Scientists at the National Institute of Water and Atmospheric Research (NIWA) have discovered the land biosphere is absorbing far more carbon dioxide than previously.
NIWA atmospheric scientist Sara Mikaloff-Fletcher says the increase began in 1988.
Since then, the plant and animal ecosystems on land have been absorbing about 1 billion more tonnes of carbon per year than normal.
That is over 10% of the global fossil fuel emissions for 2010.
Dr Mikaloff-Fletcher says the increase has probably helped slow the effects of climate change but researchers don't yet know why it has happened.
If the change is temporary, she says, it could become more difficult to fight global warming in the future.