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Current Events from a Science Perspective

“How can science claim man is the cause of global warming when the temperature of the Earth was much warmer during the Medieval Warm Period (MWP)?”

The science Skeptics are quite adept at casting doubt on climate science by using clever arguments. One of their favorites is “How can science claim man is the cause of global warming when the temperature of the Earth was much warmer in the last millennium during the Medieval Warm Period (MWP)?”  You don’t really have to be a scientist to figure out that there were no accurate temperature records during the Medieval times and that much of the world was unknown.

The Skeptics usually point to historical records such as those by H.H. Lamb, which describe record heat waves in the known world during the MWP. Skeptics rather ignore the fact that H.H. Lamb was so concerned about the effect of global warming that he founded the Climate Research Unit (CRU) to study the Earth’s temperature records. The scientific questions comes down to  (1) whether the MWP was worldwide, (2) how warm the Earth actually was during the MWP, and (3) what caused the MWP?

Since there were no thermometers and no worldwide network of weather stations during the MWP, scientists have used a variety of proxy data from ice cores, isotope ratios, sediments, geological records, and even tree rings to try to reconstruct the temperatures for the last thousand years. Though there are large uncertainties in proxy records and they require careful calibration, they do show a similar pattern as you can see in the figure below, which is made up of 10 different reconstructions. The black line is the instrumental temperature record.* (See end of article for references.)

Though there are wide uncertainties in the proxy temperature records, taken together they form an overall pattern which answers the scientific questions. The proxy records show that that (1) there was a warm period from  AD 1000 to 1200, followed by a cooler period from  AD 1550 to1850  NASA identifies as the Little Ice Age, though it was not a true Ice Age. The record also show that (2) temperatures during the  MWP were quantitatively lower than the temperatures during the latter 20th century. To discover the cause of the MWP, it is necessary to look at another reconstruction.

While studying the cause of the past Ice Ages, scientists have identified the three  main factors which affect the Earth’s temperature, solar irradiance, greenhouse gases (primarily H2O and CO2), and particulates from volcanic activity. Below is a reconstruction of the three main factors controlling the Earth’s temperature. There are many interesting things in the records, but they show (3) the Earth was likely warmer worldwide during the MWP because of the higher solar radiation. It also shows that the solar radiation has been relatively constant during the last century while the other factors, primarily greenhouse gases, have increased.

 While it is possible to dispute or argue about the meaning of any of the individual records, it is rather disingenuous to claim that scientists “ have no data” or to dispute the obvious causes of the current global warming. To emphasize that, below is data from the last century, which is based on scientific records. While H20 and clouds accounts for about 75% of the greenhouse warming, their effect has increased only slightly( about 4%) while the amount of carbon dioxide has increased by about 39% in the last century.

CO2: Man is now putting about 30 billion tons of carbon dioxide into the air each year. About half of it dissolves in the ocean and they have become 20% more acidic in the last century. Much of the rest stays in the air, and  CO2 is building up in air:

Temperature: CO2 is one of the greenhouse gases that warm the Earth, and NASA’s graph shows how its increase is changing the Earth’s temperature. Note:  The effect of particulates from the explosion of Pinaturbo can be seen in the temperature decline from 1991 to 1995.

The Sun: The current global warming is often wrongly attributed to an increase in intensity of the sun. The sunspot activity does not show up above the noise in the temperature record above. The solar irradiance increased slightly until 1960 and has declined slightly since then.

There is the scientific story. Disputes in science are settled by the data. Though Skeptics may dispute the evidence showing the current global warming is caused by man, the question is ” Where is the evidence?”

* References for temperature reconstructions:  The original version of this figure was prepared by Robert A. Rohde from publicly available data from NOAA and the references therein. The article stated: “For the purposes of this comparison, the author is agnostic as to which, if any, of the reconstructions of global mean temperature is an accurate reflection of temperature fluctuations during the last 2000 years. “ The reconstructions used, in order from oldest to most recent publication are:

• (dark blue 1000-1991): P.D. Jones, K.R. Briffa, T.P. Barnett, and S.F.B. Tett (1998). “High-resolution Palaeoclimatic Records for the last Millennium: Interpretation, Integration and Comparison with General Circulation Model Control-run Temperatures”. The Holocene 8: 455-471. doi:10.1191/095968398667194956

• (blue 1000-1980): M.E. Mann, R.S. Bradley, and M.K. Hughes (1999). “Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations”. Geophysical Research Letters 26 (6): 759-762.

