Inter-hemispheric temperature variability over the past millennium

Neukom, Raphael; Gergis, Joëlle; Karoly, David J.; Wanner, Heinz; Curran, Mark A. J.; Elbert, Julie; González-Rouco, J. Fidel; Linsley, Braddock K.; Moy, Andrew D.; Mundo, Ignacio A.; Raible, Christoph C.; Steig, Eric J.; Ommen, T. D. van; Vance, Tessa R.; Villalba, Ricardo; Zinke, Jens; Frank, David

doi:10.1038/nclimate2174

Cited by 266 publications

(291 citation statements)

References 38 publications

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“…Nevertheless, the spatio-temporal structure of the temperature changes is complex, with warm and cold periods being generally not synchronous between different regions (PAGES 2k Consortium, 2013). Those conclusions are in overall agreement with the results derived from global climate models driven by estimates of natural and anthropogenic forcings, although mod-H. Goosse et al: Simulated Alpine glacier length over the past millennium els tend to underestimate the magnitude of the changes in some regions and to simulate more homogenous changes than in the reconstructions (Goosse et al, 2005;Raibble et al, 2006;Gonzalez-Rouco et al, 2006;Jungclaus et al, 2010;Fernández-Donado et al, 2013;Landrum et al, 2013;Neukom et al, 2014;Moberg et al, 2015;PAGES2k-PMIP, 2015;Otto-Bliesner et al, 2016).…”

Section: Introductionsupporting

confidence: 79%

“…The syntheses of the available climate records indicate a general temperature decrease from the beginning of the second millennium to the beginning of the 19th century, followed by a large warming over the 20th century (Jones et al, 2009;Mann et al, 2009;PAGES 2k Consortium, 2013Neukom et al, 2014). Nevertheless, the spatio-temporal structure of the temperature changes is complex, with warm and cold periods being generally not synchronous between different regions (PAGES 2k Consortium, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

et al. 2018

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Abstract.It is standard to compare climate model results covering the past millennium and reconstructions based on various archives in order to test the ability of models to reproduce the observed climate variability. Up to now, glacier length fluctuations have not been used systematically in this framework even though they offer information on multidecadal to centennial variations complementary to other records. One reason is that glacier length depends on several complex factors and so cannot be directly linked to the simulated climate. However, climate model skill can be measured by comparing the glacier length computed by a glacier model driven by simulated temperature and precipitation to observed glacier length variations. This is done here using the version 1.0 of the Open Global Glacier Model (OGGM) forced by fields derived from a range of simulations performed with global climate models over the past millennium. The glacier model is applied to a set of Alpine glaciers for which observations cover at least the 20th century. The observed glacier length fluctuations are generally well within the range of the simulations driven by the various climate model results, showing a general consistency with this ensemble of simulations. Sensitivity experiments indicate that the results are much more sensitive to the simulated climate than to OGGM parameters. This confirms that the simulations of glacier length can be used to evaluate the climate model performance, in particular the simulated summer temperatures that largely control the glacier changes in our region of interest. Simulated glacier length is strongly influenced by the internal variability in the system, putting limitations on the model-data comparison for some variables like the trends over the 20th century in the Alps. Nevertheless, comparison of glacier length fluctuations on longer timescales, for instance between the 18th century and the late 20th century, appear less influenced by the natural variability and indicate clear differences in the behaviour of the various climate models.

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

et al. 2018

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“…1a it is clear that the temperature anomalies over the last millennium are small, and clearly common MCA and LIA periods are not easily identifiable across models. This is consistent with the notion that both periods are partially a result of internal climate variability (PAGES 2k Consortium, 2013), particularly the MCA (Neukom et al, 2014). The hypothesis that guides our analysis used to asses the SAMS variability in models is that both periods are primarily a result of internal (non-forced) variability…”

Section: Definition Of Periodssupporting

confidence: 72%

The South American monsoon variability over the last millennium in climate models

et al. 2016

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Abstract. In this paper we assess South American monsoon system (SAMS) variability in the last millennium as depicted by global coupled climate model simulations. Highresolution proxy records for the South American monsoon over this period show a coherent regional picture of a weak monsoon during the Medieval Climate Anomaly and a stronger monsoon during the Little Ice Age (LIA). Due to the small external forcing during the past 1000 years, model simulations do not show very strong temperature anomalies over these two specific periods, which in turn do not translate into clear precipitation anomalies, in contrast with the rainfall reconstructions in South America. Therefore, we used an ad hoc definition of these two periods for each model simulation in order to account for model-specific signals. Thereby, several coherent large-scale atmospheric circulation anomalies are identified. The models feature a stronger monsoon during the LIA associated with (i) an enhancement of the rising motion in the SAMS domain in austral summer; (ii) a stronger monsoon-related upper-tropospheric anticyclone; (iii) activation of the South American dipole, which results in a poleward shift of the South Atlantic Convergence Zone; and (iv) a weaker upper-level subtropical jet over South America. The diagnosed changes provide important insights into the mechanisms of these climate anomalies over South America during the past millennium.

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“…units, respectively; Supplementary Table S13). These coldest bin transitions and individual bins are contemporaneous with the onset of the globally coherent Little Ice Age recorded in many Northern and Southern Hemisphere continental regions 7,17,18 , suggesting that there was a global mean ocean SST fingerprint associated with this interval.…”

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confidence: 99%

Robust global ocean cooling trend for the pre-industrial Common Era

et al. 2015

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International audienceKnowledge of natural climate variability is essential to better constrain the uncertainties in projections of twenty-first-century climate change 1–5. The past 2,000 years (2 kyr) have emerged as a critical interval in this endeavour, with sufficient length to characterize natural decadal-to-centennial scale change, known external climate forcings 6 and with distinctive patterns of spatiotemporal temperature variations 7. However, reconstructions for the full 2 kyr interval are not available for the global ocean, a primary heat reservoir 8 and an important regulator of global climate on longer timescales 9–11. Here we present a global ocean sea surface temperature (SST) synthesis (Ocean2k SST synthesis) spanning the Common Era, which shows a cooling trend that is similar, within uncertainty, to that simulated by realistically forced climate models for the past millennium. We use the simulations to identify the climate forcing(s) consistent with reconstructed SST variations during the past millennium. The oceans mediate the response of global climate to natural and anthropogenic forcings. Yet for the past 2,000 years — a key interval for understanding the present and future climate response to these forcings — global sea surface temperature changes and the underlying driving mechanisms are poorly constrained. Here we present a global synthesis of sea surface temperatures for the Common Era (ce) derived from 57 individual marine reconstructions that meet strict quality control criteria. We observe a cooling trend from 1 to 1800 ce that is robust against explicit tests for potential biases in the reconstructions. Between 801 and 1800 ce, the surface cooling trend is qualitatively consistent with an independent synthesis of terrestrial temperature reconstructions, and with a sea surface temperature composite derived from an ensemble of climate model simulations using best estimates of past external radiative forcings. Climate simulations using single and cumulative forcings suggest that the ocean surface cooling trend from 801 to 1800 ce is not primarily a response to orbital forcing but arises from a high frequency of explosive volcanism. Our results show that repeated clusters of volcanic eruptions can induce a net negative radiative forcing that results in a centennial and global scale cooling trend via a decline in mixed-layer oceanic heat content

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Inter-hemispheric temperature variability over the past millennium

Cited by 266 publications

References 38 publications

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

The South American monsoon variability over the last millennium in climate models

Robust global ocean cooling trend for the pre-industrial Common Era

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