scholarly journals Facilitating proxy-data interpretation of abrupt climate events using model simulations

PAGES news ◽  
2008 ◽  
Vol 16 (2) ◽  
pp. 16-18 ◽  
Author(s):  
Ane P Wiersma ◽  
DM Roche ◽  
H Renssen
Keyword(s):  
Data Interpretation ◽  
Proxy Data ◽  
Model Simulations ◽  
Climate Events

Misinterpreting proxy data for paleoclimate signals: A reply to Srivastava and Jovane, 2020

The Holocene ◽  
2020 ◽  
Vol 30 (12) ◽  
pp. 1874-1883
Author(s):  
Tanuj Shukla ◽  
Manish Mehta ◽  
Dwarika Prasad Dobhal ◽  
Archna Bohra ◽  
Bhanu Pratap ◽  
...  
Keyword(s):  
Late Holocene ◽  
Data Interpretation ◽  
High Energy ◽  
Magnetic Data ◽  
Climate Variations ◽  
Magnetic Mineralogy ◽  
Proxy Data ◽  
Glacier Valley ◽  
Future Work ◽  
Rule Out

Srivastava and Jovane (2020) have made several comments on our assessment of proxy data and challenged the outcome of Shukla et al. (2020) based mainly on interpretation of environmental magnetic parameters. We respond to their criticisms and re-evaluate our paper, remove ambiguities and validate our conclusions through additional proxies (grain-size and geochemistry). We welcome their comments and do not entirely rule out their interpretation for magnetic mineralogy. We highlight the importance of proxy validation for high-energy environments like Chorabari lake. However, single proxy data correlation is likely to produce biased results with no relevant meaning. The objective of our study was to understand complexities in the glacial-climate system by reconstructing late-Holocene climate variations using the glacial lake sediment records from the Mandakini River Basin, Central Himalaya, India. We presented the complexities in Shukla et al. (2020), and this was also highlighted by Srivastava and Jovane (2020). In response, we provide additional justification of proxy response and substantiate our results with present-day estimates from the Chorabari glacier valley. We disagree with the thesis put forward by Srivastava and Jovane (2020) in their conclusion as they overemphasize the interpretation of a single proxy. We maintain that the investigation of present-day glacial settings is an important precursor of paleoclimatic data interpretation and that this supports our conclusions. We will try to incorporate the important suggestions of Srivastava and Jovne (2020) relating to the interpretation of magnetic data in future work.

scholarly journals Dating historical droughts from religious ceremonies, the international pro pluvia rogation database

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Fernando Domínguez-Castro ◽  
María João Alcoforado ◽  
Nieves Bravo-Paredes ◽  
María Isabel Fernández-Fernández ◽  
Marcelo Fragoso ◽  
...  
Keyword(s):  
Climate Variability ◽  
Agricultural Drought ◽  
Climate Variability And Change ◽  
Proxy Data ◽  
Model Simulations ◽  
Climate Proxy ◽  
Drought Variability ◽  
Instrumental Period ◽  
Share Information ◽  
International Initiative

AbstractClimate proxy data are required for improved understanding of climate variability and change in the pre-instrumental period. We present the first international initiative to compile and share information on pro pluvia rogation ceremonies, which is a well-studied proxy of agricultural drought. Currently, the database has more than 3500 dates of celebration of rogation ceremonies, providing information for 153 locations across 11 countries spanning the period from 1333 to 1949. This product provides data for better understanding of the pre-instrumental drought variability, validating natural proxies and model simulations, and multi-proxy rainfall reconstructions, amongst other climatic exercises. The database is freely available and can be easily accessed and visualized via http://inpro.unizar.es/.

scholarly journals Comparing proxy and model estimates of hydroclimate variability and change over the Common Era

2017 ◽  
Author(s):  
Jason E. Smerdon ◽  
Jürg Luterbacher ◽  
Steven J. Phipps ◽  
Kevin J. Anchukaitis ◽  
Toby Ault ◽  
...  
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Last Millennium ◽  
Proxy Data ◽  
Model Simulations ◽  
Model Comparisons ◽  
Proxy Model ◽  
Hydroclimate Variability ◽  
The Common ◽  
Common Era

