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Global Warming:
A Chilling Perspective

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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

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A Brief History of Ice Ages and Warming

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 its 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 its end than its 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 Bering Strait was drowned, cutting off the migration of men and animals to North America from Asia.
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.

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[TD="width: 72%"]The World 18,000 Years AgoBefore "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. Forestswere rare.
Not a very fun place to live.
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[TD="width: 72%"]Our Present World"Global warming" over the last 15,000 years has changed our world from an ice box to agarden. Today extreme deserts and glaciershave largely given way to grasslands, woodlands, and forests.
Wish it could last forever, but . . . .
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In the 1970s 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 1970s temperature declines slowed to a halt and ground-based recording stations during the 1980s and 1990s 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.

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"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

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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.

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"...the Earth was evidently coming out of a relatively cold period in the 1800s 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)

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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?

Causes 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.

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Major Causes of Global Temperature Shifts

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(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:
http://www.ngdc.noaa.gov/paleo/milankovitch.html
http://www.abc.net.au/science/news/enviro/EnviroRepublish_233658.htm

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. temperaturesshow 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 little or 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).

A Matter of Opinion

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:
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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[/TD]
[TD="width: 43%"]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 humans invented industrial pollution.[/TD]
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Figure 1
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[TD="width: 78%"]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 on the increase for 18,000 years. Interestingly, CO2 lags an average of about 800 years behind the temperature changes-- confirming that CO2 is not a primary driver of the temperature changes (9).
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.
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Figure 2
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[TD="width: 80%"]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.
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Figure 3
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[TD="width: 80%"]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".
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FUN FACTS about CARBON DIOXIDE
Of the 186 billion tons of carbon from 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 380 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!

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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.

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"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 Nobody is interested in solutions if they don't think there's a problem. Given that starting point, I believe it is appropriate to have an over-representation of factual presentations on how dangerous (global warming) is, as a predicate for opening up the audience to listen to what the solutions are...
former Vice President Al Gore
(now, chairman and co-founder of Generation Investment Management--
a London-based business that sells carbon credits)
(in interview with Grist Magazine May 9, 2006, concerning his book, An Inconvenient Truth) "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) "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."
Petr Chylek
(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, former Minister of the Environment of Canada
quote from the Calgary Herald, 1999

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Unraveling the Earth's Temperature Record

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.
ice core photo by: Vin Morgan
Palaeo Environment (Ice Cores) Field WorkBased 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.

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 1970s to the "global warming" threat of the 1980s and 1990s.
Now, as we begin the 21st century the terminology is morphing toward"climate change," whereby no matter the direction of temperature trends-- up or down-- the headlines can universally blame humans while avoiding the necessity of switching buzz-words with the periodicity of solar cycles. Such tactics may, however, backfire as peoples' common sensibilities are at last pushed over the brink.
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 its 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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[TD="colspan: 2"] THIS PAGE BY:

Monte HiebThis site last updated October 5, 2007[/TD]
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References
(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
(4) Excerpts from,"Our Global Future: Climate Change", Remarks by Under Secretary for Global affairs, T. Wirth, 15 September 1997. Site maintained by The Globe - Climate Change Campaign
(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.
(9) Ice Core Studies Prove CO2 Is Not the Powerful Climate Driver Climate Alarmists Make It Out to Be; CO2 Science;
Volume 6, Number 26: 25 June 2003; http://www.co2science.org/articles/V6/N26/EDIT.php



Additional Reading
Understanding Common Climate Claims: Dr. Richard S. Lindzen; Draft paper to appear in the Proceedings of the 2005 Erice Meeting of the World Federation of Scientists on Global Emergencies.
Geological Constraints on Global Climate Variability: Dr. Lee C. Gerhard-- A variety of natural climate drivers constantly change our climate. A slide format presentation. 8.5 MB.
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.
NOAA Paleoclimatology: An educational trip through earths distant and recent past. Also contains useful information and illustrations relating to the causes of climate change.
Cracking the Ice Age: From the PBS website-- NOVA online presents a brief tour of the causes of global warming.
Little Ice Age (Solar Influence - Temperature): From the online magazine, "CO2 Science."
Solar Variability and Climate Change: by Willie Soon, January 10, 2000
Earth's Fidgeting Climate: NASA Science News "It may surprise many people that science cannot deliver an unqualified, unanimous answer about something as important as climate change"

1. We should not worry about carbon dioxide since the main greenhouse gas is water vapor. This statement misrepresents the heating process. It is the carbon dioxide (and methane) that controls the thermal structure of the atmosphere. Water vapor content is highly variable and essentially follows the carbon dioxide, providing a positive feedback that amplifies the effects of carbon dioxide.
   
