Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

Was the Little Ice Age more or less El Niño-like than the Medieval Climate Anomaly? Evidence from hydrological and temperature proxy data

The El Niño–Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial)...

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Bibliographic Details
Published in:Climate of the past Vol. 13; no. 3; pp. 267 - 301
Main Authors: Henke, Lilo M. K., Lambert, F. Hugo, Charman, Dan J.
Format: Journal Article
Language:English
Published: Katlenburg-Lindau Copernicus GmbH 29-03-2017
Copernicus Publications
Subjects:
Archives & records
Climate change
Climate models
Climate variability
Computer simulation
Economics
El Nino
El Nino phenomena
El Nino-Southern Oscillation event
Empirical analysis
General circulation models
Glaciation
Global climate
Global climate variability
Hydrologic data
Hydrology
Ice ages
Little Ice Age
Ocean circulation
Orthogonal functions
Precipitation
Proxies
Records
Sediments
Socioeconomic aspects
Southern Oscillation
Stability
Statistical analysis
Temperature
Variability
Northern Hemisphere
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Summary:The El Niño–Southern Oscillation (ENSO) is the most important source of global climate variability on interannual timescales and has substantial environmental and socio-economic consequences. However, it is unclear how it interacts with large-scale climate states over longer (decadal to centennial) timescales. The instrumental ENSO record is too short for analysing long-term trends and variability and climate models are unable to accurately simulate past ENSO states. Proxy data are used to extend the record, but different proxy sources have produced dissimilar reconstructions of long-term ENSO-like climate change, with some evidence for a temperature–precipitation divergence in ENSO-like climate over the past millennium, in particular during the Medieval Climate Anomaly (MCA; AD  ∼  800–1300) and the Little Ice Age (LIA; AD  ∼  1400–1850). This throws into question the stability of the modern ENSO system and its links to the global climate, which has implications for future projections. Here we use a new statistical approach using weighting based on empirical orthogonal function (EOF) to create two new large-scale reconstructions of ENSO-like climate change derived independently from precipitation proxies and temperature proxies. The method is developed and validated using model-derived pseudo-proxy experiments that address the effects of proxy dating error, resolution, and noise to improve uncertainty estimations. We find no evidence that temperature and precipitation disagree over the ENSO-like state over the past millennium, but neither do they agree strongly. There is no statistically significant difference between the MCA and the LIA in either reconstruction. However, the temperature reconstruction suffers from a lack of high-quality proxy records located in ENSO-sensitive regions, which limits its ability to capture the large-scale ENSO signal. Further expansion of the palaeo-database and improvements to instrumental, satellite, and model representations of ENSO are needed to fully resolve the discrepancies found among proxy records and establish the long-term stability of this important mode of climatic variability.
ISSN:1814-9332
1814-9324
1814-9332
DOI:10.5194/cp-13-267-2017