He also pointed out, as relief agencies have done, that another horror is about to strike the survivors of the earthquake in the form of bitter winter weather. Kofi Annan, the UN secretary general, said much the same this week when he told a donors' conference in Geneva that "the scale of this tragedy almost defies our darkest imagination". According to Jan Egeland, the UN's under secretary general for humanitarian relief, 2 to 3 million people are at risk, and the world has only a few days in which to prevent many more deaths than the 79,000 thought to have died in the earthquake.
As with the tsunami, international aid to Pakistan began as a trickle. Unlike the tsunami, a disaster which was in the end over-subscribed - some donated cash has even been returned or diverted to other programmes - it has stayed that way. In December, President Bush was criticised for remaining on holiday for four days after huge waves struck South-east Asia and pledging only $15m to help people whose towns and villages had been swept away. By the end of the first week after the disaster, Bush had managed to find $350m, while the British government upped its offer of aid from an initial £1m to £50m.
This time, the US is the second-largest donor among the world's leading economies to the UN's Pakistan appeal, pledging $10.8m. Britain is first, with £17.4m, while Japan has promised $8m, Germany $3.9m and Italy $1.2m. But these sums amount to small change, given the scale of the impending catastrophe, and Oxfam claimed this week that seven wealthy countries - France, Austria, Belgium, Finland, Greece, Portugal and Spain - had given nothing to the UN appeal.
The UN has raised the target to around $550m, from an initial $312m, and since Wednesday's conference another $525m has been pledged by the international community. Yet it is hard to avoid the conclusion that, in comparison to the outpouring of sympathy and cash that followed the tsunami, the response to this latest disaster has been sluggish and mean-spirited.
British towns and cities with links to Pakistan have done their utmost, collecting cash and sending volunteers to the worst-affected areas, but there has been no comparable response from the wider population. In January, pubs and gyms up and down the country staged events to raise money for victims of the tsunami, collecting £60m from the public in a matter of days. If anything, the response to the tsunami tipped over into sentimentality, creating an emotional atmosphere reminiscent of the aftermath of the death of Diana.
This is not in any way to diminish the tragedy that struck Indonesia, Sri Lanka, Thailand and India. A couple of months later, I went to Thailand and saw for myself the staggering scenes of destruction on the islands of Phuket and Phi Phi Don, where fishing villages had been flattened and multi-storey hotels reduced to their foundations. On Phuket, signs directing people to temporary embassies and consulates were a grim reminder of how many nationalities had died on the island.
At Bangtao, a fishing village on Phuket, I saw evidence of the way international aid was beginning to restore local people's livelihoods. One evening at sunset, I watched as a group of fisherman fitted an engine, donated by the Austrian government, to a new boat, one of 200 given to islanders by the King of Sweden. Behind them, half their houses had been turned into rubble, but the men still found the energy to hang garlands on the fishing boat and push it into the sea.
The death toll among Swedish visitors to Phuket was the highest among foreigners, resulting in harrowing TV and newspaper photographs of bewildered blond children who had been orphaned or separated from their families. Many of the places affected by the tsunami are popular holiday destinations, which cannot be said of Pakistani-controlled Kashmir, and I wonder if that is one of the explanations for the starkly differing responses to the two disasters.
Compassion fatigue is another possibility, and it is true that the US, in particular, has had its own share of natural catastrophes in recent months. Huge amounts of damage still have to be cleared up in Louisiana, Florida and other states hit by this season's unusually ferocious hurricanes, yet it is also clear that government agencies and the media hugely over-estimated the loss of life in Hurricane Katrina. Some harrowing stories about a breakdown in civilised values in New Orleans - another popular holiday destination for Europeans - turned out to be inventions, yet they were relayed to a mesmerised world as fact.
In Pakistan, the opposite has happened, and the physical difficulty of getting to some of the worst-affected regions does not seem to me an adequate explanation. The grim truth is that some disasters grip people's imaginations, others do not, and the fate of hundreds of thousands - in this instance, perhaps millions - hangs on such subjective reactions. Human compassion is arbitrary and irrational, whether it manifests itself in excessive mourning for a dead royal or throwing too much money at one natural disaster and then failing to respond adequately to another months later.
That being the case, it is surely folly or worse to allow this kind of gruesome beauty contest to continue. Instead of being forced to beg for cash once a disaster has happened - as survivors are crying out to be pulled from the rubble - the UN needs to have a permanent emergency fund topped up by annual contributions from the world's richest countries. Nor should the government of an affected country have to wait so long for military assistance, such as helicopters, which were criminally slow to arrive in Pakistan.
But there is also a lesson here for the British public, whose generosity was praised to the skies in January and February. Charitable donation in this country has become inextricably tied up with showy gestures and televised feel-good events, rather than the desperate needs of people in faraway countries. It might provide less emotional satisfaction, but quiet, regular giving to organisations like the Red Cross and Oxfam would be much more effective for victims of natural disasters than periodic spasms of generosity and noisy self-congratulation.Reuse content