Global warming XIII – The Carbon Dioxide Control Knob


EPA Administrator Scott Pruitt appeared on CNBC’s Squawk Box on March 9. Here’s one question and answer:

JOE KERNEN (HOST): Let me ask you this, let me ask you one other thing, just to get to the nitty gritty. Do you believe that it’s been proven that CO2 is the primary control knob for climate? Do you believe that?

SCOTT PRUITT (EPA ADMINISTRATOR): No, I think that measuring with precision human activity on the climate is something very challenging to do, and there’s tremendous disagreement about the degree of impact. So, no, I would not agree that’s a primary contributor to the global warming that we see. But we don’t know that yet, as far as — we need to continue debate — continue the review and analysis.

The question is awkward, since no one asserts the premise of the first question. No one says that CO2 is the primary control knob for climate. What knowledgeable people believe is that of the various “control knobs” for the climate, humans are “turning up” the CO2 knob and warming the planet. Thus, by accident, Pruitt’s first word is correct: “No.” After another accidental correct claim, that measuring the effects of human activity on the climate is challenging, the rest of his answer is wrong.

Pruitt asserts that there is “tremendous disagreement about the degree of impact” (of human activity on the climate). This is incorrect. There is general agreement that increasing levels of CO2 in the atmosphere due to people burning carbon fuels is warming the Earth. In the various models, as in all scientific endeavors, models and theories produce somewhat different predictions based upon different starting points, different methods, and different interpretations. All professional studies of the effect of the increasing CO2 agree that it will increase the Earth’s temperature. Some predict an increase of, say, 2 C, in 50 years given no changes in present fossil fuel use, others 4 C. None predict no effect. None predict that there will be a cooling. Pruitt says that because some scientists say 2 C and some 4 C, they have no idea what the warming will be. This is the claim of many opponents of scientific knowledge, that if scientists don’t know everything about a phenomenon to infinite precision, then they might as well know nothing.

All climate researchers would agree that neither they, nor anyone else, knows all there is to know about the climate. Contrary to Pruitt and to many other global warming deniers, the climate researchers know plenty, and, as it typical in research, they have sought the causes of the big effects first. Those are well-known and have been for decades, some more than a century.

Pruitt says that he does not agree “that’s a primary contributor to the global warming that we see.” Now the contraction in this sentence is “that it is” where the “it” refers to the question: carbon dioxide. Filling this in, we see Pruitt’s meaning: “I would not agree that carbon dioxide is a primary contributor to the global warming that we see.” The question from Kernen: “Is CO2 the primary control knob for the climate?” The answer from Pruitt: “No. CO2 is not a primary contributor to global warming.” At least Pruitt says that the globe is warming.

That CO2 is not a primary contributor to global warming is false. The Earth’s climate arises, of course, from many factors. To understand it involves assessing the Earth’s energy balance in accordance with the 1st Law of Thermodynamics or the Conservation of Energy. This great law, known with increasing depth and precision, arose in scientific thought in the 1800s.

To summarize the matter, consider the Earth including its atmosphere as a thermodynamic system. That system contains a certain amount of energy, known as internal energy. (That is, I’m not considering the kinetic energy of the Earth’s motion around the Sun, although I could.) The Earth’s internal energy has various parts, potential energy and kinetic energy. Potential energy is in all the Earth’s chemical bonds and nuclear bonds. Kinetic energy is in the random shaking, jiggling, and zipping about of the atoms and molecules, and directed kinetic energy is in motions such as winds and water currents. Energy flows in and out across the outer boundary of the Earth system. Energy comes to us from the Sun, and the Earth radiates energy to the cosmos. If energy from the Sun exceeds the energy the Earth radiates, the Earth’s internal energy must increase. If that increase occurs in the random kinetic energy part of the Earth’s internal energy, the Earth’s temperature increases.

The Sun radiates energy to us across 90 million miles of space. The Sun is an incandescent sphere with a surface temperature of about 6000 K, where the K is short for Kelvins. Scientists prefer this scale, whose degrees are the same size as the more familiar Celsius scale (used in sensible nations) and are 9/5th of the size of the Fahrenheit scale (used in the United States). But the zero of the Celsius scale, the melting or freezing temperature of water, is 273 K. Zero K is the unreachable absolute zero. As an incandescent object at this temperature the Sun radiates most of its energy in the infrared, (the short wavelength infrared around 1 millionth of a meter). It radiates throughout the visible, with a peak in the green (around ½ a millionth of a meter). And it radiates some energy in the ultraviolet. To our eyes, the Sun is white. At the top of the atmosphere, the imaginary boundary of the thermodynamic system, power from the Sun is about 1 kW/m2.

