MENU

Social Channels

SEARCH ARCHIVE


Additional Options
Topic

Date Range

Receive a Daily or Weekly summary of the most important articles direct to your inbox, just enter your email below:

CC0 1.0
Bettmerhorn, Bettmeralp, Switzerland.
GLACIERS
12 December 2016 16:00

Shrinking glaciers are ‘categorical evidence’ of climate change, study says

Robert McSweeney

Robert McSweeney

12.12.16
Robert McSweeney

Robert McSweeney

12.12.2016 | 4:00pm
GlaciersShrinking glaciers are ‘categorical evidence’ of climate change, study says

It is virtually certain that the retreat of many glaciers around the world has been caused by climate change, a new study suggests.

Using records of glacier length that go back over 400 years, the researchers show that shrinking of mountain glaciers in five continents could almost certainly not have happened if the Earth wasn’t warming up.

The findings suggest that future reports from the Intergovernmental Panel on Climate Change (IPCC) should have stronger conclusions around how human-caused climate change is affecting the world’s glaciers, the researchers say.

Attribution

The study, just published in Nature Geoscience, is the latest in the relatively new field of attribution, where scientists identify the fingerprints of human influence on observed changes in temperature, rainfall, and other climate parameters.

Attribution studies typically focus on specific extreme events. Recent research has found, for example, that climate change boosted the odds of the UK’s very wet winter in 2013-14 by 43%. Another paper identified how many extra deaths there were in London and Paris during the 2003 summer heatwave because of our warming climate.

Rather than an event of a few hours, weeks or months, the new study looks at how glaciers have changed over the past century.

The near-global retreat of these rivers of ice “seems improbable” without the influence of climate change, the paper says, but most studies to date have only been able to test this theory on a few glaciers at most.

So the researchers collected together records of glacier length for 37 glaciers in North America, South America, Europe, Asia and Australasia. The records were selected for their length and completeness – the longest goes back to 1534.

You can see the glacier locations in our interactive map below.

Location of the 37 glaciers used in the study. Data from Roe et al. (2016). Map by Rosamund Pearce for Carbon Brief.

Whether a glacier retreats or advances each year largely depends on its mass balance – the difference between how much snow it receives and the amount of its ice that melts away. Glaciers that lose more mass through melting than they gain from snow will shrink and retreat back up the valley.

The chart below shows how the length of each glacier has changed over their observed records.

Chart of annual retreat of 35 of the 37 glaciers examined in the study. Click and drag across to zoom in. Data from Leclercq et al (2012). Chart by Rosamund Pearce for Carbon Brief using Highcharts.js.

Using the long-term records, the researchers estimated how glacier lengths have varied in response to the yearly ups and downs of temperature and snowfall. They then compared these natural fluctuations with the large-scale retreat seen in the glaciers in the 20th and 21st centuries.

Their findings show there’s only a very small chance that the retreat of these glaciers could have happened without climate change, says lead author Prof Gerard Roe from the Earth and Space Sciences department at the University of Washington. He tells Carbon Brief:

“Our paper demonstrates that the worldwide retreat of glaciers necessarily requires a climate change that is centennial in duration and global in extent.”

The findings constitute “categorical evidence” that the climate is warming, the paper says.

‘Virtually certain’

The results suggest for all but one of the 37 glaciers, there’s a more than 90% probability that their retreat is a result of a change in climate. In the vernacular of the IPCC, this level of likelihood means it is “very likely” that the changes are attributable to human-caused climate change.

For 21 of the 37, the findings are even more emphatic. They find that it is over 99% likely – or “virtually certain” – that glacier retreat is being driven by climate change.

These likelihoods are stronger than the findings on glaciers in the most recent IPCC assessment report (“AR5”), published in 2013, the paper notes.

According to AR5, there is “high confidence that a substantial part of the mass loss of glaciers is likely due to human influence.” Here, “likely” means a greater than 66% probability. This lower level of confidence reflected the lack of published literature on attributing glacier change, says Roe:

“There were very few studies [available in 2013] that tried to do what we have done. In the absence of such studies, they [the IPCC] were right to be cautious.”

The new study convincingly shows that the retreat of these glaciers is a response to a changing climate, says Dr Alex Gardner, a solid earth research scientist at the Jet Propulsion Laboratory at Caltech, who wasn’t involved in the study. He tells Carbon Brief:

“It is now almost certain that we will continue to see the near global demise of low latitude glaciers in the coming centuries as our planet warms in response to increased concentration of greenhouse gases in the atmosphere.”

The question to answer next, he adds, is how quickly they’ll retreat and by how much.

