Robert Giegengack
Credentials
- PhD, Geology, Yale University (1968).1โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
- MS, Geology, University of Colorado (1962).2โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
- BA, Geology major, Yale University (1960).3โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
Background
Robert Giegengack is an emeritus professor and former chairman of the Earth & Environmental Science department at the University of Pennsylvania.4โEmeritus Faculty,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/cneTH 5โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
A February 2007 profile in Philadelphia Magazine described Giegengack as a โrelatively obscure geologist who taught more than he publishedโ who later โstepped into the swirling tempest surrounding global warming, in part because he says itโs not even one of the top 10 environmental problems we face.โ6โAl Gore Is a Greenhouse Gasbag,โ Philadelphia Magazine, February 2007. Archived February 26, 2007. Archive URL: https://archive.is/67OPh
The following was Giegengackโs profile accompanying his appearance in the first Climate Hustle movie by Marc Morano and the Committee for a Constructive Tomorrow (CFACT):7โBackground on Key Scientists Appearing in Climate Hustle,โ Climate Hustle. Archived August 15, 2019. Archived .pdf on file at DeSmog.
โGeologist Dr. Robert Giegengack, chaired the Department of Earth and Environmental Science at the University of Pennsylvania for 12 years. Has done field research on six continents, conducted peer-review studies on the geological archives of climate and spent much of his academic career doing field work on the history of climate. Authored 200 peer-reviewed papers. Giegengack: โCO2 is not the villain that it has been portrayed.โ
According to his archived profile at the University of Pennsylvania, Giegengack has been a geology professor at both Yale University and the University of Pennsylvania. From 1975 to 1976 he worked as a Geologo Asesor (Geologist/Advisor) to the Ministry of Energy and Mines at the Government of Venezuela ( Ministerio de Energia y Minas, Republica de Venezuela).8โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
A search of Google Scholar suggests most of Giegengackโs scientific publications appear to be in the area of geology or geoarchaeology.9โRobert Giegengack,โ Google Scholar. Accessed September 24, 2020. Archive.fo URL: https://archive.fo/r5M7v
CFACT features Giegengack in its sequel, Climate Hustle 2, which premiered in September 2020. Between 1998 and 2007, CFACT has received at least $582,000 from oil giant ExxonMobil. In 2019, CFACT was also named as a creditor in Murray Energy‘s bankruptcy filings.10Lee Fang. โCOAL GIANT PROVIDED SECRET FINANCING TO GROUP CHALLENGING CLIMATE LAWSUITS,โThe Intercept, December 17, 2019. Archive.ph URL: https://archive.ph/hUjRt
Stance on Climate Change
November 11, 2019
In an article at Marc Moranoโs Climate Depot, Giegengack outlined his โkey pointsโ on climate change:11Marc Morano. โProminent Geologist Dr. Robert Giegengack dissents โ Laments โhubrisโ of those who โbelieve that we can โcontrolโ climate โ Denounces โsemi-religious campaignโ,โ Climate Depot, November 11, 2019. Archived September 24, 2020. Archive.fo URL: https://archive.fo/wip/X4n0j
- โGlobal Warming/Climate Change began as a scientific discussion. It has evolved into a polarizing political argument (whenever a scientific understanding depends on a โconsensusโ, we know it has become political), and from there to a semi-religious campaign advanced by well-intended people who feel, deep in their hearts, that they are โsaving the planetโ. Many of those people have chosen to allow their good intentions to override their scientific objectivity. As soon as people who disagree about scientific conclusions start calling each other pejorative names, we know that the discussion has become primarily political, not scientific.
- โI know the work of [MITโs Dr. Richard] Lindzen, [Climatologist Dr. Roy] Spencer, [Georgia Tech Climatologist Dr. Judith] Curry, [Climatologist Dr. John] Christy, [Princeton Physicist Dr. Will] Happer, etc. I share the skepticism that these people have expressed that anthropogenic CO2 emissions represent the primary driver of the climate change now under way.
- โWe know that the climate โwarmedโ, with a few unexplained reversals, from ~18,000 years ago until ~1830 AD, as a consequence of factors that have controlled climate for all of Phanerozoic time. It defies the imagination to suggest that those factors abruptly ceased to operate ~300 years ago just to accommodate our need to attribute contemporary climate change to human activity.
- โIt beggars the imagination to assert that the natural factors that drove the warming trend from 18,000 years ago to ~300 years ago (with some unexplained temperature reversals) abruptly stopped operating at the end of the Little Ice Age to accommodate our political need to attribute climate variability to human industrial activity.
- โClimate models are instructive, but they lead to scenarios, not predictions. They can be manipulated to yield desired outputs.
