Skip to comments.Hit and myth of global warming
Posted on 07/08/2003 3:06:38 AM PDT by Tailgunner JoeEdited on 07/12/2004 3:40:27 PM PDT by Jim Robinson. [history]
A press release from the federally supported National Center for Atmospheric Research claims a "New Look at Satellite Data Supports Global Warming Trend." This claim is likely to be played out big by supporters of the Kyoto Protocol, who want to restrict drastically the use of energy.
(Excerpt) Read more at washingtontimes.com ...
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The point of this article, it seems to me, is to show that the tropospheric and stratospheric satellite-derived temperatures have not been honestly analyzed by global warming proponents.
The scientific theory of global warming (as shaded by it's political side) does not account for natural fluctuations in average global temperatures - which are regulated by the polar ice caps, among other things (such as sunspot activity). To my knowledge, there is no concensus that the perceived temperature change is anything out of the normal cyclic pattern of global climate.
My Uncle is a world-renown Geophysicist/Climatologist who works with both NCAR and satellite data. One of his specialties is long term geophysical changes.
I will give him a ping today to see what he thinks on this.
To my knowledge, there is no concensus that the perceived temperature change is anything out of the normal cyclic pattern of global climate.
Agreed. In fact, my understanding is that the consensus is that any effect by mankind is completely undemonstrated.
I believe, however that a warming trend that has been going on since the early 1800's has been demonstrated, along with a cooling trend, starting around 1400, that lasted until the mid 1800's.
Assuming a temperature change in the Earth's atmosphere is detected it still is not clear what caused it. Detecting an event and determining the cause are two different stories.
It appears that the main motivation of the persons that "believe" in climatic warming is control. They want to be able to tell you what you have to do for whatever reason.IMHO
And to spread socialism.
Yeah, but think of all the fish those things would attract. However, the view off Cape Cod is enjoyed by millions, not just wealthy "liberals," which means that that particular view has a major impact on Massachusetts tax revenue.
"FOLLOW THE MONEY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
That is part of the problem for sure. Chasing grants is probably much easier, when the study concerns the dramatic. A study demonstrating that climate changes are normal doesn't quite have the same public relations impact.
A Chilling Perspective
A Brief History of Ice Ages and Warming
Causes of Global Climate Change
Playing with Numbers
A Matter of Opinion
Unraveling the Earth's Temperature Record
Stopping Climate Change
Global warming started long before the "Industrial Revolution" and the invention of the internal combustion engine. Global warming began 18,000 years ago as the earth started warming it's way out of the Pleistocene Ice Age-- a time when much of North America, Europe, and Asia lay buried beneath great sheets of glacial ice.
Earth's climate and the biosphere have been in constant flux, dominated by ice ages and glaciers for the past several million years. We are currently enjoying a temporary reprieve from the deep freeze.
Approximately every 100,000 years Earth's climate warms up temporarily. These warm periods, called interglacial periods, appear to last approximately 15,000 to 20,000 years before regressing back to a cold ice age climate. At year 18,000 and counting our current interglacial vacation from the Ice Age is much nearer it's end than it's beginning.
Global warming during Earth's current interglacial warm period has greatly altered our environment and the distribution and diversity of all life. For example:
Approximately 15,000 years ago the earth had warmed sufficiently to halt the advance of glaciers, and sea levels worldwide began to rise.
By 8,000 years ago the land bridge across the Bearing Strait was drowned, cutting off the migration of men and animals to North America.
Since the end of the Ice Age, Earth's temperature has risen approximately 16 degrees F and sea levels have risen a total of 300 feet ! Forests have returned where once there was only ice.
Over the past 750,000 years of Earth's history, Ice Ages have occurred at regular intervals, of approximately 100,000 years each.
Courtesy of Illinois State Museum
During ice ages our planet is cold, dry, and inhospitable-- supporting few forests but plenty of glaciers and deserts. Like a spread of collosal bulldozers, glaciers have scraped and pulverized vast stretches of Earth's surface and completely destroyed entire regional ecosystems not once, but several times. During Ice Ages winters were longer and more severe and ice sheets grew to tremendous size, accumulating to thicknesses of up to 8,000 feet!. They moved slowly from higher elevations to lower-- driven by gravity and their tremendous weight. They left in their wake altered river courses, flattened landscapes, and along the margins of their farthest advance, great piles of glacial debris.
During the last 3 million years glaciers have at one time or another covered about 29% of Earth's land surface or about 17.14 million square miles (44.38 million sq. km.) . What did not lay beneath ice was a largely cold and desolate desert landscape, due in large part to the colder, less-humid atmospheric conditions that prevailed.
During the Ice Age summers were short and winters were brutal. Animal life and especially plant life had a very tough time of it. Thanks to global warming, that has all now changed, at least temporarily.
( view full size map)
The World 18,000 Years Ago
Before "global warming" started 18,000 years ago most of the earth was a frozen and arid wasteland. Over half of earth 's surface was covered by glaciers or extreme desert. Forests were rare.
Not a very fun place to live.
(view full size map)
Our Present World
"Global warming" over the last 15,000 years has changed our world from an ice box to a garden. Today extreme deserts and glaciers have largely given way to grasslands, woodlands, and forests.
Wish it could last forever, but . . . .
In the 1970's concerned environmentalists like Stephen Schneider of the National Center for Atmospheric Research in Boulder, Colorado feared a return to another ice age due to manmade atmospheric pollution blocking out the sun.
