Why I Am A Global Warming Skeptic

The debate over anthropogenic global warming—a theory propounded by the UN IPCC—is often portrayed as an argument between deniers and true believers. The deniers supposedly claim that there is no global warming, man made or otherwise, and that the whole theory is a plot by left-wing agitators and closet socialists bent on world domination. The true believers, conversely, accept every claim of pending future disaster uttered by scientists and activists alike. As with most controversies both extreme positions are wrong and the truth lies somewhere in-between. As a scientist, I have studied the evidence and find the case for imminent, dangerous, human caused global warming unconvincing—here is why I am an AGW skeptic.

According to www.dict.org, a skeptic is “one who is yet undecided as to what is true; one who is looking or inquiring for what is true; an inquirer after facts or reasons”.* This is a much more accurate description of the stand taken by Al and myself in our book, The Resilient Earth. Specifically, I am skeptical of the claim that human produced carbon dioxide will have the dramatic effect on Earth's temperature projected by the IPCC and other global warming doomsayers. To understand why I have reached this conclusion requires starting with some basic science.

*[That site also notes that this word and its derivatives are often written with c instead of k in the first syllable: sceptic, sceptical, scepticism, etc. Dr. Johnson, struck with the extraordinary irregularity of giving c its hard sound before e, altered the spelling, and his example has been followed by most lexicographers]


There is no doubt that the “greenhouse effect” warms Earth, this has been known for two centuries. Because of the mix of gases in the atmosphere, the air surrounding our planet is transparent to visible light coming from the sun, but opaque at many wavelengths in the infrared band. When sunlight strikes Earth's surface, it re-radiates solar energy back toward space in the form of infrared light. Greenhouse gases (GHG) in the atmosphere absorb much of that radiation, trapping thermal energy and warming the planet. This has a significant impact on surface temperatures.

The result can be calculated using simple physics. The Stefan-Boltzmann law shows that if there were no greenhouse gases in the atmosphere, Earth's average surface temperature would be –18˚C (–1˚F). This is well below the freezing point of water and would make life as we know it impossible. Earth's actual observed average surface temperature is 15˚C (59˚F). By empirical measurement, the greenhouse effect raises our planet’s surface temperature by 33˚C (60˚F). To this extent, global warming has already taken place—and a darn good thing for us it has.

The primary greenhouse gases are H2O (water vapor), CO2, and CH4 (methane). I have often stated that water vapor is the most important GHG, but a comparison of water vapor and carbon dioxide highlights some interesting facts. The data in Table 1 were computed by assuming that one gas is removed from the atmosphere, leaving the others unchanged. If you remove all water vapor from the atmosphere, the infrared absorption will decrease by 36 percent. If you remove all greenhouse gases (and clouds) and leave only water vapor, the infrared absorption will decrease by 34 percent.

Greenhouse gas removed% Decrease in IR absorption
H2O vapor36
All except H2O vapor34
All except CO274
H2O vapor + CO253
Other GHG5

Table 1: Contributions to the greenhouse effect by different greenhouse gases. Source realclimate.org.

Since GHG have overlapping bands of infrared absorption, the absorption from one gas affects the absorption from another gas. Some wavelengths of infrared light are absorbed by both water vapor and CO2. If water vapor alone is removed, leaving the CO2, the CO2 will absorb the infrared light in the overlap region. Conversely, if the CO2 is removed from the atmosphere, water vapor will absorb that infrared light. Thus the absorption by one gas depends on the other gases present in the atmosphere.

Note that removing all GHGs with the exception of water vapor would result in absorption of 66% of the IR radiation absorbed by the current atmosphere (100 – 34). If all GHGs except CO2 are removed the absorption rate is reduced to only 26%. Clearly H2O is more important than carbon dioxide, but CO2 does make a significant contribution. So far this has been a matter of basic physics, but things are about to get more complicated.

Most of the claims about the impact of AGW are predicated on specific amounts of temperature increase. The temperature increase is attributed to increasing atmospheric CO2 levels, another fact that very few scientists deny. For reasons soon to be discussed, future temperature increases are calibrated on an assumed increase for doubling the amount of CO2 in the atmosphere over “preindustrial” levels. Long-term atmospheric data show that CO2 levels remained stable around 280 ppm (parts per million) during the most of the past 10,000 years. When climate scientists talk about CO2 levels doubling this is the base level from which the increase is measured.

The simplest, and incorrect, way to estimate of the impact of doubling atmospheric CO2 levels would be to double its greenhouse temperature contribution. Such a linear estimate for doubling all GHG would would result in an additional increase of 33˚C (60˚F), giving an average surface temperature of the earth of 48˚C (119˚F). Fortunately that is not the way things work in the real world. Doubling CO2 levels will only result in a small rise in temperature due to two factors, both having to do the absorption spectra of greenhouse gases as shown in the graph below.

Greenhouse gas absorption spectra. Source The Resilient Earth.

The two complicating factors are band saturation and spectral overlap. The first has to do with how much radiation is already being absorbed at specific frequencies. If the absorption at a certain wavelength is close to 100 percent, doubling the CO2 level will have little effect—absorption can not exceed 100% no matter how much more gas is added. Think of if this way: if a totally opaque curtain is placed over a window, blocking all of the light, adding more layers of curtain cannot make the room any darker.

The second limiting factor, spectral overlap, comes from the relationships between the frequencies of light GHG absorption. As already stated, water vapor has areas of infrared light absorption that overlap the absorption by CO2. As with saturation, in regions where infrared light is already strongly absorbed by water vapor, the addition of more CO2 will make little or no difference. Given these complications, doubling atmospheric CO2 levels will result in a much lower temperature rise than a linear estimation.

The impact of such a doubling can still be calculated using formulas from a standard textbook. If nothing else in the system changes, a doubling of CO2 from the preindustrial levels is estimated to produce a temperature rise of 1.2 to 1.3˚C (2.2 to 2.3˚F). Again, the calculation is straightforward and there is little controversy about the figure among scientists. Now recall that over the last century and a half CO2 levels have risen from a preindustrial 280 ppm to around 380 ppm. At the same time global average mean temperature has risen (depending on who you believe) 0.8 to 1.0˚C. This implies that, once the CO2 level reaches 560 ppm, the dreaded doubling, temperatures should rise by another 0.2 to 0.5˚C. So where do the IPCC estimates of 2.0 to 6.0˚C come from?

Where things start to get murky

The IPCC temperature estimates for doubling atmospheric CO2 come from amplifying the amount of warming from the actual greenhouse increase due to assumed positive feedback. The concept of feedback has its roots in electrical engineering and the study of electronic circuits. The term “feedback” first appeared in the 1920s and supposedly came from the broadcasting industry. When the volume of a microphone is set too high sound from a nearby monitor speaker can be picked up and amplified even more. The resulting sound is usually a loud, unpleasant screech. Since the sounds that enter a microphone are referred to as feeds, the unpleasant sounds were called “feed-back.”

