Methane Catastrophes in Earth's Past and Near Future




Permian Period. Texas, about 280 million years ago. In a small ox-bow lake, Orthacanthus, a large shark, lurks in shallow water to attack Eryops, a tetrapod related to frogs and salamanders. The enigmatic lepospondyls consist of the terrestrial microsaur Pantylus crawling on a log and the boomerang-skulled Diplocaulus swimming below. The aquatic anthracosaur Cricotus, a large, crocodile-like predator on the right, is related to the more terrestrial Diadectes seen in the far left background.
Painting by Robert J. Barker, 1996. American Museum of Natural History.


Dan Dorritie

Note: Despite this web site having
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The Prime time version still needs a small amount of editing, additions, clarifications, and so on. Symbols (as for 'per mil'), bullets, subscripts (as in CO2), and superscripts (as in 13C) cannot be rendered via the web page program I am currently using. Therefore, I write out 'per mil,' do not employ bullets, use the symbol "" to designate a subscript (as in CO2), and the symbol "^" to designate a superscript (as in ^13C). Some computers also fail to properly render the chemical formula 'yield' sign (an arrow), and instead display it as an upper case phi (the Greek letter), a circle with a slash.

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2004, 2005, by Dan Dorritie, except for those public or private items which cannot be copyrighted.
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To my friends, for your companionship, kindness, generosity, intelligence, creativity, humor, and deep commitment to social justice.

To my teachers, including my fellow students, and those whom I have had as students.
Thank you.

To that great international community of scientists, past and present, without whom this book could not have been conceived, much less written.


Attempting to determine what happened some 250 million -- a quarter of a billion -- years ago is not something that any single scientist can hope to achieve. Vast amounts of information, from all over the planet, is necessary, and this information must be put together and published by hundreds of investigators. Some of the many who have attempted to assemble the often ill-fitting, jagged little pieces of the end-Permian puzzle are Richard Twitchett, Paul Wignall, Doug Erwin, Arthur Hallam, Luann Becker, Paul Renne, Asish Basu, Robert Poreda, Greg Retallack, William Holser, Michael Benton, and Peter Ward, to name just a few.

Numerous scientists have personally aided me by answering my questions, sending copies of their papers, or just providing personal encouragement. These include: Thomas Algeo, Robert Zierenberg, Kunio Kaiho, Jay Melosh, Jim Kasting, Wally Broecker, Mike Kirby, Ken Farley, Alan Trujillo, Hal Lescinsky, Chris Ballentine, Ford Doolittle, Matthew Hornbach, Dave Tinker, Maarten deWit, Keith Kvenvolden, and Paul Weimer.

Two who deserve special recognition for their assistance are David Archer, a geophysicist at the University of Chicago who works on present-day methane hydrates, about which we had extended discussion, and Greg Racki, a paleontologist at the University of Silesia in Poland. Greg's kindnesses are too many to enumerate, but they include his providing comments on this work and my work elsewhere, copies and drafts of his own papers (often on the end-Permian), copies of others' papers to which I would not have had access, and his personal encouragement and support. He has been an excellent, exemplary colleague.

A work like this could not have possibly been completed without the efforts of many librarians. I received considerable help from those at the California Capitol Research Bureau and the University of California system.

Creating a web book of necessity requires some computer skills, though thanks to the frequently stunning ingenuity of software engineers, less than one might initially expect. Nonetheless, the novice (like me) inevitably requires assistance, and in my case I received it from the MacNexus MacIntosh Users Group, from my friend Chris Agruss, and my son Richard.

The unenviable and protracted task of weeding out inevitable typographical and logical errors was largely accomplished by my steadfast proofreader, Carol Wallisch.

Finally, writing a book necessitates at least a modicum of organization, and that is my personal limit: a modicum. Fortunately for me, there are those who can supply a higher level of organization and clerical assistance. Thank you, Betty Wong.


This book is about methane catastrophe. Methane catastrophes have occurred several times in Earth's history, and when they have occurred, they have sometimes caused abrupt changes in the history of life, and at least one significant extinction. That extinction, at the end of the Permian Period 250 million years ago, is the greatest in the history of life. More than 90% of the then-existing species perished, and the course of life on Earth was altered forever.

If a methane catastrophe were to happen in the near future, it is likely that not only would a considerable percentage of existing plants and animals be killed off, but a large percentage of the human population as well, as a result of the climate change and significantly more hostile environmental conditions. Yet we are heading toward such a catastrophe. It will happen because we continue to warm the planet by our burning of carbon fuels, and particularly fossil fuels. It is against the background of global warming that a methane catastrophe will take place.