Abstract. Water availability is fundamental to societies and ecosystems, but our understanding of variations in hydroclimate (including extreme events, flooding, and decadal periods of drought) is limited because of a paucity of modern instrumental observations that are distributed unevenly across the globe and only span parts of the 20th and 21st centuries. Such data coverage is insufficient for characterizing hydroclimate and its associated dynamics because of its multidecadal-to-centennial variability and highly regionalized spatial signature. High-resolution (seasonal to decadal) hydroclimatic proxies that span all or parts of the Common Era (CE) and paleoclimate model simulations are therefore important tools for augmenting our understanding of hydroclimate variability. In particular, the comparison of the two sources of information is critical for addressing the uncertainties and limitations of both, while enriching each of their interpretations. We review the principal proxy data available for hydroclimatic reconstructions over the CE and highlight contemporary understanding of how these proxies are interpreted as hydroclimate indicators. We also review the available last-millennium simulations from fully-coupled climate models and discuss several outstanding challenges associated with simulating hydroclimate variability and change over the CE. A specific review of simulated hydroclimatic changes forced by volcanic events is provided, as well as a discussion of expected improvements in estimated forcings, models and their implementation in the future. Our review of hydroclimatic proxies and last-millennium model simulations is used as the basis for articulating a variety of considerations and best practices for how to perform proxy-model comparisons of CE hydroclimate. This discussion provides a framework for how best to evaluate hydroclimate variability and its associated dynamics using these comparisons, as well as how they can better inform interpretations of both proxy data and model simulations. We subsequently explore means of using proxy-model comparisons to better constrain and characterize future hydroclimate risks. This is explored specifically in the context of several examples that demonstrate how proxy-model comparisons can be used to quantitatively constrain future hydroclimatic risks as estimated from climate model projections.

scholarly journals Hydrological variability in the Northern Levant: a 250 ka multi-proxy record from the Yammoûneh (Lebanon) sedimentary sequence

2011 ◽  
Vol 7 (4) ◽  
pp. 1261-1284 ◽  
Author(s):  
F. Gasse ◽  
L. Vidal ◽  
A.-L. Develle ◽  
E. Van Campo
Keyword(s):  
Data Interpretation ◽  
Dead Sea ◽  
Climate Modelling ◽  
Paleoenvironmental Reconstruction ◽  
Proxy Data ◽  
Climatic Fluctuations ◽  
Hydrological Variability ◽  
Effective Moisture ◽  
Combined Time Series

Abstract. The Levant is a key region in terms of both long-term hydroclimate dynamics and human cultural evolution. Our understanding of the regional response to glacial-interglacial boundary conditions is limited by uncertainties in proxy-data interpretation and the lack of long-term records from different geographical settings. The present paper provides a 250 ka paleoenvironmental reconstruction based on a multi-proxy approach from northern Levant, derived from a 36 m lacustrine-palustrine sequence cored in the small intra-mountainous karstic Yammoûneh basin from northern Lebanon. We combined time series of sediment properties, paleovegetation, and carbonate oxygen isotopes (δc), to yield a comprehensive view of paleohydrologic-paleoclimatic fluctuations in the basin over the two last glacial-interglacial cycles. Integration of all available proxies shows that Interglacial maxima (early-mid MIS 7, MIS 5.5 and early MIS 1) experienced relatively high effective moisture, evidenced by the dominance of forested landscapes (although with different forest types) associated with authigenic carbonate sedimentation in a productive waterbody. Synchronous and steep δc increases can be reconciled with enhanced mean annual moisture when changes in seasonality are taken into account. During Glacials periods (MIS 2 and MIS 6), open vegetation tends to replace the forests, favouring local erosion and detrital sedimentation. However, all proxy data reveal an overall wetting during MIS 6, while a drying trend took place during MIS4-2, leading to extremely harsh LGM conditions possibly linked to water storage as ice in the surrounding highlands. Over the past 250 ka, the Yammoûneh record shows an overall decrease in local effective water, coincident with a weakening of seasonal insolation contrasts linked to the decreasing amplitude of the eccentricity cycle. The Yammoûneh record is roughly consistent with long-term climatic fluctuations in the northeastern Mediterranean region (except during MIS 6). It suggests that the role of seasonality on effective moisture, already highlighted for MIS 1, also explains older interglacial climate. The Yammoûneh record shares some features with speleothem isotope records of western Israel, while the Dead Sea basin generally evolved in opposite directions. Changes in atmospheric circulation, regional topographic patterns and site-specific hydrological factors are invoked as potential causes of spatial heterogeneities. Further work is needed to refine the Yammoûneh chronology, better understand its functioning through hydrological and climate modelling, and acquire other long records from northern Levant to disentangle the relative effects of local versus regional factors.

