Leading article: A week in which our political leaders need to deliver

From the economy to climate change, now is the time for action

The dominant themes of this week's G20 summit in London have been emerging for several weeks now. There is expected to be a consensus on new funds for the International Monetary Fund. An agreement on the need for tighter regulation of banks and other financial institutions is likely. The summit will also probably produce a commitment to resist national protectionism.

There remains, however, disagreement between the larger economies over the scale of the discretionary fiscal stimulus needed by the world economy. Expect some sort of fudge in the final summit communiqué, to prevent either side losing face.

Yet there will be more to this week's high-powered diplomatic wrangling than money. And we should beware the assumption that all that matters this week is the statement that will emerge from the G20 conclave, orchestrated by Gordon Brown in London's Docklands, on Thursday.

Several significant meetings will take place away from the main summit. President Barack Obama will hold his first face-to-face talks with his Russian counterpart, Dmitry Medvedev, in which the two leaders will discuss possible cuts in stockpiles of nuclear missiles and co-ordinated pressure on Iran not to develop such weapons.

The implications of President Obama's recent offer to "re-set" relations between America and Russia are significant.

If agreement can be reached between these two former Cold War giants on nuclear disarmament, the peace dividend for the world could be as valuable as co-ordinated action on boosting global economic demand.

The US President will also hold meetings with the leaders of those emerging economic powers, China and India, with a new treaty on curbing global carbon emissions on the agenda. This follows Mr Obama's announcement at the weekend of a meeting of "major economies" on climate change next month. This "environmental G20" is being presented as a diplomatic stepping stone on the road to the crucial United Nations summit in Copenhagen next December.

All this activity confirms that the new US President is serious about reaching a global deal on a replacement to the Kyoto Protocol. Again, the consequences of such a breakthrough on curbing carbon emissions would be just as far-reaching as anything agreed by world leaders on regulating hedge funds in London this week.

Some express a cynical view of international summits, accusing them of producing little more than platitudes and of failing to justify all the excitement. Certainly, many gatherings of world leaders over the years have been guilty of under -delivering. But this meeting promises to be different, not least because of the turbulent global environment in which it is taking place in. The world economy is in the midst of a synchronised financial crisis and economic downturn. Whatever agreement these global leaders produce will affect confidence in the financial markets.

And the sense of crisis and opportunity is strong in other areas too. The window of opportunity for governments to come together and take serious measures to curtail carbon emissions is fast closing. And serious efforts towards nuclear demilitarisation would appear to be in diplomatic play again for the first time since the break-up of the Soviet Union. The stakes are high, and true political leadership is urgently called for. We need to hope that this generation of politicians will rise to the formidable challenges of the moment and prove the cynics wrong.