- โRemoving the groundwater contribution, not directly the consequence of climate change, yields a rate of global sea-level rise that is the slowest in the last 18,000 years. In prior โinterglacialโ times, most recently to ~125,000 years ago, global sea level rose to levels higher than the present sea level, and no humans were burning fossil fuels.
- โWe run an insidious risk: When/if a) we learn that anthropogenic CO2 is not the primary driver of contemporary climate change; b) we drastically reduce anthropogenic output of CO2 and the climate does not respond as we have predicted; or c) we enter a period of unexplained cooling, as the mid-20th-century cooling episode, or the Little Ice Age, the credibility of climate scientists will be dashed, and with it the credibility of any scientist who tries to inform environmental policy via rigorous science.โ
December 7, 2015
Giegengack was featured in Climate Hustle, a film produced by the Committee for Constructive Tomorrow (CFACT) and Marc Morano. Below are some of his comments from the movie:12Climate Hustle (2015) video on file at DeSmog.
On the 97 percent consensus around man-made climate change, Giegengack commented:
โThat’s a marketingโฆ that’s an advertising ploy. I don’t think it means anything. I don’t think 97 percent of the people who look at the climate data critically share the opinion that anthropogenic emissions of CO2 is a primary driver of climate.โWhen asked โis carbon dioxide the control knob [for climate change],โ Giegengack responded:
โI don’t see anything in the long-term geologic record to support that conclusion. CO2 is one of many, many, many variables that influence the Earth’s temperature.โ
Morano: โAre you afraid of rising CO2 concentrations?
Giegengack: โNo. No I’m not. CO2 is not the villain that it has been portrayed.โ
He later suggested climate is colder than it’s ever been:
โI’m impressed by the fact that the present climate, from the perspective of a geologist, is very close to the coldest it’s ever been. The concentration of CO2 in the atmosphere today is closest to the lowest it’s ever been.โ
On Al Gore:
โI voted for [Al] Gore in 2000, yea. And I think that if he ran again, depending on who he ran against, I might vote for him. He’s a smart man.โ
Hover, regarding Gore’s film An Inconvenient Truth, Giegengack said:
โ[cuts inโฆ] I was appalled. I was appalled because he either deliberately misrepresented the point it was making, or didn’t understand it. So it was irresponsible of Al Gore [cuts off]โ
October 26, 2007
Giegengack was quoted in a speech by Oklahoma senator Jim Inhofe as saying:13โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
โThe driving mechanism is exactly the opposite of what Al Gore claims, both in his film and in that book. It’s the temperature that, through those 650,000 years, controlled the CO2CO2 that controlled the temperature.โ
May/June 2007
Giegengack was interviewed in an issue of The Pennsylvania Gazette, the alumni magazine for the University of Pennsylvania. During the interview, Giegengack voiced his displeasure about Al Gore’s film, An Inconvenient Truth.14โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
โIโm just unhappy about the way Gore presented it,โ he said. Giegengack claimed Gore produced โa political statement [that] has to go head-to-head with what comes out of Washington or the American Petroleum Institute.โ15โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
According to the Gazette’s Carter Johns, โGiegengack contends that natural warming periods in our planetโs past have triggered the release of CO2 into the atmosphere from ocean- and land-based reservoirs, and that the most significant consequence of human fossil-fuel consumption is that we have altered that balance by pouring CO2 into the atmosphere and those terrestrial reservoirs simultaneously. Since that relationship has been disturbed, he says, even a drastic reduction in CO2 pollution may not restore the natural dynamic.โ16โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
Below are some of the questions and answers from that interview:
Q: What is your assessment of the threat global warming poses to the environment?
A: There are plenty of environmental problems out there; most of them are the consequence of a lot of people using a lot of energy. Global warming is a symptom of that fundamental problem. Itโs one of many symptoms; itโs not the most severe. In terms of its capacity to cause the human species harm, I donโt think it makes it into the top 10.
Q: What problem do you have with Goreโs film?
The advocates of change are now appealing to fear as brazenly as the proponents of business-as-usual. [The latter] tell us we canโt afford to cut back on our carbon emissions because it would destroy the economy. The other side says the world is going to hell and the polar bears are drowning. Both are extreme positions. Scientists have gotten tied up in this political argument because they were frustrated that the politicians werenโt paying attention to what they said. In order to make the message more apparent to the public, theyโre exaggerating the risks. An Inconvenient Truth is a prime example.
Q: What are some examples of these misleading statements?
A: He claims that temperature increases solely because more CO2 in the atmosphere traps the sunโs heat. Thatโs just wrong โฆ Itโs a natural interplay. As temperature rises, CO2 rises, and vice versa. Variations in planetary alignment are most likely responsible โฆ When gravitation from other planetsโ orbits causes the Earth to move closer to or further from the sun, temperatures increase or decrease. When we find that CO2 levels follow that directly, itโs hard for us to say that CO2 drives temperature. Itโs easier to say temperature drives CO2.