2. What we are seeing are "natural variations" caused primarily by variations in solar output. This is false; we have been monitoring solar energy for a quarter century, and the variations are taken into account in all the climate models. Most of the temperature variations up to the beginning of the twentieth century can be traced to small changes in solar output, plus long-term cyclical changes in Earth's orbit and short-term cooling associated with large volcanic eruptions. There are also heating and cooling events associated with El Nino and other shifts in the circulation of the ocean and atmosphere. Since mid-century, however, the rapid heating from carbon dioxide in the atmosphere is overwhelming these "natural" cycles.
   
3. The apparent increase in temperature is an artifact caused by the fact that much of the data are from cities, which are warmer than their surroundings. This is also wrong; the "heat island" effect has been corrected in plots of global temperatures. A great deal of scientific effort is going into understanding and combining the various measurements of temperature to produce a consistent data set, combining direct measurements on the ground and from space with indirect "proxy" information, for example from isotopic measurements that track temperature very closely. Also, of course, there are large-scale effects of rising temperature that are easily seen, such as retreat of glaciers, melting on the Greenland and Antarctic icecaps, and loss of sea ice in the Arctic.
   
4. While temperatures seem to have been rising in the lower atmosphere (the troposphere), they are dropping in the stratosphere. People who say this don't realize that this is the expected signature of greenhouse warming (because greenhouse gases in the troposphere impede the flow of radiant heat from Earth's surface to the stratosphere). If there were an external cause, such as increased energy from the Sun, both troposphere and stratosphere would be heating. Today's computational models allow greenhouse warming to be distinguished from other causes and reveal the primacy of greenhouse warming over the past several decades.
   
5. Human activity and volcanic eruptions both add to the cloud cover and cause more sunlight to be reflected from the atmosphere. This largely counteracts any heating from the greenhouse effect. Atmospheric pollution, both natural (from volcanoes) and human-caused (from smoke and other aerosols), does influence temperature, reflecting sunlight and reducing the warming we would have from increased greenhouse effect alone. Without these contributions to cooling, the added greenhouse heating would be significantly greater than what we measure. There are also temperature increases caused by darkening of the surface, because more sunlight is absorbed. As the ice melts in the Arctic Ocean, the dark water absorbs a great deal more sunlight, an effect that will accelerate future global warming.
   
6. The warming trend during the 1990s is no big deal; temperatures are actually lower than they were in the medieval warm period. This is wrong; over at least the past few thousand years, temperatures have never been as high as they are today. By the middle of the twentieth century the temperature passed the record highs from about a thousand years ago, and they have been rising ever since, taking us into unknown climate territory.
   
7. While there was warming in the 1990s, this has stopped and the world is now beginning what may be a long-term cooling cycle. This is a misinterpretation of the temperature measurements. There are always short-term fluctuations in global temperature superimposed on the the overall warming trend. Those who say the temperature has plateaued or is cooling over the past decade start with the anomalously high temperature in 1998, reflecting a major El Nino event that year. If you adopt such a high temperature excursion as your baseline, of course the values tend to be lower for the next several years (called the regression to the mean). But putting aside the temperature spike in 1998, temperatures during the past decade have continued the warming trend of the 1990s.
   
8. More carbon dioxide is good, since it makes plants grow better. This might be true if we could increase carbon dioxide without greenhouse heating, but high temperatures are not good for most plants. In addition, the increase in carbon dioxide acidifies the oceans, which can destroy coral reefs or have deleterious effects on zooplankton, on which much ocean life depends. Over much of the Earth, localized long-term droughts caused by global warming will have a major negative effect on plants.
   
9. There is no consensus; many scientists disagree about global warming. This is not true at all. Dissenters have published hardly any peer-reviewed scientific papers in the past decade. The dissenters are mostly not climate scientists, and they have offered no alternative models to explain the data. The national academies of science in all of the industrialized countries have endorsed the findings of the Intergovernmental Panel on Climate Change (IPCC), which represents a strong scientific agreement on both the reality of global warming and the challenges it implies.
   
10. How can we trust climate scientists when numerous e-mails from the U.K. climate scientists show that they have distorted their data and actively suppressed dissenting opinions? These stolen e-mails from a British climate center reveal how real scientists work, warts and all. People write things in personal e-mails that they would never want published. There is no evidence, however, of fudging or suppressing the climate data. There appear to have been efforts to influence editors of scientific journals not to publish papers by global-warming deniers. At one level this is exactly what scientists normally do: vet papers through the peer-review process to weed out poor science. If the actions go further and represent impropriety, that will be revealed by the current investigation. But there is nothing in this controversy that undercuts the overwhelming scientific consensus about human-caused global warming.
    

