Changes in the Greenland Ice Sheet Mass: Crisis in the Making, or Example of Uncertainty in Climate Science?

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by Michael F. Cochrane, Ph.D.

“Much climate reporting today highlights short-term changes when they fit the narrative of a broken climate but then ignores or plays down changes when they don’t, often dismissing them as ‘just weather’,” wrote theoretical physicist Steven Koonin, former Under Secretary for Science at the Department of Energy in the Obama administration, in a Wall Street Journal op-ed earlier this year. Such reporting frequently occurs regarding polar ice melt and its impact on sea-level rise.

Reporting on melting polar ice often falls into this category. It is frequently cited as prima facie evidence for global warming. In its 2021 “Arctic Report Card,” the National Oceanic and Atmospheric Administration (NOAA) concluded, “Rapid and pronounced warming continues to drive the evolution of the Arctic environment.”

The authors of the NOAA report card documented the change in mass of the Greenland Ice Sheet (GIS) from 1 September 2020 to 31 August 2021, reporting a total mass loss of 85 gigatons (Gt) plus or minus 16 Gt (a gigaton is about the weight of 1 cubic kilometer of water). Though the authors note that the 85 Gt annual mass loss of the GIS was less than the 264 Gt/year average loss over the period from 2002 to 2021, they still concluded, “the ice sheet has now lost mass almost every year since 1998, with tied years of record ice loss in 2012 and 2019). … Ice loss is exposing land, adding substantial freshwater into the ocean, and raising sea levels globally.”

“While a warming globe might eventually be the dominant cause of Greenland’s shrinking ice,” Koonin acknowledges, nonetheless “natural cycles in temperatures and currents in the North Atlantic that extend for decades have been a much more important influence since 1900. Those cycles, together with the recent slowdown, make it plausible that the next few decades will see a further, perhaps dramatic slowing of ice loss.”

Possible evidence for such a dramatic slowing of ice loss in the GIS came recently with a report from the climate website, where Cap Allon announced a record-breaking 7 Gt gain in surface ice mass in a single day, June 18, 2022. Using data from Denmark’s Polar Portal, an Arctic climate and ice monitoring resource, Allon documented that “Impressive surface mass balance (SMB) readings… have been posted across the Greenland ice sheet all season,” but the 18 June record gain of 7 Gt is highly unusual, “particularly when you consider the glacier should be losing mass at this time of year.”. (Polar Portal explains, “The term surface mass balance is used to describe the isolated gain and melting of the surface of the ice sheet—i.e., not including the losses that occur when glaciers calve icebergs and melt when meeting relatively warm seawater.”

As can be seen in this graph from the Danish Meteorological Institute (DMI), this season’s gains in ice mass have pushed the Greenland Ice Sheet’s SMB above the 1981–2010 average for this time of year:

The report concludes that this year’s gain is not an anomaly. The SMB for the years between 2016 and 2018 shows annual SMB ranges consistently greater than the mean:

The National Snow & Ice Data Center (NSIDC) had similar findings, reporting last year that the surface melting and total melt-day area for the GIS at the end of the 2021 spring season was below the 1981 to 2010 average. “Snowfall and rain (minus runoff) added mass to the ice sheet. As of June 20 [2021], total mass gain for the ice sheet since September 2020 was slightly above average.”

The importance of monitoring and documenting changes in SMB of the polar ice sheets is not simply to provide evidence of a warming planet, but to attempt to predict the degree to which these changes contribute to rising sea levels. Koonin, in his 2021 book, Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters, acknowledges that global warming would, indeed, put more water into the oceans, resulting in rising sea levels, but cautions that any prediction of future sea-level rise “largely depends upon how much of the ice on the land melts as temperatures increase, together with the expansion of the warming oceans.”

Citing recent work on glacial ice mass changes, Koonin, points out in Unsettled that “the contribution from glacier melting has slightly declined since 1900 and is the same now as it was fifty years ago; the contribution from Greenland went through a minimum around 1985 and is now no higher than it was in 1935.”

His point is that the predictability of future global sea-level rise is highly uncertain because of two key factors: the uncertain dynamics of the Greenland and Antarctic ice sheets, as well as the uncertainties inherent in the temperature predictions of global climate models.

It should come as no surprise that a scientist would underscore the importance of uncertainty in drawing conclusions from observational data. After all, the scientific method—based on observation, hypothesis, and experimentation (where possible)—demands that any conclusions drawn from this process are, by definition, uncertain. Yet governmental organizations such as NOAA and the Intergovernmental Panel on Climate Change (IPCC) continue to couch their findings and conclusions in terms that practically beg media outlets to report on them as if they were absolutely certain.

Acknowledging the uncertainty surrounding climate science should lead to a strong sense of humility. Scientists are not advocates. They must provide policy makers with the best evidence, but do so humbly, acknowledging that their conclusions will likely have a major impact, not only on the world economy, but also on the flourishing of billions of vulnerable human beings. Michael Cochrane, Ph.D., Engineering Management and Systems Engineering, a defense and technology reporter for World News Group, is founder of Value Function Analytics and a Contributing Writer for The Cornwall Alliance for the Stewardship of Creation.

via Watts Up With That?

June 29, 2022