The figure, which was almost 50 per cent above the global average for the period, was unreliable, the trust says.
The dispute relates to readings from the "Seven-station Series'' (7SS) - stations in Auckland, Masterton, Wellington, Nelson, Hokitika, Lincoln and Dunedin - used by Niwa for national temperature records.
The NZ Climate Science Coalition is made up of people who are sceptical about global warming and share concerns about ``misleading information'' on climate change, according to the website.
The trust's lawyer told the court the group was not asserting climate change did no exist, "we're saying let's at least make sure that evidence of this for New Zealanders is accurate''.
He challenged the way Niwa had adjusted temperatures recorded at stations, which he said were moved half a degree downwards on average in early readings.
But Niwa's lawyer, Justin Smith said court was not the place to test whether Niwa's temperature data was invalid.
Justin Smith also said that "expert'' witnesses called by the trust were not qualified to give evidence on climate science.
The trust had asked the court to invalidate the temperature record, to stop Niwa from using the the record to advise the Government and the public and for Niwa to provide "full and accurate'' temperature record.