Copenhagen offers the prospect of a robust political deal, endorsed by the world's leaders and witnessed by the world's people, that sets out clear targets and a timeline for translating it into law. To be a truly historic achievement, such a deal must do two things.
First, it must lay the basis for a global regime and subsequent agreements that limit global temperature rise in accordance with the scientific evidence. Second, it must provide clarity on the mobilization and volume of financial resources to support developing countries to adapt to climate change.
The stakes are enormous. Economic growth has been achieved at great environmental and social cost, aggravating inequality and human vulnerability. The irreparable damage that is being inflicted on ecosystems, agricultural productivity, forests and water systems is accelerating. Threats to health, life and livelihoods are growing. Disasters are also increasing in scale and frequency.
But despite the mounting evidence of negative impacts, reaching a deal will not be easy. It will require extraordinary political courage -- both to cut the deal and to communicate its necessity to the public.
A mindset shift is required. Distrust and competition persist between regions and nations, manifest in a 'no, you must show your cards first' attitude that has dogged the negotiations leading up to Copenhagen. This has to be overcome.
A deal that is not based on the best scientific evidence will be nothing better than a line in the sand as the tide comes in. But short term considerations, including from special interest groups and electoral demands, are working against long term solutions.
Success in reaching a deal will require leaders to think for future generations, and for citizens other than their own. It will require them to think about inclusive and comprehensive arrangements, not just a patched up compilation of national or regional interests.
A deal that stops at rhetoric and does not actually meet the needs of the poorest and most climate vulnerable countries simply will not work. The climate cannot be 'fixed' in one continent and not another. Climate change does not respect national borders. We are all in the same boat; a hole at one end will sink us all.
For it to work, climate justice must be at the heart of the agreement. An unfair deal will come unstuck.
Industrialized countries such as the United States must naturally take the lead in reducing emissions and supporting others to follow suit, but developing countries like India or China also have an increasing responsibility to do so as their economies continue to grow.
Tragically, it is the poorest and least responsible who are having to bear the brunt of the climate challenge as rising temperatures exacerbate poverty, hunger and vulnerability to disease for billions of people. They need both immediate help to strengthen their climate resilience as well as long-term support to enable them to adapt to changing weather patterns, reduce deforestation, and pursue low-emissions, clean energy growth strategies.
The deal must include a package of commitments in line with the science and the imperative of reducing global emissions by 50-85 percent relative to 2000 levels by 2050.
This requires a schedule for richer countries to move to 25-40 percent emission cuts by 2020 from 1990 baselines; clear measures for emerging economies to cut emissions intensity; and clarity about both immediate and longer term finance and technical support for developing countries, notably the poorest and most vulnerable among them.
Will we get there? The targets that have been proposed for emission reductions by many industrialized countries such as the EU, Japan and Norway are encouraging, as are those being made by the big emerging economies including Brazil, China, India, Indonesia, and South Korea.
Recent announcements by the US on emission targets represent a significant shift and provide a basis for scaling up commitments in the coming years. So does the recognition by emerging economies that they also have a role in supporting the most vulnerable countries.
Welcome too are the proposals for financial support to LDCs and small island states made at the Commonwealth Summit in Trinidad, as well as proposals by the Netherlands, France, and the UK, among others.
But much greater specificity on finance is needed. Existing ODA commitments to help the poorest countries meet the Millennium Development Goals need to be met. And significant additional finance that is separate from and additional to ODA needs to be mobilized to support them meet the incremental costs generated by climate change.
A deal which is not clear on the finance will be both unacceptable to developing countries, and unworkable. Finding the additional resources and communicating its necessity will not be easy, particularly in the current economic climate, but it must be done.
A successful deal could incentivize not only good stewardship of forests and more sustainable land use, but also massive investment into low carbon growth and a healthier planet, including in sectors such as energy generation, construction and transportation.
And it could usher in an era of qualitatively new international cooperation based upon common but differentiated responsibilities - not just for managing climate change, but for human development, social justice and global security.
Ultimately, at stake is whether our leaders can work to help us save ourselves from ... well, from ourselves. The legacy of today's politicians will be determined in the weeks to come.
Kofi A. Annan is Former UN Secretary-General, Chairman of the Kofi Annan Foundation and the Africa Progress Panel, President of the Global Humanitarian Forum.