In previous remarks on the HOME page, I've quoted authorities, such as Prof. Reid Bryson, and well-known history, such as the Norse settlement of Greenland and Vinland, to assure you that the global warming "crisis" is exaggerated. Serious scientists, such as Prof. Bryson (and others on the references page) tell us so; the recorded history of Western civilization (and other civilizations) tell us so as well.
This page talks about the science behind "global warming," which disputes it as well.
The fundamental fallacy in the man-made global warming hoax is the claim that carbon dioxide (CO2) is an important greenhouse gas. It isn't, for several reasons. I'm going to explain the reasons, qualitatively, and then give you some quantitative numbers that show how unimportant CO2 is.
Reason #1: A greenhouse can get only so warm...
Let's remember what a greenhouse gas (GHG) does. It's called that because, like the glass in a physical greenhouse, it prevents heat from escaping. The glass prevents heat from blowing away with the wind; water vapor (H2O) and CO2 prevent infrared (heat) photons from escaping. Adding more GHG doesn't guarantee more warming, anymore than adding a fifth blanket on the bed will make you warmer than the fourth blanket. The upper limit is 98.6 F; once you're there, you won't get any warmer. Once you have enough GHG to intercept all the infrared photons, adding more GHG has no effect. Over most of the earth, this is true. Because of H2O (not CO2), the greenhouse effect is maxed out. Adding CO2 has no effect.
Mathematically, GHG's obey a logarithmic law. Like adding multiple blankets to the bed, each successive increment of GHG has only half the warming effect of the previous increment. That's because the newly-added molecules of GHG have to compete with the ones already there - both H2O and CO2. Eventually the atmosphere (at a particular wavelength) becomes opaque; no infrared photons can escape. Additional GHG has no effect beyond that point. In the real atmosphere, CO2 added by humans has to compete with much more natural CO2 and vastly more H2O. It just doesn't make any difference across most of the spectrum.
Reason #2: CO2 is not an important absorber.......
We need to remember that molecules (H2O, CO2) have resonant frequencies (wavelengths); the tri-atomic molecules,
depending on their geometry, may absorb infrared radiant energy by vibrating and by rotating. Take a look at the sketch on the right, a representation of the two major greenhouse gasses, H2O and CO2. Notice H2O is asymmetrical, and slightly polarized. That is, the hydrogen (H) end of the molecule tends to be slightly positive, and the oxygen (O) end slightly negative. An electromagnetic (E-M) wave, alternating between positive and negative, causes the H2O molecule to rotate, and absorb anergy. In addition, electromagnetic waves of a resonant frequency cause the H-O bonds to resonate, to vibrate. Both vibration and rotation absorb energy from the E-M wave.
Now look at the CO2 molecule (C-O-C). It's symmetrical and unpolarized, so it doesn't rotate when an E-M wave passes by. It has only one vibrational mode, along the C-O-C axis. It's a much less efficient absorber of E-M energy than H2O, and that's what the greenhouse effect is all about.
Because of its single (vibrational) resonance, CO2 has only a single absorption line in Earth's infrared spectrum, around 14.8 micrometers (um). What kind of infrared photons does a CO2 molecule "catch" at 14.8 um? They come from an object whose temperature is about 200 degrees K - about 100 degrees F below zero. Nothing on earth is really that cold, but everything emits radiant energy photons across the infrared spectrum. There just aren't many of them emitted at 14.8 um, and they carry very, very little energy. Capturing them does very little to keep Earth warm, like a blanket that covers only a small part of your body. 
The figure on the left illustrates the broad spectrum of absorption (top) by the H2O molecule - across the emission spectrum of the earth and lower atmosphere - in comparison with the narrow spectrum (bottom) of CO2. CO2 just doesn't catch most of the infrared energy leaving the earth - effectively, it isn't there.
Reason #3: There's very little CO2 around.......
One reason global warming due to CO2 is unimportant is because there's very little of it - 385 parts per million by volume (ppmv). That's less than 0.04 % of the atmosphere. Water vapor, on the other hand, ranges up to 4% - 100 times as much.
The real reason man-made global warming is unimportant is because natural CO2 is more than 96% of all the CO2 in the atmosphere. Even if CO2 were an important greenhouse gas (as it isn't), complete elimination of all human CO2 emission would have no practical effect. Suppose we were to cut all human CO2 emission by 25% (which would cripple our economy). That would be 1% of all the CO2 in the atmosphere. Changing anything by 1% is unlikely to lead to catastrophe.
Incidentally, greenhouse gases lead to warming, not cooling. I hope that's obvious from the discussion above, but as "global warming" becomes less and less credible, the alarmists are beginning to claim the crisis is "climate change" - including cooling.
Another major agent of climate change - much more important than CO2 - is cloud cover. We all have experience of that; we know how a cloudy sky cools a hot Summer day, and how clouds warm a Winter night. In radiative terms, clouds are black bodies - objects which absorb all the infrared photons they receive. This is true across the IR spectrum; they're even better than gaseous H2O and CO2 in their "greenhouse effect." In daylight, they scatter sunlight back, away from Earth. So what is their net effect? Cooling? Warming? Nobody knows. Whatever it is, it's more important than CO2, and it's not controllable by humanity. Another fatal flaw in controlling the "climate crisis."
Those are the qualitative explanations of the unimportant greenhouse warming due to CO2. Let's now look at some numbers describing the magnitude of CO2's greenhouse effect. The numbers come from the IPCC's Fourth Assessment Report, Working Group 1. This document can be downloaded from the University Corporation for Atmospheric Research, at
Working Group 1 Working Group 1 contains the scientific rationale and data on which other parts of the IPCC report are based.
In AR4WG1_Pubs_FAQs, FAQ 1.1, Figure 1, you'll find a diagram of the solar energy that warms our planet's surface (168 watts/sq meter) and atmosphere (67 w/sq m), totalling 235 w/sq m. If the earth is not to warm or cool on a long term basis, that incoming solar energy must be balanced by outgoing energy in the longwave infrared (5 - 15 micrometers) spectrum. As may be seen on the right in the diagram, 235 w/sq m eventually escapes.