As it turns out, the concept of feedback can be applied to a wide range of dynamical systems, both natural and man made. Here is a description of dynamical systems and feedback by Karl Johan Åström and Richard M. Murray in their book, Feedback Systems: An Introduction for Scientists and Engineers:

A dynamical system is a system whose behavior changes over time, often in response to external stimulation or forcing. The term feedback refers to a situation in which two (or more) dynamical systems are connected together such that each system influences the other and their dynamics are thus strongly coupled. Simple causal reasoning about a feedback system is difficult because the first system influences the second and the second system influences the first, leading to a circular argument. This makes reasoning based on cause and effect tricky, and it is necessary to analyze the system as a whole.

Feedback in natural systems is well accepted, this is not the problem. The problem lies in calculating the impact that all the various natural feedback loops have on global temperature. Some feedback mechanisms are positive, amplifying any input signal changes, while others are negative, applying an opposing influence and limiting signal change. An example of positive climatic feedback is water vapor. An increase in temperature causes more evaporation from the ocean that releases more water vapor into the atmosphere causing further temperature rise.

To further complicate things, some factors can participate in both positive and negative feedback loops. Water vapor, cited above as a positive feedback, can provide a negative feedback in this way: rising temperature increases atmospheric water vapor levels, which in turn causes more precipitation; if the precipitation falls as snow this can raise Earth's albedo, reflecting more sunlight and lowering the planet's overall temperature. This chain of influences is why some scientists claim that Earth must first warm up in order to get colder. More water vapor can also cause more clouds that, depending on their type, can either cool or warm the planet—as I said, it's complicated. Some of the known climate feedback factors are shown in the figure below.

Climate feedback loops. After Robock.

It is the nature, magnitude and characteristics of the natural feedback loops that are at the heart of the AGW controversy. Without feedback loops amplifying the impact of increasing carbon dioxide levels on Earth's temperature the global warming proponents have no case—and skeptics like myself are unconvinced that the IPCC has got them right.

Mainstream climate scientists have decided that the net impact of all the feedback relationships within the Earth system is positive. In effect, they multiply the marginal temperature increase from the enhanced greenhouse warming by an “amplification factor.” This assumption is both unwarranted and a dangerous oversimplification of Earth's climate system. You cannot analyze a system as a whole if you do not know and understand all the pieces that comprise the system.

For instance, there must be limiting factors or opposing negative feedback to counter the proposed positive ones or Earth's temperature, once warming began, would spiral ever upward—a runaway greenhouse like that of Venus. We know such limiting factors exist because Earth's climate has remained within a range conducive to life for a half a billion years. Still, this has not prevented climate change proponents from positing a number of simple positive feedback relationships which they say will cause a dangerous rise in planetary temperature. Usually, the primary positive feedback claimed to amplify the warming effect of CO2 is a supposed link to water vapor.

A recent report in Science suggests that stratospheric water vapor between 1980 and 2000 probably increased the rate of surface warming during the 1990s by about 30%. The research, led by respected NOAA climate scientist and IPCC climate change assessment report co-chair Susan Solomon, states that from 2000 to 2009 diminished water vapor levels in the upper atmosphere depressed global warming by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. The research, based on data from the state-of-the-art AIRS instrument on the NASA Aqua satellite, suggests that water vapor is responsible for twice the global warming effect of carbon dioxide, whether man-made or naturally occurring. As I have said, “it's the water vapor, stupid!” As for the feedback connection, this was during a period when CO2 levels were constantly rising, yet water vapor levels in the stratosphere fell.

Data from the Atmospheric Infrared Sounder (AIRS) instrument. NASA

In fact, given these new results, human CO2 would actually be responsible for a negative feedback that cancels at least some of the warming it causes by pushing water vapor back to the surface of the earth and out of the stratosphere, where it acts as a potent greenhouse gas. Climate change alarmist claims of a CO2 amplifier may not only be exaggerated, they may have it backwards. Dr Solomon has not abandoned her belief in global warming but admitted that the research does imply that human emissions having a much smaller role in climate change than previously thought.

Another new estimate of the overall feedback between temperature and atmospheric CO2 concentration has been derived from a comprehensive comparison of temperature and CO2 proxy records spanning the past 1000 years. The study in Nature, by David Frank et al., was based on more than 200,000 individual comparisons over the period from 1050 to 1800. Their results imply that the amplification of current global warming by carbon-cycle feedback will be significantly less than commonly suggested. This report goes so far as to suggest ~80% less potential amplification for ongoing global warming.

These are just two of the most recent published studies that cast doubt on our understanding of Earth's climate and how climate might react to increasing levels of atmospheric CO2. A survey of published papers over the past few years makes it abundantly clear, this is not “settled science” as AGW adherents and eco-alarmists have claimed. As I said, the climate change alarmists' assertions regarding CO2 feedback are unconvincing.

It's a nonlinear world

There are many complicating factors with dynamical systems containing multiple feedback loops. Most feedback is only manifest after a time delay. An example of this in nature is heavy winter snowfall resulting in higher than normal freshwater runoff in the spring. Different factors may respond on markedly different time scales with the full impact of feedback interactions remaining unclear for years, decades or even centuries.

Another example of delay is the absorption of heat by H2O creating water vapor. Later, this latent heat may be released at a far distant location when the water vapor condenses to form rain. This mechanism is only one of a myriad of ways that energy is transported around the planet. These types of delayed reaction can cause yearly, decadal or longer cycles. Such factors are ubiquitous in nature and require the use of delay differential equations to model them. These delayed responses of natural feedbacks seem to indicate that climate change takes a while to propagate through the Earth system. But we do know, from paleoclimate data, that there have been relatively sudden climate shifts in the past. Past bouts of rapid change is another argument that climate change alarmists use to prove the urgency of their cause.

Climate feedback loops. After Pittock.

One of the favorite scare tactics of global warming promoters is to warn that there are “tipping points” lurking in nature that can suddenly throw the climate into a tizzy. To some extent they are correct, there are historical examples of nonlinear responses from the climate system that have caused reactions far more dramatic than the level of forcing that triggered them. In fact, the mechanisms responsible for the sudden transition from glacial to interglacial conditions could well be labeled a tipping point.

In mathematics, a nonlinear system is one whose output is not proportional to its input. A recent paper reported that dropping sea levels during a glacial period can cause a nonlinear response by exposing the Bearing Strait land bridge between Siberia and Alaska. When this happens the flow of salty water from the northern Pacific into the Arctic basin is cut off, triggering other rapid changes in ocean circulation patterns. The response is a general warming that allows sea levels to rise, restoring the northward flow from the Pacific. A side effect may be to create large lakes within the continental ice sheets containing huge amounts of fresh melt-water.

As I reported in “The Long Road Ahead,” scientists are now quite certain that for Earth's climate to shift from glacial conditions, huge continental ice sheets must exist in the Norther Hemisphere. The Milankovitch cycles still operate during glacial periods, cycling the climate between cold and relatively warmer conditions. But, once a glacial period has started, orbital variations do not seem sufficient to bring the planet back to a warm, interglacial climate. However, things do warm up enough create instabilities in the ice sheets, leading to pulses of iceberg discharge and allowing the formation of vast ice dammed lakes filled with glacial melt water. These lakes represent a bigger lurking nonlinearity than the Bering Strait land bridge.

Glacial lake Missoula. Painting by Byron Pickering.

