Evaluation of proxy-based millennial reconstruction methods

Lee, Terry C. K.; Zwiers, Francis W.; Tsao, Min

doi:10.1007/s00382-007-0351-9

Cited by 97 publications

(132 citation statements)

References 31 publications

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“…Nevertheless, quantitative agreement has been so far elusive and thus a matter of considerable debate in the last few years (e.g. von Mann et al, 2005;Bürger and Cubasch, 2005;Bürger et al, 2006;Moberg et al, 2005;McIntyre and McKitrick, 2005;Wahl et al, 2006;Mann et al, 2007aMann et al, ,b, 2008Smerdon and Kaplan, 2007;Wahl and Ammann, 2007;Ammann and Wahl, 2007;Lee et al, 2008) …”

Section: Paleoclimate Contextmentioning

confidence: 99%

Borehole climatology: a discussion based on contributions from climate modeling

et al. 2009

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Abstract. Progress in understanding climate variability through the last millennium leans on simulation and reconstruction efforts. Exercises blending both approaches present a great potential for answering questions relevant both for the simulation and reconstruction of past climate, and depend on the specific peculiarities of proxies and methods involved in climate reconstructions, as well as on the realism and limitations of model simulations. This paper explores research specifically related to paleoclimate modeling and borehole climatology as a branch of climate reconstruction that has contributed significantly to our knowledge of the low frequency climate evolution during the last five centuries.The text flows around three main issues that group most of the interaction between model and geothermal efforts: the use of models as a validation tool for borehole climate reconstructions; comparison of geothermal information and model simulations as a means of either model validation or inference about past climate; and implications of the degree of realism on simulating subsurface climate on estimations of future climate change.The use of multi-centennial simulations as a surrogate reality for past climate suggests that within the simplified reality of climate models, methods and assumptions in borehole reconstructions deliver a consistent picture of past climate evolution at long time scales. Comparison of model simulations and borehole profiles indicate that borehole temperatures are responding to past external forcing and that more realism in the development of the soil model components in climate models is desirable. Such an improved degree of Correspondence to: J. F. González-Rouco (fidelgr@fis.ucm.es) realism is important for the simulation of subsurface climate and air-ground interaction; results indicate it could also be crucial for simulating the adequate energy balance within climate change scenario experiments.

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Section: Paleoclimate Contextmentioning

confidence: 99%

Borehole climatology: a discussion based on contributions from climate modeling

et al. 2009

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“…Further confirmation and analysis of results for the nineteenth and twentieth centuries requires extended historical reanalyses 9,20 , higher spatiotemporal resolution SST reconstructions from other marine palaeoclimate marine archives [21][22][23] and climate model simulations 10 . regional variability 12,13 , and: (1) minimizes bias owing to any individual reconstruction overprinting the average trend [14][15][16] (Fig. 1), which suggests that the Ocean2k SST network, on bicentennial timescales, should contain a common global signal.…”

mentioning

confidence: 97%

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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“…Nevertheless, it has been the most frequently used type of noise (Smerdon 2012). Mann et al (2007) argued that a value of r 5 0.32 is more reasonable for annually resolved proxies and this value has been used in some pseudoproxy studies (e.g., Mann et al 2007;Lee et al 2008;Moberg et al 2008;Riedwyl et al 2009). The substantially larger value of r 5 0.70 or r 5 0.71 is also sometimes used Mann et al 2007;Moberg et al 2008;Riedwyl et al 2009), although Mann et al (2007) argued that this value is unrealistically large for many annually resolved proxies.…”

Section: A Pseudoproxy Experimentsmentioning

confidence: 99%

Comments on “Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability”

Moberg

2012

Journal of Climate

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Christiansen and Ljungqvist have presented an extratropical NH temperature reconstruction using a method (LOC) that they claim ''preserves'' low-frequency variability, at the expense of exaggerated highfrequency variability. Using theoretical arguments and a pseudoproxy experiment, it is demonstrated here that the LOC method is not guaranteed to preserve variability at any frequency. Rather, LOC reconstructions will have more variance than true large-scale temperature averages at all frequencies. This variance inflation, however, can be negligible at those frequencies where the noise variance in individual proxies is small enough to be effectively cancelled when computing an average over the available proxies. Because the proxy noise variance at low frequencies cannot be directly estimated, and thus has to be regarded as unknown, it is safer to regard a reconstruction with the LOC method as providing an estimate of the upper bound of the large-scale low-frequency temperature variability rather than one with a correct estimate of this variance.

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Evaluation of proxy-based millennial reconstruction methods

Cited by 97 publications

References 31 publications

Borehole climatology: a discussion based on contributions from climate modeling

Borehole climatology: a discussion based on contributions from climate modeling

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

Comments on “Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability”

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