Can we make better graphs of global temperature history?

Scotese is an expert in reconstructions of continental positions through time and in creating his ‘temperature reconstruction’ he is basically following an old-fashioned idea (best exemplified by Frakes et al’s 1992 textbook) that the planet has two long-term stable equilibria (‘warm’ or ‘cool’) which it has oscillated between over geologic history. This kind of heuristic reconstruction comes from the qualitative geological record which gives indications of glaciations and hothouses, but is not really adequate for quantitative reconstructions of global mean temperatures. Over the last few decades, much better geochemical proxy compilations with better dating have appeared (for instance, Royer et al (2004)) and the idea that there are only two long-term climate states has long fallen by the wayside.

However, since this graphic has long been a favorite of the climate dismissives, many different versions do the rounds, mostly forwarded by people who have no idea of the provenance of the image or the lack of underlying data, or the updates that have occurred. Indeed, the 2004 version is the most common, having been given a boost by Monckton in 2008 and many others. Most recently, Patrick Moore declared that this was his favorite graph.

Better graphs

While more realistic graphs of temperature and CO2 histories will not prevent the basic fallacy we started discussing from being propagated, I think people should be encouraged to use actual data to make their points so that at least rebuttals of any logical fallacies wouldn’t have to waste time arguing about the underlying data. Plus it is so much better to have figures that don’t need a week to decipher (see some more principles at Betterfigures.org).

Some better examples of long term climate change graphics do exist. This one from Veizer et al (2000) for instance (as rendered by Robert Rohde):

Phanerozoic Climate Change

IPCC AR4 made a collation for the Cenozoic (65 Mya ago to present):

IPCC AR4 Fig 6.1

and some editors at Wikipedia have made an attempt to produce a complete record for the Phanerozoic:

Wikipedia multi-period collation

But these collations are imperfect in many ways. On the last figure the time axis is a rather confusing mix of linear segments and logarithmic scaling, there is no calibration during overlap periods, and the scaling and baselining of the individual, differently sourced data is a little ad hoc. Wikipedia has figures for other time periods that have not been updated in years and treatment of uncertainties is haphazard (many originally from GlobalWarmingArt).

I think this could all be done better. However, creating good graphics takes time and some skill, especially when the sources of data are so disparate. So this might be usefully done using some crowd-sourcing – where we collectively gather the data that we can find, process it so that we have clean data, discuss ways to fit it together, and try out different plotting styles. The goal would be to come up with a set of coherent up-to-date (and updatable) figures that could become a new standard for representing the temperature history of the planet. Thus…

The world temperature history challenge

The challenge comes in three parts:

  1. Finding suitable data
  2. Combining different data sets appropriately
  3. Graphically rendering the data

Each part requires work which could be spread widely across the participants. I have made a start on collating links to suitable data sets, and this can both be expanded upon and consolidated.

Period

Reference

Data download

0-600 Mya

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References

  1. J. Veizer, Y. Godderis, and L.M. Fran├žois, "", Nature, vol. 408, pp. 698-701, 2000. http://dx.doi.org/10.1038/35047044