• (light blue 1000-1965): Crowley and Lowery (2000). “Northern Hemisphere Temperature Reconstruction”. Ambio 29: 51-54. Modified as published in Crowley (2000). “Causes of Climate Change Over the Past 1000 Years”. Science 289: 270-277. doi:10.1126/science.289.5477.270

• (lightest blue 1402-1960): K.R. Briffa, T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, S.G. and E.A. Vaganov (2001). “Low-frequency temperature variations from a northern tree-ring density network”. J. Geophys. Res. 106: 2929-2941.

• (light turquoise 831-1992): J. Esper, E.R. Cook, and F.H. Schweingruber (2002). “Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability”. Science 295 (5563): 2250-2253. doi:10.1126/science.1066208.

• (green 200-1980): M.E. Mann and P.D. Jones (2003). “Global Surface Temperatures over the Past Two Millennia”. Geophysical Research Letters 30 (15): 1820. doi:10.1029/2003GL017814.

• (yellow 200-1995): P.D. Jones and M.E. Mann (2004). “Climate Over Past Millennia”. Reviews of Geophysics 42: RG2002. doi:10.1029/2003RG000143

• (orange 1500-1980): S. Huang (2004). “Merging Information from Different Resources for New Insights into Climate Change in the Past and Future”. Geophys. Res Lett. 31: L13205. doi:10.1029/2004GL019781

• (red 1-1979): A. Moberg, D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén (2005). “Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data”. nature 443: 613-617. doi:10.1038/nature03265

• (dark red 1600-1990): J.H. Oerlemans (2005). “Extracting a Climate Signal from 169 Glacier Records”. Science 308: 675-677. doi:10.1126/science.1107046

• (black 1856-2004): Instrumental data was jointly compiled by the w:Climatic Research Unit and the UK Meteorological Office Hadley Centre. Global Annual Average data set TaveGL2v [2] was used.

(c) 2012 J.C. Moore

Note added on 07/09/2013 : In a new study by the PAGES 2k project, that was  published in Nature Geoscience , 78 researchers from 24 countries worked for seven years on the most extensive climate reconstruction to date of the past 2000 years.  It is based on 511 climate archives from around the world, from sediments, ice cores, tree rings, corals, stalagmites, historical documents and measurements.  Their  graph below confirms the basic “hockey stick” shape of the graph:

A group of Skeptics once managed to take over an editorship at a peer-reviewed journal  and publish articles hostile to mainstream climate science. With the help of politicians and large funding sources, the hostilities have continued to this day.

What will the weather be like in the future? Dr. Heidi Cullen, noted climatologists and author of the book, The Weather of the Future , gave a public talk in Tulsa explaining how global warming is causing the weather to be more extreme. She explained that our future holds an increasing number of extreme weather events unless we act to reduce our carbon emissions.  There was an article in the local Tulsa World newspaper announcing the talk; however,  there was no follow-up article describing the talk or her research on climate change. Tulsa Oklahoma was once considered the oil capital of the world and many of the local politicians and oil company executives that live there do not have a favorable opinion of climate change, so her message was one many Oklahomans needed to hear. To correct the newspaper’s oversight, the author sent the following letter to the editor, which outlined the main points of her talk. The letter generated some controvery and there were a number of comments on the letter.

In her talk, Dr. Cullen explained how global warming is changing our climate. Climate describes the average weather, and research shows the Earth’s average weather has been changing. It is difficult to recognize the pattern of change and only by analyzing millions of weather and temperature records is it possible to see the pattern. Over the last century, NASA’s temperature records show that the Earth’s temperature has increased by about 1°F. That has increased the energy in the atmosphere and the moisture in the air over the oceans. That combination is causing our weather to become more extreme, as you have probably noticed from the events that have happened lately.

Dr.Cullen explained that climate is complex, made up of both natural and man-made factors, and the scientific research has been directed toward identifying the contributions of each. Carbon dioxide was identified in the 19th century as one component of the atmosphere that helps warm the Earth. Our activities have increased the CO2 concentration in the air by 37% since then, and undoubtedly much of the recent warming has been caused by man. Detailed studies of extreme weather events have shown that global warming contributed to their severity. Although that may seem bad news, the upside of that is that if we are responsible for it, we can change it.

