The nation's top climate-change official expressed China's readiness on Wednesday to play an active and constructive role in international efforts to combat global warming ahead of a major UN climate conference in Doha, Qatar.

China is seeking a turning point in terms of its emissions and attempting to peak its carbon emissions as early as it can, Xie Zhenhua, vice-minister of the National Development and Reform Commission, said.

The world is paying close attention to when China hits peak emissions.

"At this stage, it would be unfair and unreasonable to require China to reduce its carbon emissions in absolute terms," Xie said.

But measures have been put in place to make sure emissions are curbed, he said.

The two-week UN climate change conference opens in the Qatari capital on Monday.

Regarding the motion at last year's UN climate change conference in Durban, South Africa, that a climate deal would be reached by 2015, at the latest, and come into effect in 2020, Xie said China's attitude is both active and open.

"We cannot pass judgment on the possible result. But we are certain we will implement whatever final document that is adopted by all nations."

He pointed out that the Durban conference agreed that negotiations for the post-2020 treaty should to adhere to the principles of "fairness, common but differentiated responsibilities and respective capabilities''.

China's is adamant that these positions must be followed in negotiations, he said.

Xie said China expects "comprehensive and balanced" results from the Doha conference.

The core issue of the Doha conference is that developed countries should "substantially" reduce emissions, in line with "common but differentiated responsibilities" and set targets for a second-commitment period for the Kyoto Protocol, said Xie. The first commitment period ends at the end of December.

"We hope to reach a legally binding second-commitment period that can be ratified at the Doha conference. Developed countries that didn't join the protocol or decided to opt out of any new commitments need to take comparable reduction measures by setting specific targets," said Xie.

As China's per-capita emissions are close to, or almost equal to, the global average, the country is facing challenges in coping with climate change and must adopt a greener, low-carbon path, he said.

The Doha conference is a nexus of climate negotiations and all parties must come up with clear targets in a second commitment, said a report by the Chinese Academy of Social Sciences.

The report, Green Book of Climate Change, was released on Wednesday.

One of the academy's leading environmentalists echoed the view of developed countries committing to meet specific targets.

"Those countries that don't join should make comparable commitment as 'role models'. Otherwise developing countries won't have the confidence to reduce greenhouse gas emissions," said Pan Jiahua, director of the Institute for Urban and Environmental Studies of the Chinese Academy of Social Sciences.

Jiang Kejun, researcher at the Energy Research Institute at the National Development and Reform Commission, said China's large population, GDP base and energy mix are the main reasons behind the emissions.

Jiang said China should make more efforts in cutting its emissions.

Instead of pledging more emissions, each country, especially key developing economies, should find ways of reducing emissions by innovating technology and restructuring the energy mix, said Jiang.

China is one of the most vulnerable countries to climate change. The NDRC said in a report this year that extreme weather events in 2011 brought direct economic losses of 309 billion yuan ($49.6 billion).

Action on climate change needs to be accelerated immediately if the world is to have a real chance of keeping a global average temperature rise below 2 degrees Celsius this century, said a report released by the UN Environment Program and the European Climate Foundation on Tuesday.

The report showed the emission gap is bigger than earlier assessments. Greenhouse gas emissions levels are now around 14 per cent above where they need to be in 2020.

China has made strong commitments to act on addressing climate change. These include lowering emissions per unit of GDP by 40-50 percent by 2020 compared to the 2005 level; increasing the share of non-fossil fuels in primary energy consumption to around 15 percent by 2020 and increasing forest coverage by 40 million hectares and forest stock volume by 1.3 billion cubic meters by 2020 from the 2005 level.

Contact the writers at [email protected] and [email protected]

Wu Wencong contributed to this story.