Of particular interest are the two energy exchanges in the lower right of the figure, 390 w/sq m radiated (up) from the surface, and 324 w/sq m radiated down from the atmosphere. This 324 w/sq m is the "greenhouse effect"; it's the radiant energy the atmosphere captures and returns to the surface, like a second sun in the sky. Fortunately, this "sun" shines even during the night. The greenhouse radiant energy warms the earth by about 33 degrees C, or 60 F. Without it, the earth would be uninhabitable. How much of this beneficial greenhouse effect is due to water vapor, and how much is due to carbon dioxide? A later table in the IPCC report tells us (though they try to hide the values).
In AR4WG1_Pubs_FAQs, you'll find FAQ 2.1, figure 2. This figure itemizes the anthropogenic greenhouse gasses
that contribute to global warming. The total radiative forcing from carbon dioxide and all other anthropogenic gasses is only 1.6 watts/ square meter. That's out of the total of 324 w/sq m due to the total greenhouse effect. The rest - i.e., 322 w/sq m - comes from natural greenhouse gasses, which don't appear on Figure 2. If they did, any casual reader would immediately recognize how natural water vapor and natural carbon dioxide dominate the greenhouse effect.
In case you're wondering how many degrees C or F these "radiative forcings" amount to, the 324 w/sq m from the atmosphere warms the earth by 33 C, so it's about a 10:1 ratio (9.81818...) of w/sq m to degrees C. So the 1.6 w/sq m of radiative forcing due to all man-made greenhouse gasses causes a warming of 0.16 C or 0.29 F.
Yes, that's what this "global warming crisis" is all about. All the carbon dioxide and other industrial greenhouse gasses added to the atmosphere have warmed the earth by a third of a Fahrenheit degree.
The Pacific Decadal Oscillation (PDO)
Science is about data and theories to explain the data, and to predict future data. AGW tells us that cooling temperatures and increased snowfall are unusual, but perhaps these - such as the very cold 2008 across the US - are just statistical anomalies, "weather" rather than "climate," small, random variations from the overall trend. Believers in AGW assure us that the cold 2008 in the US is just an anomaly; it doesn't disprove AGW. But, just in case, believers are replacing the "global warming" phrase with "climate change."
On the other hand, there is a different theory (one of several), the Pacific Decadal Oscillation (PDO), that tells us storms and cold weather should be expected in the coming climate, the next 20 to 30 years. The Pacific Decadal Oscillation was identified at the University of Washington in 1996. The theory postulates - based on observational data - that the Pacific Ocean, Earth's largest, goes through shifting phases of warm and cold in East and West. From a selfish point of view, we in the US are warmed by a warm phase, and chilled by a cold phase. The climate models of the Intergovernmental Panel on Climate Change don't include the PDO.
As we see from the diagram on the right, there was a warm phase from 1915 to 1945, which included the "Dust Bowl" years, the warmest period in American climate. From 1945 to 1977, the PDO was in its cool phase, and climatologists - and The Media - considered a returning Ice Age. (TIME magazine had a cover story in July 1974 about the coming doom.) Fortunately, Doom was averted when the PDO entered a new warm phase in 1977, when many climatologists noted a Great Pacific Climate Shift. This warm phase of the PDO lasted until 1998, culminating in the major El Nino of 1997 - 1998 (hyped by Mr. Gore as "the warmest year of the Millenium.") PDO phases typically last about 30 years.
Following 1998, the PDO appears to have gone back into its cool phase. What does this mean? Normal circulation in the Pacific includes an equatorial transport of water westward, due to the prevailing Trade Winds. The water transported westward is replaced by cold water, upwelling from lower depths along the coast of South America. Similar cold upwelling takes place along the California Coast, leading to Twain's famous remark that "the coldest Winter I ever spent was a Summer in San Francisco." This pattern of strong equatorial westward flow is referred to as "La Nina." During La Nina conditions, warm water "piles up" around Indonesia and Australia; sea level there may be two feet higher than along the South American Coast.
Occasionally, for reasons we don't yet understand, the Trades weaken, or cease altogether, the westward current halts, and warm water flows back Eastward. The cold upwelling along the coast is replaced by warm water. The warm water off the west coasts of the Americas provides an energy source (evaporation) for developing storms; the most famous such episode was in the extended El Nino of 1997 - 1998, when storms battered the California Coast and the Santa Monica pier was destroyed. In South America, El Nino reduces or eliminates fishing, since the fish follow the nutrient in the cold upwelling water. No upwelling, no fish.
What was recognized only recently is that El Ninos are stronger, and more frequent, during the warm phase of the PDO; La Ninas dominate during the cold phase. An example is the 1945 - 1977 cold phase, when The Media warned us of a coming ice age. On the figure, that 1945 - 1977 cold phase has been extrapolated to our own time. Both the University of Washington and NASA/JPL agree that the PDO has entered its warm phase, with more cold La Ninas to be expected. Cooling temperatures and increased snowfall may be the dominant climate for the next generation.
Climate change and solar activity
Another hypothesis of climate change is obvious (but not considered by the IPCC). Our sun is a variable star; we have records of its variability, manifested in the number of sunspots visible through a telescope (developed by Galileo in the early 1600's).
