Is there a low-frequency bias in multiproxy reconstructions of tropical pacific SST variability?

Abstract Decadal and longer-term variability in the tropical Pacific has the potential to impact climate worldwide, yet paleoclimate observations and climate model simulations disagree on the nature of this variability. In this study we investigate whether biases from paleoclimate reconstruction methodology and the currently available proxy network cause reconstructions of ENSO to overestimate the multidecadal-century scale variability of the Pacific. We build new reconstructions using a variety of commonly employed methods and test the effects of four types of bias on analogous pseudoproxy reconstructions. These biases include (1) the number of records used in the reconstruction, (2) chronological uncertainty, (3) noise in individual proxy records, and (4) the geographical distribution of the proxy network. We find that each of these biases cause ENSO reconstructions to overestimate the importance of low-frequency variability. These biases may partially explain why multiproxy reconstructions of Pacific variability have stronger low-frequency variability than predicted by historical observations or climate models, and why these reconstructions do not have coherent signals over the multidecadal-century scale.