"It seems likely that other Greenland outlets will undergo similar changes, which would impact the mass balance of the ice sheet more rapidly than predicted," the study said.

It said the fact that the two major outflow glaciers had shown the same sudden acceleration despite being more than 300km apart suggested the cause was not local but more likely climatic or oceanic in origin.

"In both of these glaciers the acceleration and retreat has been sudden, despite the progressive nature of warming and thinning over some years," the report said.

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"The longevity of this flux increase is unknown but could be substantial," it added.

The report followed a warning earlier this week from Britain's Hadley Centre for Climate Prediction and Research – a branch of the Meteorological Office – that the Greenland ice sheet could be disappearing faster than previously thought.

The ice sheet contains one-tenth of the world's freshwater reserves.

Scientists predict that global average temperatures will rise by between one and six degrees Celsius this century unless urgent action is taken now to cap and reduce carbon emissions.

Even a rise of three degrees could result in cataclysmic species loss, melting polar icecaps raising sea levels by many metres and wholesale famine and disease.

Greenland is only part of the picture, and there is also evidence of local warming and melting on the giant Western Antarctic ice sheet.

Scientists said on Monday the world had to halt greenhouse gas emissions and reverse them within two decades or watch the planet spiralling towards destruction.

The first phase of the global Kyoto protocol on cutting greenhouse gas emissions runs until 2012, and negotiations have only just started on finding a way of taking it beyond that.

The United States, the world's biggest polluter, has rejected both the protocol in its current form and any suggestion of expanding or extending it.

The people in the crowd were packed so closely together that it took police and rescue workers until 9 a.m. to reach those who were hurt, resulting in a number of deaths that a faster response could have prevented, he added.

"The gates were being partially opened then shut," said Myrna Britania, 42, who spoke at a hospital where the injured were being treated, AP reports.

"The raffle tickets can be obtained at the gate so everyone was in a hurry. There was pushing and people in front of the gate were crushed."

Britania, who had spent all night in line, said "people at the back of the line were pushing not knowing there were already people dead lying on the ground in front."

Police Superintendent Gerry Galvan told AP at least 50 people died at the stadium and the rest at hospitals where they were taken.

Radio DZBB reported that hospitals were overwhelmed with the scores of injured and were using parking lots to accommodate them.

Gordon blamed poor organization of the event for the tragedy.

"If you predict that there's going to be a huge crowd, you should be ready with ambulances and communications," AP quotes him as saying.

"You should plan for the worst. We have a lot of people who wanted to help but could not get in immediately."

The princess came under intense palace pressure to have another baby after giving birth to her only child, Aiko, in 2001. Her subsequent illness has sparked a succession crisis and forced the government to begin revising the Imperial House Law, which prevents females from ascending the throne.

A government panel has recommended changing the law and polls suggest that the public supports the idea of an empress. But, with just over a month left before the revision is sent to parliament, the plan has run into opposition from conservatives, including members of the ruling Liberal Democratic Party (LDP).

The former prime minister, Yoshio Mori, and the head of the LDP's Diet Affairs Committee, Hiroyuki Hosada, warned recently that the succession issue could "split the country" if handled badly. "Opposition is growing. The situation is precarious," Mr Hosada said.

The Association of Shinto Shrines, which has traditionally harvested votes for the LDP, has warned that it will withdraw support from anyone who votes for the bill, a potentially serious threat to the Prime Minister, Junichiro Koizumi, who supports a female emperor. Opponents were galvanised on Wednesday by a Tokyo rally at which more than 170 Diet members signed a cross-party petition opposing the legislation.

At least one member of the imperial family has told the government not to buck tradition. The emperor's cousin, Prince Tomohito, believes that the imperial bloodline should not be diluted by "outsiders". "There is no need to change the law," said the prince.

The speculation about Masako's state of mind has gathered pace as the debate on the succession issue heats up. "There are very few people who actually say the words divorce, but they think it," said Yagi Hidetsugu, a professor at Takasaki Keizai University. "Her withdrawal from the imperial family would certainly solve a lot of problems."