Intergovernmental Panel on Climate Change chairman Dr Rajendra Pachauri has told a UNSW audience that nations like Australia need to "act resolutely on the basis of the scientific evidence" that global warming is due to greenhouse gas emissions from human activity.

Delivering the Jack Beale Memorial Lecture last Thursday at UNSW's John Niland Scientia Building, Dr Pachauri said Australia had to "seize this opportunity for reassessing its position and chart out a new path of sustainable development."

Dr Pachauri told the audience of 800 that major developing countries such as China and India were watching developed countries like Australia and the US for signs of serious action on cutting greenhouse gas emissions.

"Each party is waiting to see who's going to blink first, and unfortunately the developed countries, if I may say it, have created an atmosphere of lack of confidence," Dr Pachauri said in a press report on Thursday.

"Somehow one has to restore (some) credibility, because in the absence of that, we really won't see any party willing to do anything that might seem politically burdensome. So I think it's extremely important for the developed countries to show a certain level of resolve."

"If you talk to policymakers in the developing countries, they will say, 'Look, we know (developed nations) are not going to do anything on their own and when push comes to shove they're going to ask us to take action.'"

"Not only is it urgent for the world to reduce emissions of greenhouse gases adequately to stabilize the earth's atmosphere and climate system, but also essential is the need to address the equity aspects of this threatening problem.

"The international community has provided hardly any resources for adaptation measures in the most vulnerable countries, such as the small island developing states where the very survival of human beings is at stake."

Climate change policy discussions are on the agenda at next month's APEC summit in Sydney, ahead of a UNFCCC meeting set down for Bali in December this year.

The Federal Government has deferred setting a long-term target for reducing Australian greenhouse gas emissions until next year when it receives a report it has commissioned into environmentally sustainable development options. The Federal Opposition has committed to a 60 percent cut in emissions by 2050.

While governments continue to refine their climate change policies, 2007 has seen series of record-breaking weather events, including flooding in Asia, heatwaves in Europe and snowfalls in South Africa.

The World Meteorological Organisation said global land surface temperatures in January and April were likely the warmest since records began in 1880, at more than 1C higher than the average for those months.

"The start of the year 2007 was a very active period in terms of extreme weather events," Omar Baddour of the agency's World Climate Program told journalists in Geneva.

While most scientists believe extreme weather events will be more frequent, Mr Baddour said it was impossible to say with certainty what the second half of 2007 would bring.

The IPCC noted in its report this year that an increasing trend in extreme weather events over the past 50 years and said irregular patterns were likely to intensify.

South Asia's worst monsoon flooding in recent memory has affected 30 million people in India, Bangladesh and Nepal, destroying croplands, livestock and property and raising fears of a health crisis in the densely-populated region.

Heavy rains saturated southern China in June, with nearly 14 million people affected by floods and landslides that killed 120 people. England and Wales this year had their wettest May and June since records began in 1766, resulting in extensive flooding, more than $6 billion in damage, and nine deaths. Huge waves swamped 68 islands in the Maldives in May, and the Arabian Sea had its first documented cyclone in June, touching Oman and Iran.

A weekend press report has cited predictions by scientists that global temperatures will plateau before climbing again to a succession of record-breaking highs.

The Jack Beale Memorial Lecture honours the memory of Mr Beale AO, a distinguished environmental leader and UNSW alumnus, who passed away in 2006. He was the first NSW environment minister and maintained a close association with the University throughout his working life.