Global perspective Human stories

Greenhouse effect could melt nearly all world's glaciers, says UN-backed report

Greenhouse effect could melt nearly all world's glaciers, says UN-backed report

Dramatic scenarios from man-made global warming can no longer be excluded, including the complete disappearance of glaciers from entire mountain ranges, leading to processes "without precedent in the history of the earth," according to the latest update of a five-yearly United Nations-supported report.

"The last five-year period of the 20th century has been characterized by an overall tendency of continuous if not accelerated glacier melting," says the World Glacier Monitoring Service (WGMS) 1995-2000 edition of the Fluctuations of Glaciers report, complied with the support of the UN Environment Programme (UNEP).

"The two decades [from] 1980-2000 show a trend of increasingly negative balances with average annual ice thickness losses of a few decimetres," it adds. "The observed trend of increasingly negative mass balances is consistent with accelerated global warming."

Analysis of repeated inventories shows that glaciers in the European Alps have lost more than 50 per cent of their volume since the middle of the 19th century, and that a further loss of roughly one fourth the remaining volume is estimated to have occurred since the 1970s, the report states.

"With a realistic scenario of future atmospheric warming, almost complete deglaciation of many mountain ranges could occur within decades, leaving only some ice on the very highest peaks," it says.

Since the initiation in 1894 of a worldwide programme for collecting standardized information on glacier changes, various aspects involved have changed "in a most remarkable way," the report notes.

Concern increases that the ongoing trend of worldwide and fast if not accelerating glacier shrinkage at the century time scale is of non-cyclic nature, there is definitely no more question of the originally envisaged 'variations périodiques des glaciers' as a natural cyclical phenomenon, it states.

"Due to the human impacts on the climate system (enhanced greenhouse effect), dramatic scenarios of future developments – including complete deglaciation of entire mountain ranges – must be taken into consideration," it stresses.

"Such scenarios may lead far beyond the range of historical/holocene variability and most likely introduce processes (extent and rate of glacier vanishing, distance to equilibrium conditions) without precedence in the history of the earth."