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On the News Hour (August 1, 2007), scientists spoke with residents of Greenland, who reported their experiences of climate change.

Greenland Residents Detect Sea Changes

Below are some excerpts:

"GREENLAND RESIDENT: You don't have to be a scientist to see the changes. They're big changes.

SPENCER MICHELS: But you do need to be a scientist to know just how big the changes are, how fast they'll come, and what they mean. That's why researchers are focusing on the Jakobshavn glacier, one of the world's largest. It is so large that the icebergs that break off from it, a process called calving, are sometimes more than 40 stories high and three city blocks wide.

Glaciers are slowly moving rivers of ice. The Jakobshavn used to creep along at a pace that could truly be called glacial. Then, in 1997, it doubled its speed. It's now moving more than the length of a football field each day, making it the world's fastest glacier.

Its ice also thinned, and the calving front -- the place where the icebergs break off -- has retreated inland. When these icebergs reach the ocean and eventually melt, they raise sea level. But not enough is known scientifically about the reasons for these changes, or their impact, or how fast they will happen in the future, here and elsewhere.

Even a recent report from the Intergovernmental Panel on Climate Change, or the IPCC, couldn't answer those questions. It said scientists simply did not have enough understanding of the melting process to make solid predictions of future sea level rise. That's where researchers like New York University's David Holland come in.

DAVID HOLLAND, Oceanographer, New York University: So the IPCC report, there are two headlines from it. One is that, in the next century, the air temperature is going to increase. That is solid science, totally credible, believable, good observations, good models.

The second headline is that sea level will rise between 20 and 60 centimeters. That's totally incredible and unbelievable. That's just a guess based on past behavior, how much sea level has risen in the past century. We cannot predict yet sea level change, and we're stuck, and we're stuck because we aren't able to model processes that we have not observed.

"A poster child for global warming"

SPENCER MICHELS: To make those observations, oceanographer Holland and a team of scientists headed this summer to the Jakobshavn glacier, which, because of publicity it has received, has become a poster child for global warming.

...

DAVID HOLLAND: What's really needed is a decade-long period of observation. We need to be able to correlate when the ocean is warm and cold in this fjord to when the ice is moving and not. So little snapshots are good, but the key observational thing is to get long term. We make the observations; we synthesize, understand the time series; and we will be able to make models that predict the future sea level, hopefully soon enough.

SPENCER MICHELS: Those models may have implications beyond Greenland.

MARK FAHNESTOCK: It may be that Greenland can teach us something that will allow us to better project forward what Antarctica may do in a warming climate, but we have to learn the story in Greenland first. We have a lot to learn.

SPENCER MICHELS: What they do learn over the next decade could help them predict how far sea levels could rise in the future and ultimately whether apocalyptic visions of massive coastal flooding are valid or not."