Q: What response have you gotten about your thoughts on the film?
A: People appreciated that I was drawing attention to the weaknesses in the film. Al Gore missed out on a really terrific opportunity with his name recognition, his access to these resources, and his pretty good understanding of climate processes. He could have put together a film that would have presented this problem in a rational context, and that would have been an enormous contribution. But he has abandoned the credibility of the scientific establishment. He missed the point in studying the cycles from prior periods, and he missed the point that it is the temperature that controls the CO2. Now, we have probably changed that because of the excess CO2 in the atmosphere, and we know or suspect that because we know we have reversed the flux. Thatโs probably the most significant finding: that we changed the way those systems operate. (Emphasis added).
Q: So itโs not that Gore is wrong, but that he portrayed the โcrisisโ inaccurately?
A: He focused on fear. CO2 may make this change, but weโd like to be sure of that. And even if it does, he didnโt offer any solution, and neither has anybody else. He ignored the real threat, which is India and China, and he ignored other more immediate environmental problems.
Key Quotes
February 2007
โFor most of Earth history the globe has been warmer than it has been for the last 200 years. It has only rarely been cooler,โ Giegengack said during an interview for Philadelphia Magazine.17โAl Gore Is a Greenhouse Gasbag,โ Philadelphia Magazine, February 2007. Archived February 26, 2007. Archive URL: https://archive.is/67OPh
Date Unconfirmed
โNone of the strategies that have been offered by the U.S. government or by the EPA or by anybody else has the remotest chance of altering climate if in fact climate is controlled by carbon dioxide,โ Giegengack was quoted by Marc Morano at Climate Depot.18โTrump ignores Goreโs advice, instead picks skeptic to head EPA & dismantle climate agenda,โ Climate Depot, December 7, 2016. Archived September 23, 2020. Archive URL: https://archive.vn/ua5o4
Key Deeds
September 24, 2020
Giegengack appeared in Marc Moranoโs 2020 film Climate Hustle 2: Rise of the Climate Monarchy, produced by the Committee for a Constructive Tomorrow (CFACT). He questioned the scientific consensus on the causes of climate change, stating:19Climate Hustle 2: Rise of the Climate Monarchy. CFACT/ CDR Communications, Inc., 2020
โyou don’t find strong empirical support for the idea that atmospheric concentrations of CO2 are the primary drivers of atmospheric temperature and global climate.โ
In reference to the consensus among scientists on man-made global warming, Morano asked Giegengack: โare 97% of your colleagues against you?โ to which he responded:
โI think the people with a geologist’s perspective on the history of climate do not share the consensus that anthropogenic emissions of CO2 are the primary driver of climate.โ
December 7, 2015
Robert Giegengack appeared in the first Climate Hustle movie, which made its world premiere in Paris, France during the United Nations COP21 climate summit. Other โKey Scientistsโ featured in the first Climate Hustle included:20โBackground on Key Scientists Appearing in Climate Hustle,โ Climate Hustle. Archived August 15, 2019. Archived .pdf on file at DeSmog.
- Patrick Moore
- Judith Curry
- Richard Tol
- Ivar Giaever
- Roy Spencer
- Don Easterbrook
- Bob Carter
- Patrick Michaels
- Christopher Monckton
- Anthony Watts
- Walter Cunningham
- William Briggs
- Roger Pielke Sr.
