Perhaps the most common climatic effect of global warming is rapid extension of ice melt. Mount Kilimanjaro in Africa and the Himalayas will very likely lose most of their glacial ice within the next two decades, affecting local water resources. NASA scientists determined Greenland’s ice sheet is thinning by about 1m per year. The additional melt water, especially from continental ice masses and glaciers, is adding to a rise in sea level worldwide. Satellite remote sensing is monitoring global sea level, sea ice, and continental ice. Worldwide measurements confirm that sea level rose during the last century.

Okay, so how much is melting of Greenland contributing to sea level rise? Estimates are about 270 gigatons of water per year. The melting of an ice sheet can occur from the surface as air temperatures and sunlight warm the upper layer of ice. It can also occur from the edges as ice shelves collapse and fall into the oceans in large pieces. The bedrock underneath the ice sheet is not also flat. There are undulations that rise and fall and change the water-ice-ground connection, which can make it easier for ice to melt and can increase the rate of ice shelf collapse. So scientists have a real interest in learning about the land underneath ice sheets so that they can better predict ice collapse and sea level rise.

Greenland ice has its feature, meaning it acts slowly but once it gets going, it’s hard to stop. So predicting how fast this melt will take is interesting from a scientific advantage point but there are also enormous social and economic consequences. Right now, 150 million people live within 3 feet of today’s sea level. If you live near the coast, the question of “when” is really important. This suggests that “when” may be sooner than we hoped.

【小题1】What does Paragraph 1 mainly talk about?

A．A rapid extension of ice melt.	B．Himalayan ice.
C．Greenland’s ice sheet.	D．A big rise of sea level.

【小题2】What probably speed(s) the bottom melting of an ice sheet in Greenland?

A．The rise of sea level.	B．The undulant bedrock.
C．The temperature and sunlight.	D．The shape of ice sheet.

【小题3】Which of the following can be inferred from the last paragraph?

A．Greenland ice is sure to melt as fast as before.

B．Scientist are indifferent to the melt of Greenland ice.

C．Greenland ice is a potential danger to people living near the coast.

D．People living within 3 feet of today’s sea level will have to move next year.

【小题4】In which programme does this text probably appear?

A．Historical Legend.	B．Planet Earth.
C．Bear Grylls: Mission Survive.	D．Beyond the Red Carpet.