Taking Stock: What Do All These Large Numbers Mean?

When the debate on drilling in the Alaska National Wildlife Reserve (ANWR) picked up around the year 2000, I was informed by a Texan that there were 900 billion gallons of oil in the ANWR. (Turns out that is the estimated amount of oil-in-place, not the ultimate recovery, which is far less.) Since such numbers are normally expressed in barrels, I wondered who had published this number and what their agenda was? It occurred to me that any reasonable fact could be obscured by picking units of measure which virtually no one can grasp. Example: The length of a football field is (exactly) 914.4 Giga-Ångstroms. That's 914 Billion Ångstroms. The calculations:

One credible estimate of the ultimate amount of conventional (pumpable) oil on the earth is 1,750 Gb (billion barrels). What does that mean?

1,750 Gb, the estimate of all the conventional oil that there ever was or ever will be, is less than the amount of sunlight that intersects the earth in one 24 hour day. (This is not to say that all of the solar energy that intersects the earth hits the earth’s surface. The earth’s atmosphere absorbs and reflects a large portion of that solar energy. The point is to provide readers with a sense of the scale of the solar resource.)

In the short term view of one year, the total global annual consumption of energy (400 quads) is roughly equivalent to 40 minutes of sunlight:

Some people say that "solar" is a diffuse, insignificant source of energy. How long would humanity survive if we had only oil to heat the earth?!

[Note: 49 million mi^² is the area of the earth -- at 7,918 miles diameter -- intersecting the sun's light.]

Global Solar Energy Balance1	Amount in Terawatts
Solar Energy Input	178,000
Reflected to Space Immediately	53,000
Absorbed and Then Reflected as Heat	82,000
Used to Evaporate Water (Weather)	40,000
Captured by Plant Photosynthesis (Net Primary Productivity)	100
Total Energy Used by Human Society	102
Total Energy Used by US Society	2.5
Total Human Food Energy	0.6

• These figures are from: Ged R. Davis. Energy for planet earth. Scientific American. September, 1990, p. 55-62. They give the rate at which energy is used. A terrawat is 1,000,000,000,000 watts or 10^12 watts.
  
• As of the study in 1990. In 2005 that figure had risen to 13 TW.
• The "bottom lines" from these figures:
  • most of the solar energy is rapidly reflected back into space
  • a large proportion goes to evaporate water in the weather cycle
  • most of the energy we use comes to us through plant photosynthesis: about 100 terrawatts
  • society is using energy at a rate ~ 10% of photosynthesis (most of this energy -- perhaps 85% -- comes from past photosynthesis- fossil fuels)
  • the US uses 25% of the energy captured by society

Cited by Ecology 10 Tutorial, Lecture 4: Physical Background: Energy, Frank Orme, Instructor

See also:

• zebu.uoregon.edu/1999/phys161.html
• www.foundationwebsite.org/canam4x.htm
• Fundamentals of Thermodynamics by Thomas L. Wayburn, based on work by Dave Bowman, PhD, Professor of Physics, Georgetown College, Georgetown, Kentucky

  "Dave Bowman, a physicist at Georgetown College ... has provided nearly every theoretical idea worth considering in this attempt to get an availability balance around the entire Earth..."

1,750 Gb of oil is equal to 67 cubic miles. The (conventional) oil already consumed globally, plus all the oil yet to be consumed, could be fit into a cube slightly over 4 miles on a side!

If spread over the entire surface of the earth -- land and oceans combined -- 1,750 Gb of oil would constitute a layer 21.5 mils thick -- about the equivalent of a spark-plug gap!

On the other hand, the USA population consumes its entire weight in oil every week!

revised 2004 December 8
revised 2004 September 6
previously revised 2000 August 7