The first step in that process is to immediately begin to reduce our carbon dioxide emissions from fossil fuel energy sources. Dr. Cullen outlined what our energy needs will be by 2050 and showed how we can reduce our carbon emissions and meet our energy needs by then with mostly renewable sources. She explained that building the infrastructure for renewable energy will create jobs and contribute to our economy. Rather than considering the cost of doing so a mortgage on future generations, we should consider reducing pollution and developing sustainable energy sources as an investment in our future.

(c) 2011 J.C. Moore

Science is about using observation and reason to understand the physical world. Some people are suspicious of computer models and theories; so here is the basic data about global warming in pictures and graphs.

Ice Ages: In the past, the Earth’s temperature has varied from the Ice Ages to the much warmer temperatures of the interglacial periods.  Ice core data gives a good picture of what has happened to the Earth’s temperature in the last half million years, as shown by the blue line. The changing temperatures are attributed to the Milankovitch Cycles, small variations in the Earth’s orbit that cause the Earth to receive different amounts of sunlight. The Earth becomes slowly warmer during the periods where the solar energy increases. As the Earth begins to be warmed by sunlight, CO2 becomes less soluble in the ocean and the CO2 concentration in the atmosphere increases, which further amplifies the warming since CO2 is a greenhouse gas.

As you can see in the graph, the red line shows how intricately the CO2 concentrations and temperatures are related. The CO2 concentration drops to about 180 ppm during the glacial periods and rises to about 290 ppm during the warmer interglacial periods. As the far right of the graph shows, we are now in an interglacial period that began about 6000 years ago. The Milankovitch Cycles predict that Earth should slowly cool for the next 20,000 years, but it is warming instead.  Please note that the concentration of CO2 did not rise above 300 ppm in any previous warmer periods but on the far right side of the graph, the red line indicating the CO2 concentration is now approaching 380 ppm. http://www.daviesand.com/Choices/Precautionary_Planning/New_Data/IceCores1.gif

Current CO2 Levels: In the past, the warming oceans released the CO2 as a natural process. However, man is now putting about 30 billion tons of carbon dioxide into the air each year. Much of it stays there and the Keeling curve below shows how CO2 is building up in air. What might that mean for man? In 2011, the CO2 concentration reached 387 ppm, far higher than it has been for perhaps 15 million  years.

 This article explains what the Earth may have been like then: “The last time carbon dioxide levels were apparently as high as they are today — global temperatures were 5 to 10 degrees Fahrenheit higher , the sea level was approximately 75 to 120 feet higher, there was no permanent sea ice cap in the Arctic, and very little ice on Antarctica and Greenland.”

Earth’s Temperature: Carbon dioxide is one of the greenhouse gases that warm the Earth. NASA’s graph below shows how its increase is changing the Earth’s temperature. Though the Earth’s mean temperature varies widely from year to year, the graph on the right is a moving average that allows you to see the trend in the temperature much easier.

                                                           htp//data.giss.nasa.gov/gistemp/2010november/fig2.gif

  The effect of particulates, which cool the Earth, can be seen around 1991 when Mount Pinaturbo exploded. The flat place in the graph from about 1940 to 1970 is attributed to particulates generated by World War II, atmospheric atomic bomb testing, and postwar industrialization – before particulate emissions were regulated. Clearly, the Earth is getting warmer.

Record Temperatures: Nine of the 10 hottest years on record occurred in the last decade. The other record-breaking year was 1998. the chart gives the record temperatures for 50 years and the inset for the last last 160 years.

This has led to extreme heat waves  in areas such as Moscow.

Effect on the Weather:  According to NOAA, global warming is affecting the El Niño and La Niña ocean currents cycles which affect  the weather patterns in North America.  The cycles are occurring at higher temperatures and are becoming more unpredictable . Changes in ocean currents may be a major tipping point in climate change.

Effect on the Earth: Scientist tell us that the increasing CO2 concentration is leading to a warmer Earth, more extreme weather, melting glaciers and polar ice, crop failure, droughts, and wildfires. We have certainly experienced many of those things recently, which should make us think about what effect our activities are having on the Earth. Many of the changes in the Earth are subtle, but here are two of NASA’s pictures that clearly show how the Earth is changing. Between 1979 and 2010, about 30% of the Arctic ice has disappeared.

