Category Archives: transfer function

The Humpty Dumpty theory of palaeoecology

“When I use a proxy,” Humpty Dumpty said, in rather a scornful tone, “it means just what I choose it to mean – neither more nor less.” “The question is,” said Alice, “whether you can make a proxy mean so … Continue reading

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Replicating the Lake Żabińskie reconstruction

Having shown that the archived chironomid data from Lake Żabińskie are strange in several ways and have bad reconstruction diagnostics, I want to see how well I can replicate the August air-temperature reconstuction. First, I need to build the transfer … Continue reading

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Reconstruction diagnostics for the Lake Żabińskie chironomid reconstruction

The evaluation of reconstruction diagonstics is an essential part of the process of generating palaeoenvironmental reconstructions from microfossil assemblages using transfer functions. If the reconstruction diagnostics are bad, we should be especially cautious about interpreting the reconstruction. The problems is … Continue reading

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Curious chironomid counts

In January 2015, shortly after Larocque-Tobler et al published their remarkably good chironomid-inferred August air temperature reconstruction from Lake Żabińskie, Poland, some data were posted online as a condition of publication. Since I found it difficult to believe that chironomids could … Continue reading

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The limits of high-resolution quantitative palaeoecology and Larocque-Tobler et al (2015)

The first quantitative palaeoclimate reconstructions from microfossil assemblages were low resolution, with a sample spacing of hundreds or thousands of years and focused on seasonal climate. Reconstructions focusing on a single month are now published at annual resolution. Can resolution … Continue reading

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50 chironomids or fewer – corrigendum for Larocque-Tobler et al 2015

Last year, Isabelle Larocque-Tobler and coauthors published a chironomid-inferred August air-temperature reconstruction for the 20th century from a Polish lake in Quaternary Science Reviews. The correlation between instrumental temperature records and the near-annual resolution reconstruction from Lake Żabińskie is remarkably … Continue reading

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Assessing performance and seasonal bias of pollen-based climate reconstructions in a perfect model world

With transfer functions (numerical methods for estimating environmental conditions from species assemblages), it is trivially easy to make reconstructions of many different climate variables. If you want to reconstruct December sunshine from pollen assemblages, simply train your model with December … Continue reading

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