A former grasslands scientist says changes in plant life are a convincing indication that global warming is occurring.
John Lancashire is questioning the move by a climate change sceptics group to challenge in the courts the way that the National Institute of Water and Atmospheric Research (NIWA) has compiled New Zealand's official temperature records.
The New Zealand Climate Science Coalition wants the High Court to invalidate the records, arguing they have been manipulated to show a rise in temperatures during the past century when none has occurred.
But Mr Lancashire, who was a scientist at the Grasslands Research Centre, considers the debate over temperature records to be somewhat irrelevant.
He says plants are a better guide to what is happening with global warming, saying that a study of subtropical grasses showed some species spread to new areas in the 1980s and 1990s, which he said would not have taken place if the climate hadn't been getting warmer.
Mr Lancashire says gardeners and cropping farmers have had a similar experience with the invasion of sub-tropical weeds.