Since about 1940 the global climate did in fact appear to be cooling. Then a funny thing happened-- sometime in the late 1970's temperature declines slowed to a halt and ground-based recording stations during the 1980's and 1990's began reading small but steady increases in near-surface temperatures. Fears of "global cooling" then changed suddenly to "global warming,"-- the cited cause:
manmade atmospheric pollution causing a runaway greenhouse effect.
What does geologic history have to offer in sorting through the confusion?
Quite a bit, actually.
"If 'ice age' is used to refer to long, generally cool, intervals during which glaciers advance and retreat, we are still in one today. Our modern climate represents a very short, warm period between glacial advances." Illinois State Museum
Periods of Earth warming and cooling occur in cycles. This is well understood, as is the fact that small-scale cycles of about 40 years exist within larger-scale cycles of 400 years, which in turn exist inside still larger scale cycles of 20,000 years, and so on.
Example of regional variations in surface air temperature for the last 1000 years, estimated from a variety of sources, including temperature-sensitive tree growth indices and written records of various kinds, largely from western Europe and eastern North America. Shown are changes in regional temperature in ° C, from the baseline value for 1900. Compiled by R. S. Bradley and J. A. Eddy based on J. T. Houghton et al., Climate Change: The IPCC Assessment, Cambridge UniversityPress, Cambridge, 1990 and published in EarthQuest, vol 5, no 1, 1991. Courtesy of Thomas Crowley, Remembrance of Things Past: Greenhouse Lessons from the Geologic Record
Earth's climate was in a cool period from A.D. 1400 to about A.D. 1860, dubbed the "Little Ice Age." This period was characterized by harsh winters, shorter growing seasons, and a drier climate. The decline in global temperatures was a modest 1/2° C, but the effects of this global cooling cycle were more pronounced in the higher latitudes. The Little Ice Age has been blamed for a host of human suffering including crop failures like the "Irish Potato Famine" and the demise of the medieval Viking colonies in Greenland.
Today we enjoy global temperatures which have warmed back to levels of the so called "Medieval Warm Period," which existed from approximately A.D. 1000 to A.D. 1350.
"...the Earth was evidently coming out of a relatively cold period in the 1800's so that warming in the past century may be part of this natural recovery."
Dr. John R. Christy
(leading climate and atmospheric science expert- U. of Alabama in Huntsville) (5)
Global warming alarmists maintain that global temperatures have increased since about A.D. 1860 to the present as the result of the so-called " Industrial Revolution,"-- caused by releases of large amounts of greenhouse gases (principally carbon dioxide) from manmade sources into the atmosphere causing a runaway "Greenhouse Effect."
Was man really responsible for pulling the Earth out of the Little Ice Age with his industrial pollution? If so, this may be one of the greatest unheralded achievements of the Industrial Age!
Unfortunately, we tend to overestimate our actual impact on the planet. In this case the magnitude of the gas emissions involved, even by the most aggressive estimates of atmospheric warming by greenhouse gases, is inadequate to account for the magnitude of temperature increases. So what causes the up and down cycles of global climate change?
Climate change is controlled primarily by cyclical eccentricities in Earth's rotation and orbit, as well as variations in the sun's energy output.
"Greenhouse gases" in Earth's atmosphere also influence Earth's temperature, but in a much smaller way. Human additions to total greenhouse gases play a still smaller role, contributing about 0.2% - 0.3% to Earth's greenhouse effect.
Major Causes of Global Temperature Shifts
(1) Astronomical Causes
- 11 year and 206 year cycles: Cycles of solar variability ( sunspot activity )
- 21,000 year cycle: Earth's combined tilt and elliptical orbit around the Sun ( precession of the equinoxes )
- 41,000 year cycle: Cycle of the +/- 1.5° wobble in Earth's orbit ( tilt )
- 100,000 year cycle: Variations in the shape of Earth's elliptical orbit ( cycle of eccentricity )
(2) Atmospheric Causes
- Heat retention: Due to atmospheric gases, mostly gaseous water vapor (not droplets), also carbon dioxide, methane, and a few other miscellaneous gases-- the "greenhouse effect"
- Solar reflectivity: Due to white clouds, volcanic dust, polar ice caps
(3) Tectonic Causes
- Landmass distribution: Shifting continents (continental drift) causing changes in circulatory patterns of ocean currents. It seems that whenever there is a large land mass at one of the Earth's poles, either the north pole or south pole, there are ice ages.
- Undersea ridge activity: "Sea floor spreading" (associated with continental drift) causing variations in ocean displacement.
For more details see:
Playing with Numbers
Global climate and temperature cycles are the result of a complex interplay between a variety of causes. Because these cycles and events overlap, sometimes compounding one another, sometimes canceling one another out, it is inaccurate to imply a statistically significant trend in climate or temperature patterns from just a few years or a few decades of data.
Unfortunately, a lot of disinformation about where Earth's climate is heading is being propagated by "scientists" who use improper statistical methods, short-term temperature trends, or faulty computer models to make analytical and anecdotal projections about the significance of man-made influences to Earth's climate.
During the last 100 years there have been two general cycles of warming and cooling recorded in the U.S. We are currently in the second warming cycle. Overall, U.S. temperatures show no significant warming trend over the last 100 years (1). This has been well - established but not well - publicized.
