The National Institute of Water and Atmospheric Research (NIWA) is backing its official temperature records, which climate change sceptics are seeking to challenge in court.
The New Zealand Climate Science Coalition wants the High Court to invalidate the data because it says NIWA used flawed methodology to reach certain figures.
The Coalition says the records are important as they are the central piece of information used to support the case for man-made global warming.
NIWA says it remains absolutely confident in the integrity of its science.
The case will be heard next month at the High Court in Auckland.