Sunspots, which show up as dark patches on the surface, are indicators of increased solar output of radiance, of mass (the solar wind), and of a stronger solar magnetic field. A recent hypothesis put forward by Svensmark and Calder ("The Chilling Stars", 2007) suggests that a strong solar magnetic field shields the earth (which it surrounds) from high-energy Galactic Cosmic Rays (GCRs). The GCRs, presumed to come from supernovae far outside our Solar system, have enough energy to create ions in Earth's atmosphere. These ions act as nuclei for the formation of cloud droplets in the lower atmosphere, which cool the earth. Thus (it is hypothesized), an active Sun warms the Earth, not by increased Total Solar Irradiance (TSI), but by shielding it from GCRs. Likewise, a weak Sun permits more GCRs to penetrate, creating more clouds and cooling. Archaeologists are aware of this effect as well, since the increase (and decrease) of GCRs and ionization leads to more (or less) Carbon-14, used for dating organic material from the past - fabric, wood, human tissue, etc. Experiments are underway at CERN to test this hypothesis. Incidentally, this hypothesis explains the long-term cooling of Antarctica, even during the worldwide warming since 1977, as the CO2 warming hypothesis does not. That explanation is too long to repeat here.
It's well known that there was an extended minimum of sunspots from 1645 through 1715, known as "The Maunder Minimum." Climatologists have noted that the Maunder Minimum coincides with the coldest part of "The Little Ice Age" (LIA). As described in the book of the same name by Brian Fagan (see the References), crops failed, the Norsemen withdrew from Greenland, English viniculture ended, transportation became more difficult, and the Seine and Thames Rivers and the Dutch canals froze in the winters. The Indian civilizations of Kahokia (Illinois) and Chaco Canyon ended. Every cloud has some silver lining; Antonio Stradavari found the spruce wood of the time so hard and dense - it grew very slowly - that it had a resonance that was perfect for his violins.
Probably not a coincidence - especially since it happened again in The Dalton Mimimum, 1790 - 1820. That period of minimum solar activity - sunspots - includes the terrible retreat of Napoleon's army from Moscow in 1812.
There's an interesting contrast here with the UN-fostered CO2 theory of AGW. The hypothesis of solar control of climate change is based on observed data; it's inductive. On the other hand, the CO2 theory is deductive; it's a theory in search of some supporting data. Such an approach is very susceptible to "cherry-picking", that is, choosing only the data that supports the hypothesis, and ignoring the contrary. An example is the cool period from 1945 through 1977, when CO2 was increasing in the postwar boom, and temperature was decreasing. In the 1970's, we heard a great deal from climatologists and the Media about a coming Ice Age. The anti-correlation is one of the internal contradictions of the assertion of AGW by CO2.
Is there a more recent example of decreased solar activity and correlated colder temperatures? Yes. In the early years of the 20th Century, 1912 - 1913, there was a similar period of minimal solar activity.
The number of sunspots in those years is plotted above; the US annual temperature is plotted at left. 1911 had 200 spotless days; 1912 had 253 days without spots; 1913 - the champ in modern times - had 311 spotless days. Now we have gone 266 spotless days in 2008, preceeded by 163 in 2007. Was the previous period of few sunspots a cold one? Yes!
Here are the ranks of the years, out of 114 years: 1911(#65), 1912 (#2), 1913 (#32), 1914 (#47), 1915 (#22), 1916 (#6), 1917 (#1), 1918 (#49), 1919 (#25), 1920 (#9). 1911 was an average year; all the rest were below average, with the average rank of the decade at #26 - the coldest decade in the 20th Century. Note there was a decade of cold, not just during the years of less sunspots. Incidentally, 1910 and 1917 are also the two driest years in American climate history - yes, drier than the Dust Bowl years. In Colorado, except for 1910 and 1917, all years of the decade were wetter/snowier than average. The Colorado River Compact, allocating Colorado River water among the various states, was signed in 1922, rather unrealistically. Because of the preceeding wet period, the Compact allocates more water than is normally available. The reader can find climatological data online at the National Climatological Data Center.
So, a period of few or no sunspots seems to be followed by several years of colder, wetter climate. Now we're in a period of few or no sunspots. AGW theory, based on CO2, predicts warmer and drier years ahead. A prominent CU faculty member, Prof Mark Williams of the Geography Dept, recently (Dec 2008) completed a study for the Aspen Ski Institute, predicting disaster due to warming (10.4 C) and decreasing precipitation - so much that the lifts would have to be moved up the mountain. Prof Williams' prediction came out (and was dutifully reported by Bill Scanlon of the Rocky) as Aspen and all Colorado resorts were reporting record December snow.
Continental Drift and the Ice Epoch
A few tens of millions of years ago, Earth was much warmer. The dinosaurs ruled the earth, roaming huge rain forests (as in "Jurassic Park"). Those rain forests are the source of our coal and petroleum today. The continents were near the Equator. There were no permanent ice caps on the earth, and only a few mountain glaciers, because warm ocean currents circulated freely over the poles, melting the Winter ice.
By 25 million years ago, continental drift had moved Antarctica over the South Polar cap, blocking the warm ocean currents and allowing permanent ice to accumulate there. This instituted an Ice Epoch, in which a major part of the Earth became permanently glaciated. Fortunately, Antarctica is isolated from the other continents by warm oceans. Glacial ice breaking off is rapidly melted, without forming glaciers on South America or Australia.
By 7 million years ago, the Northern Hemisphere continents had drifted into the present position around the North Polar cap, blocking warm ocean currents and allowing permanent ice to accumulate from year to year, over Greenland and on the American and Asian continents. The continents provided a path for the glaciers to move South. The grip of the Ice Epoch was now stronger. For tens of thousands of years at a time, the glaciers accumulated and moved south, covering the land with ice thousands of feet thick. Because of current continental configuration, the Earth is "normally" much colder - 20 degrees Fahrenheit colder - than present, for 80% of the time. It's the climate depicted in movies about cavemen and mammoths. In the figure below, the warm "interglacial" periods, every 100,000 years or so, make human civilization possible. The figure (from "A Primer on CO2 and Climate" by Howard C. Hayden; copyright 2007 by Vales Lake Publishing, LLC; Pueblo West, CO 81007-0609) illustrates the Milankovitch Cycle. The Milankovitch Cycle features long 80,000 year Glacial periods, interrupted briefly by short, 10,000 year Interglacials.
