With no more than a week left, climate talks in Copenhagen hit a critical stage on Monday when representatives from over 190 countries need to be in high gear for a success.

Countries involved need to address four issues before they could make the ongoing talks a success.

The first issue is about history.

Climate change is a global challenge. Yet developed countries are historically responsible for today's global warming since they had been the major polluters for the past centuries.

From 1900 to 2005, developed countries, with less than 20 percent of the world's population, accounted for 80 percent of the greenhouse gas emissions around the globe. Before 1950, 95 percent of greenhouse gases were discharged by developed countries.

Developed countries should face that responsibility by setting ambitious reduction targets and supporting the developing world cut down emissions and adapt to the impact of global warming in terms of money, technology transfer and capacity building.

The second issue is about per capita emissions.

During the negotiations in the past week, developed countries were trying to get major developing countries bear the same burden of reduction, ignoring the fact that those developing countries are more populous and much poorer.

Statistics show that in 2006, per capita greenhouse gas emissions in developed countries were nearly four times higher than in developing ones. Not to mention that developing countries have to keep a certain level of emissions to sustain development and improve social well-being at this stage.

The third issue is about the legal framework.

Currently, the United Nations Framework Convention on Climate Change (UNFCCC) and its Kyoto Protocol are the two basic legal instruments on climate change. The UNFCCC established the principle of "common but differentiated responsibilities" for developed and developing countries. The Kyoto Protocol set mandatory reduction targets for developed countries.

The Copenhagen conference was designed to hammer out a deal to curb global warming after the first commitment period of Kyoto Protocol ends in 2012. Logically, the legal instruments should remain.

However, certain developed countries had been trying to overthrow the UNFCCC and its Kyoto Protocol, aiming to bring developing countries under the same mandatory obligation to cut emissions. Those developed countries were disavowing their commitments to the existing legal framework.

The last issue is about the call of people all over the world.

In face of global warming, the international community is united behind the call for urgent actions. In the negotiations during the past week, the majority of countries stressed that both the UNFCCC and its Kyoto Protocol must be kept, and a legally binding deal must be done in accordance with the Bali Roadmap, which was agreed by both developed and developing countries in 2007.

Demanding an ambitious, fair and legally binding deal on climate change, thousands of people held demonstrations across the world on Saturday -- global day for action on climate change. Their call must be answered.

If countries want to reach a deal to mitigate global warming at the Copenhagen conference, they need not only political will but also actions. Developed countries, in particular, need to make strong commitments.