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Sources for the video

Were the glaciers ever smaller before?

Swiss stone pines once grew beneath the Pasterze, so the glaciers were smaller once before. In one minute, set in the Pasterze’s own valley, the video shows why that was so back then and why the ice is going anyway today. These are its sources, statement by statement.

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Video · 1:00 · with sound, in German

What the video shows

The video opens with Gustav Jägermayer’s photo of the Pasterze from 1863, exactly aligned in Google’s 3D of today: in the window the valley jumps between the ice of 1863 and today. In front of the Pasterze, the glacier stream washes out wood and peat thousands of years old, among them trunks of Swiss stone pines. Finds have been made since 1963, and again since 1990; in September 2014 a stone pine trunk 7.9 metres long. Nobody knows exactly where the trees grew: the sources place the sites under today’s ice, up to four kilometres up the valley.

So the glaciers were smaller once before; according to the dating by Kurt Nicolussi and his co-authors, the Pasterze was probably shorter than around 2010 for almost 7,000 years, from about 10,200 to 3,500 years ago. The reason back then was mainly the Earth’s orbit, which gave the summer more sun in the northern hemisphere. About 10,000 years ago, about 9 % more sunlight reached the top of the atmosphere above the Pasterze in mid-July than today, 495 instead of 455 watts per square metre.

Then the Earth’s orbit gave the summer less sun, and over millennia the glaciers grew, with retreats in between. Around 1850 they were larger than at any time in thousands of years; volcanic eruptions and a weak sun also drove that peak. Today the Earth’s orbit gives the summer just as little sun as around 1850, 455.0 against 455.4 watts per square metre. And the ice is going anyway: the window with the 1863 photo returns and jumps to today.

Back then it was mainly down to the Earth’s orbit; not this time. According to the IPCC, solar and volcanic activity have changed the Earth’s temperature since 1850–1900 by only −0.1 to +0.1 °C, while it rose by about 1.1 °C up to 2011–2020, and in Austria by about 2.9 °C up to 2023. That the glaciers have been shrinking since the 1990s is, according to the IPCC, very likely mainly due to humans.

At the end come Austria’s glaciers in their outline of around 1850, with their ice of 2021 to 2023 inside. Together, just under a third of the area is left, as the top of the panel says; 63 % of the Pasterze, half of the Hallstätter Gletscher. The video asks: which glacier is yours? And it thanks reinhardpaulseyer and Erich, whose questions in the comments it answers.

The pictures are real: Google’s photorealistic 3D of today, with the ice edges of the Pasterze around 1850, 1998, 2009 and 2022 from the Austrian Glacier Inventory, and the 1863 photo from the Albertina. The curve of the July sun is our own calculation from the orbital elements of Berger and Loutre 1991; the contour lines behind the final panel come from the geoland.at terrain model. Only the voice and the sound effects are AI-generated.

Sources and image credits

Data

For the film we cropped, converted and redrew the data.

Google 3D

The Pasterze today: the view from the Franz-Josefs-Höhe, where the 1863 photo was taken (at the beginning and at the turning point), the flight above the Pasterzensee up the valley and back to the Margaritze, and the climb over the whole glacier: Google’s photorealistic 3D. In the film the credit stays in the picture for as long as Google’s image is visible: Heute in 3D: Google Maps · Kartendaten: CNES / Airbus, Airbus, Maxar Technologies, Landsat / Copernicus, Data SIO, NOAA, U.S. Navy, NGA, GEBCO

Picture

  1. Gustav Jägermayer (photographer), Johannesberg mit Pasterze von der Franz-Josefs Höhe aus OSO, 1863. Albertina, Vienna, inv. no. Foto2001/22/13. Licence: gemeinfrei (Public Domain). Change: cropped, rotated by 3.13° and adjusted in perspective to Google’s camera, inserted as a window labelled “1863” into Google’s 3D of today, exactly aligned from the same standpoint (the skyline lies 0.1° from Google’s in the median); at the beginning the window jumps back and forth between 1863 and today, at the turning point it returns and jumps to today at “Und das Eis geht trotzdem”.