Quote:The scientific agreement that climate change is happening, and that it's caused by human activity, is significant and growing, according to a new study published Thursday. The research, which is the most comprehensive analysis of climate research to date, found that 97.1% of the studies published between 1991 to 2011 that expressed a position on manmade climate change agreed that it was happening, and that it was due to human activity.

The study looked at peer reviewed research that mentioned climate change or global warming. Peer review is the way that scientific journals approve research papers that are submitted. In peer review, group of scientists that weren't involved in the study, but who are experts in the field, look at the research being submitted and have approved that it meets scientific process standards, and the standards of that journal.

In 2011, 521 of those peer reviewed papers agreed that climate change is real, and that human activity is the cause. Nine papers in 2011 disagreed.

John Cook, founder of skepticalscience.com and the lead author on the study, said the motivation for the analysis was the importance of scientific consensus in shaping public opinion, and therefore policy. "When people understand that climate scientists agree on human-caused global warming, they're more likely to support climate policy," Cook said. "But when the public are asked how many climate scientists agree that humans are causing global warming, the average answer is around 50%."

This "consensus gap" is what Cook and the research team is trying to close. "Raising awareness of the scientific consensus is a key step towards meaningful climate action," Cook said.

This study is not the first to examine the overwhelming agreement among climate scientists. Surveys of actively publishing climate scientists as well as analyses of climate change papers have shown similar results.

In 2004 Naomi Oreskes, Professor of History and Science Studies at the University of California San Diego, published what many scientists consider the seminal study on climate change consensus. She also co-authored the book Merchants of Doubt, which identifies and examines the similarities between today's climate change conversation and previous controversies over tobacco smoking, acid rain, and the hole in the ozone layer.

Oreskes believes that the public isn't aware of the consensus because of deliberate efforts to cause confusion. "There has been a systematic attempt to create the impression that scientists did not have a consensus, as part of a broader strategy to prevent federal government action," Oreskes said. "The public have been confused because people have been trying to confuse us."

The study published Thursday is the first to take so many papers and authors into account. Doing a search on the popular science article website Web of Science for "climate change" or "global warming" produces over 12,000 results. Of these, 4,014 papers were identified to state a position on climate change. Among those, 3,896, or 97.1% endorsed the consensus that climate change was happening and that it was caused by human activity.

In an interesting result, Cook and his team found that over time, scientists tend to express a position on climate change less and less in their research papers. This is likely a result of consensus -- that if a scientific conclusion has been reached, there's no need to continue to state that conclusion in new research. "Scientists tend to take the consensus for granted," says Cook, "perhaps not realizing that the public still think it's a 50:50 debate."

Quote:NOAA posts regularly updated measurements of the amount of heat stored in the bulk of the oceans. For the upper 2000 m (deeper than that not much happens) it looks like this:


Change in the heat content in the upper 2000 m of the world's oceans. Source: NOAA


The amount of heat stored in the oceans is one of the most important diagnostics for global warming, because about 90% of the additional heat is stored there (you can read more about this in the last IPCC report from 2007). The atmosphere stores only about 2% because of its small heat capacity. The surface (including the continental ice masses) can only absorb heat slowly because it is a poor heat conductor. Thus, heat absorbed by the oceans accounts for almost all of the planet's radiative imbalance.

If the oceans are warming up, this implies that the Earth must absorb more solar energy than it emits longwave radiation into space. This is the only possible heat source. That's simply the first law of thermodynamics, conservation of energy. This conservation law is why physicists are so interested in looking at the energy balance of anything. Because we understand the energy balance of our Earth, we also know that global warming is caused by greenhouse gases which have caused the largest imbalance in the radiative energy budget over the last century.

If the greenhouse effect (that checks the exit of longwave radiation from Earth into space) or the amount of absorbed sunlight diminished, one would see a slowing in the heat uptake of the oceans. The measurements show that this is not the case.

The increase in the amount of heat in the oceans amounts to 17 x 10[SUP]22[/SUP] Joules over the last 30 years. That is so much energy it is equivalent to exploding a Hiroshima bomb every second in the ocean for thirty years.

The data in the graphs comes from the World Ocean Database. Wikipedia has a fine overview of this database. The data set includes nine million measured temperature profiles from all of the world's oceans. One of my personal heroes, the oceanographer Syd Levitus, has dedicated much of his life to making these oceanographic data freely available to everyone. During the Cold war that even landed him in a Russian jail for espionage for a while, as he was visiting Russia on his quest for oceanographic data (he once told me of that adventure over breakfast in a Beijing hotel).