Rapid climate change is a result of nonlinearities in the Earth system's natural processes, and many physical systems are inherently nonlinear in nature. In this case, the freshwater glacial lakes were waiting for just enough forcing warmth to weaken an ice dam and cause it to break. Scientist speculate that an outpouring of freshwater from such glacial lakes can disrupt the flow of ocean currents sufficiently to cause wild swings in climatic conditions.

What causes the warming in the first place is still a mater of raging debate. Some claim it is the melting of mid-latitude glaciers, which are very sensitive to warm summer weather but not cold winters. Others argue that extensive cover of sea ice in the Norther Pacific and Atlantic oceans create more zonal climatic circulation system than exists today. During termination changes in freshwater runoff destabilizes the zonal ocean current patterns, forcing warm water north resulting in a sudden thaw. This science is certainly not settled.

I have heard climate change boosters claim that in the past historical climate shifts have been out of proportion to the forcings that seem to have caused them. This, they say, justifies their assumption that the climate system's feedback loops are a net amplifier of temperature. In the face of discoveries about the nonlinearities that control glacial-interglacial transitions the argument is not compelling.

Global warming proponents have yet to identify the mechanisms present in Earth's current environment that will cause a rapid nonlinear climate warming. Today there are no continent spanning ice sheets, precariously holding back glacial mega-lakes. Sea levels are rising marginally, so no chance of exposing a new land bridge that would block ocean currents. We can only conclude that, barring some unforeseen and unidentified future disaster, there will be no rapid global warming.

Other factors

There are also questions regarding the data on which the AGW theory is based. Most climate data are proxy data. This means those data both inexact and open to multiple interpretations. For example, different groups of scientists, working from the same set of tree ring data, arrived at much different interpretations of Holocene climate history (see “Medieval Warm Period Rediscovered”). Furthermore, the farther back in time science looks, the more uncertain the data become.

A good example of the uncertainty surrounding paleoclimate data is the recent announcement that, after nearly 30 years of often heated debate, a team of researchers has finally produced a 50,000 year calibration curve for radiocarbon dating. The basic principles of radiocarbon dating are fairly simple and one would expect that consensus would be easy to achieve among scientists on how to perform such dating. But as with most climate related experimental data there were many data sets that had to be combined. These data sets diverged from each other by up to several thousand years after 26,000 years ago, and researchers could not agree on which ones were most accurate or how to combine them.

For the first 12,000 years the team used thousands of overlapping tree-ring segments from the Northern Hemisphere. For dates older than the available tree-ring record, the researchers had to turn to several other, less-precise data sets, including fossil diatoms and corals. How important can this work be? Surely the differences that the scientists were arguing over were small and any changes from using the new work would merely reinforce previous, if less accurate work. As it turns out, not really.

One case in point, the raw radiocarbon dates for the spectacular paintings of horses, lions, bison, and other animals at Chauvet Cave in southern France, the oldest known cave art, indicate the paintings were made 32,000 years ago. This was right after a major cold spell hit Europe. Using the new calibration curve dates the earliest paintings at Chauvet 36,500 years old, a period of relative warmth. According to Clive Gamble, an archaeologist at the University of London, getting those dates right is critical to understanding questions such as whether humans began painting caves when the climate was colder or warmer. You can imagine how accurate dating could change the interpretation of other climate related data.

Paintings from the Chauvet-Pont-d’Arc Cave in southern France.

Although the new curve is a major improvement in radiocarbon calibration, it is “definitely not the last word,” says team leader Paula Reimer, a geochronologist at Queen's University Belfast in Northern Ireland. Her team is already planning an update for 2011. Remember, this is for a fairly simple historical measurement. Most historical climate data has known uncertainties with the same order of magnitude as the predictions offered up by the IPCC and other climate change alarmists. The only “good” climate data we have has been collected since the maturation of orbiting remote sensing satellites within the past 20 years or so. You simply cannot accurately predict Earth's climate a century in the future based on a couple of decades of data.

Finally, this brings us to climate modeling. Some critics claim that the entire skeptical case against anthropogenic global warming is built around the flaws found in GCM climate modeling software—this is not true. Just as the output from climate models does not provide proof of global warming, the use of computer models in climate research does not invalidate that research. Indeed, computer modeling can be an important and useful tool in most any scientific endeavor. Unfortunately, is seems that many climate modelers have committed the greatest sin a modeler can commit—believing that their models and the system being modeled are one in the same.

As most experienced modelers know, all models are wrong but some are useful—climate models, GCM, are no exception. As previously reported, GCM are inherently inaccurate (see “Climate Models Irreducibly Imprecise”). I have also highlighted the errors and sensitivity of climate models to small changes in configuration in “Extinction, Climate Change & Modeling Mayhem.” And this is only scratching the surface. By their very nature computer are simplifications of the real world. Simplifying assumptions must be made to make the models computationally tractable, otherwise not even the largest supercomputers in the world could run them. So all climate models are, by necessity, dumbed down representations of an incomplete theory calibrated and fed with uncertain data.

Even when asked to make near term predictions—essentially extended weather forecasts—climate models are woefully inaccurate. As reported in Geophys. Res. Lett., David Lavers of Princeton University and colleagues tested eight seasonal climate forecast models for their skill at predicting temperature worldwide and precipitation over land masses. The problem, according to this new analysis, is that existing climate models show very little accuracy more than one month out. Even during the first month, predictions are markedly less accurate for the second half than the first. According to the researchers, current models simply cannot account for the chaotic nature of climate. Now extrapolate that inaccuracy to predictions decades, even centuries into the future.

A new article in the Journal of Climate by Knutti et al. discuss some major sources of differences between models,. According to a review of the paper by H. Jesse Smith in Science the work is important “because it is not normally clear which models' scenarios are likely to be the most realistic, the question arises of which specific models to believe and why.” Knutti et al. themselves state: “there is little agreement on metrics to separate ‘good’ and ‘bad’ models, and there is a concern that model development, evaluation and posterior weighting or ranking are all using the same datasets.” In other words, they are tuning and then judging their models using the same restricted set of uncertain and error prone data that has been used in the past. No wonder their models don't work.

In Summary

To summarize, Earth's climate is amazingly, mind-blowingly complex and science has only just begun to figure out how it works. While our theoretical knowledge improves and our data become more accurate with each passing year, it is safe to say that there is still more we don't know about climate change than things we think we understand. Here are some fundamental questions about the state of Earth's climate:

  • Is Earth's climate warming? Yes, by around 1°C (1.8°F) during the 150 years leading up to the present.
  • Do human activities impact the climate? Yes, all numerous and widespread species do to some extent (see the concluding remarks of “What Killed The Mastodons?”).
  • Do atmospheric CO2 levels rise and fall with temperature? Yes, according to historical data.
  • Are atmospheric CO2 levels rising because of people? Yes, it would appear so.
  • Does this mean that the theory of anthropogenic global warming is correct? Absolutely not.

For the reasons given in the article above, and those described in greater detail in The Resilient Earth, I have concluded that science does not understand the climate system well enough to make the predictions that climate change alarmists keep making. Scientists continue to argue about fundamental mechanisms and the accuracy of historical data. In the absence of better theoretical knowledge and sufficient accurate data, climate scientists have filled the void in understanding with output from computer models, which are the most fickle and fallible of tools.

