Peak Oil reference list
March 2015
Cartoon swarm of arrows pointing to a graph on gridpaper

By now, you’ve hopefully read my Peak Oil comic about the career of geologist M. King Hubbert.

This blog post is simply a list of reference sources that sit behind the Peak Oil comic.

I expect you will only want to read this post if there is a specific fact or figure that you want to verify.

  • Facts about the API conference and Hubbert’s phone call: “Hubbert’s Speech” (2006) and Hubbert (1989g).
  • Hubbert was “a scientist who cared only for the objective truth”. This statement is not intended as a slight against so-called ‘black hat’ scientists, who were motivated by ill intentions. I intended this more an indication that Hubbert was charting his own course, guided by the best data that he found. Hubbert was doing this with certain insights that others lacked (which was not the fault of the other scientists).
    Doel (2006) says Hubbert wanted the freedom to pursue research and “draw whatever conclusions the facts led to”. Hubbert (1989h) said whilst working for the USGS “my first loyalty was to the American taxpayer”.
  • Facts about Hubbert’s birth and journey to Chicago: Hubbert (1989a), “Biography: Hubbert, Marion King” (2008, pp. 395–6), Hubbert (2006).
  • ‘Half-tonne rails’ used by Union Pacific Nebraska: Rails of the 1920s-era weighed 90 lbs/yd (source: personal correspondence with Piers Connor from Piers also stated it is likely that the Union Pacific rails were 33ft long during this time. So each rail would have been 449.1kg heavy (“Wolfram Alpha”, n.d.). i.e. roughly half a tonne.
  • Hubbert’s university subjects and majors: Hubbert (1989a), Hubbert (1989b), Hubbert (2006), Clark (1983).
  • Description of the University of Chicago Economic Geology subject and the class’s discussion of freight hauled by railways: Hubbert (1989b), Clark (1983).
  • A shovelful of coal weighing 11 kilograms. Derived from Dahl (2011): a shovelful of coal weighing “about 25 pounds.” Converted to metric via Wolfram Alpha.
  • The condensed energy in an 11kg shovelful of coal equalling 150kg of fossilised plant matter. See my working in ‘calculations’ section (below).
  • Oil as ‘ancient sunshine’. More info about the chemical formation of oil in Hopkins (2009, pp. 8–10).
  • Coal growing at an exponential rate. From Hubbert (1989b)’s recollections, though he personally describes the phenomenon as ‘logarithmic’, despite his comments suggesting exponential growth.
  • Immediate summer job with Amerada Petroleum Corporation: Hubbert (1989b), Clark (1983).
  • Energy density of coal and oil (27 MJ/kg and 45 MJ/kg): Staffell (2011, p. 2: higher heating values used). Oil was an energy-density step above coal: Hallett and Wright (2011, pp. 15–16).
  • Oil was comparatively easy to extract and often pressurised: Heinberg (2011, pp. 158–9).
  • Examples of the ways oil has boosted our lifestyles (plastics, air travel, agriculture, etc): Hallett and Wright (2011, p. 82), Heinberg (2003, p. 66), Heinberg (2004, pp. 1–5), Heinberg (2011, p. 106) .
  • Hubbert’s job running the Shell research laboratory: “Biography: Hubbert, Marion King” (2008, pp. 396–7), Hubbert (2006), Hubbert (1989d), Clark (1983).
  • Hubbert’s 1956 oil forecasting method improved on standard techniques of the industry: “Biography: Hubbert, Marion King” (2008, pp. 397–8).
  • King and Miriam Hubbert’s trip from Houston to San Antonio: Strang (1955) and Hubbert (1989g).
  • Geophysical factors make an oil well’s production rate impossible to maintain. Hubbert (1989g) said: “you can’t possibly keep that up”.
  • Pennsylvania was on the ‘decline side’ of its oil production curve. Refers to the fact that Pennsylvania had two peaks (1891 and 1937) and then a decline in production by the time of Hubbert’s 1956 study. From Hamilton (2010) and “Pennsylvania” (2000).
  •  “The oil that fuels our economy behaves differently to the oil that fuels our cars”: Hopkins (2009, p. 8).
  • King and Miriam Hubbert getting mobbed by journalists at their hotel: Hubbert (1989g). This incident really happened, but probably didn’t occur in the dramatic ‘media scrum’ way that I depicted!
  •  “Hubbert’s views about the bell-shaped nature of oil production were known prior to the conference.” Hubbert publicly challenged the estimates of petroleum geologist A. I. Levorsen at a United Nations meeting in 1949: Hubbert (1989f). Because of this, Hubbert’s assertions appeared on the front page of the New York Times the following day Clark (1983).
  • Hubbert knew that mathematically “the curve had to, eventually, return to zero”. This “limited his options”: Hubbert (1976, pp. 120–2), Hubbert (1989g), (Clark (1983).
  • Chose the best reserve estimates “on geological merit”. In 1956 he plotted two scenarios for the ‘high’ and ‘low’ estimates of 150 and 200 billion barrels of oil: Hubbert (1989g), Clark (1983). In 1962 Hubbert used a single ‘best estimate’ of 170 bbl: “Biography: Hubbert, Marion King” (2008, p. 398), Clark (1983).
  • “The American roller coaster had started being built in 1859”. Oil was first drilled commercially in the United States in the state of Pennsylvania in 1859: Heinberg (2003, p. 57) and Hubbert (1976, p. 115).
  • Hubbert gave date range for U.S. Peak Oil occurring “between 1966 and 1971”: “Biography: Hubbert, Marion King” (2008).
  • Most geologists accepted Hubbert’s Peak Oil prediction: “Biography: Hubbert, Marion King” (2008, p. 398) and Hubbert (1989g).
