, Andrew R.; Hawkins, Ed; Iles, Carley; Müller, Wolfgang A.; Schurer, Andrew; Undorf, Sabine

doi:10.1088/1748-9326/ab4557

Cited by 122 publications

(71 citation statements)

References 241 publications

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“…The two warming periods differ mostly in the Kuroshio region, the extratropical South Pacific and the Southern Ocean; the differences are reflected by a pattern correlation of only r =0.36 between the two periods. The differences in the patterns of the two warming periods can be due to the large observational uncertainty in the early warming period (see Figures S2, S4, and S5 for a comparison between the different observational data sets), due to differences in the forcing that drives the warming or due to multidecadal to centennial variability (e.g., Latif et al, 2013; Stevens, 2015; Hegerl et al, 2019).…”

Section: Global and Local Consistency Of Sst Changesmentioning

confidence: 99%

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

Olonscheck

Rugenstein

Marotzke

2020

Geophysical Research Letters

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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

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Section: Global and Local Consistency Of Sst Changesmentioning

confidence: 99%

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

Olonscheck

Rugenstein

Marotzke

2020

Geophysical Research Letters

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“…The underlying decadal SST anomalies in the 1930s resembled the warm phases of the Atlantic Multidecadal Oscillation (AMO) 16,17 and the Pacific Decadal Oscillation (PDO) 18,19 (Fig. 1b).…”

Section: Resultsmentioning

confidence: 93%

Ocean and land forcing of the record-breaking Dust Bowl heatwaves across central United States

et al. 2020

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The severe drought of the 1930s Dust Bowl decade coincided with record-breaking summer heatwaves that contributed to the socioeconomic and ecological disaster over North America's Great Plains. It remains unresolved to what extent these exceptional heatwaves, hotter than in historically forced coupled climate model simulations, were forced by sea surface temperatures (SSTs) and exacerbated through human-induced deterioration of land cover. Here we show, using an atmospheric-only model, that anomalously warm North Atlantic SSTs enhance heatwave activity through an association with drier spring conditions resulting from weaker moisture transport. Model devegetation simulations, that represent the widespread exposure of bare soil in the 1930s, suggest human activity fueled stronger and more frequent heatwaves through greater evaporative drying in the warmer months. This study highlights the potential for the amplification of naturally occurring extreme events like droughts by vegetation feedbacks to create more extreme heatwaves in a warmer world.

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“…ERAf has demonstrated interannual and multidecadal surface heat fluxes comparable with the reanalyses (cf. figure 7 in Hegerl et al, 2019).…”

Section: Century-long Reanalyses and Forced Ocean Model Experimentsmentioning

confidence: 99%

Observed Subdecadal Variations of European Summer Temperatures

Müller

Borchert

Ghosh

2020

Geophysical Research Letters

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We identify subdecadal variations in European summer temperatures in coupled and uncoupled century‐long reanalyses. Spectral analyses reveal significant peaks at 5–10 years in the midtwentieth century. The subdecadal variations show substantial amplitudes of ~1–1.5 °C, associated with extremely warm summers during their positive phases. We use forced ocean model experiments and show that the European summer temperature variations are associated with the subdecadal coupled North Atlantic climate system. A positive winter NAO‐like forcing is associated with changes in the ocean circulation and mass and heat convergence occurring 1–2 years prior to European summer temperature rise. Ocean heat content and sea surface temperature increase in the subtropical North Atlantic. The atmospheric response is barotropic and induces wave activity fluxes toward the European continent, modulation of the jet positions, and blocking frequency. The atmospheric response establishes a pathway connecting the subdecadal coupled North Atlantic climate system to European summer temperature.

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Causes of climate change over the historical record

Cited by 122 publications

References 241 publications

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

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

Ocean and land forcing of the record-breaking Dust Bowl heatwaves across central United States

Observed Subdecadal Variations of European Summer Temperatures

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