Strangely, a graph like this appears in "An Inconvenient Truth" (AIT). The important information it contains - that most of the last several hundred thousand years have been glacially cold - is never mentioned. The fact that warm Interglacials are short, and that ours is nearing its end, is never mentioned. AIT completely perverts the truth about long-term climate change.
Additionally, temperature changes before carbon dioxide. This is a general relationship between carbon dioxide and temperature, as seen in data from many ice core samples - the change in temperature LEADS the change in carbon dioxide by several hundred years. (Ice core samples include trapped bubbles of air, which allow measurement of carbon dioxide content and an estimate of temperature, through comparison of relative amounts of oxygen isotopes.) Since the change of temperature happens before the carbon dioxide concentration changes, this makes nonsense of the claim that carbon dioxide causes temperature change. AIT is careful not to mention the time difference between the two variables. Here's what section 6.4.1 ("Paleoclimate") of the Working Group 1 Report of the IPCC says:
“The ice core record indicates that greenhouse gases co-varied with antarctic temperatures over glacial-intergalcial cycles, suggesting a close link between natural atmospheric greenhouse gas variations and temperature (Box 6.2). Variations in CO2 over the last 420 kyr broadly followed antarctic temperature, typically by several centuries to a millennium (Mudelsee, 2001). The sequence of climatic forcings and responses during deglaciations (transitions from full glacial conditions to warm interglacials) are well documented. High-resolution ice core records of temperature proxies and CO2 during deglaciation indicates that antarctic temperature starts to rise several hundred years before CO2 (Monnin et al, 2001; Caillon et al, 2003).” [emphasis added]
The Milankovitch Cycle
Milutin Milankovitch, a Serb mathematician, was the first to realize that the major climate question is to explain the warm Interglacials. He did so, making calculations of Earth's orbit by hand (no computers then), during the 1920's and 1930's. His results were published in 1940, and were dismissed by geologists of the time. More accurate dating of geological periods, based on radioactive decay, proved Milankovitch correct.
A warm Interglacial requires maximum heating of the North Polar region during Summer, in order to melt the accumulated Winter snow and ice. The necessary astronomical conditions occur only at 100,000 year intervals. Our present interglacial is due to the coincidence of Northern Hemisphere Summer (when the North Polar region is in sunlight) with earth's closest approach to the Sun (i.e., perihelion). It's also necessary to have maximum eccentricity of Earth's orbit, and a high inclination (24.8 degrees or more) of Earth's spin axis. Those conditions came about 20,000 years ago, melting - for a while - the Glacial Ice. Since then, the situation has reversed; we now have Northern Hemisphere Summer (June 21) closely coincident with farthest distance from the Sun (July 3). We are living on borrowed time. The average Interglacial lasts 10,000 years; we're 1,500 years overdue. That's why the unexplained cold weather from 1940 to 1975 had climatologists concerned that a Glacial Age was returning. Inevitably, it will - perhaps in a thousand years, perhaps a hundred, perhaps....When it does, the glaciers will begin to crowd humanity toward the Tropics - where homo sapiens originated 150,000 years ago.
The main factor that causes the Milankovitch Cycle to slip into, then out of, Interglacials, is the precession of the Earth's spin axis - the 23,000 year "wobble". When precession causes the North Pole to point toward the Sun at perihelion (i.e., Summer at perihelion), conditions are favorable to melt accumulated glacial ice. Half a cycle later (i.e., 11,500 years), precession causes the North Pole to point away from the Sun (i.e., Winter) at perihelion. That doesn't melt the polar ice.
Additional factors are the 100,000 year cycle of orbital eccentricity (we need to be as close as possible) and the 41,000 years cycle of axial inclination. Everything has to be aligned to the maximum to melt the North Polar ice; it doesn't happen often.
The important part of the Milankovitch Cycle is Summer - when the Sun shines continuously on the sunlit polar region. During an Interglacial - as now - the sunlight is strong enough to melt accumulated ice and snow from Winter. Open water in polar regions - even at the North Pole - is commonplace in human history (i.e., during an Interglacial), and has nothing to do with "global warming." We need that melting; when the North Polar ice doesn't melt in Summer is when the next Glacial Age begins, marking the end of the (warm) Holocene Epoch. Perhaps we should name that new (cold) epoch "The Gorecene."
The Milankovitch Cycle has no effect on Winter. When the Sun dips below the horizon, it becomes cold in the Polar regions; snow and ice accumulate. Some of the "global warming crisis" hysteria would lead one to believe that the Polar Regions will be hot all year, due to global warming - as if Winter will disappear. There was a demonstrator at a recent Presidential Candidate debate carrying a sign saying "Save Our Seasons." This is typical ignorance of science; as long as the earth's axis is tilted, we'll have seasons. Temperature in polar Winter (North or South) will still be -40 F - or, perhaps, due to warming, only -38 F. This is still more than cold enough to start the glaciers flowing when the Milankovitch Cycle takes us out of maximum Summer warming.
Ocean Currents
One of the serious fears about a catastrophic climate change has been a possible weakening or cessation of the circulation in the North Atlantic - the Gulf Stream and the North Atlantic Drift that bring warm water to Northern Europe. That was the thesis of "The Day After Tomorrow," a 2004 movie. It did happen 9000 years ago, as the Ice Age glaciers melted, and caused serious climatic changes. Fortunately, it's unlikely now.
"The concern had previously been that we were close to a threshold where the Atlantic circulation system would stop," said Susan Solomon, a senior scientist at the National Oceanic and Atmospheric Administration. "We now believe we are much farther from that threshold, thanks to improved modeling and ocean measurements. The Gulf Stream and the North Atlantic Current are more stable than previously thought." ['Scientists back off another global warming scare' by Walter Gibbs, The New York Times, 15 May 2007] Dr. Solomon - who is here in Boulder - is a well-known climate scientist, a primary author of the Summary for Policy Makers (SPM).