 This has greatly affected the way of life of the native Inuit who live and hunt on the Polar ice.  While they may adapt, their way of life and culture which sustained them for centuries will be destroyed. The Polar bears, uniquely adapted to live in on the Polar ice, have been put on the threatened species list because their habitat is clearly declining.  As their habitat disappears, so will be the Polar bear. It is something man should think about – as our habitat is deteriorating, also.

 Note: This was posted on 09/01/2011 and updated on 03/06/2013 to include data that was not presented in this more comprehensive collection of pictures and graphs of global warming data.

(c) 2011/ 2013 J.C. Moore

Science is about using observation and reason to understand the physical world. Some people are suspicious of computer models and theories; so here is some of the the basic data in pictures and graphs.

Ice Ages: In the past, the Earth’s temperature has varied from the Ice Ages to the much warmer temperatures of the interglacial periods.  Ice core data gives a good picture of what has happened to the Earth’s temperature in the last half million years, as shown by the blue line. The changing temperatures are attributed to the  Milankovitch cycles,  small variations in the Earth’s orbit that cause the Earth to receive different amounts of sunlight. The Earth becomes slowly warmer during the periods where the solar energy increases. As the Earth begins to be warmed by sunlight, CO2 becomes less soluble in the ocean and the CO2 concentration in the atmosphere increases, which further amplifies the warming since CO2 is a greenhouse gas.  The CO2 did not rise above 300 ppm in any of the the warmer interglacial periods but it is now 398 ppm and rising.

  CO2: Man is now putting about 30 billion tons of carbon dioxide into the air each year. About half of it dissolves in the ocean, making them 20% more acidic, and the rest increases the concentration in the air.

Temperature: CO2 is one of the greenhouse gases that warm the Earth, and NASA’s graph shows how its increase is changing the Earth’s temperature:

.                            NASA GISS Data.

The Sun: The current global warming is often wrongly attributed to an increase in intensity of the sun. The sunspot activity does not show up above the noise in the temperature record above – and the solar irradiance increased slightly until 1960 and has declined slightly since then.

Arctic Ice: Many of the changes in the Earth are subtle but this NASA picture clearly shows  how the Earth is changing:

Arctic ice:  The next two graphs show quantitatively how both the extent and the volume of the Arctic ice is changing.

Arctic ice volume at each years minimum.

Antarctica: Research by Steig and by O’Donnell  show that Antarctica is warming. The warmer oceans result in more snowfall which increases the inland glacier mass, but the erosion of ice by the warmer oceans is causing an overall loss of ice mass.

Antarctic ice mass from GRACE satellite data.

Greenland: The Greenland ice sheets are also beginning to decline.

Ocean Level Rise: The melting ice sheets, melting glaciers, and thermal expansion are causing the oceans to rise by about 3 mm per year which, though it seems small, amounts to an increase in ocean volume of 1190 cubic kilometers/yr.

Rise in Sea Level.

Severe Weather: Warmer temperatures increase both the rate of evaporation and the energy and moisture in the air. This has doubled the incidence of severe weather, floods, droughts, and wildfires.

Permission Courtesy of Munich Re.

Economic Costs: Large insurance companies such as Suisse Re now consider global warming a risk factor as there has been a fivefold increase in billion-dollar weather events in the last 30 years.

Droughts: The Palmer Drought Index below includes most of the continental areas used for food production. Zero represents average rainfall and -4 represents extreme drought. Since 1980, drought conditions have grown worse worldwide, and no one disputes the effect of droughts on food production.

Note : This was posted on 08/31/2011 and  updated on 04/03/2012,08/11/2012, and o2/12/2013.

(c) 2011  J.C. Moore

2011 Wildfire Terlton OK

In 1998, the US refused to ratify the Kyoto Treat which would have limited the release of greenhouse gases, primarily CO2, into the atmosphere. The refusal was based mainly on the highly inflated financial costs, without adequately considering the costs of inaction. On a per capita basis the US emits six times as much CO2 as any other country. Without our participation and leadership, the world has failed to stem the release of CO2 into the air, and scientists tell us that this is leading to a warmer Earth, more extreme weather, crop failure, droughts, and wildfires. We have  certainly experienced many of those things recently and it should make us think about what our failure to ratify the Kyoto Treaty may mean to us.

