31 janeiro, 2006 - Published 04:54 GMT

Efeito estufa é pior que o previsto

The ice cap on Greenland holds a tenth of the world's fresh water. It's more than a mile thick and if it melts it will slowly raise sea level round the world.

Recently the ice has been shrinking at the edges as the local climate warms. Scientists would be even more disturbed if the ice in the middle melted.

Today's document is an edited and peer-reviewed report of a government-sponsored conference last year. It warns that the tipping point beyond which the cap may begin to thaw is estimated to be a global temperature rise of two degrees celsius. It says that to be relatively certain of avoiding this sort of warming we should keep emissions of the greenhouse gas carbon-dioxide below 400 parts per million in the atmosphere.

The government's chief scientist Sir David King told the BBC that target was highly desirable but politically unfeasible because it would mean turning power stations off. The lowest realistic figure for halting emissions, he said, was 550 parts per million. But today's report makes it plain that that's well above the predicted melting point of the ice cap. The scientific advice on emissions, says Professor King, is that we shouldn't be where we are.

Roger Harrabin, BBC

ice cap
camada de gelo.

raise sea level
aumentar o nível do mar.

shrinking
encolhendo.

peer-reviewed
revisto por outros especialistas da área (no caso, cientistas).

tipping point
ponto de virada (no caso, a temperatura crítica em que a camada começará a derreter).

a global temperature rise
um aumento na tempertura global.

emissions
emissões.

politically unfeasible
politicamente inviável.

realistic figure
número realista.

we shouldn't be where we are
a situação atual é preocupante.