An intercontinental comparison of chironomid palaeotemperature inference models: Europe vs North America

Chironomid-temperature inference models based on North American, European a nd combined surface sediment training sets were compared to assess the over all reliability of their predictions. Between 67 and 76% of the major chiro nomid taxa in each data set showed a unimodal response to July temperature, whereas between 5 and 22% of the common taxa showed a sigmoidal response. July temperature optima were highly correlated among the training sets, but the correlations for other taxon parameters such as tolerances and weighte d averaging partial least squares (WA-PLS) and partial least squares (PLS) regression coefficients were much weaker. PLS, weighted averaging, WA-PLS, and the Modern Analogue Technique, all provided useful and reliable tempera ture inferences. Although jack-knifed error statistics suggested that two-c omponent WA-PLS models had the highest predictive power, intercontinental t ests suggested that other inference models performed better. The various mo dels were able to provide good July temperature inferences, even where neit her good nor close modern analogues for the fossil chironomid assemblages e xisted. When the models were applied to fossil Lateglacial assemblages from North America and Europe, the inferred rates and magnitude of July tempera ture changes varied among models. All models, however, revealed similar pat terns of Lateglacial temperature change. Depending on the model used, the i nferred Younger Dryas July temperature decrease ranged between 2.5 and 6 de grees C. (C) 1999 Elsevier Science Ltd. All rights reserved.