Orbitally driven evolution of Asian monsoon and stable water isotope ratios during the Holocene: Isotope-enabled climate model simulations and proxy data comparisons

2021 ◽  
Vol 252 ◽  
pp. 106743
Author(s):  
Thejna Tharammal ◽  
Govindasamy Bala ◽  
André Paul ◽  
David Noone ◽  
Astrid Contreras-Rosales ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Climate Model ◽  
Isotope Ratios ◽  
Proxy Data ◽  
Model Simulations ◽  
The Holocene ◽  
Climate Model Simulations ◽  
Water Isotope

scholarly journals Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium

2012 ◽  
Vol 8 (1) ◽  
pp. 263-320 ◽  
Author(s):  
A. Hind ◽  
A. Moberg ◽  
R. Sundberg
Keyword(s):  
Climate Model ◽  
Distance Measure ◽  
Last Millennium ◽  
Proxy Data ◽  
Simulation Data ◽  
Model Simulations ◽  
Climate Proxy ◽  
Statistical Framework ◽  
Climate Model Simulations ◽  
Instrumental Series

Abstract. A statistical framework for comparing the output of ensemble simulations from global climate models with networks of climate proxy and instrumental records is developed, focusing on near-surface temperatures for the last millennium. This framework includes the formulation of a joint statistical model for proxy data, instrumental data and simulation data, which is used to optimize a quadratic distance measure for ranking climate model simulations. An essential underlying assumption is that the simulations and the proxy/instrumental series have a shared component of variability that is due to temporal changes in external forcing, such as volcanic aerosol load, solar irradiance changes and greenhouse gas concentrations. Two statistical tests are formulated. Firstly, a preliminary test to establish whether a significant temporal correlation exists between instrumental/proxy and simulation data. Secondly, the distance measure is expressed in the form of a test statistic of whether a forced simulation is closer to the instrumental/proxy series than unforced simulations. The proposed framework allows any number of proxy locations to be used jointly, with different seasons, record lengths and statistical precision. The new methods are applied in a pseudo-proxy experiment. Here, a set of previously published millennial forced model simulations, including both "low" and "high" solar radiative forcing histories together with other common forcings, were used to define "true" target temperatures as well as pseudo-proxy and pseudo-instrumental series. The pseudo-proxies were created to reflect current proxy locations and noise levels, where it was found that the low and high solar full-forcing simulations could be distinguished when the latter were used as targets. When the former were used as targets, a greater number of proxy locations were needed to make this distinction. It was also found that to improve detectability of the low solar simulations, increasing the signal-to-noise ratio was more efficient than increasing the spatial coverage of the proxy network. In the next phase of the work, we will apply these methods to real proxy and instrumental data, with the aim to distinguish which of the two solar forcing histories is most compatible with the observed/reconstructed climate.

scholarly journals Greenland temperature and precipitation over the last 20 000 years using data assimilation

2020 ◽  
Vol 16 (4) ◽  
pp. 1325-1346
Author(s):  
Jessica A. Badgeley ◽  
Eric J. Steig ◽  
Gregory J. Hakim ◽  
Tyler J. Fudge
Keyword(s):  
Data Assimilation ◽  
Spatial Patterns ◽  
Climate Model ◽  
Ice Core ◽  
Ice Sheet ◽  
Proxy Data ◽  
Model Simulations ◽  
Temperature And Precipitation ◽  
Climate Model Simulations ◽  
Paleoclimate Data

Abstract. Reconstructions of past temperature and precipitation are fundamental to modeling the Greenland Ice Sheet and assessing its sensitivity to climate. Paleoclimate information is sourced from proxy records and climate-model simulations; however, the former are spatially incomplete while the latter are sensitive to model dynamics and boundary conditions. Efforts to combine these sources of information to reconstruct spatial patterns of Greenland climate over glacial–interglacial cycles have been limited by assumptions of fixed spatial patterns and a restricted use of proxy data. We avoid these limitations by using paleoclimate data assimilation to create independent reconstructions of mean-annual temperature and precipitation for the last 20 000 years. Our method uses oxygen isotope ratios of ice and accumulation rates from long ice-core records and extends this information to all locations across Greenland using spatial relationships derived from a transient climate-model simulation. Standard evaluation metrics for this method show that our results capture climate at locations without ice-core records. Our results differ from previous work in the reconstructed spatial pattern of temperature change during abrupt climate transitions; this indicates a need for additional proxy data and additional transient climate-model simulations. We investigate the relationship between precipitation and temperature, finding that it is frequency dependent and spatially variable, suggesting that thermodynamic scaling methods commonly used in ice-sheet modeling are overly simplistic. Our results demonstrate that paleoclimate data assimilation is a useful tool for reconstructing the spatial and temporal patterns of past climate on timescales relevant to ice sheets.