A methane catastrophe consists of a sudden and massive release of methane from ocean bottom muds within a short period of time. At present, most of this methane is trapped in ice in seafloor sediments; the rest is free methane gas trapped below the methane ice. (Some additional methane in ice may be found in permanently frozen ground, called permafrost, in polar regions.) As we continue to warm the planet by dumping carbon dioxide into the atmosphere, this methane will inevitably be released. It will be released just as surely as global warming is now releasing great quantities of melt water from glaciers, pack ice, and ice caps.

A methane catastrophe is abrupt because it can be initiated by a major submarine landslide, which can happen in a matter of days or even hours, or by the venting of vast quantities of seafloor methane over a period of decades. These events can take place in a geological eyeblink. Additional slumping and/or venting can continue for centuries to millennia.

The amount of methane that can be released is massive. Estimates of the amount of seafloor methane generally range from about 5000 billion metric tons to around 20,000 billion metric tons (a metric ton is equal to 1.1 imperial tons, the standard ton used in the United States), though they usually range around 10,000 billion metric tons. This amount of methane contains about 7500 billion metric tons of carbon, vastly more than all the estimated carbon in all fossil fuels: petroleum, coal, and natural gas.

Based upon a seafloor temperature increase of 5C (9F), it is estimated that at least 2000 billion metric tons of methane could be released. (A 5C increase is within the predicted range of global warming for the end of this century, according to the IPCC, the UN's Intergovernmental Panel on Climate Change. Warming the seafloor sediments to that temperature would take longer, but sediment warming of that magnitude is probably not necessary for a major methane release.) Other estimates place the amount of warming needed to release seafloor methane at only about 3C (5.4F). No matter: with continued global warming, virtually all seafloor methane will eventually be released.

There is a simple way to put 2000 billion metric tons of methane into perspective: it contains more than two and a half times the amount of carbon (largely in the form of carbon dioxide) as does the entire atmosphere. In addition, methane is more than twenty times more powerful a greenhouse gas as is carbon dioxide. Though this methane would quickly be oxidized -- to carbon dioxide -- in the atmosphere, even its short-term presence would deliver a sudden and stunning jolt of heat to the planet. The derivative carbon dioxide would maintain much of that heat for several centuries, or even millennia.

A methane catastrophe, therefore, is an abrupt surge of greenhouse gas that could rival or exceed the carbon dioxide warming of the planet. It can potentially overwhelm the natural heat regulatory system of the Earth, which operates in a much more gradual way, and on a much more protracted time scale. The quantity of methane that could be released is so massive there is no remedial action that people will be able to take to mitigate it except in the most superficial way. Once a methane catastrophe begins, there will be major consequences for the planet and its inhabitants, human and other, and we will be able to do little except wait it out. Methane, in a very real sense, is the joker in the deck of global warming.

As with the current increase in atmospheric carbon dioxide, a large methane release will undoubtedly contribute to an increase in acid rain, and, through its impact on global warming, a further rise of sea level, increased desertification, increased heavy precipitation, and extreme weather events. The slowing of ocean circulation or its actual stagnation are also possibilities. Such a slowing would produce a decreased transport of warm water to the coasts of northeastern North America and northernmost Europe, making for much colder winters. In addition, the destabilization of methane within seafloor sediments can send 20 meter (60 foot) high tsunamis crashing into nearby coastlines.

A methane catastrophe can have other major consequences in addition to sudden global warming. It can accelerate the slow but deadly acidification of the surface ocean (down to about 100 meters, or about 300 feet), which is occurring as a result of the higher carbon dioxide in the atmosphere and ocean. The methane can combine with dissolved oceanic oxygen, depleting the deeper part of the ocean (that is, the ocean below about 100 meters) of oxygen, and killing off the oxygen-using (aerobic) organisms at those depths. As acidification penetrates the deep ocean, even organisms that do not use oxygen (anaerobes) will be affected.

Then there are the worst case scenarios. With the warming of the world ocean, its chemical balance and biological composition will change. The ocean will become stratified, with mixing between its surface and the deep ocean becoming increasingly limited. If the deep ocean becomes fully anoxic (devoid of oxygen), it will also become toxic, as the remaining anaerobic organisms pump out the deadly gas hydrogen sulfide. In sufficient quantities, that gas could escape oceanic confinement poison the atmosphere, and, combining with the iron in the blood's hemoglobin, kill terrestrial organisms, including us.

But the composition of the atmosphere will also be changing in a second way, because the amount of free oxygen depends on two things: the actual production of oxygen (by the ocean's photosynthetic plankton and terrestrial green plants) and the delivery of large amounts of carbon (as part of a "rain" of organic debris from organisms closer to the surface) to the ocean's bottom. This carbon, if not removed from the global carbon cycle in this manner, would combine with oxygen and lower its concentration in the atmosphere. But once oceanic anoxia kills off aerobic marine organisms, far less carbon will reach the seafloor, and atmospheric oxygen may drop to just 50 to 65% of its current level.


