New Zealand could revert to the hot tropical climate of the Paleogene period if we do not mitigate current levels of carbon dioxide emissions, a new study from the UK warns.

The early Paleogene period, 48 - 45 million years ago, was one of extreme warmth.

Carbon dioxide levels in that period were similar to those predicted for the end of this century.

A return to a hot tropical climate in Western Europe and New Zealand will bring with it arid land, fires, extreme rainfall, and threats to health and infrastructure, a University of Bristol (UoB) study published in Nature Geoscience says.

"We know that the early Paleogene was characterised by a greenhouse climate with elevated carbon dioxide levels," lead author Dr David Naafs from UoB's School of Earth Science said.

"Most of the existing estimates of temperatures from this period are from the ocean, not the land - what this study attempts to answer is exactly how warm it got on land during this period."

Scientists estimated the land temperature 50 million years ago using molecular fossils of microorganisms in ancient peat.

They found annual land temperatures in Western Europe and New Zealand were higher than expected, between 23 and 29degC. This is 10 to 15degC higher than current average temperatures in the areas.

This led scientists to conclude that temperatures similar to those experienced in the current heatwave in Western Europe could become the norm by the end of the century if CO2 levels continue to rise.

Professor Rich Pancost, Director of the University of Bristol Cabot Institute, said: "Our work adds to the evidence for a very hot climate under potential end-of-century carbon dioxide levels.

"We also study how the Earth system responded to that warmth. For example, this and other hot time periods were associated with evidence for arid conditions and extreme rainfall events."

Newshub.