How to deny data
Ideologically motivated "climate skeptics" know that these data contradict their claims, and respond … by rejecting the measurements. Millions of stations are dismissed as "negligible" the work of generations of oceanographers vanish with a journalist's stroke of a pen because what should not exist, cannot be. "Climate skeptics'" web sites even claim that the measurement uncertainty in the average of 3000 Argo probes is the same as that from each individual one. Thus not only are the results of climate research called into question, but even the elementary rules of uncertainty calculus that every science student learns in their first semester. Anything goes when you have to deny global warming. Even more bizarre is the Star Trek argument but let me save that for later.

Slowdown in the upper ocean
Let us look at the upper ocean (for historic reasons defined as the upper 700 m):

Change in the heat content of the upper 700 m of the oceans. Source: NOAA
And here is the direct comparison since 1980:

Changes in the heat content of the oceans. Source: Abraham et al., 2013. The 2-sigma uncertainty for 1980 is 2 x 10[SUP]22[/SUP] J and for recent years 0.5 x 10[SUP]22[/SUP] J
We see two very interesting things.

First: Roughly two thirds of the warming since 1980 occurred in the upper ocean. The heat content of the upper layer has gone up twice as much as in the lower layer (700 2000 m). The average temperature of the upper layer has increased more than three times as much as the lower (because the upper layer is only 700 m thick, and the lower one 1300 m). That is not surprising, as after all the ocean is heated from above and it takes time for the heat to penetrate deeper.

Second: In the last ten years the upper layer has warmed more slowly than before. In spite of this the temperature still is changing as rapidly there as in the lower layer. This recent slower warming in the upper ocean is closely related to the slower warming of the global surface temperature, because the temperature of the overlaying atmosphere is strongly coupled to the temperature of the ocean surface.

That the heat absorption of the ocean as a whole (at least to 2000 m) has not significantly slowed makes it clear that the reduced warming of the upper layer is not (at least not much) due to decreasing heating from above, but rather mostly due to greater heat loss to lower down: through the 700 m level, from the upper to the lower layer. (The transition from solar maximum to solar minimum probably also contributed a small part as planetary heat absorption decreased by about 15%, Abraham, et al., 2013). It is difficult to establish the exact mechanism for this stronger heat flux to deeper water, given the diverse internal variability in the oceans.

Association with El Niño
Completely independently of this oceanographic data, a simple correlation analysis (Foster and Rahmstorf ERL 2011) showed that the flatter warming trend of the last 10 years was mostly a result of natural variability, namely the recently more frequent appearance of cold La Niña events in the tropical Pacific and a small contribution from decreasing solar activity. The effect of La Niña can be seen directly in the following figure, without any statistical analysis. It shows the annual values of the global temperature with El Niño periods highlighted in red and La Niña periods in blue. (Weekly updates on the current El Niño situation can be found here.)

Global surface temperature (average of the three series from NOAA, NASA and HadCRU). Years influenced by El Niño are shown in red, La Niña influenced years in blue. Source: Climate Central, updated figure from the World Meteorological Organization (WMO) p. 15.

One finds that both the red El Niño years and the blue La Niña years are getting warmer, but given that we have lately experienced a cluster of La Niña years the overall warming trend over the last ten years is slower. This can be thought of as the "noise" associated with natural variability, not a change in the "signal" of global warming (as discussed many times before here at RealClimate).

This is consistent with the finding that reduced warming is not mainly a result of a change in radiation balance but due to oceanic heat storage. During La Niña events (with cold ocean surface) the ocean absorbs additional heat that it releases during El Niño events (when the ocean surface is warm). The next El Niño event (whenever it comes that is a stochastic process) is likely to produce a new global mean temperature record (as happened in 2010).

Kevin Trenberth, who has recently published a paper on this topic, explains the increased heat uptake in the deep ocean:

The reason for the change is a specific change in the winds, especially in the subtropical Pacific, where the trade winds have become noticeably stronger. That altered ocean currents, strengthening the subtropical sea water circulation thus providing a mechanism to transport heat into the deeper ocean. This is related to the decadal weather pattern in the Pacific associated with the La Niña phase of the El Niño phenomenon.