Climate models
Much climate science - and much of the hysteria over a supposed "crisis" - is based on output from numerical models. Numerical models are only as good as the understanding of physics incorporated into the computer code. Unfortunately, that's not very good. See Dr. Roger A. Pielke's recent weblog
on climate models for more discussion of models.
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Rev. EarthDay 2007
Reason #1: A greenhouse can get only so warm...
Let's remember what a greenhouse gas (GHG) does. It's called that because, like the glass in a physical greenhouse, it prevents heat from escaping. The glass prevents heat from blowing away with the wind; water vapor (H2O) and CO2 prevent infrared (heat) photons from escaping. Adding more GHG doesn't guarantee more warming, anymore than adding a fifth blanket on the bed will make you warmer than the fourth blanket. The upper limit is 98.6 F; once you're there, you won't get any warmer. Once you have enough GHG to intercept all the infrared photons, adding more GHG has no effect. Over most of the earth, this is true. Because of H2O (not CO2), the greenhouse effect is maxed out. Adding CO2 has no effect.
Mathematically, GHG's obey a logarithmic law. Like adding multiple blankets to the bed, each successive increment of GHG has only half the warming effect of the previous increment. That's because the newly-added molecules of GHG have to compete with the ones already there - both H2O and CO2. Eventually the atmosphere (at a particular wavelength) becomes opaque; no infrared photons can escape. Additional GHG has no effect beyond that point. In the real atmosphere, CO2 added by humans has to compete with much more natural CO2 and vastly more H2O. It just doesn't make any difference across most of the spectrum.
Reason #2: CO2 is not an important absorber.......
We need to remember that molecules (H2O, CO2) have resonant frequencies (wavelengths); the tri-atomic molecules,
Now look at the CO2 molecule (C-O-C). It's symmetrical and unpolarized, so it doesn't rotate when an E-M wave passes by. It has only one vibrational mode, along the C-O-C axis. It's a much less efficient absorber of E-M energy than H2O, and that's what the greenhouse effect is all about.
Because of its single (vibrational) resonance, CO2 has only a single absorption line in Earth's infrared spectrum, around 14.8 micrometers (um). What kind of infrared photons does a CO2 molecule "catch" at 14.8 um? They come from an object whose temperature is about 200 degrees K - about 100 degrees F below zero. Nothing on earth is really that cold, but everything emits radiant energy photons across the infrared spectrum. There just aren't many of them emitted at 14.8 um, and they carry very, very little energy. Capturing them does very little to keep Earth warm, like a blanket that covers only a small part of your body. The figure on the left illustrates the broad spectrum of absorption (top) by the H2O molecule - across the emission spectrum of the earth and lower atmosphere - in comparison with the narrow spectrum (bottom) of CO2. CO2 just doesn't catch most of the infrared energy leaving the earth - effectively, it isn't there.
Reason #3: There's very little CO2 around.......
One reason global warming due to CO2 is unimportant is because there's very little of it - 385 parts per million by volume (ppmv). That's less than 0.04 % of the atmosphere. Water vapor, on the other hand, ranges up to 4% - 100 times as much.
The real reason man-made global warming is unimportant is because natural CO2 is more than 96% of all the CO2 in the atmosphere. Even if CO2 were an important greenhouse gas (as it isn't), complete elimination of all human CO2 emission would have no practical effect. Suppose we were to cut all human CO2 emission by 25% (which would cripple our economy). That would be 1% of all the CO2 in the atmosphere. Changing anything by 1% is unlikely to lead to catastrophe.
Incidentally, greenhouse gases lead to warming, not cooling. I hope that's obvious from the discussion above, but as "global warming" becomes less and less credible, the alarmists are beginning to claim the crisis is "climate change" - including cooling.
Another major agent of climate change - much more important than CO2 - is cloud cover. We all have experience of that; we know how a cloudy sky cools a hot Summer day, and how clouds warm a Winter night. In radiative terms, clouds are black bodies - objects which absorb all the infrared photons they receive. This is true across the IR spectrum; they're even better than gaseous H2O and CO2 in their "greenhouse effect." In daylight, they scatter sunlight back, away from Earth. So what is their net effect? Cooling? Warming? Nobody knows. Whatever it is, it's more important than CO2, and it's not controllable by humanity. Another fatal flaw in controlling the "climate crisis."
Those are the qualitative explanations of the unimportant greenhouse warming due to CO2. Let's now look at some numbers describing the magnitude of CO2's greenhouse effect. The numbers come from the IPCC's Fourth Assessment Report, Working Group 1. This document can be downloaded from the University Corporation for Atmospheric Research, at
Working Group 1 Working Group 1 contains the scientific rationale and data on which other parts of the IPCC report are based.
In AR4WG1_Pubs_FAQs, FAQ 1.1, Figure 1, you'll find a diagram of the solar energy that warms our planet's surface (168 watts/sq meter) and atmosphere (67 w/sq m), totalling 235 w/sq m. If the earth is not to warm or cool on a long term basis, that incoming solar energy must be balanced by outgoing energy in the longwave infrared (5 - 15 micrometers) spectrum. As may be seen on the right in the diagram, 235 w/sq m eventually escapes.
Of particular interest are the two energy exchanges in the lower right of the figure, 390 w/sq m radiated (up) from the surface, and 324 w/sq m radiated down from the atmosphere. This 324 w/sq m is the "greenhouse effect"; it's the radiant energy the atmosphere captures and returns to the surface, like a second sun in the sky. Fortunately, this "sun" shines even during the night. The greenhouse radiant energy warms the earth by about 33 degrees C, or 60 F. Without it, the earth would be uninhabitable. How much of this beneficial greenhouse effect is due to water vapor, and how much is due to carbon dioxide? A later table in the IPCC report tells us (though they try to hide the values).
In AR4WG1_Pubs_FAQs, you'll find FAQ 2.1, figure 2. This figure itemizes the anthropogenic greenhouse gasses
In case you're wondering how many degrees C or F these "radiative forcings" amount to, the 324 w/sq m from the atmosphere warms the earth by 33 C, so it's about a 10:1 ratio (9.81818...) of w/sq m to degrees C. So the 1.6 w/sq m of radiative forcing due to all man-made greenhouse gasses causes a warming of 0.16 C or 0.29 F.