scholarly journals A model-data comparison of the Holocene global sea surface temperature evolution

2012 ◽  
Vol 8 (2) ◽  
pp. 1005-1056 ◽  
Author(s):  
G. Lohmann ◽  
M. Pfeiffer ◽  
T. Laepple ◽  
G. Leduc ◽  
J.-H. Kim
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Climate Model ◽  
Sea Surface ◽  
Model Data ◽  
Proxy Data ◽  
Habitat Depth ◽  
Model Simulations ◽  
The Holocene ◽  
Temperature Trends

Abstract. We compare the ocean temperature evolution of the Holocene as simulated by climate models and reconstructed from marine temperature proxies. We use transient simulations from a coupled atmosphere-ocean general circulation model, as well as an ensemble of time slice simulations from the Paleoclimate Modelling Intercomparison Project. The proxy dataset comprises a global compilation of marine alkenone- and Mg/Ca-derived sea surface temperature (SST) estimates. Independently of the choice of the climate model, we observe significant mismatches between modelled and estimated SST amplitudes in the trends for the last 6000 yr. Alkenone-based SST records show a similar pattern as the simulated annual mean SSTs, but the simulated SST trends underestimate the alkenone-based SST trends by a factor of two to five. For Mg/Ca, no significant relationship between model simulations and proxy reconstructions can be detected. We tested if such discrepancies can be caused by too simplistic interpretations of the proxy data. We therefore considered the additional environmental factor changes in the planktonic organisms' habitat depth and a time-shift in the recording season to diagnose whether invoking those environmental factors can help reconciling the proxy records and the model simulations. We find that invoking shifts in the living season and habitat depth can remove some of the model-data discrepancies in SST trends. Regardless whether such adjustments in the environmental parameters during the Holocene are realistic, they indicate that when modeled temperature trends are set up to allow drastic shifts in the ecological behavior of planktonic organisms, they do not capture the full range of reconstructed SST trends. These findings challenge the quantitative comparability of climate model sensitivity and reconstructed temperature trends from proxy data.

scholarly journals Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium – Part 1: Theory

2012 ◽  
Vol 8 (4) ◽  
pp. 1339-1353 ◽  
Author(s):  
R. Sundberg ◽  
A. Moberg ◽  
A. Hind
Keyword(s):  
Climate Model ◽  
Distance Measure ◽  
Last Millennium ◽  
Proxy Data ◽  
Simulation Data ◽  
Model Simulations ◽  
Climate Proxy ◽  
Statistical Framework ◽  
Climate Model Simulations ◽  
Instrumental Records

Abstract. A statistical framework for comparing the output of ensemble simulations from global climate models with networks of climate proxy and instrumental records has been developed, focusing on near-surface temperatures for the last millennium. This framework includes the formulation of a joint statistical model for proxy data, instrumental data and simulation data, which is used to optimize a quadratic distance measure for ranking climate model simulations. An essential underlying assumption is that the simulations and the proxy/instrumental series have a shared component of variability that is due to temporal changes in external forcing, such as volcanic aerosol load, solar irradiance or greenhouse gas concentrations. Two statistical tests have been formulated. Firstly, a preliminary test establishes whether a significant temporal correlation exists between instrumental/proxy and simulation data. Secondly, the distance measure is expressed in the form of a test statistic of whether a forced simulation is closer to the instrumental/proxy series than unforced simulations. The proposed framework allows any number of proxy locations to be used jointly, with different seasons, record lengths and statistical precision. The goal is to objectively rank several competing climate model simulations (e.g. with alternative model parameterizations or alternative forcing histories) by means of their goodness of fit to the unobservable true past climate variations, as estimated from noisy proxy data and instrumental observations.

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