When the history of this century is written, this conference, and the results of this conference, may constitute one of its defining chapters.
History will record it as a time when either the peoples of the world, mindful of a common threat to us all, decided to act in concert against that threat - and so turned the tide of history.
Or else history will record this conference as a time when once again, we became so consumed with the petty nationalisms of the past, that we turned instead against each other and failed to act on this great common challenge of the future.
This history of much of the last century is littered with the carnage and the wreckage of ideologies incapable of embracing the common needs of all our peoples.
Yet here at the dawn of this century, we are privileged to have been given by history this opportunity and this responsibility to write a different narrative of human cooperation:
* to act for those who have no voice, but who depend on us to give them voice;
* to act for our children and our grandchildren and those not yet born, but who depend on us to give them voice;
* to act for the planet.
These are the deep choices which lie before us.
In the next two days, we will assemble together as the largest gathering of global leaders in history.
This is no accidental gathering.
We gather because the peoples of the world demand that we gather.
And the peoples of the world will judge us not just as nations.
Each and every one of us here will be judged as individuals.
For what we say.
For what we do.
And for what we fail to do.
On how we as individual women and men gathered at this great conference have responded to the scientific reality of climate change.
And whether we have responded in conscience to the indisputable facts that science has put before us.
And history will be a harsh judge of us all.
None of us comes to this conference with clean hands.
The inescapable truth is that we the developed world carry the overwhelming historical responsibility for the accumulation of greenhouse gases in the atmosphere.
Any developed nation, large or small, which seeks to absolve itself of past responsibility for the problem the planet now confronts, is being dishonest.
Yet we must also bring the same spirit of inquiry to the problems of the future.
But if the developed world became carbon neutral and the developing world continued to grow on current trends, then the truth is that the emerging economies alone would be responsible for more than half of total global emissions by 2050 - and this would create a temperature rise of between 3.2 degrees and 4 degrees Celsius and even possibly higher.
The truth is that unless we all act together - because we are all in this together - there will be limited prospects of development because the planet itself will no longer sustain it.
That is why history is calling on us all to frame a Grand Bargain on climate change:
* a Grand Bargain between past responsibility and future responsibility;
* a Grand Bargain between the developed world and the developing world;
* a Grand Bargain between the strongest and the most vulnerable;
* a Grand Bargain between ourselves as the current custodians of the planet and those who will come after;
* a Grand Bargain on climate change.
So what then is to be done in the little time that is left?
Words without deeds are a dead letter.
There have been millions of words spoken here, but as one of our colleagues said, it is time to stop talking, and start working.
It is time to take up the pen to define precisely the finite number of major policy differences between us:
* On mitigation, our collective national ambitions now make up about two thirds of what we need to get on a path to our common ambition of 450 parts per million - and the task we have is to find the remaining 5 gigatonnes reduction across the largest economies;
* On climate change finance to deal with the adaptation and mitigation needs of the poorest countries, we already have substantial agreement on fast start funding for the next three years and the prospect of agreement for the remaining seven;
* On verification, I believe we can achieve a consensus on international and national means of accounting whether we honour our carbon commitments or not;
* And on the future of the Kyoto Protocol and its intersection with a new Copenhagen Accord, we can I believe accommodate a common and integrated future for both international instruments which embrace the legal responsibilities of all parties - developed and developing.
These are the four major disagreements between us all.
You would not know that if you examine, as I have done, the 102 square bracketed areas of disagreement that lie in the existing text before us.
Nor would you know that if you listened to the avalanche of procedural interventions in this conference which is seen to be guided by a single purpose - to prevent the conference from distilling down our areas of disagreement to a manageable list so that leaders can decide.
I fear a triumph of form over substance; I fear a triumph of inaction over action.
Let us instead resolve to decide for our future - not simply to defer.
Climate change is no respecter of persons.
No respecter of cultures.
No respecter of nations.
Its consequences are vast.
Whether it is the washing away of villages in Tuvalu, Kiribati or the Maldives.
Whether it is the melting of the glaciers of the Tibetan Plateau.
Whether it is the 30 million of the most vulnerable people in the low lying areas of Bangladesh.
Whether it is the Chinese peasants dealing with unprecedented drought on the North China Plain.
Or the destruction of arable farmland in sub-Saharan Africa.
Or, in our own country, the destruction of one of the wonders of the world - the Great Barrier Reef.
Australia is one of the hottest and driest continents on earth.
That is why we need decisive action globally here in Copenhagen.
That is why the Australian government is committed to acting nationally through a Carbon Pollution Reduction Scheme as the cheapest and most effective way to act at home.
It is global and national action together that makes a difference.
Before I left Australia, I was presented with a book of handwritten letters from a group of 6 year olds.
One of the letters is from Gracie.
Gracie is six - "Hi" she wrote. "My name is Gracie. How old are you?"
Gracie continues "I am writing to you because I want you all to be strong in Copenhagen... Please listen to us as it is our future."
I fear that at this conference, we are on the verge of letting little Gracie down.
And all of the little children across the world.
I would ask every Leader at this summit right now to ask themselves this simple question.
When I arrive home at the end of this week, will I be able to sit down, look my children in the eyes and tell them in clear conscience that I did absolutely everything I could to achieve action to avoid dangerous climate change.
Because if we cannot, then we will have failed in our basic duties as leaders of our nations, as fathers and mothers of our children and custodians of our nations' future.
The children of the world are watching.
They are listening.
And history will be the judge of each of us here today.