On page 287 of his error-filled book Ian Plimer claims:
The Arctic was warmer than now between 1920 and 1940. This is
reflected in the sea ice and the local climate.“
 Benestad, R.E. (2002) I. Hanssen-Bauer, T.E. Skaugen and E.J. FÃ¸rland:
Associations between the sea-ice and the local climate on Svalbard,
met.no, Klima, 07/02.
I emailed R.E. Benestad to see if he felt that Plimer had accurately described his work. He replied:
The analysis we did was for the Svalbard islands, and for these, it is not true. Year 2006 was a record warm one by a significant margin. My report also did not address those issues.
And you can look at the graph of sea ice from the paper and judge for yourself whether it is correct to describe this as showing that the Arctic was warmer than now between 1920 and 1940.
Benestad sent me a more recent paper with a graph of temperatures at Svalbard. You can again judge for yourself the accuracy of Plimer’s claim about the Arctic being warmer from 1920 to 1940.
And this is typical of Plimer — the papers he cites do not say what he says they do.
Update: Wikipedia has an up to date temperature graph for Svalbard.