AI, voice and music

Nothing in the film is painted or animated with AI: the 1863 photo is real, the views of today are Google’s 3D, and the ice edges, the curve and the final panel are drawn from the data. Voice and sound effects are AI-generated: the voice with Gemini 3.8 Flash TTS (“Charon”), the sound effects (glacier stream, high wind, cracking ice) with ElevenLabs. There is no music.

Each statement in the film and its sources

  1. Swiss stone pines once grew beneath the Pasterze.

    Nobody knows exactly where the stone pines grew: all sources place the sites under today’s ice. That is why the film says “beneath the Pasterze”, not “where there was ice until recently”; the lines on screen are the ice edges of 2009 and 2022, not find sites. The two main sources are not fully independent: they partly describe the same finds, and Slupetzky et al. refer to Nicolussi’s tree-ring data.

  2. Now the meltwater is washing out their wood, thousands of years old.

    Finds have been made since 1963, and again since 1990, as the ice retreats. Besides stone pines, Nicolussi and Patzelt also found larch; the film names the stone pine because every source names it.

  3. Yes, the glaciers were smaller once before. But why?

    “Smaller” in the sources means smaller than at the end of the 20th century, than in 1985 or than around 2010. According to the IPCC, the glaciers of the northern hemisphere are in most places still larger today than in the early and middle Holocene (chapter 2, p. 345).

  4. Back then the Earth’s orbit gave the summer more sun, and for almost 7,000 years the Pasterze was probably shorter than in 2009. On screen, the source: “Pasterze wohl kürzer als 2009: Nicolussi u. a. 2020” (Pasterze probably shorter than in 2009).

    “Probably” and “almost” belong to it: the abstract says “probably”, and 10,200 to 3,500 years is 6,700 years. It compares with the extent around 2010; on screen lies the 2009 ice edge from the glacier inventory. No source traces the Pasterze individually back to the Earth’s orbit: the IPCC says it for the glaciers of the northern hemisphere, and the short Pasterze falls into the time of the strong July sun. “Earth’s orbit” stands, as in the IPCC’s “orbital forcing”, for the orbit and the tilt of the Earth’s axis.

  5. Then it gave the summer less, and the ice grew.

    A trend over millennia, interrupted by retreats, for example in Roman times and the Middle Ages. Volcanic eruptions and a weak sun also drove the maximum around 1850; that is why the film does not say the Earth’s orbit caused it, and shows no arrow from the curve to the ice.

  6. Around 1850 the glaciers were larger than at any time in thousands of years.

    Deliberately “the glaciers”, not “the Pasterze”: for the Pasterze alone it is not documented; after the ice age it reached the Margaritze rock at each of ten to twelve maxima (Slupetzky et al. 1998, p. 226). The sentence holds for the glaciers as a whole, not for each one: some earlier advances, in the Alps too, were similar in size to those of the Little Ice Age (Solomina et al. 2016, pp. 82 f.).

  7. Today the Earth’s orbit gives the summer just as little sun as around 1850.

    Our own calculation, checked against two further solutions for the Earth’s orbit; it applies at the top of the atmosphere, without clouds. The film deliberately does not say “as little as in over 10,000 years”: it would be true for mid-July but not for the solstice, and it was just as true around 1850.

  8. And the ice is going anyway. On screen the 1863 photo jumps to today, then the ice edges of 1998 and 2022.

    “Anyway” refers to the sentence before: the same July sun from the Earth’s orbit as around 1850, when the glaciers were at their largest.

  9. Back then it was mainly down to the Earth’s orbit. Not this time.

    “Mainly”, because some phases also fit a stronger sun. The film says “Earth’s orbit”, not “the sun”: the sun itself varied by only about 0.1 % over millennia, the July sun at 47° north by about 9 % because of the orbit. With “the sun” one would hear solar activity, and that does not explain the great minima.