Consider the following main points:

  • Climate is a nonlinear system.
  • Not all feedback relationships are known or well characterized.
  • Based on known empirical evidence a doubling of atmospheric CO2 levels will only cause a further increase of 0.2 to 0.5°C in global temperature.
  • In order to achieve the temperature levels predicted by the IPCC requires amplifying positive feedback from the climate system.
  • There is no compelling proof that Earth's climate system acts as a temperature change amplifier.
  • Not all known factors are included in climate models.
  • Models cannot predict nonlinear responses not built into them.
  • Baseline data used to calibrate the models are uncertain and possibly erroneous.
  • Different climate models predict different future outcomes because they make different assumption or use different values for model parameters.
  • All climate models contain errors that are fundamental to their construction.

In the wake of Climategate and Glaciergate it is tempting to dismiss the theory of anthropogenic global warming as bogus science foisted off on a gullible public by a number of bad scientists. The reasons for this climate science chicanery are not clear: the torrent of grant money, the novelty of fame or simply error amplified by ego. As entertaining as the news accounts of unfolding scandal have been, it is important to remember that many serious scientists believe in human caused global warming to one degree or another. But science is a human endeavor and as prone to mistakes as any other. This will not be the first time that a majority of the scientific community believed in an erroneous theory, and it certainly will not be the last. Eventually, science will decide the fate of AGW based on empirical evidence—nature itself will provide the proof, one way or the other.

To date, climate science has not produced any incontrovertible proof that rising CO2 levels will, in fact, cause the temperature increases predicted by GCM models. The information presented above reinforces the observations I made in my earlier post, “The Crumbling Pillars of Climate Change.” The theoretical understanding is incomplete, the historic data are spotty and uncertain, and the models are not an accurate representation of the climate system. Further, models have been used inappropriately to bolster the IPCC's case—models are not scientific evidence and should not be used to predict long-term real world behavior.

The truth is, climate science uses computer models like a drunk uses a lamppost, not for illumination but for support. Even AGW supporters agree that if the only evidence for global warming were computer models, then skepticism would be entirely justified. But, while models are most definitely a sore point in the global warming debate, they are not the central point. It is the science itself that is uncompelling. Neither current scientific knowledge nor historical data prove the theory of anthropogenic global warming as put forth by the IPCC. If anything, new data and new studies reveal that current climate change dogma has got it very wrong. That is why I remain a global warming skeptic.

Be safe, enjoy the interglacial and stay skeptical.

Why has only the lower atmosphere been warming?

I'm currently taking a Climate Change course through the University of Exeter. As you alluded to at one point in your article, IPCC is basing their conclusion on more than just climate models. One such piece of evidence they cite is the changing temp of the lower atmosphere. They said that the sun's power has only very slightly increased in power since 1750, and moreover, that a more active sun would cause ALL layers of the atmosphere to warm. However, they said that is not what's been happening; that there's been a cooling of the upper atmosphere, and that only the surface and lower parts of the atmosphere are warming. They say this piece of evidence shows the surface of the Earth is in fact warming, and is warming because greenhouse gases are trapping an increasing amount of heat in the lower atmosphere. Would like to get your take on this additional piece of evidence that IPCC is also factoring into their conclusion. Thanks.

Your link on the sun and atmospheric heating

Thank you for the link. Will share it with my professors to get their take on it. Do you know if this report and models referenced in it were peer-reviewed?

The article

The article cited appeared in Science. Follow the link in the blog post.

The article

I checked, but didn't see any mention in that link as to whether it was peer reviewed. So assume it was not.

Peer review

Ask your professor(s) whether the AAAS journal Science is peer reviewed.

co2 saturation

Hi there! There is (at least) one factual error in your text. You say "If the absorption at a certain wavelength is close to 100 percent, doubling the CO2 level will have little effect—absorption can not exceed 100% no matter how much more gas is added. Think of if this way: if a totally opaque curtain is placed over a window, blocking all of the light, adding more layers of curtain cannot make the room any darker."

Unfortunately you have misunderstood how it works. In short: the amount of energy that escapes the earth's atmosphere depends on the height from where the radiation is emitted into space. If you add more CO2 to the atmosphere, the radiation doesn't escape into space until it reaches a higher altitude. The temperature of the layer of the atmosphere from where radiation finally escapes determine the energy of the radiation. (Think of blackbody radiation.) I recommend this text, it can explain it better:


Actually, no

It is you who has misunderstood how it works. Oh, you have the general theory correct, but no appreciation for the setting in which it is applied. You see, the amount of CO2 we are talking about is small, around 400 parts per million with respect to the total atmosphere. Though the amount of CO2 humans release sounds like a lot, 5-6 Gt, in fact it is a minuscule amount compared with the atmosphere as a whole (that's why it is called a trace gas). Even doubling the amount of carbon dioxide would have practically no impact on the thickness (height) of Earth's atmosphere.

In fact, the upper atmosphere expands and contracts under the influence of the Sun. Though variation in total insolation is only around 0.1%, the variation in UV can be 5-8%. It is the Sun that changes the height of the atmosphere, not man's paltry emissions. Only massive amounts of CO2 would have a noticeable effect—think Venusian levels. Even then the major impact would be from absorption spectrum broadening due to a rise in pressure. If you want the real story read the chapter on atmospheric gases in The Resilient Earth.

Global warming

Great article. It should be widely circulated at all climate conferences!

But we still should use renewable energy sources

You may be right, perhaps there is not enought evidence for global warming.

But even then...
It has been proven that coal plants emit toxic substances other than greenhousegasses, such as SO2, or nuclear material. It has been calculated that all coal plants produce 100 times more nuclear waste than nuclear plants.

Eventually all sources of fossil fuel will be exhausted.

We should use oil for making plastics instead of burning it.

So, even if global warming is not true, we should still use renewable energy sources.


Actually, I agree with all of that. We need better energy sources, coal is filthy stuff and we should stop using it, oil is more important as a chemical feedstock than as a fuel, etc. If you read more of my articles, you will find that I support nuclear energy strongly, and “green” renewables where they are safe and make economic sense. Using advanced fast neutron reactors, nuclear power will last us 1,000 years, throw in thorium as a fuel and estimates go as high as 4,000 years. We will eventually need to either harness fusion, put solar power satellites in high orbit or both—but we don't have to do it tomorrow. Dangerous global warming is a sham, but the dangers of pollution are real. Even China is coming to realize that having booming industry but cities where it is not safe to breath the air isn't a good trade.


Climategate was sufficiently disturbing that I finally started seriously looking into this AGW/IPCC/Climate Science stuff. There is so much to master: thermodynamics, IPCC reports, GCM complexity, GHG provoked AGW theory, statistics (polynomial cointegration, etc), etc.

My head has been swimming with all the new material but your article has helped me integrate the various facts/ideas into a couple of clear opinions:

1. Understanding (much less modeling or predicting) global climate is an enormous challenge that Climate Science has not yet accomplished. Progress has been made but there remains a lot of work to be done before we understand the earth's climate well enough to make reliable climate predictions.