Each year Government press releases declare the previous year to be the "hottest year on record." The UN's executive summary on climate change, issued in January 2001, insists that the 20th century was the warmest in the last millennium. The news media distribute these stories and people generally believed them to be true. However, as most climatologists know, these reports generally are founded on ground-based temperature readings, which are misleading. The more meaningful and precise orbiting satellite data for the same period (which are generally not cited by the press) have year after year showed no warming.
Dr. Patrick Michaels has demonstrated this effect is a common problem with ground- based recording stations, many of which originally were located in predominantly rural areas, but over time have suffered background bias due to urban sprawl and the encroachment of concrete and asphalt ( the "urban heat island effect"). The result has been an upward distortion of increases in ground temperature over time(2). Satellite measurements are not limited in this way, and are accurate to within 0.1° C. They are widely recognized by scientists as the most accurate data available. Significantly, global temperature readings from orbiting satellites show no significant warming in the 18 years they have been continuously recording and returning data (1).
Has manmade pollution in the form of carbon dioxide (CO2) and other gases caused a runaway Greenhouse Effect and Global Warming?
Before joining the mantra, consider the following:
Compiled by R.S. Bradley and J.A. Eddy based on J.T. Houghton et al., Climate Change: The IPCC Assessment, Cambridge University Press, Cambridge, 1990 and published in EarthQuest, vo. 1, 1991. Courtesy of Thomas Crowley, Remembrance of Things Past: Greenhouse Lessons from the Geologic Record 1. The idea that man-made pollution is responsible for global warming is not supported by historical fact. The period known as the Holocene Maximum is a good example-- so-named because it was the hottest period in human history. The interesting thing is this period occurred approximately 7500 to 4000 years B.P. (before present)-- long before human's invented industrial pollution.
2. CO2 in our atmosphere has been increasing steadily for the last 18,000 years-- long before humans invented smokestacks ( Figure 1). Unless you count campfires and intestinal gas, man played no role in the pre-industrial increases.
As illustrated in this chart of Ice Core data from the Soviet Station Vostok in Antarctica, CO2 concentrations in earth's atmosphere move with temperature. Both temperatures and CO2 have been steadily increasing for 18,000 years. Ignoring these 18,000 years of data "global warming activists" contend recent increases in atmospheric CO2 are unnatural and are the result of only 200 years or so of human pollution causing a runaway greenhouse effect.
Incidentally, earth's temperature and CO2 levels today have reached levels similar to a previous interglacial cycle of 120,000 - 140,000 years ago. From beginning to end this cycle lasted about 20,000 years. This is known as the Eemian Interglacial Period and the earth returned to a full-fledged ice age immediately afterward.
3. Total human contributions to greenhouse gases account for only about 0.28% of the "greenhouse effect" (Figure 2). Anthropogenic (man-made) carbon dioxide (CO2) comprises about 0.117% of this total, and man-made sources of other gases ( methane, nitrous oxide (NOX), other misc. gases) contributes another 0.163% .
Approximately 99.72% of the "greenhouse effect" is due to natural causes -- mostly water vapor and traces of other gases, which we can do nothing at all about. Eliminating human activity altogether would have little impact on climate change.
4. If global warming is caused by CO2 in the atmosphere then does CO2 also cause increased sun activity too?
This chart adapted after Nigel Calder (6) illustrates that variations in sun activity are generally proportional to both variations in atmospheric CO2 and atmospheric temperature (Figure 3).
Put another way, rising Earth temperatures and increasing CO2 may be "effects" and our own sun the "cause".
Of the 186 billion tons of CO2 that enter earth's atmosphere each year from all sources, only 6 billion tons are from human activity. Approximately 90 billion tons come from biologic activity in earth's oceans and another 90 billion tons from such sources as volcanoes and decaying land plants.
At 368 parts per million CO2 is a minor constituent of earth's atmosphere-- less than 4/100ths of 1% of all gases present. Compared to former geologic times, earth's current atmosphere is CO2- impoverished.
CO2 is odorless, colorless, and tasteless. Plants absorb CO2 and emit oxygen as a waste product. Humans and animals breathe oxygen and emit CO2 as a waste product. Carbon dioxide is a nutrient, not a pollutant, and all life-- plants and animals alike-- benefit from more of it. All life on earth is carbon-based and CO2 is an essential ingredient. When plant-growers want to stimulate plant growth, they introduce more carbon dioxide.
CO2 that goes into the atmosphere does not stay there but is continually recycled by terrestrial plant life and earth's oceans-- the great retirement home for most terrestrial carbon dioxide.
If we are in a global warming crisis today, even the most aggressive and costly proposals for limiting industrial carbon dioxide emissions would have a negligible effect on global climate!
The case for a "greenhouse problem" is made by environmentalists, news anchormen , and special interests who make inaccurate and misleading statements about global warming and climate change. Even though people may be skeptical of such rhetoric initially, after awhile people start believing it must be true because we hear it so often.
"We have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we may have. Each of us has to decide what the right balance is between being effective and being honest."
Stephen Schneider (leading advocate of the global warming theory)
(in interview for Discover magazine, Oct 1989)
"In the United States...we have to first convince the American People and the Congress that the climate problem is real."
former President Bill Clinton in a 1997 address to the United Nations
"In the long run, the replacement of the precise and disciplined language of science by the misleading language of litigation and advocacy may be one of the more important sources of damage to society incurred in the current debate over global warming."