  10. That the glaciers have been shrinking since the 1990s is, according to the IPCC, very likely mainly due to humans.

    The time reference belongs to the retreat, not to the cause: like the IPCC, the sentence says nothing about the time before 1990. “Very likely” is the IPCC’s calibrated level, “mainly” renders “main driver”, i.e. more than half; it refers to the global retreat. The film says “die Gletscher” (the glaciers) rather than “sie” (they), because after the previous sentence “sie” would mean the Earth’s orbit. The two studies feed into the IPCC’s assessment, so they are not fully independent of it.

  11. On screen, the curve “Julisonne aus der Erdbahn” (July sun from the Earth’s orbit): on the left “rund 9 % mehr” (about 9 % more), at its tip a sun with the time below it, from “vor 10.500 Jahren” (10,500 years ago) to “vor 1.000 Jahren” (1,000 years ago), then “um 1850” (around 1850), dashed on to “heute” (today), with “genauso wenig” (just as little) above. Source on screen: “Julisonne: 47° Nord, Ausschnitt, Berger und Loutre 1991” (July sun: 47° north, detail, Berger and Loutre 1991).

    “July sun”, not “summer sun”: the 9 % applies to mid-July; over June to August it is about 6 %, over the summer’s total solar energy about 1 %. The vertical axis is cropped, which is why the source says “Ausschnitt” (detail); the time from 1850 to today is not to scale, hence the dashes. The curve only says “um 1850”, not “maximum”, otherwise one would read a maximum of the sun. The time below the sun counts back from today, rounded to 500 years.

  12. On screen, the box: “Erwärmung weltweit seit 1850–1900: rund 1,1 °C (bis 2011–2020) · davon Sonne und Vulkane: −0,1 bis +0,1 °C” (global warming since 1850–1900: about 1.1 °C, up to 2011–2020; of which solar and volcanic activity: −0.1 to +0.1 °C), source on screen “Weltklimarat (IPCC) 2021”.

    “Weltweit” (global) and the period are on screen so that nobody reads the 1.1 °C as the figure for the Pasterze: Austria has warmed considerably more, by 2.9 °C up to 2023 according to GeoSphere Austria. The IPCC gives the split into solar and volcanic activity only up to 2010–2019, which is why its figure stands with its period, although according to the WMO warming is now 1.34 to 1.41 °C.

  13. On screen, the Pasterze’s ice edges with their years: first “Eisrand 2009” (ice edge 2009) and “2022”, from “und das Eis wuchs” (and the ice grew) also “um 1850” (around 1850), after the jump to today “1998” and “2022”. Source on screen: “Eisränder: Gletscherinventar Österreich” (ice edges: Austrian glacier inventory).

    The years are those in which the inventories recorded the Pasterze. “Around 1850” is the maximum, which falls in a different year for each glacier. The lines lie on Google’s terrain; the year labels sit on their edge with heights from the geoland.at terrain model.

  14. On the final panel, at the top “knapp ein Drittel übrig” (just under a third left), below it Austria’s glaciers in their outline of around 1850 with their ice of 2021 to 2023, and “Gepatschferner 66 %”, “Pasterze 63 %”, “Ochsentaler Gletscher 52 %”, “Obersulzbachkees 52 %” and “Hallstätter Gletscher 50 %”. Sources on screen: “Gletscherfläche Österreichs: Umriss um 1850, Eis 2021 bis 2023” (Austria’s glacier area: outline around 1850, ice 2021 to 2023) and “Daten: Österreichisches Gletscherinventar” (data: Austrian Glacier Inventory).

    “Just under a third”: 285 km² in 2021 to 2023 against 941 km² around 1850 is 30.3 %, or 27.6 to 33.7 % given the accuracy of the area around 1850 (±10 %). The percentages of the five glaciers are our own evaluation of the two inventories: area 2021 to 2023 against area around 1850, each glacier within its outline of around 1850, fragments added up. In the Ötztal Alps, where the Gepatschferner lies, the file for around 1850 contains less area than published, so the value there may be slightly too high.

Literature and sources

How wohnwahn measures