Age endows the gift of perspective and perhaps even a little wisdom. As we consider what remains of our own lives, one issue that looms above all in potential scale and consequence: climate change. We cannot ignore the changing weather patterns that are already causing immense suffering, and that climate change is potentially undermining the lives and livelihoods of future generations.
What worries us too, is that world leaders are applying "politics as usual" to what is essentially an apolitical problem. There is no compromise in the science of climate change. The laws of physics will not wait.
The UN climate change talks in Copenhagen are as historic a moment as our generation has experienced. We recognise that today's leaders face enormous pressures and that daily challenges can steal our best intentions, but on this issue we really need the boldest, most far-sighted leadership we can muster, not political compromises and further delay.
This is why we joined our fellow Elders in writing to every head of state and government on the planet, urging them to attend the Copenhagen talks in person, and outlining what is needed to effectively tackle climate change.
We also make a personal plea to those leaders. We ask all of them, whether they come to Copenhagen or not, to look into the eyes of their children and grandchildren, if they are lucky enough to have them, and think of their future. It is for them that the summit is being held.
Many of those already suffering the effects of climate change are women, and most of them live in the poorest countries on earth -- the nations that have contributed least to global warming. These people have told us of changing rainfall patterns, droughts, floods, cyclones and fires that defy any of their previous experience. For them, the changing climate makes living at the margins of the world economy even more precarious.
However, we should not be tempted to look upon these afflictions with the artificial distance of relative wealth, nor from the arrogant sanctuary of denial, because we are all in this together; no one will escape the consequences of climate change. Wealth will be no barrier, nor will technology be the panacea, even if we can afford it. Climate change cannot be stopped unless we act together.
Our group, The Elders, was brought together by Nelson Mandela to use our influence as best we can in the service of humanity. The following outcomes are, to the best of our knowledge, what is necessary in Copenhagen to address current suffering and begin to limit the most serious effects of climate change.
This is no idle policy recommendation offered from the fringes. We have some experience of how policy is made and this framework is broadly agreed by experts to be what is needed to deliver just a 50 per cent chance of limiting global warming to 2 degrees Celsius.
First of all, in Copenhagen, leaders need to agree that a 2-degree Celsius target is the outer limit of global temperature increase that humankind can tolerate. It is astounding that there is still disagreement on this fundamental point, but beyond two degrees, the risks become far greater and outcomes far less predictable.
Leaders should, therefore, agree that global greenhouse gas emissions must be reduced by at least 50 per cent by 2050 and that developed countries will cut emissions by 25-40 per cent by 2020, and 80-95 per cent by 2050, relative to 1990 levels. National mid-term targets should be set that are binding, measurable and verifiable.
Leaders must also agree to develop low-carbon growth plans, so that we can begin to build sustainable economies. The big emerging economies must agree to limit their emissions through national action plans that are measurable, reported and verifiable.
The leaders should also agree to provide immediate large-scale, predictable and additional funding for adaptation as well as mitigation in developing countries, reducing emissions in forestry, agriculture and other land-use sectors.
Industrialised countries - governments together with the private sector - should agree to provide the majority of financial support (estimated to be at least US$100 billion per year by 2020) to help developing countries, which will also require technological and capacity-building support.
Finally, all governments should be prepared to periodically review the latest science and the early learning from the Copenhagen agreement and adjust global and national targets, actions and funding accordingly.
We call on industrialised nations in particular to meet their historical obligations as they have benefited most from unfettered consumption of fossil fuels. Developing and emerging nations need to implement low-carbon plans too, to ensure their gross domestic product grows, but not their carbon footprint. All have a responsibility to the poorest and most vulnerable nations.
But words alone are not the route to a viable agenda. The solution is, as we have told world leaders, in the eyes of your loved ones and in the future you can envisage for them. This is the time when short-term national interests must be surmounted in the interests of humanity. This is a summit for future generations.