Study into Greenland’s speeding glaciers prompts yet more confusion
- 04 May 2012, 11:50
- Verity Payne
Greenland's glaciers melting faster, say scientists according
to one headline.
Greenland glaciers may be melting slower according to another.
Once again new glacier research is making headlines, and once again
they are contradictory.
Confused? Here's what's going on.
New research, published in
the journal Science this week, finds that on average glaciers
on Greenland sped up over the first decade of the 21st century. The
researchers from the University of Washington analysed data from
satellites monitoring over 200 glaciers around the margins of the
Greenland ice sheet between 2000 and 2010. They found that how fast
the glaciers moved varied from region to region, and that different
types of glacier grow and shrink at different rates - echoing previous
Despite what it an obviously complicated picture of regional ice
loss, the study finds that on average Greenland's glaciers sped up
by around 30 per cent between 2000 and 2010. Since faster-moving
glaciers are associated with increased meltwater
ice loss, the contribution of Greenland's glaciers to sea level
rise probably continued to
increase over that period, as satellite
measurements suggest it has over the last couple of
The research has led to a range of wildly different
interpretations in the media. News agencies Reuters and AFP, for
example plump for almost directly opposing headlines, leading with
Greenland glaciers speed up, swelling rising seas: reports,
Greenland glaciers may melt slower than thought: study (AFP)
respectively. The Guardian go for the more revealing
Sea-level rises 'may not be as high as worst-case scenarios have
So how have the media reached such different interpretations of
the same piece of work? As is often the case, it's the details of
the paper which matter.
It's pretty clear where the 'Greenland glaciers getting faster'
headlines come from, after all the paper finds that on average
Greenland's glaciers sped up over the study period.
Why can you argue the paper shows the glaciers may melt slower
than thought? Whilst the study focuses on how fast Greenland's
glaciers have flowed over the past decade, in the concluding
paragraph Moon and colleagues consider how this might change in the
future and impact sea levels.
previous research from William Pfeffer, University of Colorado
Boulder, and colleagues, that aimed to give a "'most likely'
starting point for refinements in sea-level forecasts". Pfeffer and
colleagues estimated the range of how much Greenland might
contribute to sea level by 2100 as between 0.8 and 2 metres.
The 2 metre estimate assumed that Greenland's glaciers "quickly
accelerated to extremely high limits", whereas 0.8 metres - which
the authors said was more plausible - assumed less glacier
Moon and colleagues write that the increase in average Greenland
glacier speed they measured does not match the acceleration assumed
by Pfeffer and colleagues to reach their upper bounds,
"sea level rise from Greenland may fall
well below proposed upper bounds."
"We found we are certainly not on the
worst-case scenario, but the glaciers are speeding up and we see no
sign of that stopping."
However, the possibility of a larger Greenland contribution to
sea level rise still remains, as co-author Ian Howat, Ohio
State University, explains:
"There's the caveat that this 10-year
time series is too short to really understand long-term behavior
[...] So there still may be future events - tipping points - that
could cause large increases in glacier speed to continue. Or
perhaps some of the big glaciers in the north of Greenland that
haven't yet exhibited any changes may begin to speed up, which
would greatly increase the rate of sea level rise."
Clearly, the nuanced conclusions reached by Moon and colleagues
are not the same as saying that all previous sea level forecasts
are wrong, as some headlines seem to indicate.
The scientific community have made an effort to point this out,
saying that Pfeffer and colleagues' paper was
not intended to be realistic, and was "a
thought experiment, or a 'what if' scenario."
Glaciers and sea level: a recipe for
This isn't the first time that we've seen a flurry
of confusing headlines about research into glaciers and global
sea level. New analysis earlier this year of the amount of ice lost
from global glaciers prompted some seemingly conflicting headlines.
They ranged from the Independent's
Billions of tons of water lost from world's glaciers, satellite
reveals through to the Guardian's
The Himalayas and nearby peaks have lost no ice in past 10 years,
The trouble is that putting new findings about melting ice and
sea level into the context of previous findings is a pretty nuanced
affair. Capturing these nuances in a headline is pretty difficult.
In our experience it's easier to make headlines
snappy or accurate
- getting both is somewhat harder.
Interestingly the Mail, eschewing its recent trend for
misleading climate stories, has written a
pretty accurate article. Although this might be because it
seems - to us at least - to be nearly identical to the
article from Associated Press science writer Seth Borenstein.
At least for once the Mail didn't plump for yet another '
Forget global warming...' headline. Well done that paper.