‘Ingenious approach’

The researchers hope their findings will feed into future IPCC reports, strengthening the panel’s conclusions on how climate change is affecting glaciers around the world.

This would be helped by other studies building on their “ingenious approach,” says Prof Peter Stott, head of the climate monitoring and attribution at the Met Office Hadley Centre and professor of detection and attribution at the University of Exeter, who also wasn’t involved in the study. He tells Carbon Brief:

“[Their conclusions] depend crucially on the scientific robustness of their techniques so it will be interesting to see if investigations by independent teams support these new results.”

The influence of climate change on glacier retreat could also be used to help communicate the consequences of human activity, says Roe:

“Alongside the dry, technical information of the data and the numbers, I think it is important for students, the public, policymakers, and scientists to have something more definite and easy to grasp, that they can understand and reflect on. Hopefully, in strengthening the link between glaciers and climate, our study facilitates that happening.”

Roe, G. H. et al. (2016) Centennial glacier retreat as categorical evidence of regional climate change, Nature Geoscience, doi:10.1038/ngeo2863

  • ritesharya

    Glaciers will recede due to Climate change……..what is the BIG DEAL….. we are in the warming part of the Climate change cycle comprising of COOLING Warming and and cooling ..In Indian Hiamlayas Major glaicers are extinct or on the verge of extinction but all this happened much before industrialisation Khardungla glacier receded 29.4 kms since last iCe Age and Siachen 78.4 kms since last ICe age 11714 years from today

    https://www.youtube.com/watch?v=52tN_OAAy_E

    http://www.academia.edu/8915481/Aryas_C_Cycle_-_Climate_change_natural_—Dr_Ritesh_arya

    https://www.youtube.com/watch?v=jGKB2jo6B0Q&t=1244s

    http://agneyodara.blogspot.in/2016/11/climate-change-in-ladakh-indian.html

    • Graham P Davis

      According to best evidence, we should have been in a cooling phase of a 100-year cycle since about 1940 followed by an upturn starting around 1990. We should now have a global temperature about where it was at the end of the nineteenth century.

      • ritesharya

        Please see Aryas C cycles and paper link to see climate change cyc;les based on Geological evidences

        [DOC] Climate change natural–Impact on water resources in Himalaya
        R Arya – academia.edu
        Abstract: Present paper is based on discovery of paleoclimatic signatures made by Indus
        glacier/river on the granites of Ladakh batholiths on the banks of river Indus since 11714
        years. Author discovered these signatures while exploring, drilling and developing
        All 2 versions Cite Saved More

      • Dano2

        “evidence”

        Best,

        D

    • Jonbo69

      Not a peer reviewed study – you can’t even find it on google scholar

      • ritesharya

        This is a document in Google scholar
        [DOC] Climate change natural–Impact on water resources in Himalaya
        R Arya – academia.edu
        Abstract: Present paper is based on discovery of paleoclimatic signatures made by Indus
        glacier/river on the granites of Ladakh batholiths on the banks of river Indus since 11714
        years. Author discovered these signatures while exploring, drilling and developing
        All 2 versions Cite Saved More

        • Jonbo69

          I’m sorry, but this document has been published without peer review. It seems to be claiming that current world wide glacial melt is part of a natural cycle; if so, this contradicts the findings of that which is currently in the scientific literature such as ,that written about in the article above, where scientists are claiming that the current trend in glacial melt is a result of AGW – I suggest it therefore requires more validation than publication on an internet website and that it needs to be submitted to peer review in a legitimate scientific journal before it can be taken seriously by a lay person such as myself.

        • Al Rodger

          The links provided by the commenter do not work outside the Google Scholar page.
          The paper is entirely purile in its content. The paper asserts that eight and a half erroded bands found in granite outcrops alongside Himalayan rivers can be dated to post-11,715ypb, which is taken as thedate of the end of the last ice age. So being adjudged post-11,715ypb, if they were created by glaciation during cool periods and those periods were spaced equally in time, one erosion band would be created every 1,300 years or so. And that is the sum of it. As I said, entirely purile.

  • gduggan

    How soon before we turn into another Venus? Should we sign up for Mars?

  • Graham P Davis

    A study of retreats of glaciers over a century and the reduction in area and thickness of Arctic Sea Ice over the previous fifty years found no natural explanation for the changes. This study was published in 1950.


Related Articles

THE BRIEF

Expert analysis directly to your inbox.

Get a Daily or Weekly round-up of all the important articles and papers selected by Carbon Brief by email.

THE BRIEF

Expert analysis directly to your inbox.

Get a Daily or Weekly round-up of all the important articles and papers selected by Carbon Brief by email.