Media outlets put their own spin on Antarctic ice core records showing recent rapid warming
- 28 Aug 2012, 11:10
- Freya Roberts
Source: British Antarctic Survey
study published in Nature last week documents temperature
changes in the Antarctic Peninsula over the last 15,000 years - and
predicts that if recent rapid warming continues, previously stable
ice shelves could be threatened. Although the research makes no
attempt to attribute the warming effect to any one cause, it would
be hard to work that out from some of the coverage of the report
online and in the media, which has absorbed the findings into
familiar arguments about whether climate change is happening or
The ice sheet covering Antarctica is simply enormous, concealing
an entire continent and extending into the surrounding ocean as
great ice shelves. The research concentrated on documenting
temperature changes in just one part of the continent - the
Antarctic Peninsula - which has experienced
rapid warming over the last few decades.
The study's authors were, in fact, very careful to put the modern
changes, observed in weather station records and satellite images,
into the context of longer-term climate trends without any attempt
to attribute their causes.
That hasn't stopped several outlets from imposing their own
narrative on the study. Climate skeptic IT blog
The Register claims, for example, that this latest research
proves "warming is nothing unusual", despite the paper itself
describing warming in recent decades as specifically 'unusual'.
Another skeptic blog,
Watts Up With That, headlines its article "Antarctic peninsula
was 1.3°C warmer than today 11,000 years ago".
In contrast to the 'nothing to see here' stories, others have
inferred that the warming is human-caused.
The Australian headlines its article 'Humans partly to blame
for Antarctic ice shelf collapse: study'.
NPR, meanwhile, says 'Humans' Role In Antarctic Ice Melt Is
Unclear'. But the study itself doesn't discuss the causes of
What the study found
The research uses an ice core drilled from James Ross Island, just
off the Antarctic Peninsula. Scientists were able to analyse the
chemical composition of tiny air bubbles trapped in the ice to
reconstruct temperatures over the last 15,000 years in the
The records show that as the earth emerged from glaciation about
11,000 years ago, temperatures on the Antarctic Peninsula reached
roughly 1.3 degrees Celsius warmer than today. In these conditions
some of the surrounding ice shelves retreated.
In time, the region began cooling and ice shelves regrew. The
Antarctic Peninsula experienced stable conditions for a period of
about 7000 years before cooling again - with temperatures reaching
their lowest about 600 years ago.
The ice core shows that from around 1400, warming began again.
While the warming was comparatively slow to begin with,
temperatures over the last century rose at a rate of about 1.56
degrees Celsius per century, and the last 50 years saw warming
happening even faster.
Over recent decades, a number of ice shelves on the peninsula have
collapsed, which the
study links to warming in the region. Dr Nerilie Abram,
co-author of the paper,
suggests the gradual warming over many centuries left ice
shelves "poised for the succession of collapses that we have
witnessed over the last two decades", during the recent rapid
Unusual but not unprecedented warming
Putting recent temperature rise into context, the authors explain
that the speed at which the Antarctic Peninsula has warmed over the
last few decades "is unusual but not unprecedented".
original press release had contradicted this, stating:
"The scientists reveal that the rapid
warming of this region over the last 100 years has been
The press release was quickly changed - although not before
The Register pointed it out. Lead author of the study, Dr
Mulvaney, told us that this was an error made by an editor that was
It should be noted though that the term 'unusual' might not
really encapsulate how rapid the recent warming is. The ice core
shows that over the last century, mean temperatures on the
peninsula increased by about 1.56 degrees Celsius. The authors say
that that this puts the last century in the top 0.3 per cent of
hundred year periods from the last 2000, ranked by speed of
to put it another way, as Realclimate say, the
paper shows the most recent warming is faster than 99.7% of any
other given 100-year period in the last 2000 years.
So recent warming in the region isn't unprecedented, but has
happened this fast only very infrequently over the past two
Caused by climate change?
On its own, this one temperature record proves very little about
changes happening to the climate on a global scale. It doesn't tell
us about the cause of temperature change in the region, or more
Factor this study into what's being observed worldwide, however,
and it contributes to the broader picture. Ice sheets in
both the northern and southern hemisphere are experiencing loss
at the same time - and that is out of the ordinary.
previously highlighted research comparing Arctic and Antarctic
ice shelf retreat over the last twelve thousand years, which shows
that the last few decades is the only point in that period when ice
shelves have retreated simultaneously at both poles. Adding to
research shows that the current warming is the first instance
over the last twenty thousand years in which both hemispheres have
So while the Nature study's ice core record of temperature change
doesn't speculate about causes, it documents recent warming, seen
elsewhere in both the north and south hemispheres. Dr Mulvaney and
his team predict that if the peninsula continues to warm,
previously stable ice shelves will be threatened. And that could
change the Antarctic Peninsula beyond anything that's been
witnessed in the last 15,000 years.