Dr. Richard S. Lindzen
(leading climate and atmospheric science expert- MIT) (3)
"Researchers pound the global-warming drum because they know there is politics and, therefore, money behind it. . . I've been critical of global warming and am persona non grata."
Dr. William Gray
(Professor of Atmospheric Sciences at Colorado State University, Fort Collins, Colorado and leading expert of hurricane prediction )
(in an interview for the Denver Rocky Mountain News, November 28, 1999)
"Science should be both compelling and widely accepted before Federal regulations are promulgated."
Dr. David L. Lewis
(27-year veteran of the U.S. Environmental Protection Agency and
critic of the agency's departure from scientific rationale in favor of political agenda)
(in an interview for Nature Magazine, June 27, 1996)
"Scientists who want to attract attention to themselves, who want to attract great funding to themselves, have to (find a) way to scare the public . . . and this you can achieve only by making things bigger and more dangerous than they really are."
(Professor of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia)
Commenting on reports by other researchers that Greenland's glaciers are melting.
(Halifax Chronicle-Herald, August 22, 2001) (8)
"Even if the theory of global warming is wrong, we will be doing the right thing -- in terms of economic policy and environmental policy."
Tim Wirth , while U.S. Senator, Colorado.
After a short stint as United Nations Under-Secretary for Global Affairs (4)
he now serves as President, U.N. Foundation, created by Ted Turner and his $1 billion "gift"
"No matter if the science is all phony, there are collateral environmental benefits.... Climate change [provides] the greatest chance to bring about justice and equality in the world."
Christine Stewart, Minister of the Environment of Canada
recent quote from the Calgary Herald
Unraveling the Earth's Temperature Record
photo by: Vin Morgan
Palaeo Environment (Ice Cores) Field Work
Because accumulating layers of glacial ice display annual bands which can be dated, similar to annual rings of a tree, the age of ice core samples can be determined. Continuous ice cores from borings as much as two miles long have been extracted from permanent glaciers in Greenland, Antarctica, and Siberia. Bubbles of entrapped air in the ice cores can be analyzed to determine not only carbon dioxide and methane concentrations, but also atmospheric temperatures can be determined from analysis of entrapped hydrogen and oxygen.
Based on historical air temperatures inferred from ice core analyses from the Antarctic Vostok station in 1987, relative to the average global temperature in 1900 it has been determined that from 160,000 years ago until about 18,000 years ago Earth temperatures were on average about 3° C cooler than today.
Except for two relatively brief interglacial episodes, one peaking about 125,000 years ago (Eemian Interglacial), and the other beginning about 18,000 years ago (Present Interglacial), the Earth has been under siege of ice for the last 160,000 years.
Compiled by R.S. Bradley and J.A. Eddy based on J. Jouzel et al., Nature vol. 329. pp. 403-408, 1987 and published in EarthQuest, vol. 5, no. 1, 1991. Courtesy of Thomas Crowley, Remembrance of Things Past: Greenhouse Lessons from the Geologic Record
As illustrated in this final graph, over the past 800,000 years the Earth has undergone major swings in warming and cooling at approximately 100,000 year intervals, interrupted by minor warming cycles at shorter intervals. This represents periods of glacial expansion, separated by distinct but relatively short-lived periods of glacial retreat.
Temperature data inferred from measurements of the ratio of oxygen isotope ratios in fossil plankton that settled to the sea floor, and assumes that changes in global temperature approximately tracks changes in the global ice volume. Based on data from J. Imbrie, J.D. Hays, D.G. Martinson, A. McIntyre, A.C. Mix, J.J. Morley, N.G. Pisias, W.L. Prell, and N.J. Shackleton, in A. Berger, J. Imbrie, J. Hats, G. Kukla, and B. Saltzman, eds., Milankovitch and Climate, Dordrecht, Reidel, pp. 269-305, 1984.Courtesy of Thomas Crowley, Remembrance of Things Past: Greenhouse Lessons from the Geologic Record
The Polar Ice Cap Effect
As long as the continent of Antarctica exists at the southern pole of our planet we probably will be repeatedly pulled back into glacial ice ages. This occurs because ice caps, which cannot attain great thickness over open ocean, can and do achieve great thickness over a polar continent-- like Antarctica. Antarctica used to be located near the equator, but over geologic time has moved by continental drift to its present location at the south pole. Once established, continental polar ice caps act like huge cold sinks, taking over the climate and growing bigger during periods of reduced solar output. Part of the problem with shaking off the effects of an ice age is once ice caps are established, they cause solar radiation to be reflected back into space, which acts to perpetuate global cooling. This increases the size of ice caps which results in reflection of even more radiation, resulting in more cooling, and so on.
Continental polar ice caps seem to play a particularly important role in ice ages when the arrangement of continental land masses restrict the free global circulation of equatorial ocean currents. This is the case with the continents today, as it was during the Carboniferous Ice Age when the supercontinent Pangea stretched from pole to pole 300 million years ago.
Stopping Climate Change
Putting things in perspective, geologists tell us our present warm climate is a mere blip in the history of an otherwise cold Earth. Frigid Ice Age temperatures have been the rule, not the exception, for the last couple of million years. This kind of world is not totally inhospitable, but not a very fun place to live, unless you are a polar bear.
