Leading article: One world, one agenda

The world has already changed. Whatever is agreed or not agreed at the summit on climate change that begins in Copenhagen tomorrow, momentous change has already occurred.

Sometimes it is difficult to see the longer cycles of history amid the oscillations of the day-to-day. So it may be disappointing that there will be no treaty emerging from the talks scheduled to last for the next two weeks. And it may seem an awfully long time since this process began in Rio de Janeiro in 1992, via the Kyoto protocol of 1997 to a possible treaty next year. Just as we are dealing with a global ecosystem in which change is measured in centuries, and a climatic warming caused by humans driven by economic and population changes measured in decades, so the political response to it is going to take a long, long time.

On that outlook, The Independent on Sunday, as ever, prefers to take the positive view. As a newspaper that was founded two years before the Rio treaty, we may exhibit the optimism of youth, but we also have been in at the start, and have been concerned about the environment from issue number one. Thus we are old enough, and hope to be informed enough, to take the long view of Copenhagen. In that view, the formal announcements by the US and Chinese governments last month that they are committed to reducing their outputs of greenhouse gases were historic.

For the past 17 years, international climate negotiations have been obstructed by the refusal of the world's largest economy and the future largest economy to take part. Yet even George Bush, towards the end of his second term, accepted the science of global warming, and one year ago the US elected a President who wanted to do something about it. Of course, the American political system is one of checks and balances – mostly, when it comes to climate change policy, checks. And, of course, the logistics of securing agreement of all the countries of the world – the Danish government invited 191 heads of government to attend the summit – are fiendishly complex. Indeed, many smaller countries hide behind the climate-change sceptics in the US Senate in the hope that agreement will be frustrated or implementation stalled.

But the big picture is that the entire caravan is now moving. The governments of all the main economies in the world have agreed that the greenhouse effect must be mitigated. The talks are now about the how, not the whether. The huge fuss over the University of East Anglia emails is the deceptive dying twitch of the sceptics. The folly of climate researchers in massaging their data has given brief new life to a conspiracy theory, which remains absurd, as Joss Garman argues on page 41.

The efforts of serious policy-makers, meanwhile, need to focus with ever more rigour on the challenges ahead. There are important technological riddles to solve. Can carbon capture provide clean power from coal at an economic cost? How do carbon cycles in forests and oceans actually work? Are there technological fixes that could counter the greenhouse effect? There are hard policy questions. How to measure the impacts of trade; how to balance production of food, especially meat, against that of biofuels; above all, the design of carbon-trading regimes.

The focus of the next two weeks will be overwhelmingly on horse-trading over targets for cutting greenhouse gas outputs and, in effect, cash subsidies from the carbon-rich world to the carbon-poor. The big early argument, which will take place on Thursday in Brussels, will come as European Union leaders decide their common position for the talks. We, the EU, have already offered to cut greenhouse gases by 20 per cent from a 1990 base by 2020, and have said that we will increase that to 30 per cent if there is a good global agreement. EU leaders are under pressure to go straight to 30 per cent. But that seems to be the wrong priority at this stage. Surely the more important matter is to solidify the consensus and concentrate on moving towards a legally binding treaty. Rhetoric about "isolating" America does not seem the best way to respond to the changes that have come since Barack Obama took office. Pragmatically, holding back on the 30 per cent cut – as a response to deeper cuts from others – seems a better negotiating tactic.

Let us keep our eye on the long view. The Copenhagen summit is a hugely important moment in the history of global co-operation to meet a common threat. The fact that it is taking place at all is reason for celebration; the priority now is to turn a common purpose into practical action.