We are the brink of a methane catastrophe. By our own actions -- by our continuing and increasing use of carbon fuels -- we are slowly but inexorably creating the conditions during which a methane catastrophe will occur. We probably have time to prevent such a catastrophe, but there is a certain possibility that we have already crossed -- or will shortly cross -- an invisible threshold that will render a methane catastrophe inevitable and unstoppable.

Anthropogenic global warming and methane catastrophe will be events more cataclysmic than any that can befall Earth, except for an impact with a giant asteroid or comet, or a stellar explosion in our neighborhood of the Milky Way. These other events, however, are quite rare and unlikely in our immediate future.

Anthropogenic global warming and methane catastrophe, by contrast, are highly likely and much more immediate. More importantly, unlike those other possible cataclysms, both are preventable -- probably -- if we take them seriously, begin to understand them, and -- most difficult of all -- begin to take steps to avert them.


It has become fashionable to dismiss predictions of catastrophe, partly because they have become so common. People have become jaded, what with one such prediction after another. We used to hear a good deal about nuclear holocaust, or nuclear winter, but as those threats seem to have dimmed in the public consciousness, there are others which have replaced it. We now hear of doomsday asteroids, the ozone hole, SARS (severe acute respiratory syndrome), bird flu, global warming, and the obliteration of species. The number of threats seems to be increasing.

And, actually, that number is increasing.

Prior to this epoch in human history, people simply did not have the ability to impact our planet in potentially catastrophic ways. Unfortunately, we now do have that ability. The ozone hole is a simple example. Never before was humanity on the verge of destroying this gaseous umbrella which protects us (and all other organisms that live at or near the surface of the Earth) from deadly ultraviolet light. Humanity simply didn't have that kind of power. But the advent of chloro-flouro-carbon (CFC) refrigerants gave us that ability, and the ozone layer sustained significant damage before the problem began to be addressed. Luckily, this is a problem for which there is a ready solution, and by banning the production of these ozone-harming chemicals, we have begun to bring the problem under control.

The problem of carbon-dioxide emissions, consequent global warming, and the prospect of methane catastrophe, however, will not be addressed so easily. We currently have no technology to trap and hold large quantities of carbon dioxide, and we are not likely to have such a technology for many decades in the future -- if indeed we ever do. Some of the excess carbon dioxide is in fact currently slipping beyond our potential grasp, entering the oceans at the astonishing rate of about a million metric tons (a metric ton = 1.1 standard ton) per hour, and increasing the acidity of seawater. There is, in addition, a great disincentive in a world economy driven and dominated by fossil fuels, particularly petroleum and natural gas, to shifting the energy base of that economy. Enormous corporate profits and personal fortunes, and the success of political efforts on their behalf, are also at stake. Slowing the stampede to catastrophically higher global temperatures and ocean destruction will require substantial international effort. Even so, should we today stop spewing carbon dioxide into the atmosphere, global temperatures will continue to increase for some time into the future.

Despite our aversion to warnings of imminent catastrophe, our problem may be that we are not alarmed enough. Because of the delayed consequences of our dumping carbon dioxide into the atmosphere, the major effects of global warming will only be starting just as the world supply of oil is well on its way to depletion (about 2050). But already startling environmental changes -- the early, "minor" effects of global warming -- are occurring on Earth:

With the exception of 1996, the years from 1995 to 2004 constitute 9 of the 10 warmest years since systematic record keeping began in 1861.

Globally, glaciers have retreated, on average, almost some 15% since 1850. Glacial retreat has been recorded in Tibet, Alaska, Peru, the Alps, Kenya, Antarctica.

Alaskan temperatures have risen about 2.8C (5F) in the past few decades.

In the past several decades, about 40% of Arctic Ocean sea ice has disappeared. (Some researchers now believe, however, that at least part of this sea ice loss may be due to changing wind patterns over the North Pole, but these wind changes, also, may be due to warming climate.)

Between 1965 and 1995, the amount of melt water from the Arctic region going into the North Atlantic was about 20,000 cubic kilometers (about 4800 cubic miles), the equivalent of the fresh water in all of the Great Lakes combined (Superior, Huron, Erie, and Ontario) with the exception of Lake Michigan. Preliminary calculations indicate that an additional 18,000 cubic kilometers (4300 cubic miles) or so could shut down ocean circulation in the North Atlantic, chilling the eastern United States by several degrees. That shutdown could occur in two decades or less.

Upper ocean temperatures have risen between 0.5 and 1.0C (0.9 to 1.8F) since 1960. Deeper water has also warmed, but not by as much. The total amount of energy that has gone into the oceans as a consequence of global warming, however, is staggering: enough to run the state of California for 200,000 years.

The deep waters of the Southern Ocean (that which encircles Antarctica) have become significantly colder and less salty than they were just ten years ago. This is presumably due to the melting of Southern Ocean sea ice and parts of the Antarctic ice cap. Deep ocean waters have been presumed to be fairly isolated from climate warming but the data obtained from depths of four to five kilometers (more than two to three miles) suggests otherwise. Such changes could significantly impact global ocean circulation.

Huge expanses of floating ice around Antarctica have collapsed into fragments in just weeks, after existing for tens of thousands of years. In addition, the ice that currently covers West Antarctica, known as the West Antarctic Ice Sheet (WAIS), which was quite recently (as of 2001) judged by the UN's Intergovernmental Panel on Climate Change (IPCC) as unlikely to collapse before the end of this century, or even for the next millennium, may now be starting to disintegrate, according to the head of the British Antarctic Survey. If this ice sheet does collapse, global sea level will rise by about 5 meters (16 feet).

While global daytime temperatures, on average, increased only about 0.33C (0.6F) between 1979 and 2003, nighttime temperatures have risen more than 1C (1.8F).

These environmental changes have had significant biological effects:

In the eastern North Atlantic, warm-water phytoplankton has moved north 1000 km (600 miles) over the past 40 years.

In 2004, almost a quarter of a million breeding pairs of seabirds in islands north of Scotland failed to produce more than a few dozen offspring. Their reproductive failure is most likely due to the North Atlantic phytoplankton changes, and the consequent breakdown of the marine food chain. Many of the affected birds migrate back and forth between the Scottish islands and areas around the Southern Ocean (off Antarctica) over the course of the year. Starved in the north, they will never make it back to the south.

Krill, small (about 5 cm/2 inches in length), shrimplike creatures which are a main food source for seals, whales, and penguins in the Southern Ocean, have declined in places to just 20% of their previous number in just 30 years.

Grass now survives the winter in places on the Antarctic Peninsula, the warmest part of that frigid continent. When grass last was able to survive Antarctic winters is unknown.

The small increase in global nighttime temperatures indicated above (1C/1.8F), is sufficient to have reduced the biomass (the total mass of roots, stems, leaves, and grain) of rice, humankind's most important crop, by 10%.

These are only the early effects, ripples from the storm which is to come. Remedial action is still possible, but the likelihood of catastrophe becomes more certain with each passing year.


I discovered the possibility of methane catastrophe as a student of paleontology. Paleontologists study fossils in order to reconstruct the history of life on Earth. Inevitably, many students of paleontology are interested in those episodes of biological cataclysm and change known as mass extinctions. Our interest has certainly been stimulated, in part, by the determination in 1980 of the cause of the extinction of the dinosaurs some 65 million years ago. (There is still some dispute about that cause, but most scientists accept that it was an extraterrestrial impact.)

My particular interest was in finding the cause of the end-Permian extinction, the greatest extinction event of them all. (The event that killed off the dinosaurs was only the second greatest.) As I worked on that problem, however, I quickly realized that what I presumed to be the cause of that extinction was still around in today's world, and, with global warming, will become a significant threat.

This book is the result of that recognition. I have here traced the history of our understanding of mass extinction, our discovery of the vast quantities of methane that lie just off the shores of our continents, the various theories of the Permian extinction, the evidence for methane catastrophe at that time, the reasons why we must be concerned about the possibility of methane catastrophe today. I have attempted to write so that the general, educated reader can understand, and I have tried to do so without compromising the science. I hope to leave the reader with a sense of what we are doing to our environment, and the appalling consequences that can ensue if we fail to act to mitigate our activities. Such an understanding is essential if we as citizens are to be able to control our destinies.


This is a tale filled with superlatives. The reader will encounter the greatest extinction event of all time, the longest ice age, the greatest oceanic current, the longest period of stability in the Earth's magnetic field, the greatest volcanic eruption, the largest exchangeable carbon reservoir, the largest continent (a "megacontinent"), the biggest ocean, the longest mountain range in the world, and, of course, methane catastrophe. The tale is full of superlatives because there is no other way to tell it.



1. I have used both the metric system (meters, kilometers, grams, metric tons, degrees Celsius, etc.) and the imperial system (feet, miles, tons, degrees Fahrenheit, etc.) of measurement. I have done this to avoid excluding any potential reader. The metric system is standard for use in scientific matters, and is a vastly superior measurement system, but most American readers are insufficiently familiar with it to be able to surmount the obstacles that would come with use here. In order to prevent readers from having to repeatedly check a conversion table, the use of both measurement systems seemed an appropriate solution.

2. I use CE (Current Era) and BCE (Before Current Era) in place of the much more common but sectarian A.D. and B.C.

3. I have often used capitalization for clarity and emphasis (as with Ice Age, or the Universe), or to highlight terms (such as Early Triassic Period) that may not be familiar to the general reader.

Dan Dorritie