Glacial Retreat

A friend of mine, JP, started all of this when writing:

If you were to ask me 2 years ago what my key understandings were about climate change, I would have said the following:

Sea ice is rapidly shrinking (summer arctic sea ice to be gone by 2015)

Sea levels are rising and accelerating

Polar bear populations are under stress (have increased in the last 20 years)

The levels of glacial retreat around the world are unprecedented (similar retreats have been seen in the last century)

97% of scientists agree that global warming is real and an urgent problem

Any scientist who is skeptical about the claims made about climate change is a "denier" and is funded by oil/resource companies

We are seeing an increase in extreme weather events (they are actually getting less common)

Climate models are accurate in their predictions 

Every one of those things is either totally false, or a largely exaggerated claim.

This is the fourth in a series based on my response, which itself was split over a few emails.  The first was Sea Ice Challenge (in which I provided a little more context about JP), the second was Sea Levels Rising and the third was Polar Bears and Climate Change.  Some of the issues may also be touched on in a series of articles on the nature of climate denialism.  Please also note the caveat.

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JP’s Claim: The statement “levels of glacial retreat around the world are unprecedented” is either totally false or largely exaggerated and “similar retreats have been seen in the last century”

It is true that glaciers have been retreating quite some time.  This could be, in part, because the Little Ice Age ended, so it could be said that there was retreat through the 1800s and even through to the mid-1950s that was natural.  And yes, that would mean that there is an element of global warming that could be entirely natural.  However, there has been a noticeable acceleration in recent times:

Over a longer period, the change is quite significant:

Also:

Note that this is a selection of glaciers, across both hemispheres, but it is notable that the New Zealand glacier grew, significantly – by about a kilometre, from the mid-1980s to at least 2000.  This was certainly against the trend, but a glacier that is not in decline would likely attract the interest of a climate denialist).  Except:

All that length gained has been lost and the length gained was only about half that that had been lost since about 1940.

Even though they are still surviving at many kilometres in length (see the scales on each side), glaciers such as these are under attack at both ends.   The lower ends maybe melting slightly more quickly as the average temperature slowly rises, but more significant is the other end, the supply end, where less snow has been available to feed the glacier.

I draw the reader’s attention to the Stocking Glacier, the magenta line in the chart above.  Note that there was a decline to about the mid-1920s.

There wasn’t terribly much that I could find about glacier-based climate denial to justify JP’s claim.  Perhaps there is more out there, but what is out there appears to be based on the notion that “glaciers melted in the past” (Tony Heller (aka Stephen Goddard) and Anthony Watts).

Tony Heller was basing his claim on reports, as early as 1903, that glaciers were disappearing:

No-one is denying this.  There was what is known as the Little Ice Age from about 1300 until about 1850.  During that period the glaciers grew, with one of the Dauphine Alps glaciers, Glacier Blanc, extending down to 1874m above sea level (measured in 1815).  As of 2002, the glacier was just under six kilometres long with an area of 5.34 square kilometres.  This is what it looks like today (2020):

I’ve put on a measurement from Dôme de Neige (the source of the glacier -green) to its greatest extent at 1874m above sea level (blue).  Today the front (or terminus or snout or toe) of the glacier is at 2300m (red).  It’s actually about 250m longer today than it was in 2002 (and 2010) when it was at 2400m (yellow), when it was 5.9km long.  I have no idea how thick it is.

So, the question is, how much could it have been retreating back in 1903?  According to Hervé Cortot and Marcel Chaud in 2005, the glacier retreated one kilometre over the 20th century (Longueur : perte de 1 km au cours du XX^e siècle).  Note that they blame retreat, over the preceding 20 years, on both a lack of snow and strong summer melts.

Note also that in 1983, the terminus was advancing by 30m/year and it appears to have been at about 2500m above sea level:

Clearly there is some variation from year to year, because 30m/year since 1983 would make the glacier 1100m longer.  At 2500m altitude, the glacier would have been 5.5km long, and it’s not 6.6 kilometres long today, it’s about 400m shorter than that.  However, it is recorded that the glacier lost more than 200m in the 90s (1989 to 1999) and another 300m between 1999 and 2006, so there probably was swift advancement between 1983 and 1989 and another period of advancement after that to reach 2400m by 2010 and then another 250m advancement since then.

So yes, using this glacier as an example, there hasn’t been consistent retreat of the glaciers.  Some years they advance, quite quickly (perhaps as much as 50m a year), some years they retreat, quite quickly (about 50m a year from 1999 to 2006).   A consistent loss of fifty feet a day (as claimed in the article) seems a little much.  Perhaps it was meant that, under certain extreme conditions, such as when an ice pool breaks, or a cavity collapses, as much as 15m of glacier can be lost?

What we can say, however, is that – irrespective of the cause – glaciers are in retreat over longer periods of time, even if there might be instances where they advance over the period of a few years.

A recurring feature of certain climate denialists, including Tony Heller, is a great confidence in reporting from the 1800s and early 1900s, despite evidence that such confidence is misplaced.  In the Kansas City paper cutting shown above, it is blithely stated that French glaciers are disappearing at a rate of as much as 50 feet a day.  Four years later, the Brooklyn Daily Eagle reported that there has been “remarkable shrinkings … among the Swiss glaciers” with the Rhone glacier losing “anywhere from 20 to 40 feet” over a period of two years.  If this is “remarkable”, what word characterises 50 feet a day?  I’d suggest that there was a slight inaccuracy in the Kansas City reporting.  That hasn’t stopped Heller from reposting that cutting as recently as 10 Jan 2020 (the first posting referenced appears to be from early 2016).

Finally, Heller insists (as does Watts) on referring to “glaciers melting”.  As Heller says himself, glaciers have been melting for “a very long time” and I would go further to say as long as there have been glaciers, they have been melting.  A glacier is a river of ice that flows from a high (cold) spot to a lower (warmer) spot – especially for alpine glaciers.  An alpine glacier will flow downhill until it reaches an altitude where the air sufficiently warm to melt enough ice to prevent any further advancement (it’s not as simple as being above freezing, since you have the sun interacting with it during the day, and ice melting cools the air immediately around it so it sort of protects itself).

Note in the 1983 diagram above, the 250m deep section was advancing at 50m/year while the terminus was advancing at 30m/year and a section not far from that terminus was only 100m deep (about two thirds of what it was in 1971).  If the whole mass was moving at 50m/year (which is a big if), then there must have been considerable melting going on – 150m worth of thickness and 20m worth of length at a bit under a kilometre wide.  (Of course, it’s not quite as simple as that but the point is that something in the order of 150m*70m*800m ≈ 2.5 million cubic metres of ice was melting from the glacier each year even when it was advancing by 30m/year.)

In polar regions, glaciers calve icebergs which eventually float into warmer water and melt away (although they may spend some time fused into pack ice first – so this could conceivably be a very long time in a small number of instances, but the average lifetime of an arctic iceberg is two to three years, ditto for southern icebergs).

It’s not a problem of glaciers melting, it’s a problem of them retreating, which is indicative of a negative balance between rate of melting and rate of replenishment – so the amount of snow dumped at the source.  There isn’t linear relationship between the amount of snow and temperature – although it is possible for it to be too cold to snow.  The upshot is that, under some weather conditions, a slightly warmer climate may well provide better conditions for large dumps of snow and some glaciers may tend to advance rather than retreat as temperatures rise.  A climate denialist who isn’t too proud to cherry pick could then point at that glacier (and ignore those such as in NZ that are retreating) and say “Look, the climate alarmists are lying to you!”