The New Zealand authors of a major report on climate change have hinted it will look at the damage global warming will do if it exceeds internationally agreed targets.
The Intergovernmental Panel on Climate Change (IPCC) releases reports in stages every six years.
The Working Group One report was released late last year and focussed on the physical science of climate change. It confirmed global warming has increased at the rate the IPCC predicted it would 22 years ago and said there was a 95 percent certainty the warming was being caused by human activity.
The Working Group Two report focusses on the impacts of and vulnerabilities to climate change. It will be released at the end of this month and one chapter will focus on the current and future effects on Australia and New Zealand.
The Working Group Three report, which looks at how emissions can be reduced or mitigated, will be released on 13 April.
When the last IPCC report was released six years ago, the idea the globe could warm by 4degC by the end of the century was considered unlikely. In 2010, 194 countries, including all major emitters, agreed global warming should not exceed pre-industrial levels by more than 2degC.
But one of the lead authors of the new report, Agricultural Greenhouse Gas Research Centre deputy director Andy Reisinger, said it was no longer assuming 4degC of warming would not happen.
"We now have a lot more evidence in the scientific literature, given the failure to make demonstrable progress in serious reductions in greenhouse gas emissions globally, of what a world that warms by 4degC or more looks like," Dr Reisinger said.
"Historically that was sort of silly. (But) you certainly can't rule it out based on emissions and current policy trends."
Dr Reisinger hinted the report would look at how 4degC of warming could affect New Zealand.
"Some of it goes to questions about how resilient are we right now to climate variability. Especially with regard to things that might become more extreme in future, think of flooding in Christchurch over the last period or the heat waves in Australia."
He said there were indications that in extreme circumstances, temperatures in some parts of the world could get so high people would be unable to work.