Dr Rajendra Pachauri, who arrived in Australia on Monday, stopped short of directly linking last week's heatwave across much of the country to climate change. While it could be part of a trend, he said, conclusions could not be drawn from a single event.

But he told Fairfax Media work by the IPCC had found that some extreme weather events, including heatwaves, had become more frequent in recent decades.

He said the panel's projections found as climate change intensified, heatwaves would occur more often and with more intensity. The projections, in a 2012 IPCC special report, found a one-in-20-year hottest day will instead occur once every two years by the end of the century in most regions of the world, if rising greenhouse-gas emissions are not reduced.

''It [last week's record temperatures] could be [a result of climate change], but I wouldn't draw any conclusions on one single event. I think you have to take the whole aggregation over a period of time and then come up with the conclusion; which is precisely what we have done,'' he said.

''They [the findings] are very very clear. Heatwaves are on the increase, extreme precipitation events are on the increase, and on that there is really no room for doubt any more,'' he said.

Dr Pachauri is in Hobart for a meeting of scientists working on the IPCC's fifth climate assessment, which is prepared for the UN every five or six years. The first of three parts of the assessment - the subject of the Hobart meeting - will be released in September.

Dr Pachauri's visit follows several leaks of the panel's next assessment report in the past month.

Last week Canadian writer Donna Laframboise - author of a book critical of the IPCC's work - posted on her blog a leaked draft of the section tackling the impacts and adaptation to climate change. Ms Laframboise accused the panel of secrecy and said it needed to be upfront about each step in arriving at its conclusion.

Dr Pachauri rejected the claim that the IPCC was too secretive, saying the group processes were very transparent and would take into account more than 30,000 comments from people who had voluntarily signed up to be reviewers, including some climate sceptics.

''The very fact that we even go out and include those so-called expert reviewers who may not have the same view of climate change as most scientists shows the process is very inclusive,'' he said.

CSIRO's Dr Steve Rintoul, a co-ordinating lead author of the oceans chapter of the report, said the Hobart meeting would review all comments and develop a strategy to respond formally to each one.

The IPCC was first formed in 1988 on the request of UN member countries, and has released four major assessments of the climate, with each report approved by all governments.