Cancun can launch a new era in the pace of global action on climate change, where each year brings increasingly effective answers to keep humanity on track to a safer future.
Governments arrive here after a year of work, during which they have created the necessary elements to make further, stronger commitments to address the climate challenge, according to the principle of common but differentiated responsibilities.
Cancun will be successful, if Parties compromise, if they make sure that in the process of getting what they want, they allow others to leave with what they need.
Governments can reach a deal to launch action on adaptation, technology transfer, and forests and they can create a new fund for long-term climate finance.
Governments can clarify what to do about the Kyoto Protocol and how to anchor the many national targets and actions that countries have put forward in particular the targets of industrialized countries.
Cancun will not solve everything and the outcome needs to be pragmatic, but Cancun also needs to keep ambition very much alive.
The truth is - even if all the national targets and actions now on the table are honoured in full - and the world does expect them to be honoured - they will not meet the goal of avoiding a rise of over two degrees in global temperatures.
Climate change is humanity's biggest long-term challenge, but it is also our greatest opportunity.
The solutions to climate change not only address the environmental problem but also offer major opportunities for all nations to achieve sustainable, affordable, and equitable development.
The next few decades will see a revolution:
a revolution in the way energy is produced and consumed; a revolution in the way the environment is accounted for in terms of sustainable and happy human life; a revolution in how communities are strengthened to act against climate change to assure their own futures; a revolution in the economic opportunities afforded by a constructive approach to the climate challenge.
That revolution has in fact already begun.
The world is looking for new answers to the political, economic and social challenges which all countries face. Traditional responses are failing to produce lasting results.
That is why countries, civil society, business and citizens around the world are pressing ahead with their own climate and environment solutions.
It is obvious that they will succeed faster and more effectively together, if governments open the door wider into this new era of sustained, collective and increasingly ambitious responses to climate change.
It is in no one's interest to delay further action.