2. Climate Science has been grossly politicized. The USA should not rely on the IPCC's recommendations but should conduct its own investigations. Funding for AGW skeptical climate scientists should be increased dramatically. This will actually improve the quality of AGW science as the AGW theory flaws are detected and addressed. The "scientists" who perpetrated the outrageous violations of the scientific method (by destroying/hiding data, suppressing the publishing of articles that challenged AGW, claiming that AGW was settled science, threatening the careers of scientists who were AGW skeptics, etc) must be investigated thoroughly and punished severely. It is amazing and dismaying that so few climate scientists have spoken out against these outrages. One can only hope that it is because they are either cynical or afraid and not because they are stupid or true believers.

BTW, have you seen the paper: "Polynomial Cointegration Tests of the Anthropogenic Theory of Global Warming" by
Michael Beenstock and Yaniv Reingewertz? It looks pretty interesting.

Polynomial Cointegration Paper

Thanks for the pointer about the cointegration paper. Dr. Hoffman has a review of the Beenstock and Reingewertz paper here: "Econometrics vs Climate Science"

Temperature has not gone up enough

There is an article on Science Daily that asks Why Hasn't Earth Warmed as Much as Expected? It quotes a paper in the Journal of Climate by Stephen Schwartz, of Brookhaven National Laboratory, which says:

According to current best estimates of climate sensitivity, the amount of CO2 and other heat-trapping gases added to Earth's atmosphere since humanity began burning fossil fuels on a significant scale during the industrial period would be expected to result in a mean global temperature rise of 3.8F -- well more than the 1.4F increase that has been observed for this time span. Schwartz's analysis attributes the reasons for this discrepancy to a possible mix of two major factors: 1) Earth's climate may be less sensitive to rising greenhouse gases than currently assumed and/or 2) reflection of sunlight by haze particles in the atmosphere may be offsetting some of the expected warming.

Either way, they currently have the science wrong.


" ... AGW supporters agree that if the only evidence for global warming were computer models, then skepticism would be entirely justified."

But, in fact, they do agree that the models are the only evidence for anthropogenic GW. Twenty years ago the only evidence put forward for the CO2-driven theory -- improbable on its face -- was "our models can't reproduce the warming without incorporating the carbon dioxide increase."

Now, after two decades and $100 billion in research, careful (and very painful) reading of the only relevant part of the IPCC's AR4 (WG I, Ch. 9, "Attribution") reveals that the only evidence is still "our models can't reproduce the warming without incorporating the carbon dioxide increase." All the rest is blather demonstrating that some warming is occurring, which is not subject to any doubt -- although all of the jiggery-pokery that CRU, GISS, and others have been playing with the surface record may cast some doubt on precisely how much warming has taken place.

Two points that you don't mention, adding to long-term climate uncertainty, are the influence of cosmic rays -- the Svensmark effect -- which Shaviv has shown correlates with major climate shifts as the solar system traverses galactic areas of stronger and weaker ray intensity, and the influence of subsea volcanism, which has some effect on deep-sea currents. As if genuine climatology were not complex enough simply dealing with a hydrological cycle dedicated to moving enormous quantities of heat and moisture from point A to point B...

Milankovich cycles

Why is it that none of the models ever talk about the Milankovitch cycles? For anyone not familiar with what these are, there are three:
1. 21,000 year perihelion cycle (precession)
2. 41,000 obliquity cycle
3. 100,000 year eccentricity (of Earth's orbit) cycle

The 100,000 year cycle is a modulator of the 21,000 year cycle, so in the epochs when the two coincide the effect on the atmosphere should be more pronounced.

These are all present in the climate record, yet the GW modelers never mention them. Surely they have to be taken into account?

Cycles are mentioned

"Modelers never mention them"?? Maybe you haven't been listening? These cycles are well know. Read for example James Hanson - Storms of my grandchildren, there these effects on the climate are well explained

band saturation

I have had many people ask me about saturating the greenhouse effect and I don't understand how it is possible. I mean, what is the optical density of the atmosphere at 15 microns? I would think it's pretty low since the earth isn't as hot as it would be if GHG's were absorbing most of the emitted IR light. When I look at the spectra you have provided it's hard for me to tell how they correspond to the earth's absorption.

Since absorption depends on concentration, path length and the extinction coefficient at a particular frequency, how to the spectra in your post correspond to what is happening in the atmosphere? What were the concentrations and path lengths of the sample you used to make those measurements? Thanks.

Band Saturation

Band saturation is a real phenomenon and is well documented. Here is a quote from an article by on Chris Colose's blog regarding CO2's absorption band and outgoing longwave radiation (OLR):

If the greenhouse gas in question were absorbing only in this limited interval, then increasing its concentration further could not bring down the OLR any further, since in the spectral region where the gas is radiatively active, the atmosphere is already radiating at the coldest temperature possible. Technically, since the stratosphere cools with more greenhouse gases, this would have a minor effect on the OLR, but it is a negligible one for our purposes. If we change the amount of CO2, the intensity of light in this range does not get any lower. This is called band saturation.

He then goes on to mention that the absorption band will grow wider as more CO2 is added but does not quantify the rate of the widening in any meaningful or useful way. He does, however, use basic physics to calculate the radiative forcing due to doubling CO2:

In modern concentrations, every doubling of CO2 will reduce the OLR by about 4 W m-2. This doesn't hold at very low concentrations as we've seen, but also at very high concentrations. One could compute the temperature change for a perturbation in the OLR for just a change in CO2, leaving other climate variables constant, which gives a ~1 C rise in temperature for a 4 W m-2 radiative forcing. This would be the temperature response to a CO2 doubling if only the Planck radiative feedback were important. Unfortunately, life is not that easy, and you need to figure in the feedbacks from water vapor, clouds, albedo, etc.

This is the same conclusion Dr. Hoffman reached and, as was stated, to justify a larger climate response you have to introduce a whole plethora of feedbacks (again not quantified). Close's line of argumentation then takes a turn for the absurd when he says "now let's put some crazy amounts of CO2 into the model, say 10,000 ppm." This is a common ploy of AGW apologists, immediately jumping from supportable arguments to wild speculation. No matter, the topic here is band saturation. From Dr. Ray Pierrehumbert's RealClimate post on the subject of band saturation:

Saturation refers to the condition where increasing the amount of CO2 fails to increase the absorption, because the CO2 was already absorbing essentially all there is to absorb at the wavelengths where it absorbs at all. Think of a conveyor belt with red, blue and green M&M candies going past. You have one fussy child sitting at the belt who only eats red M&M's, and he can eat them fast enough to eat half of the M&M's going past him. Thus, he reduces the M&M flux by half. If you put another equally fussy kid next to him who can eat at the same rate, she'll eat all the remaining red M&M's. Then, if you put a third kid in the line, it won't result in any further decrease in the M&M flux, because all the M&M's that they like to eat are already gone. (It will probably result in howls of disappointment, though!) You'd need an eater of green or blue M&M's to make further reductions in the flux.

