"Everything we are looking at indicates it could be worse than the most conservative climate change predictions, and things could happen more dramatically.
"Our research shows there is something wrong with the climate models and it's now being taken into account around the world."
Rocks, shells and coral fossils across riverbeds, shorelines, and hills along the South Island coast, which once formed the Pacific Ocean floor, have been stripped back to reveal "layers and layers of time", says Dr Hollis, who's been involved in the GNS-led project since its inception in 1998.
His international team of leading paleontologists, including American professors Gerald Dickens and Matthew Huber, have studied the fossils dating back the Eocene period - 50 to 60 million years ago - when the Earth last experienced a truly greenhouse climate.
Dr Hollis said it's a critical time period for understanding the influence of extreme warmth on oceans and predicting how physical and biological systems might respond to future global warming.
New Zealand is uniquely located, between polar and tropical climate drivers, to provide a "very important understanding for global climate change," he said.
Analysis of the fossils and rocks can provide estimates of past temperatures, record how quickly they changed and what the fallout was.
"One group of fossils suffered extinction during the extreme global warming event around 55 million years ago, while others changed, adapted or moved. But there's still some uncertainty there, which is why we're looking to examine that area in further detail," Dr Hollis said.
Strategies to reduce emissions since the Kyoto Protocol have "failed dramatically", he said, and given the amount of greenhouse gas that's already been pumped into the atmosphere, climate change is "inevitable".
Soaring temperatures and rising sea levels will cause massive disruption, hardship, and famine, and are "certainly going to claim human lives", he said.
But despite the gloomy outlook, he is convinced mankind will adapt and ride out the storm, which could last for millions of years.
"Over the next few centuries, global warming will impact on human infrastructure and how and where we live," Dr Hollis said.
"It's threatening human civilisation, but we're not talking about survival of the human race. We have time to prepare and the ability to adapt, but we need more debate about how we're going to do that."
International research team took samples of fossils and rocks found across the South Island:
* Hampden, North Otago
* Waipara, North Canterbury
* Kaikoura to Ward, Marlborough
* Greymouth, West Coast
* Campbell Island, an uninhabited, subantarctic island of New Zealand
