Australasian Temperature Reconstructions Spanning the Last Millennium

Multiproxy warm season (September–February) temperature reconstructions are presented for the combined land–ocean region of Australasia (0°–50°S, 110°E–180°) covering 1000–2001. Using between 2 (R2) and 28 (R28) paleoclimate records, four 1000-member ensemble reconstructions of regional temperature...

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Bibliographic Details
Published in:Journal of climate 2016-08, Vol.29 (15), p.5365-5392
Main Authors: Gergis, Joëlle, Neukom, Raphael, Gallant, Ailie J. E., Karoly, David J.
Format: Article
Language:English
Subjects:
20th century
Anthropogenic factors
Archives & records
Atmospheric models
Bayesian analysis
Climate
Climate change
Climate models
Consortia
Estimates
Greenhouse effect
Greenhouse gases
Ice ages
Mathematical models
Natural variability
Networks
Nucleotide sequence
Paleoclimate
Paleoclimatology
Probability theory
Records
Regional development
Simulation
SPECIAL PAGES AUS2K Synthesis COLLECTION
Statistical analysis
Statistical methods
Statistics
Studies
Temperature
Temperature variations
Warm seasons
Working groups
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Summary:Multiproxy warm season (September–February) temperature reconstructions are presented for the combined land–ocean region of Australasia (0°–50°S, 110°E–180°) covering 1000–2001. Using between 2 (R2) and 28 (R28) paleoclimate records, four 1000-member ensemble reconstructions of regional temperature are developed using four statistical methods: principal component regression (PCR), composite plus scale (CPS), Bayesian hierarchical models (LNA), and pairwise comparison (PaiCo). The reconstructions are then compared with a three-member ensemble of GISS-E2-R climate model simulations and independent paleoclimate records. Decadal fluctuations in Australasian temperatures are remarkably similar between the four reconstruction methods. There are, however, differences in the amplitude of temperature variations between the different statistical methods and proxy networks. When the R28 network is used, the warmest 30-yr periods occur after 1950 in 77% of ensemble members over all methods. However, reconstructions based on only the longest records (R2 and R3 networks) indicate that single 30- and 10-yr periods of similar or slightly higher temperatures than in the late twentieth century may have occurred during the first half of the millennium. Regardless, the most recent instrumental temperatures (1985–2014) are above the 90th percentile of all 12 reconstruction ensembles (four reconstruction methods based on three proxy networks—R28, R3, and R2). The reconstructed twentieth-century warming cannot be explained by natural variability alone using GISS-E2-R. In this climate model, anthropogenic forcing is required to produce the rate and magnitude of post-1950 warming observed in the Australasian region. These paleoclimate results are consistent with other studies that attribute the post-1950 warming in Australian temperature records to increases in atmospheric greenhouse gas concentrations.
ISSN:0894-8755
1520-0442
DOI:10.1175/jcli-d-13-00781.1