Yes, that's what this "global warming crisis" is all about. All the carbon dioxide and other industrial greenhouse gasses added to the atmosphere have warmed the earth by a third of a Fahrenheit degree.
The Pacific Decadal Oscillation (PDO) Science is about data and theories to explain the data, and to predict future data. AGW tells us that cooling temperatures and increased snowfall are unusual, but perhaps these - such as the very cold 2008 across the US - are just statistical anomalies, "weather" rather than "climate," small, random variations from the overall trend. Believers in AGW assure us that the cold 2008 in the US is just an anomaly; it doesn't disprove AGW. But, just in case, believers are replacing the "global warming" phrase with "climate change."
On the other hand, there is a different theory (one of several), the Pacific Decadal Oscillation (PDO), that tells us storms and cold weather should be expected in the coming climate, the next 20 to 30 years. The Pacific Decadal Oscillation was identified at the University of Washington in 1996. The theory postulates - based on observational data - that the Pacific Ocean, Earth's largest, goes through shifting phases of warm and cold in East and West. From a selfish point of view, we in the US are warmed by a warm phase, and chilled by a cold phase. The climate models of the Intergovernmental Panel on Climate Change don't include the PDO.
As we see from the diagram on the right, there was a warm phase from 1915 to 1945, which included the "Dust Bowl" years, the warmest period in American climate. From 1945 to 1977, the PDO was in its cool phase, and climatologists - and The Media - considered a returning Ice Age. (TIME magazine had a cover story in July 1974 about the coming doom.) Fortunately, Doom was averted when the PDO entered a new warm phase in 1977, when many climatologists noted a Great Pacific Climate Shift. This warm phase of the PDO lasted until 1998, culminating in the major El Nino of 1997 - 1998 (hyped by Mr. Gore as "the warmest year of the Millenium.") PDO phases typically last about 30 years.
Following 1998, the PDO appears to have gone back into its cool phase. What does this mean? Normal circulation in the Pacific includes an equatorial transport of water westward, due to the prevailing Trade Winds. The water transported westward is replaced by cold water, upwelling from lower depths along the coast of South America. Similar cold upwelling takes place along the California Coast, leading to Twain's famous remark that "the coldest Winter I ever spent was a Summer in San Francisco." This pattern of strong equatorial westward flow is referred to as "La Nina." During La Nina conditions, warm water "piles up" around Indonesia and Australia; sea level there may be two feet higher than along the South American Coast.
Occasionally, for reasons we don't yet understand, the Trades weaken, or cease altogether, the westward current halts, and warm water flows back Eastward. The cold upwelling along the coast is replaced by warm water. The warm water off the west coasts of the Americas provides an energy source (evaporation) for developing storms; the most famous such episode was in the extended El Nino of 1997 - 1998, when storms battered the California Coast and the Santa Monica pier was destroyed. In South America, El Nino reduces or eliminates fishing, since the fish follow the nutrient in the cold upwelling water. No upwelling, no fish.
What was recognized only recently is that El Ninos are stronger, and more frequent, during the warm phase of the PDO; La Ninas dominate during the cold phase. An example is the 1945 - 1977 cold phase, when The Media warned us of a coming ice age. On the figure, that 1945 - 1977 cold phase has been extrapolated to our own time. Both the University of Washington and NASA/JPL agree that the PDO has entered its warm phase, with more cold La Ninas to be expected. Cooling temperatures and increased snowfall may be the dominant climate for the next generation.
Climate change and solar activity
Another hypothesis of climate change is obvious (but not considered by the IPCC). Our sun is a variable star; we have records of its variability, manifested in the number of sunspots visible through a telescope (developed by Galileo in the early 1600's).
It's well known that there was an extended minimum of sunspots from 1645 through 1715, known as "The Maunder Minimum." Climatologists have noted that the Maunder Minimum coincides with the coldest part of "The Little Ice Age" (LIA). As described in the book of the same name by Brian Fagan (see the References), crops failed, the Norsemen withdrew from Greenland, English viniculture ended, transportation became more difficult, and the Seine and Thames Rivers and the Dutch canals froze in the winters. The Indian civilizations of Kahokia (Illinois) and Chaco Canyon ended. Every cloud has some silver lining; Antonio Stradavari found the spruce wood of the time so hard and dense - it grew very slowly - that it had a resonance that was perfect for his violins.
Probably not a coincidence - especially since it happened again in The Dalton Mimimum, 1790 - 1820. That period of minimum solar activity - sunspots - includes the terrible retreat of Napoleon's army from Moscow in 1812. There's an interesting contrast here with the UN-fostered CO2 theory of AGW. The hypothesis of solar control of climate change is based on observed data; it's inductive. On the other hand, the CO2 theory is deductive; it's a theory in search of some supporting data. Such an approach is very susceptible to "cherry-picking", that is, choosing only the data that supports the hypothesis, and ignoring the contrary. An example is the cool period from 1945 through 1977, when CO2 was increasing in the postwar boom, and temperature was decreasing. In the 1970's, we heard a great deal from climatologists and the Media about a coming Ice Age. The anti-correlation is one of the internal contradictions of the assertion of AGW by CO2.
Is there a more recent example of decreased solar activity and correlated colder temperatures? Yes. In the early years of the 20th Century, 1912 - 1913, there was a similar period of minimal solar activity.
Here are the ranks of the years, out of 114 years: 1911(#65), 1912 (#2), 1913 (#32), 1914 (#47), 1915 (#22), 1916 (#6), 1917 (#1), 1918 (#49), 1919 (#25), 1920 (#9). 1911 was an average year; all the rest were below average, with the average rank of the decade at #26 - the coldest decade in the 20th Century. Note there was a decade of cold, not just during the years of less sunspots. Incidentally, 1910 and 1917 are also the two driest years in American climate history - yes, drier than the Dust Bowl years. In Colorado, except for 1910 and 1917, all years of the decade were wetter/snowier than average. The Colorado River Compact, allocating Colorado River water among the various states, was signed in 1922, rather unrealistically. Because of the preceeding wet period, the Compact allocates more water than is normally available. The reader can find climatological data online at the National Climatological Data Center.
