Looking for a historic record of the average temperature on Earth going back millions of years, and this 2002 graphic the from the PALEOMAP Project is currently the best I am able to find. Is it accurate, and if so, why? If it is not accurate, is there a graph that is?

average temperature on Earth going back millions; temperature range is between 25 to 10 C

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    How do you define accurate? – Peter Jansson May 6 '14 at 16:21
  • Well the range given is 10-25 C, and the graph appears to show precision within 1 C, so I'd say that accurate would be the temperature stated being off by no more than 1 C at any given point in time. – blunders May 6 '14 at 16:24
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    How does the graph show precision within 1° C? – BHF May 6 '14 at 16:28
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    I thought it was not a historic record of temperature, but a basic rendering of various palaeo-temperature proxies. Akin to using a five-year-old's drawing of a house as architectural blue-prints. – Siv May 6 '14 at 17:04
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    Just for information, as far as the Cenozoic is concerned (on your graph Tertiary+Pleistocene+Holocene, on Steve Emmerson's graph Pg+N), Zachos et al 2001 (which modifications in 2008) is still more or less considered the state of the art, though some details have been shown to be likely incorrects. – plannapus May 7 '14 at 6:34
up vote 12 down vote accepted

In a word, no.

The graph is based on work by Chris Scotese. The climate science site RealClimate.org has this to say about it:

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.

and

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

For a more detailed discussion of graphical reconstructions, see this RealClimate entry

  • The web site you linked doesn't seem to have explanation, just what is the right hand scale representing? – user2448131 Jul 4 '16 at 16:01
  • Anomaly in the oxygen-18 to oxygen-16 ratio -- which is used as a proxy for temperature. – Steve Emmerson Sep 21 '17 at 19:23

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