Global warming from a former petroleum geologist's viewpoint

Kelvin S. Rodolfo

To understand greenhouse warming from human-generated carbon dioxide
requires a proper geological grasp of two things: First, the photosynthesis-respiration cycle, the most important element of Earth's delicately balanced surface environment; second, the enormity of geological time over which the world’s petroleum accumulated, in contrast to the one and a half century during which we have burned half of it.

Photosynthesis transforms sunlight, water and carbon dioxide into hydrocarbons containing stored chemical energy, with a ”byproduct” of free oxygen. The stored energy is released by respiration, whereby animals and fungi power their existence by "burning" the hydrocarbons with oxygen, releasing "waste" water and carbon dioxide, and thus completing the cycle.

The photosynthesis-respiration cycle is very efficient, but small Amounts of hydrocarbons escape respiration by being buried in swamp deposits or in oceanic sediments.

Deep burial of the swamps transforms the organic material into coal. When the oceanic hydrocarbons are buried to depths of about 2 to 5 kilometers, the elevated pressures and temperatures slowly cook them into oil and methane, which migrate upward, being of low density. The petroleum is trapped if it enters the pores in sands or limestones that are enclosed on the top and sides by impermeable rocks.

Given enough time, all coal and petroleum eventually must undergo one of two fates. Either they are buried so deeply that Earth’s internal heat rips the hydrocarbon molecules apart, or uplift and erosion of the carbon-bearing rocks releases the coal and petroleum back into the surface environment. The Canadian and Venezuelan tar sands are oil deposits exposed by erosion that have lost their volatile components.

Natural processes over the great lengths of geological time have achieved a rough balance between carbon storage and release, leaving the global environmental balance essentially undisturbed, leaving a quasi-steady-state amount of carbon stored in Earth’s crust.

Ignoring coal and methane to look only at oil, the best geological estimates are: since about 600 million years ago, when the oldest oil we use was formed, the Earth has stored only about two trillion barrels. On average, this is little more than 3,000 barrels annually.

The most prolific oil-generating period was the 20 million years or so of late Jurassic to mid Cretaceous time, from about 110 to 90 million years ago, when more than half of the world’s oil – including all in the Middle East – was stored. Even during that period, the Earth stored only about 50,000 barrels annually.

At present, Humanity burns about 29 billion barrels a year. That is what the Earth has stored, on average, over about nine million years.

In other words, the carbon dioxide that Nature took out of the atmosphere and tucked away as oil in rocks over nine million years, we return to the air in one year. Over the last one and a half centuries – the blink of an eye in geological terms – we have burned a trillion barrels of oil and have dumped its carbon dioxide waste back into the air.

Even if TWICE as much oil has accumulated in the Earth's crust as our best estimates - a totally unrealistic figure that not even the most wildly optimistic "cornucopians" claim, we would be pumping into the air in one year the carbon dioxide that nature had sequestered in the rocks for over four million years.

Comparable amounts of carbon dioxide are also pumped into the atmosphere by burning coal and methane. To the total 6.5 billions of carbon returned to the air every year, deforestation also adds another 1-2 billion tons.

Thus is Humanity inflicting on Earth's delicately balanced living environment one of the most severe traumas it has ever had to endure. The resulting fever is what we call Anthropogenic Global Warming.

Hurricanes Katrina and Rita may be only tiny symptoms of that trauma.

The Earth occasionally undergoes a severe trauma, such as the impact of
the Chixulub meteorite, ten kilometers in diameter, that 65 million years ago caused massive extinctions of oceanic and terrestrial life including the dinosaurs. Burning a trillion barrels of oil plus an equivalent amount of coal and natural gas in less than two centuries is a geological catastrophe of similar magnitude.

Given enough time after catastrophe, the Earth’s surface environment and its life have always managed to restore equilibrium, including equable temperatures. They will do so again, regardless of whether humankind survives or not.

But such a recovery cannot possibly begin while humanity continues to
accelerate its use of fossil fuels.

Even if we were to stop all fossil-fuel combustion today, it will still take a very long time for our global environment and ecosystems to recover.

Kelvin S. Rodolfo
Professor Emeritus
Dept. of Earth & Environmental Sciences
University of Illinois at Chicago
845 W. Taylor St.
Chicago IL 60607 U.S.A.
(312) 243-8241 or (312) 733-0617
krodolfo@uic.edu