  • Some oil industry executives and U.S. Geological Survey staff did not accept Hubbert’s analysis: “Biography: Hubbert, Marion King” (2008, p. 398) and Hubbert (1989g). Hubbert’s 1989 interview with Doel goes into extensive detail about the aftermath and rival forecasts. Hubbert describes the oil industry as splitting into two camps. One group accepted the figures and realised they couldn’t change or disguise them. The other camp refused to accept the statistics and dodged reality by postulating inflated oil estimate figures. Vincent McKelvey from USGS quickly backed the inflated Zapp estimates once released (see below).
  • Oil depletion being “a vague concept for grandchildren to worry about” Hubbert (1989g) claimed that up until his API presentation the industry’s ‘stock answer’ was that the U.S. had all the oil it needed for the foreseeable future. His 1956 paper forced the industry to re-evaluate this supposition.
  • Rival forecasts were ‘written by economists’: “Biography: Hubbert, Marion King” (2008, p. 398) and Hubbert (1989g). Examples cited of alternative forecasters: Morgan Davis & Richard J. Gonzalez from Humble Oil and Bruce Netschert. Hubbert also noted that non-profit organisation Resources for the Future is primarily staffed by economists. (Note that A.D. Zapp, whose paper is shown on this page, was a geologist, not an economist.)
  • “Grossly inflated American oil reserves”: “Biography: Hubbert, Marion King” (2008, p. 398). Hubbert (1989g) noted that Bruce Netschert (1958) deliberately inflated his estimates by always using the higher figures from ranges of uncertainty. A.D. Zapp’s 1961 figure of 590 billion barrels was dramatically higher than the accepted range of 150-200 bbl. Udall (2006) recalled King Hubbert describing this process as “armchair discoveries” of “paper barrels” leading to inflated reserve estimates.
  • “Speculative assumptions about future oil discoveries in areas where oil was unlikely to be found”: Hubbert (1989g) noted that Bruce Netschert (1958) assumed that oil could be drilled from a depth of 65,000 feet when the current proven drilling depth was less than 25,000 feet. Zapp’s 1961 ‘volumetric yield’ technique extrapolated the oil production yields of well-explored, oil-rich parts of the U.S. to other unexplored parts of the U.S. (which would later be shown to oil-poor by comparison).
  • “Hubbert knew that history, not PR, would truly test his theory”: Hubbert (1989i) described his approach as like that of Galileo. In other words: let the experiment itself show the results.
  • U.S. contiguous oil production peaked in 1971: “Biography: Hubbert, Marion King” (2008, p. 398). ‘Contiguous U.S.A.’ is a term referring to the ‘lower 48 states’ of America. Alaska and Hawaii did not become U.S. states until 1959, after Hubbert published his 1956 API paper.
  • Globally, fewer and fewer barrels discovered every year since the mid-1960s: Heinberg (2003, p. 38), Hallett and Wright (2011, p. 122), Gilding (2011, p. 124) and Heinberg (2011, p. 111) state that discoveries peaked around 1963. Hubbert (1989g) stated that the peak of discoveries was “a clue of how close you were to the peak of production”.
  • Energy density of grasses eaten by livestock while grazing. Estimates include: a range from 6.5-10 MK/kg (Meat & Livestock Australia, 2006, p. 15), 7-13 MJ/kg (DEPI Victoria, 2014), 10.5-12 MJ/kg (Tried & Tested, 2013, p. 7). In the comic, I used the range of 7-12.
  • Energy density of firewood. Range of 18.4-20 MJ/kg (AIEL – Italian Agriforestry Energy Association, 2008, p. 24), 15.5-22.5 MJ/kg (“Fact Sheet 5.8: Energy Basics,” 2008, p. 189), 17.1 (Rodrigue, 2004). In the comic I used the range of 17-20.
  • Energy alternatives are unlikely to match “oil in its heyday”: Heinberg (2004, pp. 19–20), Heinberg (2011, pp. 159–61), Hallett and Wright (2011, p. 176). In other words, we will be moving to substitute fuels which are less compact and less energy-dense than oil. I use the term “heyday” to refer to the boom-era of the oil industry, when drilling was relatively cheap and easy. We may choose to turn to ‘unconventional oil’ sources, but they are relatively expensive and energy-intensive to refine.
  • From the peak of fossil fuels, we must transition to “a civilisation fuelled by a lower level of energy”: Hubbert (1976, pp. 124–6) saw that we needed cultural adjustment post-Peak Oil.
  • Hubbert’s chart extended 5,000 years in both directions was published in Hubbert (1976, p. 124). In that paper, Hubbert described its appearance as “a Washington Monument-like spike. Representing one of the most disturbing influences ever experienced by the human species in its entire biological existence”.
  • “Peak Oil is not about ‘running out of oil’.” & “The problem of Peak Oil occurs not at ’empty’, but at ‘half-empty’” sourced from: Hopkins (2009, p. 10), Heinberg (2011, p. 107),(Hallett and Wright (2011, pp. 17, 120, 229).
  • “There is no doubt that global Peak Oil will certainly happen”: Heinberg (2011, pp. 107–10), Ivanhoe (1997, p. 1), Hallett and Wright (2011, p. 17).
  • “It is likely that the track today is about as high as it will ever be”: Heinberg (2007, pp. 3–4), Heinberg (2009, p. abstract). Hallett and Wright (2011, pp. 122, 124, 244) point out that, without us noticing, many of our record-breaking achievements like lunar missions, land-speed records, etc are decades behind us.
  • We won’t be certain we’ve passed the peak until we see it over our shoulder: Hallett and Wright (2011, p. 247).
  • We can’t change the past, we can only change the future: Gilding (2011, p. 3).
  • “Half the oil is gone. Half the oil is left”: Heinberg (2004, p. 19).