...for the pre-industrial CO2 concentration, it is only the wavelength range between about 13.5 and 17 microns (millionths of a meter) that can be considered to be saturated. Within this range, it is indeed true that adding more CO2 would not significantly increase the amount of absorption. All the red M&M's are already eaten.

Pierrehumbert goes on to claim that "the atmosphere still wouldn't be saturated even if we increased the CO2 to ten thousand times the present level." This is true about the entire atmosphere, not the particular band(s) absorbed by various GHGs. If you add enough CO2 you get band widening and end up with a planet like Venus, but what isn't said is that this requires amounts of CO2 that cannot be produced by burning all of the fossil fuel humanity can lay its hands on. The subtle change in reference from band saturation to atmospheric saturation and failure to quantify the necessary amount of CO2 to effect the later invalidate his arguments. As for your initial question, yes, the atmosphere is saturated at 15 microns.

Absorption Spectra

This topic has been discussed in greater detail on this blog before. Search for it on this site or Google for it on the web. You will find a statement like the one below on any number of science sites (this one from a course in “global change” at Iowa State University):

Carbon dioxide has a more complex absorption spectrum with isolated peaks at about 2.6 and 4 microns and a shoulder, or complete blockout, of infrared radiation beyond about 13 microns. From this we see that carbon dioxide is a very strong absorber of infrared radiation. The plot for water vapor shows an absorption spectrum more complex even than carbon dioxide, with numerous broad peaks in the infrared region between 0.8 and 10 microns.

The information presented in the figure is from J. N. Howard, Proc. I.R.E 47, 1959, and R. M. Goody and G.D. Robinson, Quart. Journal of the Royal Meteorological Soc. 77, 1951. I redrew the figure for use in The Resilient Earth so you can say it is “after” Howard et al. These data have been well resolved for half a century, why in heavens name would I want to do the measurements and calculations myself?

absorption spectrum

I think your understanding of this topic is wanting.

NASA's AIRS instrument that measures the outgoing longwave radiation of the earth has a spectrometer that goes out to 15 microns. If there was no light passing beyond 13 microns, why would their instrument look in this region?

More importantly, from your figure in the post, very little of the emitted IR light given off by the earth is in the 'complete blackout' region. How much of a contribution does this fact make to the overall changes in absorption as GHG concentrations change?

I think the idea of saturation seems to be greatly misunderstood in the context of global warming. While the absorption can be close to 1, it is never saturated in a true sense of the word. Adding more molecules will always increase the amount of light absorbed. One only gets into the saturation regime when the intensity of light is sufficiently high to move most of the quantum population into the excited state. Under such conditions, putting more saturated molecules will not change the amount of light absorbed. But in order to get most of the molecules into the excited state, one needs light intensity on the order of millions of gigawatts per centimeter squared. I don't see the sun producing these kinds of intensities anytime soon.

While you may feel as though you don't need to do anymore work than what has already been done, it doesn't really make for the strongest argument. What is the measured optical density of the atmosphere at 2,4 or 15 microns? Since the papers you cite were before the satellite era, I would have to believe there was no way for them to check their predictions against observations. How do the observations look now?

Blockout doesn't mean black

The term “blockout” is a bit misleading to the uninitiated. At the transparent wavelengths photons escape into space unhindered. At the “blocked out” frequencies there is close to a 100% chance of a photon of light being absorbed. The photon smoothly transfers its radiant energy to kinetic form. Absorption is an energy transition, not a trap. Similarly, emission is the reverse kinetic to radiant transfer. All the radiation that is absorbed in this way is re-radiated in random directions. The heat energy is not held forever, but merely delayed. Eventually it will find its way into space. This is what the satellites see in the IR wavelengths.

The delay can be increased, and surface temperature raised, by adding more molecules but the volume of gas needed to register a significant boost is immense. At earthly atmospheric pressures CO2 is mostly all in after the first 100ppm with respect to warming.

I have provided references to the sources of the data I presented, you have offered opinion. If you think those "old" papers are in error please provide the appropriate contradictory data. You need to learn more about the subject and how to present a scientific argument before commenting further.

in this case, isn't the cost of inaction worse than action...?

the danger of being skeptical, catastrophic, of being persuaded, minor?
it would seem that even a 10% chance of them being right would make the cost-benefit analysis lead humanity to action!

How about a 10% chance of a severe ice age?

Suppose there is also a 10% chance that we will slip back into a severe ice age. If we follow the IPCC's recommendations, we could hasten it, and make it worse. Based on the Earth's history over the past 550 million years, a severe ice age is likely sooner or later. Half of Europe, all of Canada, and the Northern U.S. covered with 1 mile thick ice would be a real disaster -- a lot worse than slow coastal flooding and balmy winters.

Absolutely Not!

The argument, that the consequences of the climate change extremists' predictions being true are so terrible that we should take action even if that outcome is highly improbable, is among the most pernicious made by the warmists. It is disingenuous on its face and intellectually vacant. This type of argument goes back at least to “Pascal’s Wager” where that famous French mathematician claimed that there is nothing to lose by believing in God.

Pascal's reasoning went like this: If there is a God and an afterlife, belief will gain you eternal life. If it turns out that there is no God then nothing would be lost. On the other hand, if you were to chose belief that God does not exist and that proves to be wrong, then you would lose everything and be condemned to spend an eternal life of pain and suffering in hell. Essentially Pascal figured that believing in God cost him little but the down side of not believing and being wrong was horrendous. Unfortunately for the world this is not the type of bargain being offered by the IPCC.

In the case of global warming it is the taking of radical action that is the horrendous outcome. If we are to listen to those calling for an immediate crash program to reduce CO2 emissions to preindustrial levels the entire economy of the world will collapse, plague and famine will surely follow as people are reduced to living conditions not seen since the dark ages. Developing nations will have to be suppressed, lest their rapid industrial growth pollute the atmosphere. Whole nations will have their dreams of a prosperous future dashed. Heightened international tensions and war are almost a certainty.

On the other hand, even a 4°C rise in global temperatures over the next 90 years will not cause such chaos. Sea levels will rise modestly, precipitation patterns will shift (a hotter Earth means more, not less, precipitation), and the climate in northern regions will improve. For more on the possible effects of global warming see The Resilient Earth Chapter 16, “The Worst That Could Happen.” For economic and health impacts see Bjørn Lomborg's Skeptical Environmentalist or Cool It. As for cost benefit analysis, Lomborg has shown, through statistical analysis of public health records, that any increase in summer mortality rates due to heating are offset by a ten fold reduction in winter time cold related deaths. From this point of view global warming would prove a blessing not a curse.

Venus- runaway

"Perhaps Venus had once enjoyed a climate of the sort hospitable to life, but as water had gradually evaporated into the warming atmosphere, followed by CO2, the planet had fallen into its present hellish state? In a 1971 paper, James Pollack argued that Venus might once have had oceans like Earth's. It seemed that such a "runaway greenhouse" could have turned the Earth too into a furnace, if the starting conditions had been only a little different."

I don't think it's possible that Earth could become a venus furnace- unless you put earth into a venus orbit- or if "somehow" the sun output would dramatically increase.

The above article seems to be full of errors- but I don't want focus upon them. Instead I merely want to point out that earth is compared to venus in regards to global warming. At times being claimed by some, that venus has had a runaway affect and that earth could have a "similar" runaway affect.