Some say we are "nearing the end of our minor interglacial period" , and may in fact be on the brink of another Ice Age. If this is true, the last thing we should be doing is limiting carbon dioxide emissions into the atmosphere, just in case they may have a positive effect in sustaining present temperatures. The smart money, however, is betting that there is some momentum left in our present warming cycle. Environmental advocates agree: resulting in a shift of tactics from the "global cooling" scare of the 1970's to the "global warming" threat of the 1980's and 1990's.
Global climate cycles of warming and cooling have been a natural phenomena for hundreds of thousands of years, and it is unlikely that these cycles of dramatic climate change will stop anytime soon. We currently enjoy a warm Earth. Can we count on a warm Earth forever? The answer is most likely... no.
Since the climate has always been changing and will likely continue of it's own accord to change in the future, instead of crippling the U.S. economy in order to achieve small reductions in global warming effects due to manmade additions to atmospheric carbon dioxide, our resources may be better spent making preparations to adapt to global cooling and global warming, and the inevitable consequences of fluctuating ocean levels, temperatures, and precipitation that accompany climatic change.
Supporting this view is British scientist Jane Francis, who maintains:
" What we are seeing really is just another interglacial phase within our big icehouse climate. Dismissing political calls for a global effort to reverse climate change, she said, ' It's really farcical because the climate has been changing constantly... What we should do is be more aware of the fact that it is changing and that we should be ready to adapt to the change.' "
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Monte Hieb and Harrison Hieb
This site last updated May 20, 2002
Previous Table of Contents
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(1) A scientific Discussion of Climate Change, Sallie Baliunas, Ph.D., Harvard- Smithsonian Center for Astrophysics and Willie Soon, Ph.D., Harvard- Smithsonian Center for Astrophysics.
(2) The Effects of Proposals for Greenhouse Gas Emission Reduction; Testimony of Dr. Patrick J. Michaels, Professor of Environmental Sciences, University of Virginia, before the Subcommittee on Energy and Environment of the Committee on Science, United States House of Representatives
(3) Statement Concerning Global Warming-- Presented to the Senate Committee on Environmental and Public Works, June 10, 1997, by Dr. Richard S. Lindzen, Massachusetts Institute of Technology
(5) Testimony of John R. Christy to the Committee on Environmental and Public Works, Department of Atmospheric Science and Earth System Science Laboratory, University of Alabama in Huntsville, July 10, 1997.
(6) The Carbon Dioxide Thermometer and the Cause of Global Warming; Nigel Calder,-- Presented at a seminar SPRU (Science and Technology Policy Research), University of Sussex, Brighton, England, October 6, 1998.
(7) Variation in cosmic ray flux and global cloud coverage: a missing link in solar-climate relationships; H. Svensmark and E. Friis-Christiansen, Journal of Atmospheric and Solar- Terrestrial Physics, vol. 59, pp. 1225 - 1232 (1997).
(8) First International Conference on Global Warming and the Next Ice Age; Dalhousie University, Halifax, Nova Scotia, sponsored by the Canadian Meteorological and Oceanographic Society and the American Meteorological Society, August 21-24, 2001.
Thoughts of Global Warming: "The bottom line is that climatic change is a given. It is inescapable, it happens. There is no reason to be very concerned about it or spend bazillions of dollars to try and even things out.
What caused ice ages to start? : List of the causes of changes in earth temperatures.
Ice Ages and Glaciation: By 18,000 years ago ice sheets had spread as far south as PA, OH, IN, and IL.
The Kyoto Protocol-- Bad for the Environment?: Remember, the press is not your friend when it comes to accurate information.
Climate and the Carboniferous Period
West Virginia today is mostly an erosional plateau carved up into steep ridges and narrow valleys, but 300 million years ago, during the Carboniferous Period, it was part of a vast equatorial coastal swamp extending many hundreds of miles and barely rising above sea level. This steamy, tropical quagmire served as the nursery for Earth's first primitive forests, comprised of giant lycopods, ferns, and seed ferns.
North America was located along Earth's equator then, courtesy of the forces of continental drift. The hot and humid climate of the Middle Carboniferous Period was accompanied by an explosion of terrestrial plant life. However by the Late Carboniferous Period Earth's climate had become increasingly cooler and drier. By the beginning of the Permian Period average global temperatures declined by about 10° C.
Interestingly, the last half of the Carboniferous Period witnessed periods of significant ice cap formation over polar landmasses-- particularly in the southern hemisphere. Alternating cool and warm periods during the ensuing Carboniferous Ice Age coincided with cycles of glacier expansion and retreat. Coastlines fluctuated, caused by a combination of both local basin subsidence and worldwide sea level changes. In West Virginia, a complex system of meandering river deltas supported vast coal swamps that were repeatedly interrupted by layers of fluvial rocks like sandstone and shale when the deltas were building, and marine rocks like black shales and limestones when rising seas drowned coastlands. Accumulations of several thousand feet of these sediments over millions of years produced sufficient heat and pressure to transform the soft sediments into rock and the peat layers into the 100 or so coal seams which today comprise the Great Bituminous Coalfields of the Eastern U.S. and Western Europe.
Earth's climate and atmosphere have varied greatly over geologic time. Our planet has mostly been much hotter and more humid than we know it to be today, and with far more carbon dioxide (the greenhouse gas) in the atmosphere than exists today. The notable exception is 300,000,000 years ago during the late Carboniferous Period, which resembles our own climate and atmosphere like no other.