So, a period of few or no sunspots seems to be followed by several years of colder, wetter climate. Now we're in a period of few or no sunspots. AGW theory, based on CO2, predicts warmer and drier years ahead. A prominent CU faculty member, Prof Mark Williams of the Geography Dept, recently (Dec 2008) completed a study for the Aspen Ski Institute, predicting disaster due to warming (10.4 C) and decreasing precipitation - so much that the lifts would have to be moved up the mountain. Prof Williams' prediction came out (and was dutifully reported by Bill Scanlon of the Rocky) as Aspen and all Colorado resorts were reporting record December snow.
Continental Drift and the Ice Epoch A few tens of millions of years ago, Earth was much warmer. The dinosaurs ruled the earth, roaming huge rain forests (as in "Jurassic Park"). Those rain forests are the source of our coal and petroleum today. The continents were near the Equator. There were no permanent ice caps on the earth, and only a few mountain glaciers, because warm ocean currents circulated freely over the poles, melting the Winter ice.
By 25 million years ago, continental drift had moved Antarctica over the South Polar cap, blocking the warm ocean currents and allowing permanent ice to accumulate there. This instituted an Ice Epoch, in which a major part of the Earth became permanently glaciated. Fortunately, Antarctica is isolated from the other continents by warm oceans. Glacial ice breaking off is rapidly melted, without forming glaciers on South America or Australia.
By 7 million years ago, the Northern Hemisphere continents had drifted into the present position around the North Polar cap, blocking warm ocean currents and allowing permanent ice to accumulate from year to year, over Greenland and on the American and Asian continents. The continents provided a path for the glaciers to move South. The grip of the Ice Epoch was now stronger. For tens of thousands of years at a time, the glaciers accumulated and moved south, covering the land with ice thousands of feet thick. Because of current continental configuration, the Earth is "normally" much colder - 20 degrees Fahrenheit colder - than present, for 80% of the time. It's the climate depicted in movies about cavemen and mammoths. In the figure below, the warm "interglacial" periods, every 100,000 years or so, make human civilization possible. The figure (from "A Primer on CO2 and Climate" by Howard C. Hayden; copyright 2007 by Vales Lake Publishing, LLC; Pueblo West, CO 81007-0609) illustrates the Milankovitch Cycle. The Milankovitch Cycle features long 80,000 year Glacial periods, interrupted briefly by short, 10,000 year Interglacials.
Strangely, a graph like this appears in "An Inconvenient Truth" (AIT). The important information it contains - that most of the last several hundred thousand years have been glacially cold - is never mentioned. The fact that warm Interglacials are short, and that ours is nearing its end, is never mentioned. AIT completely perverts the truth about long-term climate change.
Additionally, temperature changes before carbon dioxide. This is a general relationship between carbon dioxide and temperature, as seen in data from many ice core samples - the change in temperature LEADS the change in carbon dioxide by several hundred years. (Ice core samples include trapped bubbles of air, which allow measurement of carbon dioxide content and an estimate of temperature, through comparison of relative amounts of oxygen isotopes.) Since the change of temperature happens before the carbon dioxide concentration changes, this makes nonsense of the claim that carbon dioxide causes temperature change. AIT is careful not to mention the time difference between the two variables. Here's what section 6.4.1 ("Paleoclimate") of the Working Group 1 Report of the IPCC says:
“The ice core record indicates that greenhouse gases co-varied with antarctic temperatures over glacial-intergalcial cycles, suggesting a close link between natural atmospheric greenhouse gas variations and temperature (Box 6.2). Variations in CO2 over the last 420 kyr broadly followed antarctic temperature, typically by several centuries to a millennium (Mudelsee, 2001). The sequence of climatic forcings and responses during deglaciations (transitions from full glacial conditions to warm interglacials) are well documented. High-resolution ice core records of temperature proxies and CO2 during deglaciation indicates that antarctic temperature starts to rise several hundred years before CO2 (Monnin et al, 2001; Caillon et al, 2003).” [emphasis added]
Milutin Milankovitch, a Serb mathematician, was the first to realize that the major climate question is to explain the warm Interglacials. He did so, making calculations of Earth's orbit by hand (no computers then), during the 1920's and 1930's. His results were published in 1940, and were dismissed by geologists of the time. More accurate dating of geological periods, based on radioactive decay, proved Milankovitch correct.
A warm Interglacial requires maximum heating of the North Polar region during Summer, in order to melt the accumulated Winter snow and ice. The necessary astronomical conditions occur only at 100,000 year intervals. Our present interglacial is due to the coincidence of Northern Hemisphere Summer (when the North Polar region is in sunlight) with earth's closest approach to the Sun (i.e., perihelion). It's also necessary to have maximum eccentricity of Earth's orbit, and a high inclination (24.8 degrees or more) of Earth's spin axis. Those conditions came about 20,000 years ago, melting - for a while - the Glacial Ice. Since then, the situation has reversed; we now have Northern Hemisphere Summer (June 21) closely coincident with farthest distance from the Sun (July 3). We are living on borrowed time. The average Interglacial lasts 10,000 years; we're 1,500 years overdue. That's why the unexplained cold weather from 1940 to 1975 had climatologists concerned that a Glacial Age was returning. Inevitably, it will - perhaps in a thousand years, perhaps a hundred, perhaps....When it does, the glaciers will begin to crowd humanity toward the Tropics - where homo sapiens originated 150,000 years ago.
