Monthly Archives: March 2006

WhyWhere 2.0 update 13

I received a number of emails suddenly about [tag]WhyWhere[/tag], and I thought I would answer them all here with an update on progress of the new version. This is my highest priority now, and should be available as beta in a week or so. The old version was too hard to maintain, being built on […]

AIG Article 12

The Australian Institute of Geoscientists News has published online my article “Reconstruction of past climate using series with red noise” on page 14. Many thanks to Louis Hissink the editor for the rapidity of this publication. It is actually a very interesting newsletter with articles on the IPCC, and a summary of the state of […]

Koutsoyiannis' Quiz 60

This week I am posting another quiz, although no-one has yet solved the Spaghetti Graph Quiz. This one, suggested Demetris Koutsoyiannis may require some statistical analysis to solve. I have plotted the points up, and converted them to an R statement below.

Hurst, Joseph, colours and noises 40

Demetris Koutsoyiannis contributed the following excellent piece as a comment on a previous post. I have made it into a post to ensure it gets the widest distribution. Hurst, Joseph, colours and noises: The importance of names in an important natural behaviour “What’s in a name? That which we call a rose By any other […]

How to start a science blog (nice version) 11

There are many reasons a scientist might start a blog:

  • Prepublication of work in progress to enable review by others
  • Outreach to the general community
  • Dissemination of notes
  • Provide a review of the literature
  • Advocate a position or idea
  • Facilitate project management
  • Make money

Of these the last is probably the most tricky, but I will say something about that too. After deciding to start a blog, the next question is how to do it. There are a range of possibilities available. Following are my notes on the experience.

Spaghetti graph quiz 13

Here is the ‘spaghetti graph’ of a number of prominent reconstructions, with two-sigma confidence interval. The CRU calibration temperatures are the solid black line. Can you find the random reconstruction? (Thanks to Steve McIntyre at for recon data.)

Cross validation as a test of random reconstructions 27

To recap previous posts (, about replicating the cross-validation procedure used in MBH98 for reconstruction skill of randomly generated series on raw and filtered CRU temperatures. The RE statistic correctly indicated no skill for the reconstruction in both the raw and filtered temperature data. The R2 statistic indicated no skill on the raw temperature data […]

R2 statistics for random reconstructions 7

As a follow-up om the previous post, I have examined the correlation statistics for the reconstruction of past climate from random series with red noise. I have tried to use the same approach as MBH98, where the model is tested over data for years held back from the main analysis and model development. Different intervals […]

A new temperature reconstruction 54

In honor of the National Research Council of the National Academies committee to study “Surface Temperature Reconstructions for the Past 1,000-2,000 Years” meeting at this moment, I offer my own climate reconstruction based on the methods blessed by dendroclimatology. The graph below shows reconstructed temperature anomolies over 2000 years, with the surface temperature measurements from […]

WhyWhere published in ecological modeling 21

The paper on WhyWhere entitled “Improving ecological niche models by data mining large environmental datasets for surrogate models” by David R.B. Stockwell, Ecological Modelling 192 (2006) 188–196 is finally available here. Note the source for the application is temporarily available here, due to a bad file on the main site. The WhyWhere algorithm (and accompanying […]

Scale invariance for Dummies 16

Below is an investigation of scale invariance or long term persistence (LTP) in time series including tree-ring proxies – the recognition, quantification and implications for analysis – drawn largely from Koutsoyiannis [2] (preprints available here). In researching this topic, I found a lot of misconceptions about LTP phenomena, such as LTP implying a long term […]

Predicting spatial patterns of house prices 13

Predicting real estate is like any other geospatial problem – all you need is data – e.g. see Zillow. If locations such as cities and their house prices or increases are correlated with environmental variables then a model can be developed. Here I address the question – what environmetal variables predict the increase in house […]

Peer-censorship and scientific fraud 20

The major scientific journals are often regarded as the touchstones of scientific truth. However, their reputation has been tarnished with yet another major scientific fraud unfolding over South Korean researcher Hwang Woo-suk’s peer-reviewed and published Stem Cell research. Should the publication of these results be viewed as simple ‘mistakes’, a crime by a deviant individual, […]

Presence absence or presence only? 11

There are two main forms of data about species occurrences, lists of locations where a species has been found, called presence-only (P) data, and lists of locations where species are both present and absent (PA). In developing ENMs, PA data are often said to be preferable to P data (e.g. Austin and Meyers 1996), and […]

Sigmoids in the mist 5

Have become interested in checking out dendroclimatology from the ENM point of view – particularly evaluating the model used for functional responses of alpine trees to temperature. All studies in Briffa et al. 2001 (figure below) invariably use a linear model, OLS fit of the proxy to temperature be it tree ring width (TRW) or […]

Advantages of WhyWhere 3

Some have been asking for an explanation of WhyWhere and how it fits in relation to other methods, particularly GARP. Although the details are in the paper, they are in a more academic from and I thought I would try to explain it here. Here is a nice schematic prepared by Jean Tate describing the […]

Preprint of Lifemapper 5

I have just placed the Lifemapper paper onto the arXiv pre-print archive here. The use of the GARP genetic algorithm and internet grid computing in the Lifemapper world atlas of species biodiversity Authors: David R.B. Stockwell, James H. Beach, Aimee Stewart, Gregory Vorontsov, David Vieglais, Ricardo Scachetti Pereira Comments: 17 pages, 4 figures, in press […]

Preprint of WhyWhere 6

I have just posted the WhyWhere paper to arXiv here. Improving ecological niche models by data mining large environmental datasets for surrogate models Authors: David R.B. Stockwell Comments: 16 pages, 4 figures, to appear in Ecological Modelling Subj-class: Quantitative Methods WhyWhere is a new ecological niche modeling (ENM) algorithm for mapping and explaining the distribution […]

GARP and numbers of data points 5

There are a number of issues that arise in analysis of spatial data points, not enough data and spatial auto-correlation being two often raised. As a general principle, the external accuracy (on the test set) will increase asymptotically as number of data increases, and the internal accuracy (on the training set) will decrease asymptotically as […]