Three weeks ago the local Cleveland American’s front-page story was about the heat wave and the drought. Channel 6 Weather reported that this year Oklahoma set a record for highest temperatures of any state, ever. Recently, NASA reported this has been the hottest decade since records began in 1880, with 2010 and 2005 tied for the hottest years. A recent poll of climate scientists found that 97% of those active in research agree that the Earth is getting warmer and the main factor is man’s release of carbon dioxide into the air. The other 3% of the scientists get enough publicity to keep the public confused, especially since the climate scientists cannot claim certainty in their predictions, but only increased chances.

A recent paper from the University of Colorado predicted that global warming would cause higher probabilities of extreme weather, heat waves, droughts, crop failure, and wildfires. We’ve certainly seen all that happen this year. Last week, the Cleveland American’s front page story was on the devastating wildfires in the surrounding Pawnee County. Around 15,000 acres of our county burned, 40 homes when up in flames, one person died, and many were injured.  It stretched the resources of our emergency services to the limit and had it not been for the heroic efforts of our firefighters, many of them volunteers, the devastation would have been much worse.

Skeptical scientists, and many of our politicians, dispute the scientific evidence and claim there is not really a problem. They say that efforts to stop global warming will cause us too much inconvenience and expense. We might want to think about how inconvenient and expensive it is for us to lose our crops, homes, and in some cases our loved ones?

Sen. James Inhofe (R –OK) is famous for his statement, “Global warming is a hoax”. The local Tulsa newspaper often carries letters giving the opposing viewpoint. For example, Corey Cohen, recently wrote, “Sen. Inhofe, please cease your effort to stop EPA’s ability to limit greenhouse gas emissions. The science of global warming and climate change is obvious and known. For example, excessive CO2 in the atmosphere absorbs heat reflected from the ground and traps that heat in the atmosphere, melting glaciers and ice and snow packs all around the planet. A given molecule of CO2 in the atmosphere has a life of approximately 100 years. The implications are fairly obvious: rising sea levels, loss of fresh water for humans and unpredictable growing seasons for Oklahoma farmers and their winter wheat crops due to atmospheric heating.” (1)

Mr. Jack Williams replied (2) by “pointing out a few facts”  to defend Senator Inhofe’s position:

“1. More than 31,000 scientists signed a petition opposing the concept of man-made global warming.

2. More than 100 top climate scientists have expressed their opposition.

3. A dozen recognized scientists from nine countries who initially were global-warming proponents have changed their opinion and now oppose it in light of recently published information.

4. Earth has undergone many cooling and warming periods during its history.

5. Carbon dioxide constitutes less than 0.1 percent of the atmosphere while water vapor, at least as effective a greenhouse gas as CO2, ranges from about 20 to 100 times its concentration, and is quite variable.

6. There has been no measurable increase in global temperatures during the past decade.

7. The polar bear population dramatically increased during the past decade, as has ice thickness on Antarctica.”

It’s always nice to get alleged facts in a numbered list, where it is possible to check them one by one.

Endorsements: Facts one, two and three, fall into  the category of endorsements, and as with many endorsement, it is not always clear how well qualified those who endorse the position are, or whether the numbers listed are significant. There are about 23 million graduates with degrees in science and engineering. If 31,000 scientists signed the Oregon Petition, that is about 0.13% of those – hardly significant. Even then, the petition appears to be a hoax. In 1989, the Petition was mailed to thousands of Bachelor of Science students. It was formatted to appear as if it came from the National Academy of Science, but the organization quickly responded that the information was misleading and “the petition does not reflect the conclusions of expert reports of the Academy.”  The mailing collected 17,000 signatures and 14,000 have been added since. Most anyone could sign it, many who signed were misled, and many were not scientists at all, as it is possible to get BS degrees in fields such as journalism, sociology, education, philosophy… (3)

Endorsements that matter: All the major scientific organizations in the world have endorsed a statement such as that of the American Chemical Society,  “Careful and comprehensive scientific assessments have clearly demonstrated that the Earth’s climate system is changing rapidly in response to growing atmospheric burdens of greenhouse gases and absorbing aerosol particles. There is very little room for doubt that observed climate trends are due to human activities. The threats are serious and action is urgently needed to mitigate the risks of climate change.” (4) A recent CNN poll found that 97% of scientists who are actively engaged in research in climate science agree that global warming is caused by man. (5) There is clearly a consensus among scientists on the matter and those making policy would be wise to heed it.