The main factor that causes the Milankovitch Cycle to slip into, then out of, Interglacials, is the precession of the Earth's spin axis - the 23,000 year "wobble". When precession causes the North Pole to point toward the Sun at perihelion (i.e., Summer at perihelion), conditions are favorable to melt accumulated glacial ice. Half a cycle later (i.e., 11,500 years), precession causes the North Pole to point away from the Sun (i.e., Winter) at perihelion. That doesn't melt the polar ice.
Additional factors are the 100,000 year cycle of orbital eccentricity (we need to be as close as possible) and the 41,000 years cycle of axial inclination. Everything has to be aligned to the maximum to melt the North Polar ice; it doesn't happen often.
The important part of the Milankovitch Cycle is Summer - when the Sun shines continuously on the sunlit polar region. During an Interglacial - as now - the sunlight is strong enough to melt accumulated ice and snow from Winter. Open water in polar regions - even at the North Pole - is commonplace in human history (i.e., during an Interglacial), and has nothing to do with "global warming." We need that melting; when the North Polar ice doesn't melt in Summer is when the next Glacial Age begins, marking the end of the (warm) Holocene Epoch. Perhaps we should name that new (cold) epoch "The Gorecene."
The Milankovitch Cycle has no effect on Winter. When the Sun dips below the horizon, it becomes cold in the Polar regions; snow and ice accumulate. Some of the "global warming crisis" hysteria would lead one to believe that the Polar Regions will be hot all year, due to global warming - as if Winter will disappear. There was a demonstrator at a recent Presidential Candidate debate carrying a sign saying "Save Our Seasons." This is typical ignorance of science; as long as the earth's axis is tilted, we'll have seasons. Temperature in polar Winter (North or South) will still be -40 F - or, perhaps, due to warming, only -38 F. This is still more than cold enough to start the glaciers flowing when the Milankovitch Cycle takes us out of maximum Summer warming.
One of the serious fears about a catastrophic climate change has been a possible weakening or cessation of the circulation in the North Atlantic - the Gulf Stream and the North Atlantic Drift that bring warm water to Northern Europe. That was the thesis of "The Day After Tomorrow," a 2004 movie. It did happen 9000 years ago, as the Ice Age glaciers melted, and caused serious climatic changes. Fortunately, it's unlikely now.
"The concern had previously been that we were close to a threshold where the Atlantic circulation system would stop," said Susan Solomon, a senior scientist at the National Oceanic and Atmospheric Administration. "We now believe we are much farther from that threshold, thanks to improved modeling and ocean measurements. The Gulf Stream and the North Atlantic Current are more stable than previously thought." ['Scientists back off another global warming scare' by Walter Gibbs, The New York Times, 15 May 2007] Dr. Solomon - who is here in Boulder - is a well-known climate scientist, a primary author of the Summary for Policy Makers (SPM).
Climate models
Much climate science - and much of the hysteria over a supposed "crisis" - is based on output from numerical models. Numerical models are only as good as the understanding of physics incorporated into the computer code. Unfortunately, that's not very good. See Dr. Roger A. Pielke's recent weblog
on climate models for more discussion of models.
Hi - Did you want to make a comment? or ask a question? Comments will NOT be published, either to commend or disparage anyone. I'd appreciate informed feedback; obviously, polite commentary will get a more reasoned response than remarks on my ancestry (Scots-Irish) or personal habits. Seriously, I've had thoughtful comments that caused me to change the content on this website. You've welcome to tell me when I'm wrong. depending on their geometry, may absorb infrared radiant energy by vibrating and by rotating. Take a look at the sketch on the right, a representation of the two major greenhouse gasses, H2O and CO2. Notice H2O is asymmetrical, and slightly polarized. That is, the hydrogen (H) end of the molecule tends to be slightly positive, and the oxygen (O) end slightly negative. An electromagnetic (E-M) wave, alternating between positive and negative, causes the H2O molecule to rotate, and absorb anergy. In addition, electromagnetic waves of a resonant frequency cause the H-O bonds to resonate, to vibrate. Both vibration and rotation absorb energy from the E-M wave.
that contribute to global warming. The total radiative forcing from carbon dioxide and all other anthropogenic gasses is only 1.6 watts/ square meter. That's out of the total of 324 w/sq m due to the total greenhouse effect. The rest - i.e., 322 w/sq m - comes from natural greenhouse gasses, which don't appear on Figure 2. If they did, any casual reader would immediately recognize how natural water vapor and natural carbon dioxide dominate the greenhouse effect.
Sunspots, which show up as dark patches on the surface, are indicators of increased solar output of radiance, of mass (the solar wind), and of a stronger solar magnetic field. A recent hypothesis put forward by Svensmark and Calder ("The Chilling Stars", 2007) suggests that a strong solar magnetic field shields the earth (which it surrounds) from high-energy Galactic Cosmic Rays (GCRs). The GCRs, presumed to come from supernovae far outside our Solar system, have enough energy to create ions in Earth's atmosphere. These ions act as nuclei for the formation of cloud droplets in the lower atmosphere, which cool the earth. Thus (it is hypothesized), an active Sun warms the Earth, not by increased Total Solar Irradiance (TSI), but by shielding it from GCRs. Likewise, a weak Sun permits more GCRs to penetrate, creating more clouds and cooling. Archaeologists are aware of this effect as well, since the increase (and decrease) of GCRs and ionization leads to more (or less) Carbon-14, used for dating organic material from the past - fabric, wood, human tissue, etc. Experiments are underway at CERN to test this hypothesis. Incidentally, this hypothesis explains the long-term cooling of Antarctica, even during the worldwide warming since 1977, as the CO2 warming hypothesis does not. That explanation is too long to repeat here.
The number of sunspots in those years is plotted above; the US annual temperature is plotted at left. 1911 had 200 spotless days; 1912 had 253 days without spots; 1913 - the champ in modern times - had 311 spotless days. Now we have gone 266 spotless days in 2008, preceeded by 163 in 2007. Was the previous period of few sunspots a cold one? Yes!
The Milankovitch Cycle
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