My question is how hot could earth get, assuming it stays in it's present orbit and the sun's output doesn't increase.

Now, a planet doesn't actually need any solar radiation to remain warm- Jupiter at altitude in which it is 1 atm is quite cool but at lower elevations it becomes quite hot:
"At the same pressure as Earth's atmosphere, the temperature is -110°C (-166°F), however, the tops of the visible clouds are approximately -70°C (-94°F). The temperature reaches 70°C (126°F) when the atmospheric pressure is about ten times as great as earth..."

So the question is how hot could earth get at it's current orbit and current sun output if you measure the temperature at an elevation which is 1 atm of atmospheric pressure?

In other words, you have an unlimited budget to terraform earth in any way you want, how much higher could you increase the average temperature of earth if measured at 1 atm [if you add 4 atm of pure CO2- then you measure at whatever elevation is 14.7 psi].

CO2 and Earth's future

First off, there is no way to generate 4 atmospheres of pure CO2 without burning the world's entire stock of fossil fuels and then burning the environment down to bedrock. The climate system, heavily influenced by life itself, has maintained a more or less livable environment on Earth for a half a billion years. If you check back over the Phanerozoic, temperature has been as much as 10°C higher than today. Needless to say, life adapted or we would not exist. For more see “The Grand View: 4 Billion Years Of Climate Change.”

Second, Earth is not Jupiter. Without solar radiation Earth would be a frozen rock drifting through space. Jupiter is a gas giant planet, nearly a proto-star, while our world is a rocky planet. The interior of Jupiter is hot, with core temperatures estimated at about 20,000°K. The heat is generated by the Kelvin-Helmholtz mechanism, the slow gravitational compression of the planet. Note that Jupiter does not produce energy by nuclear fusion as the Sun does—it is far too small and its interior too cool to ignite nuclear reactions.

Third, to turn Earth into Venus you would need to boil the oceans and the bake the carbonate rocks in Earth's crust to release more CO2. While the Sun is getting warmer, and will eventually burn this planet to a crisp, scientists do not see a tremendous build up of CO2 in Earth's future. Indeed, the current thinking is that Earth will eventually lose most all of its carbon dioxide. It will be a race between the Sun's heat and the flight of Earth's CO2 to see what will end life on this ball of mud (see “Too Little CO2 To End Life On Earth”). For some speculation about future climate change see “The Long Road Ahead.”

Venus- runaway

"First off, there is no way to generate 4 atmospheres of pure CO2 without burning the world's entire stock of fossil fuels and then burning the environment down to bedrock. "

According to wiki, the mass of Earth atmosphere is about 5 x 10^18 kg, with roughly 21% of being oxygen.
So there is about 1 x 10^18 kg of O2 in our atmosphere.
You can't make 2 x 10^19 kg of CO2 from the 1 x 10^18 kg of oxygen. You would need about 10 times more oxygen then exists in our atmosphere.
So merely, "burning the world's entire stock of fossil fuels and then burning the environment down to bedrock" could not get you anywhere near 4 atm of CO2.

There is plenty of Oxygen in our ocean if you were to split the H2O of sea water, though the amount energy required to do this would stagger the imagination- there probably isn't enough energy available on the planet to do this within, say, 100 year time span. Meaning if you were to efficiently harvest all the solar energy that reaches this planet, and were to use all the nuclear energy from all fissionable ore within couple miles of the surface of the planet.
There is more oxygen available in the earth crust than compared to the ocean, but extracting oxygen from this ore, requires even more energy than splitting sea water.

So Venus has about 90 atm of CO2, there isn't any way for our earth to have any kind of "runaway" which create, 1/20th of the venus atmosphere of earth- unless you change earth orbit or total Sun output of energy increases significantly.

And even if you put earth in a orbit around the sun at venus distance, it would still take thousands of years to create something vaguely like Venus- if it were to happen at all.

What would Earth be like if it were be in venus orbit or the sun output were to increase so we got the same amount solar energy as being in venus orbit?

The maximum solar flux at venus distance is 2700 watts per square meter. As compared to earth distance which is 1418 watts per sq/meter.

On the earth surface at noon, on a clear day, near the equator, one gets about 1000 watts per sq meter [about 30% less solar energy as compared not being under earth atmosphere]. If earth was at venus orbital distance, one could expect at least a similar decrease of 30% at the surface, so on clear day at noon and close to equator one would get around 1900 watt per sq/meter.

I would guess that if Earth was at venus distance, it's ocean would not boil- at least not for the first 1000 years- if ever. No doubt that the earth temperature could increase significantly.
But the ice cap wouldn't even melt as quickly as some alarmist claim will happen in earth's future, though perhaps in few centuries this would happen.
I would be hard to predict what would happen, but unlike the greenhouse affect which is mostly to warm temperate and arctic regions [and night time], temperatures [at venus distance] in tropics would increase so high that it seems as though life could have hard time surviving.

But the high temperatures could be somewhat balanced by significant increases in cloud cover due to more evaporation.

On earth presently, in hot summer days, one can sort of fry eggs on a sidewalk. Perhaps if earth was at venus distance, on some days you could sort of boil water on the sidewalk, but this wouldn't mean that ponds, lakes or oceans would boil at any time.

Now, if you put Venus in Earth's orbit, it seems to me it would take a century to see significant change in it's temperature- and centuries before temperature could possible get below 200-300 degrees at the Venus surface.

Terrestrial Carbon & Oxygen

You are correct, even burning all fossil fuels and all biologic carbon would not yield 4 atmospheres worth of “pure” CO2. There is, however, a much larger supply of both carbon and oxygen locked up in Earth's crust. According to “Distribution of Carbon in Crust of Earth: Geological Notes,” by John M. Hunt:

The total carbon in crust of the earth is about 9 × 1022 g. Continental and oceanic sediments contain 1.2 × 1022 g of organic carbon and 6.4 × 1022 g of carbonate carbon. There is about three times as much organic carbon in claystones and shales as in carbonate rocks and sandstones. The carbon in the oil and gas of petroleum reservoirs totals 1 × 1018 g or about 0.01 percent of the organic carbon in sedimentary rocks. The hydrogen in the organic matter of sedimentary rocks totals 9 × 1020 g or about 32 times as much as is needed to form all the petroleum in both reservoir and nonreservoir rocks.

So there exists 6.4 × 1019 kg of carbon in carbonate rock, almost 13 times the mass of Earth's current atmosphere. Oxygen makes up 45.2% of the planet's crust, so there is plenty of it around as well, without having to thermally split the water molecules in the ocean. By the way, the phrase “boil the oceans” was a bit of poetic license. Most likely, as the Sun warms up Earth's water will evaporate and eventually escape into space.

That would be wrong.

Over the billions of years to come Earth's oceans will, indeed, dry up.


ocean and CO2

Does not the thermal content of the ocean have the greatest influence on the atmospheric content of CO2?

Is our knowledge of ocean climate comparable to atmospheric climate?

How much hysteresis does the ocean introduce into climate change?

Ocean and CO2

"Does not the thermal content of the ocean have the greatest influence on the atmospheric content of CO2?"