Warming and Cooling: Point four is a fact, but it is not relevant to what is happening today. The Earth has in the past had many natural warming and cooling periods but the current warming trend is not part of those. In the  past, ice ages and warmer interglacial periods have occurred in roughly 100,000-year cycles. These are attributed to the Milankovitch cycles. These cycles are small variations in the eccentricity, axial tilt, and precession of the Earth’s orbit that cause the amount of sunlight the Earth receives to increase and decrease in predictable cycles The cycles predict that a slow cooling trend, which began some 6,000 years ago, will continue for the next 23,000 years. The current warming trend is too rapid and in the wrong direction for the Milankovitch Cycles to be the cause. (6)

Greenhouse gases: Point five is also a fact, but it incorrectly downplays the role of  CO2  in determining the Earth’s temperature. In 1956, G.N. Plass calculated (7) that doubling the concentration of CO2 in the air would cause a 3 to 4 C increase in the Earth’s temperature. Many dismissed his work, as it seemed impossible that CO2, which made up only 0.03% of the air, could have such a large effect on temperature.   However, in 1997, J.T. Kiehl found (8) that, under clear sky conditions, CO2 accounted for 26% of the greenhouse effect – with water vapor accounting for most of the rest. More recent research (9) has confirmed their work, and CO2 has been labeled the “Control Knob” for the Earth’s temperature.  Recent research in the Journal of Climate, covering the last five ice ages, has experimentally confirmed Plass’ work. The Earth is warming because of the greenhouse gases we emit, and research finds the increase in CO2 is the main cause.

Temperature record: Fact six is based on the idea that 1998 was so hot, it couldn’t have been hotter since. However, NASA’s temperature record shows that 2005 and 2010 are tied for the warmest year on record and the last decade has been the hottest in recorded history – and the trend is yet upward (10). There have been attempts to discredit NASA’s temperature data by challenging the accuracy of the temperature recording stations, but a study of that issue by the American Geophysical Union found that claim to be false. (11) NASA has put men on the Moon and brought them home safely, and they certainly should be able to measure temperatures on the Earth correctly.

Polar Bears:  It’s true that the Polar bear population has increased, but not because the Polar ice is increasing. The bears were hunted nearly to extinction, and their population is increasing because restrictions were placed on hunting them from aircraft . Recently, Polar bears have been put on the threatened species list, not because of their numbers, but because their habitat is disappearing.  Satellite measurements of the Arctic sea ice have shown that both the volume and extent of the sea ice has decreased remarkably over the last 30 years. (12) Polar bears are uniquely adapted to live and hunt on the Arctic Sea ice. As it disappears, so will the Polar bears.

Claiming something as “fact” does not make it so. And, even facts can be misleading if the inferences drawn from them are in error.  If Senator Inhofe bases his position on facts such as those listed by Mr. Williams, it is easy to see why he incorrectly thinks global warming is a hoax.

(1)http://www.tulsaworld.com/opinion/article.aspx?subjectid=62&articleid=20110313_222_G2_CUTLIN933913

(2)http://www.tulsaworld.com/opinion/article.aspx?subjectid=62&articleid=20110403_62_G2_InhisM784632

(3) http://jcmooreonline.com/2010/01/29/the-oregon-petition-how-can-31000-scientists-be-wrong/

(4) http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change#General_science

(5) http://articles.cnn.com/2009-01-19/world/eco.globalwarmingsurvey_1_global-warming-climate-science-human-activity

(6) http://jcmooreonline.com/2010/12/31/science-global-warming-and-the-ice-age-mystery/

(7) http://www.aip.org/history/climate/co2.htm#M_25_

(8) http://journals.ametsoc.org/doi/abs/10.1175/1520-0477%281997%29078%3C0197:EAGMEB%3E2.0.CO;2

(9) http://www.sciencemag.org/content/330/6002/356.abstract

(10) http://data.giss.nasa.gov/gistemp/2010november/fig2.gif

(11)http://www.agu.org/pubs/crossref/2010/2009JD013094.shtml

(12) http://climateprogress.org/wp-content/uploads/2011/01/NSIDC-12-10.gif

(c) 2011 J.C. Moore

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