Leading article: Reasons to be cheerful in a troubled world

The outlook for post-Blairite politics in this country also improved sharply last year with the election of a leader of the opposition worthy not just of the title but the democratic function. David Cameron made a sparkling start as leader of the Conservative Party, most strikingly by adopting the greenest stance of any serious contender for prime ministerial office. As we report today, he will this week promote the cause of organic farming. Beyond that, however, he is already removing many of the reasons why this newspaper has been anti-Conservative since its foundation in 1990. He has dropped xenophobia as the basis of immigration policy; he takes social justice seriously (Oliver Letwin, in charge of his policy review, even spoke of "redistribution"). The Cameron Conservative Party remains viscerally anti-European, but what British politics needs is humanity not homogeneity. The net effect of Cameron's arrival is to make politics vibrant, competitive and therefore healthier. Gordon Brown needs to rise to the challenge, while the Liberal Democrats need to snap out of their collective nervous breakdown.

The advance of the green cause globally was linked with another change last year: the appreciation of the growing economic force of China and India. China, we now know, builds new power stations each year that produce more than the annual output of the entire British power industry. If it was difficult to persuade American voters to take the problem of climate change seriously, how much more difficult it will be to convince 2 billion Chinese and Indians only just beginning to taste the fruits of a life beyond subsistence. But at least the problem is being discussed. Action on climate change is not the sole responsibility of either the rich nations in general or the richest nation in particular, but we and the Americans have a special responsibility to show leadership. And one of the obstacles to Western leadership on this issue, in the person of George W Bush, is weakening fast.

It would be a mistake to go too far in personalising such a complex question, either to praise Mr Blair or to damn Mr Bush. But the US President has been a malign influence for most of the past five years. He has consistently sought to frustrate the setting of binding targets, relying instead on the belief that science will solve everything. There is nothing wrong with optimism about technological progress - this newspaper is prone to it too - but it should be based on more than ignorant slogans about a hydrogen economy. Someone should tell President Bush that hydrogen technology is a means of storing energy, not generating it. It is a hopeful sign, however, that all the leading candidates to replace Mr Bush in the White House in 2008, Republican or Democrat, are more willing than he is to fulfil the duty of the US to show environmental leadership.

There are other benefits to the world of the waning power of Mr Bush, one of the lamer and more duck-like second-term presidents since the sudden flattening of his authority by Hurricane Katrina. It means that US foreign policy is more in the hands of Condoleezza Rice than of Donald Rumsfeld. Yet she can do no more than gloss over the US policy of secretly rendering prisoners to unsavoury governments that are as likely as not to torture them. And it will take many, many years to diminish the resentment of the Muslim world towards the West provoked by the lawlessness of Guantanamo Bay, of the invasion of Iraq and of the US policy that allowed cruel and inhuman treatment as long as it was not called torture.

It is worth turning back again to praise Mr Blair for his decision to make the campaign to alleviate global poverty the other priority for the G8 last year. As with climate change, the significance of 2005 was more the emergence of an international consensus than practical action, although there was some of that at Gleneagles in the summer. The issue is also similar to climate change in that the solutions are hugely complex. One of the motifs of last year was the maturing of Bob Geldof from the simplicities of "give them the money" to the considered proposals of the Africa Commission. It was the year that marked a coming to terms with the double-edged nature of globalisation. We trust that we are not betraying naïve optimism to imagine that European farm subsidies cannot survive, and that protectionism on a world scale is in retreat. It is increasingly understood that free - and, crucially, fair - trade is the best hope for the world's poor.

Globalisation is not just a matter of economics, however. It is linked to the expansion of cultural horizons as technology and the internet make the human race cleverer and more sophisticated than ever before. The pessimists who predicted that iPods and computers would lead to prole culture and the end of books have once again been confounded, most recently by the popularity of non-stop Bach on Radio 3. One of the joys of modern global culture has been the breaking down of barriers, between high brow and low, and between different parts of the world. And one of the great joys of 2006 to which so many will look forward, not least in the English part of the British Isles, will be that festival of internationalism the World Cup. We are ready for kick-off.