With this in mind the road to understanding global warming and our present climate begins with an historical journey through a chapter in Earth's history, some 30 million years before dinosaurs appeared, known as the Carboniferous Period-- a time when terrestrial Earth was ruled by giant plants and insects, and glaciers waxed and waned over a huge southern continent.
The Carbon in "Carboniferous"
An intriguing story of climate change is recorded in the rocks which comprise the geological formations of the Carboniferous Period. Coal deposits play an important role in this record.
Coal is mostly carbon residue from fossil plant material accumulating in swamps so devoid of oxygen that bacteria and other critters couldn't survive to feed on their remains. The explosion of luxuriant plant growth and coal bed formation that occurred 286 - 360 million years ago is the reason for the name, "Carboniferous Period."
North American geologists have found it convenient to divide the Carboniferous Period into two parts. The first half is called the "Mississippian Period" and is characterized by deposition of mostly thick marine limestones in shallow, tropical seas. The last half of the Carboniferous is called the " Pennsylvanian Period," and contains mostly sediments and coal seams created by meandering river deltas periodically interrupted by marine inundations. Many places around the world contain important coal beds deposited during this time period.
In West Virginia the various coal seams have each been given their own unique names: like Pocahontas, Sewell, Eagle, or Coalburg. There are subtle but noticeable changes in the character and properties of the coal beds throughout the Pennsylvanian Period, most likely due to Earth's cooling climate and quite possibly also due to declining atmospheric carbon dioxide concentrations.
Early Pennsylvanian coal seams like those found in the Pocahontas and New River Formations were characteristically friable, shiny, and "vitreous," indicating deposition in a continuously wet, humid environment.
In contrast, coals of the Allegheny Formation that followed (Middle Pennsylvanian) are predominantly hard, dull, and "splinty," indicating that by then the climate had already become drier, most likely cooler, and generally a more stressful place for terrestrial plant life. The Coalburg and Stockton seams, deposited around 307-305 million years ago, mark the geologic boundary at which a shift from tropical to temperate climate appears to have occurred.
The Kanawha Formation, represents deposition in a transitional climate, with coal seams containing alternating layers of vitreous and splinty layers, called "banded coals."
Similarities with our Present World
Average global temperatures in the Early Carboniferous Period were hot- approximately 22° C (72° F). However, cooling during the Middle Carboniferous reduced average global temperatures to about 12° C (54° F). As shown on the chart below, this is comparable to the average global temperature on Earth today!
Similarly, atmospheric concentrations of carbon dioxide (CO2) in the Early Carboniferous Period were approximately 2000 ppm (parts per million), but by the Middle Carboniferous had declined to about 350 ppm -- comparable to average CO2 concentrations today!
Earth's atmosphere today contains about 370 ppm CO2 (0.037%). Compared to former geologic times, our present atmosphere, like the Late Carboniferous atmosphere, is CO2- impoverished! In the last 600 million years of Earth's history only the Carboniferous Period and our present age, the Quaternary Period, have witnessed CO2 levels less than 400 ppm.
Global Temperature and Atmospheric CO2 over Geologic Time
Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period ).
Temperature after C.R. Scotese
CO2 after R.A. Berner, 1994
There has historically been much more CO2 in our atmosphere than exists today. For example, during the Jurassic Period (200 mya), average CO2 concentrations were about 900 ppm or about 2.5 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Ordovician Period, exceeding 6000 ppm -- more than 16 times higher than today.
The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today. To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age while at the same time CO2 concentrations then were nearly 15 times higher than today-- 5500 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.
The Carboniferous Ice Age
Two special conditions of terrestrial landmass distribution, when they exist concurrently, appear as a sort of common denominator for the occurrence of very long-term simultaneous declines in both global temperature and atmospheric carbon dioxide (CO2):
1) the existence of a continuous continental landmass stretching from pole to pole, restricting free circulation of polar and tropical waters, and
2) the existence of a large (south) polar landmass capable of supporting thick glacial ice accumulations.
These special conditions existed during the Carboniferous Period, as they do today in our present Quaternary Period.
Climate change during the Carboniferous Period was dominated by the great Carboniferous Ice Age. As the Earth alternately cooled then warmed, great sheets of glacial ice thousands of feet thick accumulated, then melted, then reaccumulated in synchronous cycles.
Vast glaciers up to 8,000 feet thick existed at the south pole then, moving from higher elevations to lower, driven by gravity and their tremendous weight. These colossal slow-motion tidal waves of ice destroyed and pulverized everything in their path, scraping the landscape to bare bedrock-- altering mountains, valleys, and river courses. Ancient bedrock in Africa, Australia, India and South America show scratches and gouges from this glaciation.
Department of Environmental and Geophysical Sciences
Manchester Metropolitan University
Earth's continents during the Carboniferous Period were arranged differently than they are today. South America, Africa, India, Australia, Antarctica, and a few minor pieces were joined together near the south pole to comprise the supercontinent known as Gondwanaland.
Gondwanaland was a formidable polar landmass. While ice caps and glaciers can't grow large over open oceans, they can and do attain great thickness over polar continents-- like Gondwanaland.
Although cycles of glaciation are believed to occur in response to solar input variations like the Milankovich Cycle and Precession of the Equinoxes, another important factor is the rearrangement of continental landmasses over geologic time by the processes of continental drift.
