Leading article: The lame duck goes a-hunting his legacy

From climate change to the Middle East and the crisis with Iran, this is a pivotal week for George Bush as he tries to prove that, despite his lame-duck status, the remaining 16 months of his presidency can still produce meaningful achievement. Alas, his speech to the UN General Assembly was not an auspicious start.

True, he announced stricter sanctions against the military regime in Burma, and reeled off the familiar list of other "brutal regimes" – from Belarus to Cuba and Zimbabwe – which he singled out for special criticism. He also demanded that UN members do more to support "young democracies" such as Georgia, Lebanon and Afghanistan. But his tone was perfunctory; he had nothing new to say, at least not to an organisation of which he sounds no more admiring than when he defied it four years ago to launch his war in Iraq.

In a sense, perhaps, he was wise. Anything of significance he might have said would almost certainly have been obscured by the Mahmoud Ahmadinejad carnival that has appalled and entertained New York in recent days. In fact, Mr Bush barely alluded to Iran in his 15-minute address, apart from an obligatory inclusion of Tehran in the list of brutal regimes.

The omission may be read two ways: either he has decided for the time being not to worsen the confrontation with Iran – or his mind is already made up, and the UN is as irrelevant to his calculations as it was over Iraq. Iran aside, though, there are plenty of areas in which even a lame-duck president needs to act.

Ever since Mr Bush was re-elected in 2004, the White House has proclaimed that it has changed its diplomatic ways. The second Bush administration, we were told, would mend broken fences over Iraq, and work closely with traditional allies.

Up to a point, the new tactic bore fruit, as testified by the warm early reviews of his new Secretary of State, Condoleezza Rice, who has clocked up frequent-flier miles on a scale unmatched by her predecessor. The replacement of Donald Rumsfeld at the Pentagon by the more cautious and moderate Robert Gates also helped, as has the trumpeted new drive by the US to promote an Israeli-Palestinian settlement.

The proof of that particular pudding will come in November at the planned international peace conference to be convened by the US. Just now, Mr Bush's foreign policy legacy looks dismal, and nowhere more so than the Middle East. Nothing would do more to burnish it than a real breakthough on the region's longest-running crisis of all. But nothing will be more difficult. Mahmoud Abbas, the beleaguered Palestinian leader, has also been at the UN this week, warning that the conference must deliver "tangible" results, and not become a glossy show that substitutes yet more "talks about talks" for decisive action.

Exactly the same goes for that other "legacy issue" for this president – climate change. Today his promised summit of countries responsible for 85 per cent of global greenhouse gases opens in Washington. As with Iran, Mr Bush barely mentioned global warming in his UN speech. The suspicion must be that the entire exercise is cosmetic, designed to deflect charges that this White House still refuses to take the subject seriously.

It is crystal clear that none of the emerging mega-polluters like China and India will commit themselves to binding action to tackle the problem unless the US does as well. But the signs are not encouraging. Mr Bush seems unwilling to go beyond voluntary, non-binding targets to reduce emissions. Yet climate change offers him his best chance to prove that lame ducks can still fly.