UN climate change experts have been accused of making 'imprecise and vague' statements and over-egging the evidence.

A scathing report into the Intergovernmental Panel on Climate Change called for it to avoid politics and stick instead to predictions based on solid science.

The probe, by representatives of the Royal Society and foreign scientific academies, took a thinly-veiled swipe at Rajendra Pachauri, the panel's chairman for the past eight years.

The country's state-owned weather and atmospheric research body is being taken to court in a challenge over the accuracy of its data used to calculate global warming.

The New Zealand Climate Science Coalition said it had lodged papers with the High Court asking the court to invalidate the official temperatures record of the National Institute of Water and Atmospheric Research (Niwa).

The lobby of climate sceptics and ACT Party have long criticised Niwa over its temperature data, which Niwa says is mainstream science and not controversial, and the raw data publicly available.