Monthly Archives: August 2013

Independent adventures in uncertainty: sea-ice reconstructions

One of the assumptions of transfer functions is that the calibration set observations are independent. If they are not independent of each other, for example because of spatial autocorrelation, the transfer function performance statistics will be biased, appearing to be … Continue reading

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Uneven adventures in uncertainty: sea-ice reconstructions

The dinocyst calibration set has an extremely uneven distribution of sites along the sea-ice gradient. In the 1171-observation calibration set (the latest 1492-observation calibration set is not yet online), just over half the sites have zero sea-ice, so the remainder of the … Continue reading

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Dinocysts and autocorrelation redux: Guiot and de Vernal’s (2011) reply

I was alerted to Guiot and de Vernal (2011; GdV11) by Google Reader one morning while reading in bed and I drafted a rejoinder before I got up.  Unfortunately not all mornings are that productive, but fortunately I don’t read many … Continue reading

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My autocorrelation papers

I’m making the papers I have published about the effects of autocorrelation on transfer functions available below for easy reference.

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Dinocysts and autocorrelation: Guiot and de Vernal (2011) line by line

I didn’t intend to write about Guiot and de Vernal (2011) as I have already published a comment on this paper, but new papers on Arctic sea-ice reconstructions are dismissing my work on transfer functions and citing Guiot and de Vernal (2011) as … Continue reading

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How good are dinocyst-inferred sea-ice reconstructions?

Dinocysts, the resting stage of dinoflagellates, have been used to reconstruct a range of palaeoceanographic variables, including summer and winter sea surface temperature (SST) and salinity, productivity and sea ice using transfer functions. I became interested in dinocysts as proxies … Continue reading

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REDFIT’s rule of thumb

Because REDFIT tests many frequencies, some are likely to appear statistically significant just by chance — a classic multiple testing problem.  Schulz & Mudelsee (2002) “follow Thomson (1990) and select a false-alarm level of (1-1/n)*100%, where n is the number of data points … Continue reading

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REDFIT & false alarms

REDFIT is a useful tool for palaeoecologists who like to test their data for periodicities as it uses the Lomb-Scargle Fourier transform which tolerates unequal time intervals and so avoids the problems inherent in interpolating data to equal intervals. Several of the papers reporting the … Continue reading

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Cyclotella choctawhatcheeana and the sun: Review of Galloway et al 2013

This is part of my critical review of the palaeoenvironmental evidence for the influence of solar activity on climate. Galloway, J.M., Wigston, A., Patterson, R.T., Swindles, G.T., Reinhardt, E. & Roe, H.M. (2013) Climate change and decadal to centennial-scale periodicities recorded in a late Holocene NE Pacific … Continue reading

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