Throughout the Carboniferous Period, continental drift was rearranging most (but not all) of the Earth's landmasses into a single supercontinent stretching from the south polar region to the north polar region. As a result, warm equatorial waters became increasingly isolated from cold polar waters, leading to ice cap formation over the earth's polar landmasses. These glaciers grew larger during periods of reduced solar input, and because ice caps are very good solar reflectors this tended to accelerate and perpetuate cyclical relapses to global cooling.
Basically, ice ages seem to occur whenever a continuous continental landmass extends from one polar region to the other, blocking the free latitudinal circulation of ocean currents, while a large continent capable of support thick ice accumulations is situated over the south pole. These conditions existed 300 million years ago during the Carboniferous Period as they do for the Earth today. However for most of geologic history, the distribution of the continents across the globe did not satisfy this criteria. Continental drift continually rearranges the continents, moving at rates of only a few centimeters per year.
We are actually in an ice age climate today. However for the last 10,000 years or so we have enjoyed a warm but temporary interglacial vacation. We know from geological records like ocean sediments and ice cores from permanent glaciers that for at least the last 750,000 years interglacial periods happen at 100,000 year intervals, lasting about 15,000 to 20,000 years before returning to an icehouse climate. We are currently about 18,000 years into Earth's present interglacial cycle. These cycles have been occurring for at least the last 2-4 million years, although the Earth has been cooling gradually for the last 30 million years.
Over the past 750,000 years of Earth's history, Ice Ages have occurred at regular intervals, of approximately 100,000 years each.
Courtesy of Illinois State Museum
Setting the Stage for Global Climate Change
Floating atop a mantle of hot, ductile rock, the continents and ocean plates drift like gargantuan icebergs, crashing into each other, building mountain ranges and volcanic belts as they go. The phenomena is known as continental drift and the process has been going on for hundreds of millions of years-- at rates measured in only a few centimeters per year.
PALEOMAP PROJECT by Christopher R. Scotese
Illustrated above is how geologists believe Earth's landmasses were arranged 306 million years ago, during the Late Carboniferous Period.
Many of the continents we know today were recognizable then-- some more easily than others. Parts of them were either under water or hadn't been assembled yet, and almost all were part of one of two larger landmasses known as Gondwanaland and Laurasia.
Antarctica, Africa, Arabia, India, Ceylon, Australia, New Zealand and South America together comprised Gondwanaland. It was positioned near the south pole, and during the Late Carboniferous Period was largely buried under large sheets of glacial ice.
Europe, Greenland, Siberia, North America, Kazakhstan, and N.China together comprised Laurasia. It was still adding real estate to itself throughout throughout the Carboniferous and into the Permian Period.
Pangea (Greek for "all lands") is the "supercontinent" created when these two giant landmasses drifted into one another, a process that was complete by the middle of the Permian Period. Later, during the Jurassic Period, the Pangean Supercontinent began to break up and the separate continents once again drifted apart-- a process which continues today.
During Late Carboniferous time the continent of North America lay much further south than it does today. North America and parts of Europe were in the tropics. The equator stretched from central Colorado to Nova Scotia and also from Great Britain to the Ukraine.
A broad Central Pangean mountain range formed an equatorial highland that during late Carboniferous was the locus of coal production in an equatorial rainy belt (1). This produced vast amounts of sediments which were transported to equatorial coastal regions, forming deltas which supported vast coal swamps. Throughout the Late Carboniferous (Pennsylvanian) Period, Pangea drifted northward to drier, cooler climates and by the mid-Permian North America and Northern Europe had become desert-like as continued mountain-building caused much of the interior of the vast Pangean Supercontinent to be in rain shadow.
The Great Bituminous Coalfields of the Eastern U.S., Europe, and Northern China were primarily deposited during the Upper Carboniferous Period, attesting to the fact that even in the cold, icehouse climate of the Carboniferous Period lush vegetation still persisted in the world's tropical and cool temperate regions. The map projection below shows the general worldwide distribution of many of the significant coal deposits of the Late Carboniferous.
Coal Beds of the Carboniferous Period:
How the World Looked when they were Deposited
During the Upper Carboniferous Period (a.k.a. Pennsylvanian Period: 286 - 320 mya) nearly all the continents were joined as one giant landmass called Pangea (meaning "all lands"). While massive glaciers existed at the south pole, tropical swampland forests along the equator produced vast peat beds which after deep burial and subsequent heat and pressure were transformed into the Great Bituminous Coalfields of the eastern U.S and western Europe.
This image courtesy of Christopher R. Scotese Paleomap Project Evaporites Calcretes
Why there is so much coal
Warm temperatures and high humidity alone do not produce all the conditions necessary for creating coal deposits. Steadily rising sea level and/or steady regional swamp subsidence are also necessary. A prerequisite to the formation of thick coal seams requires that the rate of vegetable matter accumulation is in equilibrium with the rate of rising water levels. Rise too fast, and the swamp gets drowned, rise too slowly and dead plant material is not completely submerged when it falls to the swamp floor where it will rot or oxidize rather than be preserved.
Eustatic or global sea level fluctuations were common and regular throughout the second half of the Carboniferous Period. Coal seams are found in layers alternating between marine and non-marine rocks, indicating cycles of coastal transgressions and regressions played an important role in coal formation.