New results from climate modelling

A study by Kosaka and Xie recently published in Nature confirms that the slowing rise in global temperatures during recent years has been a result of prevalent La Niña periods in the tropical Pacific. The authors write in the abstract:

Our results show that the current hiatus is part of natural climate variability tied specifically to a La Niña like decadal cooling.
They show this with an elegant experiment, in which they "force" their global climate model to follow the observed history of sea surface temperatures in the eastern tropical Pacific. With this trick the model is made to replay the actual sequence of El Niño and La Niña events found in the real world, rather than producing its own events by chance. The result is that the model then also reproduces the observed global average temperature history with great accuracy.
There are then at least three independent lines of evidence that confirm we are not dealing with a slowdown in the global warming trend, but rather with progressive global warming with superimposed natural variability:

1. Our correlation analysis between global temperature and the El Niño Index.
2. The measurements of oceanic heat uptake.
3. The new model calculation of Kosaka and Xie.

Beam me up Scotty!

Now to the most amusing attempt of "climate skeptics" to wish these scientific results away. Their argument goes like this: It is not possible that warming of the deep ocean accelerates at the same time as warming of the upper ocean slows down, because the heat must pass through the upper layer to reach the depths. A German journalist put it this way:

Winds can do a lot, but can they beam warm surface waters heated by carbon dioxide 700 meters further down?

This argument reveals once again the shocking lack of understanding of basic physics in "climate skeptic" circles. First the alleged problem is lacking any factual basis after all, in the last decades the upper layer of the oceans has warmed faster than the deeper (even if recently not quite as fast as before). What is the problem with the heat first warming the upper layer before it penetrates deeper? That is entirely as expected.

Second, physically there is absolutely no problem for wind changes to cool the upper ocean at the same time as they warm the deeper layers. The following figure shows a simple example of how this can happen (there are also other possible mechanisms).



The ocean is known to be thermally stratified, with a warm layer, some hundreds of meters thick, lying on top of a cold deep ocean (a). In the real world the transition is more gradual, not a sharp boundary as in the simplified diagram. Panel (b) shows what happens if the wind is turned on. The surface layer (above the dashed depth level) becomes on average colder (less red), the deep layer warmer. The average temperature changes are not the same (because of the different thickness of the layers), but the changes in heat content are what the upper layer loses in heat, the lower gains. The First Law of Thermodynamics sends greetings.

Incidentally, that is the well-known mechanism of El Niño: (a) corresponds roughly to El Niño (with a warm eastern tropical Pacific) while (b) is like La Niña (cold eastern tropical Pacific). The winds are the trade winds. The figure greatly exaggerates the slope of the layer interface, because in reality the ocean is paper thin. Even a difference of 1000 m across the width of the Pacific (let's say 10,000 km) leads to a slope of only 1:10,000 which no one could distinguish from a perfectly horizontal line without massive vertical exaggeration.

Now if during the transition from (a) to (b) the upper layer is heated by the greenhouse effect, its temperature could remain constant while that of the lower one warmed. Simple classical physics without beaming.

Beam me up Scotty! There is no intelligent life on this planet.

Links
Tamino provides his usual detailed analysis of the new study by Kosaka and Xie.
Dana Nuccitelli in the Guardian on the same paper with some further interesting aspects that I have not talked about here.
Another important point that is often forgotten in the discussion: The data hole in the Arctic that explains part of the reduced warming trend (maybe even more than previously thought).
And a reminder: The warming trend of the 15-year period up to 2006 was almost twice as fast as expected (0.3°C per decade, see Fig. 4 here), and (rightly) nobody cared. We published a paper in Science in 2007 where we noted this large trend, and as the first explanation for it we named "intrinsic variability within the climate system". Which it turned out to be.
Recent Literature:
Levitus et al. (Geophysical Research Letters 2012). Documentation of the heat increase in the world's oceans since 1955. Included are uncertainty analyses, maps of the measurement coverage and many illustrations of the regional and vertical distribution of the warming.
Balmaseda et al. (Geophysical Research Letters 2013) shows among other things that El Niño events are associated with a strong loss of heat from the oceans. As discussed above, during an El Niño the ocean loses heat to the surface because the surface of the ocean (see Fig. (a) above) is unusually warm. Further, during volcanic eruptions the ocean cools but for another reason: because volcanic aerosols shade the sun and thus the oceans are heated less than normal.
Guemas et al. (Nature Climate Change 2013) shows that the slower warming of the last ten years cannot be explained by a change in the radiative balance of our Earth, but rather by a change in the heat storage of the oceans, and that this can be at least partially reproduced by climate models, if one accounts for the natural fluctuations associated with El Niño in the initialization of the models.
Abraham et al. (Reviews of Geophysics 2013). Very recent, wide ranging review of temperature measurements in the oceans with a detailed discussion of the accuracy of the data, planetary energy balance and the effect of the warming on sea levels.