I would say that generally, life has greatest affect upon atmospheric content of CO2.

But sudden changes in thermal content of the ocean and/or massive global volcanic events could have a large affect upon CO2 content of the atmosphere. But we haven't had sudden changes in thermal content of the ocean or massive global volcanic events, recently [within last thousands or millions of years].

But we seem to have had a gradual increase in global CO2 level over the last century and this seems to be the issue you are referring to.

I don't think anyone would dispute that during an interglacial period when ocean temperatures are rising, that large quantities of CO2 would be released from the ocean over the period of tens to hundreds of centuries. And it could be argued that the warming from the time of the Little Ice age and the entire warming period of the our present interglacial has added to the global atmospheric CO2, but I don't think there any agreement upon how much would be added from this- such as, how much CO2 released per say 1/10 of C in increase in the entire ocean temperature.

There are a few things which can be said about this.
Our oceans are a massive body, most of total quantity of oceans is deep water. And presently this deep water is cold and will remain cold for centuries [at least:)].

"Its average depth is 3,790 metres (12,400 ft), and its maximum depth is 10,923 metres (6.787 mi). Nearly half of the world's marine waters are over 3,000 metres (9,800 ft) deep"

"There is a boundary between surface waters of the ocean and deeper layers that are not mixed. The boundary usually begins around 100-400 meters and extends several hundred of meters downward from there. This boundary region, where there is a rapid decrease of temperature, is called the thermocline. 90 % of the total volume of ocean is found below the thermocline in the deep ocean. Here, temperatures approach 0 degrees Celsius. So even though surface waters can be a comfortable 20 degrees Celsius (good for swimming in!), the majority of our ocean water has a temperature between 0-3 degrees Celsius (32-37.5 degrees Fahrenheit). "

I would guess that the cooling period of the Little Ice Age which only lasted a few centuries had little affect upon the earth's deep water- though it might have slightly slowed the longer interglacial warming of the ocean.

Oh there is also this article:
"The consumption of terrestrial vegetation by animals and by microbes (rotting, in other words) emits about 220 gigatonnes of CO2 every year, while respiration by vegetation emits another 220 Gt. These huge amounts are balanced by the 440 Gt of carbon dioxide absorbed from the atmosphere each year as land plants photosynthesise."

The ocean and CO2

Yes, in some ways, and a lot.


Thank you Doug. I particularly liked your point that many good people fit somewhere in the middle of the extreme positions. Unfortunately the politics of the issue has overwhelmed the science to the point that most (Western) politicians see the extreme alarmist position as advancing their particular political foibles.

The science is most definitely NOT settled and I will continue to read, watch,comment and wait. In the meantime I am happy to stay sceptical.

Current Temperature

As an Electronic Engineer, pretty much every device I ever built had negative feedback. It is simply impossible to build any kind of a stable system without it. The climate does seem to swing around a lot, but without some negative feedback, it would probably swing either to snowball or tropical earth. There must be negative feedbacks to hold it anywhere in between.

This article indicates that the current global temperature is 15C, but the graph of the Phanerozoic global temperature here, and in your excellent book, seems to show a current temperature of about 12C. Why are these different? Is the difference just within the error band of the graph? Should the graph be shifted up 3C? Has the temperature increased 3C since the actual end of the graph data? Is there some other explanation?

Current Temperature

As a Control Systems Engineer I agree.

We (man) would not even be here if we did not have the stability that we do. The oceans act as a MASSIVE dampening agent. Additionally, the Oceans not only dampen temperature swings they dampen swings in the GHG's through absorption and release. When you compare the amount of that dampening and the net negative feedback caused by the clouds from the water vapor with the insignificant amount of CO2 it just does not compute or compare with ANY control system I have ever worked on. Think about it, you are talking about a match in the room at the enclosed swimming pool. And the building has no other heat or cooling just the sun shining through the windows. What is that match going to do? what if you light another match when that went out, and again, and again, etc. The effect is insignificant.

All "conjectured" charts of the earth's temperature has been between limits that indicate that the likelihood of the earth turning into Venus are absurd - to the max. Even considering those swings caused by total conflagration caused by massive comet impacts, the temperatures returned to the "norm." Think of the amount of CO2 that had to be in the atmosphere at that time. Think of the amount of H2O that had to have left the earth at that time. But it came back to what we call normal . YES IT CAME BACK.

In 40 years I have never witnessed an industrial process with a "Control System" that had positive feedback THAT STOPED ALL BY ITS SELF. It continued until it ran out of fuel, material, power, etc. The charts of the earth's temperature show that it does not continue to oscillate. The charts show that, occasionally it seeks a "temperate" high and a glacial cool period. And from what I have read, we are still trying to figure out what causes one to switch to the other. There is some correlation to the Sun, earth's orbit, earth's tilt, etc. but, we don't definitively know what caused these switches. So, how can we say what an additional 0.001 PPM of CO2 is causing?

Look at the SUN on these web pages. Look at the number of sun spots. Look at how cold it is now. Look at the NASA Solar web page and the VERY low level of irradiance from the Sun. BUT the AGW group IGNORES THE SUN. It sure looks to me like the solar irradiance has decreased significantly. Look at how high the solar irradiance was during the so called "hottest years on earth." Are these just coincidences? BUT the AGW group IGNORES THE SUN.

Phanerozoic Temperatures

I believe that the temperature shown at the end of that figure, which covers the entire sweep of complex life on Earth, was representative of the average temperature at the end of the Phanerozoic—specifically during the Pleistocene. It is much warmer right now than that average because we are in an interglacial. Most of the time over the past +3 million years has been spent under ice house conditions, hence the lower temperature on the graph.

Dr. Steven Novella weighs in

Dr. Steven Novella weighs in on the idea of Climate Skepticism


Why I am a global warming skeptic

Finally, a clear and reasonable explanation! Thank you so much. I was getting very tired of the childish rhetoric that has bombarded and clouded the climate change "debate". It looks like the climate scientists have some fence-mending to do to get the public to accept anything they have to say in the future. Of course I stopped believing politicians, journalists and those with special interests and hidden agendas long ago.

DRC from Toronto, Canada


The single major problem in the current climate change debate has nothing to do with the vagaries of data collection, the reliability of proxy measurements or difficulties with computer modelling. It is that the IPCC is fundamentally a political body. It is the nature of all politicians to blend spin, deception and lies into any argument to promote their assumed political standpoint. One must never accept uncritically anything a political body expounds. Furthermore, the media like a sensational story to promote their ratings, so they are more interested in alarmism than rational debate. Finally, sufficient numbers of scientists bave been seduced by financial and career incentives to assume political positions rather than pursue objective scientific analysis. If politicians and the media could back off and let the scientists do quality research and engage in constructive debate without political, status or financial biases, we might achieve meaningful consensus.

The Saturated Greenhouse Effect

A very good article. I would add one more unknown to the mix. Dr. Ferenc M. Miskolczi has also postulated that the addition of CO2 into the atmosphere will be offset by a decrease in water vapor since according to him we are at a point where the greenhouse effect is in balance for current conditions. In view of the decrease of water vapor in the stratosphere, this theory should be looked at.