- Caleb Rossiter
- Daniel Botkin
- John Theon
- Dennis Rancourt
October 26, 2007
Giegengack’s work was cited in a floor speech by Republican senator from Oklahoma, Jim Inhofe, given to the U.S. Senate Committee on Environment & Public Works. In the speech, entitled โGlobal Warming Alarmism Reaches A Tipping Pointโ, Inhofe stated:21โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
โPerhaps the most scathing indictment of the โmore CO2 equals a warmer worldโ simplicity comes from Ivy League geologist Dr. Robert Giegengack, the chair of Department of Earth and Environmental Science at the University of Pennsylvania. Giegengack voted for Gore in 2000 and says he would do so again, but he is appalled by Gore’s ignorance of climate science.22โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
He tells his undergraduates: โEvery single one of you knows more about [global warming] than Al Gore.โ23โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
Giegengack said: โ[Gore] claims that temperature increases solely because more CO2 in the atmosphere traps the sun’s heat. That’s just wrong โฆ It’s a natural interplay.โ He continued, โIt’s hard for us to say that CO2 drives temperature. It’s easier to say temperature drives CO2.โ24โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
โThe driving mechanism is exactly the opposite of what Al Gore claims, both in his film and in that book. It’s the temperature that, through those 650,000 years, controlled the CO2CO2 that controlled the temperature,โ he added.25โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
Now this might be a bit technical, but what Giegengack is saying here is that it is temperatures that control CO2. This is crucial to understanding the reason why the scientific underpinnings of man-made global warming fears are utterly collapsing and the climate models are continuing to fail.โ26โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
Affiliations
- University of Pennsylvania โ Emeritus professor and former chairman of the Earth & Environmental Science department.27โEmeritus Faculty,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/cneTH 28โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- Yale University โ Geologist, Yale University Prehistoric expedition to Nubia, Egypt, 1963-67. Acting instructor, Yale University Geology Department, 1966-67. Assistant in Research, Peabody Museum of Natural History (1967โ1968).29โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- Ministry of Energy and Mines at the Government of Venezuela ( Ministerio de Energia y Minas, Republica de Venezuela) โ Geologo Asesor (Geologist/Advisor), 1975-76.30โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- Institute of Environmental Studies at the University of Pennsylvaniaโ Co-Director, 1992-1998.31โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
Social Media
Publications
A search of Google Scholar shows most of Giegengackโs scientific publications appear to be in the area of geology or geoarchaeology.32โRobert Giegengack,โ Google Scholar. Accessed September 24, 2020. Archive.fo URL: https://archive.fo/r5M7v
Giegengack has 56 publications listed at Researchgate.33โRobert Giegengack,โ ResearchGate. Archived September 24, 2020. Archive.fo URL: https://archive.fo/064C6
His archived profile at the University of Pennsylvania also lists publications, including a piece on sunspots published in Geophys. Res. Letters.34โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
Other Resources
Resources
- 1โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
- 2โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
- 3โPeople: Robert Giegengack,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/5o6mi
- 4โEmeritus Faculty,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/cneTH
- 5โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 6โAl Gore Is a Greenhouse Gasbag,โ Philadelphia Magazine, February 2007. Archived February 26, 2007. Archive URL: https://archive.is/67OPh
- 7โBackground on Key Scientists Appearing in Climate Hustle,โ Climate Hustle. Archived August 15, 2019. Archived .pdf on file at DeSmog.
- 8โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 9โRobert Giegengack,โ Google Scholar. Accessed September 24, 2020. Archive.fo URL: https://archive.fo/r5M7v
- 10Lee Fang. โCOAL GIANT PROVIDED SECRET FINANCING TO GROUP CHALLENGING CLIMATE LAWSUITS,โThe Intercept, December 17, 2019. Archive.ph URL: https://archive.ph/hUjRt
- 11Marc Morano. โProminent Geologist Dr. Robert Giegengack dissents โ Laments โhubrisโ of those who โbelieve that we can โcontrolโ climate โ Denounces โsemi-religious campaignโ,โ Climate Depot, November 11, 2019. Archived September 24, 2020. Archive.fo URL: https://archive.fo/wip/X4n0j
- 12Climate Hustle (2015) video on file at DeSmog.
- 13โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 14โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
- 15โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
- 16โAn Inaccurate Truth?โ The Pennsylvania Gazette (May/June 2007). Archived September 23, 2020. Archive URL: https://archive.vn/MoKA0
- 17โAl Gore Is a Greenhouse Gasbag,โ Philadelphia Magazine, February 2007. Archived February 26, 2007. Archive URL: https://archive.is/67OPh
- 18โTrump ignores Goreโs advice, instead picks skeptic to head EPA & dismantle climate agenda,โ Climate Depot, December 7, 2016. Archived September 23, 2020. Archive URL: https://archive.vn/ua5o4
- 19Climate Hustle 2: Rise of the Climate Monarchy. CFACT/ CDR Communications, Inc., 2020
- 20โBackground on Key Scientists Appearing in Climate Hustle,โ Climate Hustle. Archived August 15, 2019. Archived .pdf on file at DeSmog.
- 21โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 22โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 23โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 24โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 25โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 26โPart 2: 2007: Global Warming Alarmism Reaches A Tipping Point,โ U.S. Senate Committee on Environment & Public Works, October 26, 2007. Archived September 23, 2020. Archived .pdf on file at DeSmog.
- 27โEmeritus Faculty,โ Department of Earth & Environmental Science at Penn State University. Archived September 23, 2020. Archive URL: https://archive.vn/cneTH
- 28โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 29โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 30โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 31โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X
- 32โRobert Giegengack,โ Google Scholar. Accessed September 24, 2020. Archive.fo URL: https://archive.fo/r5M7v
- 33โRobert Giegengack,โ ResearchGate. Archived September 24, 2020. Archive.fo URL: https://archive.fo/064C6
- 34โROBERT GIEGENGACK,โ Department of Earth and Environmental Science at the University of Pennsylvania. Archived October 7, 2000. Archive URL: https://archive.is/LV53X