A glacier researcher has retracted a Nature paper after mistakenly underestimating glacial melt by as much as a factor of ten.
In September, the journal tagged “Asia’s glaciers are a regionally important buffer against drought,” originally published in May 2017 by Hamish Pritchard,a glaciologist at the British Antarctic Survey, with an expression of concern, notifying readers of the mistake. It turns out, Pritchard had missed the fine print on a data set; a figure he thought represented water loss over a decade covered, in fact, only a year.
In September, Pritchard told Retraction Watch that the mix-up strengthened his argument that glacial melt was important to Asia’s water supply.
However, in the retraction notice, published today, he indicated that the mistake affected other conclusions:
Asia’s glaciers are thus regionally a more important buffer against drought than I first stated, strengthening some of the conclusions of this study but also altering others. I am therefore retracting this Article.
The paper suggested that melting glaciers are an important water source in the region — so shrinking glaciers could exacerbate problems caused by water scarcity. One glacier researcher, who was not involved with the paper, told us the retraction is a sign of the power of post-publication review, particularly in this field. Hester Jiskoot, of the University of Lethbridge, in Canada, told Retraction Watch:
Even if reviewers don’t catch mistakes, we have enough people in the field to look at these papers.
It’s unclear which conclusions were affected by the mistake; Pritchard did not respond to Retraction Watch’s request for comment. Here’s how he explained the mistake in the notice:
I estimated net glacial melt volumes on the riverbasin scale from long-term precipitation and temperature records (1951–2007), taking into account the various mass contributions from avalanching, sublimation, snow drifting and so on. To this component (the seasonally delayed turnover of water in the glacial system) I added an estimate of the contribution due to sustained glacial mass losses, based on sparse observations of multi-decadal change. I then accounted for meltwater losses through evaporation, and compared this to net precipitation, distributed across river basins and across the catchments of a large number of dams. I estimated the second meltwater component (the additional contribution from glacier losses) as −0.35 to −0.40 metres water-equivalent per decade based on a global compilation of long-term mass-balance observations (from table 2 in ref. 32 of the Article). In this table, losses are described as “decadal averages (millimetres water equivalent)” but the units are actually intended to be decadally averaged annual values. Hence, the loss components of total meltwater that I used in my calculations are too small and the summed meltwater volumes reported here should be larger.
The paper has been cited 13 times, and was a Highly Cited paper, according to Clarivate Analytics’ Web of Science, meaning it fell in the top 1 percent of papers in its field for its publication year. It received limited news coverage from science websites, including Phys.org, when it came out, and has been cited once since the journal issued the expression of concern.
A spokesperson for Nature declined to comment on the retraction, and referred us to the notice. As with the expression of concern, the retraction notice mentioned that John Moore and Liyun Zhao, glacier researchers from the University of Lapland and Beijing Normal University, respectively, caught the mistake. Though Moore spoke to us about the expression of concern when it was issued, he declined to comment on the retraction, “due the confidentiality request from Nature.” (We contacted a representative of Nature to confirm the existence of a confidentiality request. The representative did not immediately respond. [See update at the end of this post.])
Jiskoot said she was “a little surprised” to see the paper retracted:
because it was just a mistake in some of the quantification.
But she also said the calculations of the glaciers’ input to the region’s water supply were the paper’s main contribution to the literature:
I can understand that if the major conclusions change in terms of quantities, that’s a cause for Nature to retract. Then the paper will be substantially different.
Though Pritchard’s paper was deemed “highly cited,” Jiskoot said she doesn’t expect the retraction to have too great of an impact on her field, partially because others had also concluded that Asia’s glaciers were an important water source:
The general message of the paper had been put forward in several papers before and several papers after. This paper was first time that someone tried to quantify [the importance of Asia’s glaciers]. There are many independent papers that had already showed that, with more or less quantification of glacier melt. Even some recent Nature papers have quantified melt and future melt of some of these glaciers. But this showed the whole process.
Update 20:30 UTC, 2/15/2018: A Nature spokesperson told us there was a miscommunication between the journal and Moore:
We treat all correspondence on integrity matters as confidential, which we make clear in our emails, but we do not ask involved parties not to discuss the published retraction with the press or others. Unfortunately in this incidence, the editor in question was unaware that the media had been provided with embargoed information and requested that John Moore keep the information about the retraction confidential, with the aim of ensuring only that it was not publicised prior to publication. He is clarifying with Moore that he is now free to discuss it.
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