The Carboniferous-age rocks of the Eastern U.S. and Europe record regular cycles of advancing and retreating seas; where beds of coal, shale, limestone, and sandstones were deposited in more or less repetitive sequences. These sequences, called cyclothems, have been well-documented, particularly during the Late-Upper Carboniferous.
Image credit: http://members.aol.com/JMFabiny/cyclothem.html
Although several factors influenced the timing and distribution of these cyclothems, it is generally believed that cycles of rising and subsiding sea levels were the primary cause. These changes appear to have been global in scope--brought about by repetitive cycles of ice expansion, then ice melting, during the Carboniferous Ice Age.
How Coal Forms
Although most of the Carboniferous coal seams of West Virginia are on average less than 3 feet in thickness, they occasionally can be as thick as 25 feet. The bituminous coal beds of North America and Europe were laid down in swamps along coastal environments which are often dominated by meandering river deltas. Because these deltas were always moving and changing, the distribution and thickness of individual coal beds tend to be variable, sometimes erratic.
Coal seams are often comprised of distinct, mappable benches which laterally thicken and thin, merge and split apart, and often vary in physical properties like ash and sulfur based on their proximity to channel systems and marine shorelines at the time of deposition. There are many areas in the coalfields which contain few minable coals or no coals at all. But for the most part individual seam horizons are remarkably persistent along great horizontal distances. So much so that the geologic formations of this time period are often best correlated by using the coal seams themselves as "marker beds."
When conditions were right, accumulating dead plants formed peat beds which after burial were subjected to heat and pressure as additional sediment layers continued to accumulate and add weight. Several thousand feet of sediments were added during the geologic ages that followed. In the Appalachian Region, most of this rock overburden was subsequently removed by erosion.
During deep burial the peat undergoes coalification which squeezes out up to 98% of the water and some of the volatile hydrocarbons. The older and more deeply-buried a coal seam is the less water and volatile matter it contains. The ratio of fixed carbon to volatile matter is used to determine a coal's rank. The higher the ratio, the higher it's rank.
The lowest rank of coal is peat. Next comes lignite, then sub-bituminous, bituminous, and in tectonically active regions-- anthracite. Coal beds of the Carboniferous Period are almost all ranked bituminous, or higher, because of their great age and the great burial depth and moderate tectonic forces that were applied since their deposition.
A bituminous coal bed 1 ft. thick may have required as much as 7-10 ft. of peat thickness to start with. The process of peat accumulation continues until terminated by an event like an invasion of a nearby river channel, a marine transgression, or unfavorable climate. Each time shorelines retreated coal swamps migrated with them, along vast deltas which received seemingly limitless supplies of sediment from the emerging Pangean mountain range to the southeast. Although these highlands may have rivaled the Himalayas in relief, they are now completely gone-- eroded down to nothing by the relentless forces of wind and rain over geologic time.
Thanks to the Carboniferous Ice Age, and continental drift, coal occurs in relative abundance, and is mined today for a variety of energy, manufacturing, and medicinal purposes.
Our Future Written in Stone
Today the Earth warms up and cools down in 100,000- year cycles. Geologic history reveals similar cycles were operative during the Carboniferous Period. Warming episodes caused by the periodic favorable coincidence of solar maximums and the cyclic variations of Earth's orbit around the sun are responsible for our warm but temporary interglacial vacation from the Pleistocene Ice Age, a cold period in Earth's recent past which began about 2 million years ago and ended (at least temporarily) about 10,000 years ago. And just as our current world has warmed, and our atmosphere has increased in moisture and CO2 since the glaciers began retreating 18,000 years ago, so the Carboniferous Ice Age witnessed brief periods of warming and CO2-enrichment.
Following the Carboniferous Period, the Permian Period and Triassic Period witnessed predominantly desert-like conditions, accompanied by one or more major periods of species extinctions. CO2 levels began to rise during this time because there was less erosion of the land and therefore reduced opportunity for chemical reaction of CO2 with freshly exposed minerals. Also, there was significantly less plant life growing in the proper swamplands to sequester CO2 through photosynthesis and rapid burial.
It wasn't until Pangea began breaking up in the Jurassic Period that climates became moist once again. Carbon dioxide existed then at average concentrations of about 1200 ppm, but have since declined. Today, at 370 ppm our atmosphere is CO2-impoverished, although environmentalists, certain political groups, and the news media would have us believe otherwise.
What will our climate be like in the future? That is the question scientists are asking and seeking answers to right now. The causes of "global warming" and climate change are today being popularly described in terms of human activities. However, climate change is something that happens constantly on it's own. If humans are in fact altering Earth's climate with our cars, electrical powerplants, and factories these changes must be larger than the natural climate variability in order to be measurable. So far the signal of a discernible human contribution to global climate change has not emerged from this natural variability or background noise.
Understanding Earth's geologic and climate past is important for understanding why our present Earth is the way it is, and what Earth may look like in the future. The geologic information locked up in the rocks and coal seams of the Carboniferous Period are like a history book waiting to be opened. What we know so far, is merely an introduction. It falls on the next generation of geologists, climatologists, biologists, and curious others to continue the exploration and discovery of Earth's dynamic history-- a fascinating and surprising tale, written in stone.
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This page by Monte Hieb
Last updated: April 18, 2003
1) Christopher R. Scotese: Paleomap Project
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