My Peak Oil comic includes some unique statistics that I calculated to suit the specific purposes of my comic. My calculations stem from the logic behind the paper “Burning Buried Sunshine: Human Consumption of Ancient Solar Energy” (2003) by Jeffrey S. Dukes. I adapted the paper’s figures for my purposes in consultation with Prof. Dukes via personal correspondence.

Coal calculations:

Assumption 1: the ‘ancient plant matter’ in question is 50% carbon.
Assumption 2: The contemporary ‘coal’ in question is medium rank bituminous coal. Composition: 86% carbon.
Assumption 3: 13% of the original plant carbon remains after being geologically converted from vegetation into coal. [Taken from Dukes (2003, p. 34): “the average of these products is 13%”].
This is the ‘preservation factor’ (PF) of fossil fuel-precursor into the final fossil fuel.

  • Start with 1 tonne of bituminous coal
    Bituminous coal is 86% carbon
  • 1 x 0.86 = 0.86 tonne of carbon.
    This carbon is only 13% of the original plants’ carbon.
  • 0.86 ÷ 0.13 = 6.62 tonnes (this is the mass of the original carbon precursor, before reduction during the coalification process).
    Plant matter is 50% carbon so we double this to get mass of original plant matter
  • 6.62 x 2 = 13.2 tonnes original plant matter.

This approximate 1:13 ratio allows us to make the following statement on page 18:
“Each 11 kg shovelful of coal held the condensed energy of about 150 kg worth of fossilised plant matter.”

Oil calculations:

Assumption 1: the ‘ancient plant matter’ in question is 50% carbon.
Assumption 2: The contemporary ‘oil’ in question is 85% carbon.
Assumption 3: 1.4% of the original plant carbon remains after being geologically converted from vegetation into crude oil. This is adjusted figure from Dukes, (2003, p. 35), chosen in consultation with Dukes via email correspondence. Instead of using the “2%” figure quoted in his paper, I use 1.4%
This incorporates both the ‘preservation factor’ (PF) of fossil fuel-precursor into the final fossil fuel, and the ‘genetic potential’ of the types of kerogen generated in each setting

  • Start with 1 tonne of contemporary crude oil
    Crude oil is 85% carbon
  • 1 x 0.85 = 0.85 tonne of carbon.
    This carbon is only 1.4% of the original plants’ carbon.
  • 0.85 ÷ 0.014 = 60.7 tonnes (this is the mass of the original carbon precursor, before reduction during the oil maturation process).
    Plant matter is 50% carbon so we double this to get mass of original plant matter
  • 60.7 x 2 = 121 tonnes original plant matter. Therefore we can say:

Each tonne of crude oil held the condensed energy of about 120 tonnes of fossilised plant matter.”

Note that I refer to dry weights with my coal and oil conversion calculations. e.g. the weight of the ancient vegetation matter, excluding the water in the living tree’s issue.

If I had chosen to use wet weights, the conversion factors would have been larger: roughly 2x higher for coal, and 4x higher for oil.

Sources listed above: