KILLER IN OUR MIDST | Methane Catastrophes in Earth’s Past . . . and Near Future?
KILLER IN OUR MIDST
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.
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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 CO¸2), 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. Alternatively, they may render the yield sign as the diphthong Æ.
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“The climate is like a wild beast, and we’re poking it with sticks.”
— Wally Broecker
Deep beneath the surface of the sea, buried in the oxygen-depleted muds that have accumulated over the ages on the underwater margins of the continents, lies a vast store of natural gas that probably well exceeds, in its carbon equivalence, the entire supply of all other oil, gas, and coal on the planet. Most of this immense store of natural gas, largely comprised of methane, lies trapped in icy cages called hydrates. Below these hydrates is a huge quantity of methane as free gas bubbles, blocked from release by the hydrate, and temperature and pressure conditions above. Still more methane, as hydrate, is found in the permanently frozen (permafrost) regions that surround the poles.
Methane is a much more powerful greenhouse gas than carbon dioxide, the gas which is currently warming our globe, even though methane remains in the atmosphere for a much shorter time. If released abruptly, seafloor methane has the potential to deliver a stunning jolt of heat to the planet’s already increasing temperatures. Even if released more gradually, seafloor methane will inevitably compound the problem of global warming. But abruptly or gradually, as we warm the planet by our dumping of carbon dioixde into the atmosphere, the seafloor will also warm, and its methane will inevitably be released.
This book is about the release of that methane, and, in particular, about the possibility of 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 may well be heading toward such a catastrophe, produced by our warming of the planet.
Just how rapidly seafloor methane will be released depends on numerous factors that are quite difficult to assess. It is possible that seafloor methane will be released so slowly that it will only have a relatively minor warming effect on Earth’s climate. On the other hand, because the coming methane release will be the result of our warming of the planet via the burning of fossil and other acrbon fuels, it could happen much more quickly. Indeed, it seems that we are currently pumping the greenhouse gas carbon dioxide into the atmosphere at a much faster — perhaps tens to hundreds of times faster — rate than has ever before naturally occurred in the last half billion years or so of the Earth’s history. The catastrophic warming we are causing is — to the best of our knowledge — unprecedented since the early days of our planet, billions of years ago. Such warming could well lead to methane catastrophe.
The onset of a methane catastrophe would be abrupt because it could 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 what is essentially a geological eyeblink. Additional slumping and/or venting can continue for centuries to millennia.
The amount of methane that can be released is indeed 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. There is a simple way to put 10,000 billion metric tons of methane into perspective: it contains about ten times the amount of carbon (largely in the form of carbon dioxide) as does the entire atmosphere. Moreover, though methane entering the atmosphere is quickly oxidized, it is oxidized to carbon dioxide, so the problem of its warming ability will remain with us for thousands of years into the future.
A methane catastrophe, therefore, is an abrupt surge of greenhouse gas that could rival or exceed the carbon dioxide warming of the planet. It could 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 would be no remedial action that people would be able to take to mitigate it except in the most superficial way. Once a methane catastrophe were to begin, there would be major consequences for the planet and its inhabitants, human and other, and we would 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 because of greater planetary warmth are also possibilities. Such a slowing would paradoxically 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 now occurring as a result of the increase of 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 restricted. 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 to poison the atmosphere and, combining with the iron in the blood’s hemoglobin, kill terrestrial organisms, including us.
But the composition of the atmosphere could also change 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 by sinking and eventual burial in the ocean floor, will combine with oxygen and lower its concentration in the atmosphere.
Once oceanic anoxia kills off aerobic marine organisms (those which require oxygen to live), the natural regulatory system for carbon will be sent into a tailspin. The amount of organic debris produced in surface waters will likely be reduced, the amount that rapidly descends to the ocean floor will be reduced, and the proportion that gets decomposed on the way to the bottom will be significantly reduced. Exactly how this will play out is unclear, because certain of these changes will operate to slow the removal of carbon from the global carbon cycle (which will act to decrease the amount of oxygen in the atmosphere), while others will enhance it (increasing atmospheric oxygen). When a similar disruption of the marine ecosystem occurred at the end of the Permian, a quarter of a billion years ago, atmospheric oxygen dropped to a fraction (about 2/5ths) of its previous level. But increased oxygen could be just as bad: oxygen ions (sometimes referred to as free radicals) can inflict genetic damage to DNA, causing mutations and cancer.
We are certainly on the verge of releasing a huge amount of permafrost and seafloor methane within a very short time; we may also be on the brink of 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 such a methane release, catastrophic or more gradual, could occur. We probably have time to prevent a catastrophe, but there is a certain non-negligible possibility that we have already crossed — or will shortly cross — an invisible threshold that will render a methane catastrophe inevitable and unstoppable.
Major anthropogenic global warming by carbon dioxide and possible 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.
Major anthropogenic global warming by carbon dioxide and possible 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. Many of us 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 faded 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 a major seafloor methane release, 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 will. Some of the excess carbon dioxide we produce is in fact currently slipping beyond our potential grasp, entering the oceans at the astounding 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, great resistance in a world economy driven and dominated by fossil fuels 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.
·The year 2005 was the warmest year since records have been kept. The next warmest years, in order, are, 1998, 2002, 2003, and 2004.
·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 2.8°C (5°F) 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, themselves, may be due to a 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. That shutdown could occur in two decades or less, though most scientists believe it will take much longer. The Intergovernmental Panel on Climate Change, comprised of thousands of climate scientists worldwide, puts the likely slowing at about 25% by 2100.
·Trade winds across the equatorial Pacific have slowed because of higher humidity, and are projected to do so even more as time passes. The increase in humidity is the result of increased evaporation, traceable to global warming. This slowing of Pacific winds will also slow the ocean surface currents that the winds push along. Some scientists fear that at some point “the switch will be tripped” and nutrient-rich bottom water will no longer rise to the surface in the eastern Pacific (a “permanent El Niño” situation which did exist about three million years ago). These waters feed the plankton which feed the anchovies in one of the world’s greatest fisheries. Much of the anchovy harvest is dried, ground up, and added to chicken feed, of which it is a major protein constituent. If the switch does trip, good-bye to inexpensive chicken.
·Upper ocean temperatures have risen between 0.5 and 1.0°C (0.9 to 1.8°F) 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.
·In addition to significant retreats of the glaciers on Greenland’s margins, as of 2005 Greenland’s massive ice sheet is melting at more than twice the rate it was in the previous three years. Glaciologists report that portions of the sheet which were solid ice just a few years ago are now riddled with meltwater caverns.
·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 previously 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) now suggests otherwise. Such changes could significantly impact global ocean circulation.
·The Southern Ocean, which may absorb more carbon dioxide than any other region of the global ocean, as of more than twenty-five years ago ceased to absorb additional carbon dioxide. In fact, its ability to absorb carbon dioxide seems to be declining — even as atmospheric levels of that gas are reaching ever higher levels — most likely due to increased wind speed over that part of the global ocean. The higher wind speed in turn has been attributed to both global warming and the destruction of the Antarctic ozone layer. Because oceans eventually absorb most of the carbon dioxide that goes into the atmosphere, the declining ability of the Southern Ocean to absorb carbon dioxide is a particularly ominous development.
·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 0.33°C (0.6°F) between 1979 and 2003, nighttime temperatures have risen more than 1°C (1.8°F).
These environmental changes have had significant biological effects:
·In the eastern North Atlantic, warm-water phytoplankton (marine organisms that photosynthesize, produce oxygen, and constitute the bottom of the food chain) 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. Similar changes have been observed off the West Coast of the United States in 2005.
·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.
·In the 17 year period from 1987 to 2003, the number and size of major wildfires in the western U. S. has increased dramatically. Compared to the 17 year period stretching from 1970 to 1986, the number of major wildfires has increased fourfold, and the area burned by major fires has increased sixfold. All of the presumed causes for this increase — the earlier melting of snow, increased summer temperatures, an extended fire season, and an increase in the area of high-altitude forests which is vulnerable to such fires — can be traced to global warming.
·The small increase in global nighttime temperatures indicated above (1°C/1.8°F), 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%. Rice is the primary foodstuff for more than half of the population of the world.
With the warming, the release of methane has begun to follow:
·The Western Siberian Peat Bog, comprising an area of a million square kilometers (about 385,000 square miles, roughly the combined size of France and Germany), has begun to melt. This area is underlain by permafrost (permanently frozen ground that has existed since the Ice Age) perhaps a kilometer (about 3000 feet) deep. The permafrost contains an enormous amount of methane hydrate, possibly as much as a quarter of the total inventory of continental methane. As this permafrost warms and melts — an irreversible process — methane is released. This melting may add a quantity of methane to the atmosphere roughly equivalent to that released by all other natural and agricultural sources, increasing global warming by 10 to 25%.
·Already, methane emissions from certain areas of Siberian permafrost is proceeding much more rapidly than previously estimated. These extensive areas, characterized by Ice Age deposits of wind-blown dust (called loess) with high carbon and very high ice (50 to 90%) contents, are bubbling out methane at a rate five times higher than earlier presumed. Overall, these “yedoma” regions are contributing an additional 10 to 63% the total rate of methane release from the wetlands of the north.
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 eruptions, the largest exchangeable carbon reservoir, the largest continent (a “megacontinent”), the biggest ocean, the largest known bacterium (Thiomargarita namibiensis), 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.BIBLIOGRAPHY, M-L
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© 2004, 2005, 2006, 2007, by Dan Dorritie, except for those public or private items which cannot be copyrighted.
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Dorritie, D. 2004, 2005, 2006, 2007. Killer in Our Midst.
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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.
To that great international community of scientists, past and present, without whom this book could not have been conceived, much less written.
Determining 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, are necessary, and this information must be assembled, interpreted, 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, calling attention to errors or problems, or providing personal encouragement. These include: Thomas Algeo, Robert Zierenberg, Kunio Kaiho, Jay Melosh, Rand Schaal, Jim Kasting, Wally Broecker, Mike Kirby, Ken Farley, Alan Trujillo, Hal Lescinsky, Chris Ballentine, Ford Doolittle, Matthew Hornbach, Dave Tinker, Maarten deWit, Keith Kvenvolden, Stuart Harris, Richard Cowen, and Paul Weimer.
Three 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 discussions; Ric Morante, an Australian geophysicist who generously provided copies of his many 1993-95 papers on end-Permian methane release-related Sydney Basin anoxia; 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.
Special financial assistance for this project was provided by my long-time friend, Karen Humbert.
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.