The atmosphere is, for the most part, transparent to this incoming radiation. Clouds, dust, and other things reflect some of it back through the system’s boundary. Some parts of the surface also reflect the radiation upwards, such as ice and snow. All of the rest must be absorbed by the Earth, land and sea.

To take a convenient value, consider that the surface of the Earth is 300 K, which is not far off. The Earth radiates energy upward because of its temperature, just as the Sun radiates energy upward from its surface. The Earth’s surface is about 20 times cooler than the Sun’s. Thus, the peak of the Earth’s upward radiation has a wavelength 20 times longer than does the Sun. Twenty times ½ millionth of a meter is 10 millionths of a meter. That’s the peak, but there is energy moving upward from 5 to 20 or 30 micrometers.

If the Sun’s power to the Earth, with a (blackbody, as the physicists say) spectrum at 6000 K, exceeds the Earth’s outgoing power with a blackbody spectrum at 300 K, the Earth’s surface temperature must increase: 310 K, 320 K, and this increase in temperature will increase the outgoing power until it equals the incoming power.

Water vapor and CO2 in the atmosphere add important details, without changing the picture that an imbalance of power in and out leads to temperature changes. These gases absorb energy in the long wavelength infrared, and the molecules re-radiate that energy in all directions. Some outgoing power returns to the Earth.

Consider, for the moment, if there were no water vapor or CO2. Scientists can estimate the Earth’s surface temperature in this case that will balance power in and out. With no water vapor or CO2, the Earth’s surface temperature would be about 260 or 265 K, -5 or -10 C, 20 F! That is, the world’s oceans would be frozen.

If water vapor and carbon dioxide absorb some of the out-going power, then the Earth’s surface must radiate more so that what makes it into outer space equals the incoming power from the Sun. As the Earth’s surface temperature increases, the upward moving power increases. The water vapor and carbon dioxide still absorb and re-radiate some, but the surface temperature will increase until that fraction that passes all the way through the atmosphere equals the power coming the other way. These natural processes are the greenhouse effect. They are the reason that the Earth’s temperature is about 18 or 20
C, or 295 K or thereabouts, and the oceans are liquid.

I don’t mean to say that the entire matter is simple. The details matter, and variations in any of the effects I’ve mentioned and in some I haven’t may and do influence the energy and power balance. That’s why the Earth’s climate scientists have been working so hard for decades.

The general picture I’ve explained, however, forms the basis for our understanding of the Earth’s temperature.

Of the many possible control knobs, the Sun’s output power may vary, the Earth may shift in its orbit, the Earth’s axis may shift, volcanoes may add particles and gases to the atmosphere. Any of these and more may vary and have varied in the Earth’s history. It happens to be the case, that humans have been transforming ancient sunlight, stored in the chemical bonds of fossil fuels, into energy to power our civilization, producing water and carbon dioxide and some other stuff. We have grabbed onto the CO2 control knob, and we have begun turning it up. Of course, the various natural forces and effects still operate. But the climate change science deniers do not explain why this twist of the carbon dioxide control doesn’t increase the temperature.

Note added in response to Comments from Mr. Tomlinson: (Oct. 3, 2017)

Here’s a temperature chart that shows, on the right, a short horizontal line that exhibits the supposed hiatus to which you refer. Indeed, you can see that by picking each local maximum global average surface temperature going back 50 years, that we have an uninterrupted string of hiatuses. Hmmm.Global Warming Deniers HIatuses

Note added in response to comments from Greg Tomlinson (Oct. 7, 2017)

“The figure below shows the global surface temperature record created from only raw temperature readings with no adjustments applied (blue line). The red line is the adjusted land and ocean temperature record produced using adjusted data from the US National Oceanic and Atmospheric Administration (NOAA), with the difference between the two in grey.” This is from the third link above.

adjusted data

I have begun a series of blog posts that incorporate Greg Tomlinson’s comments and my replies here:



Filed under Climate Change

16 responses to “Global warming XIII – The Carbon Dioxide Control Knob

  1. You give no arguments as to what makes CO2 a primary “control knob” for the earth’s temperature, except for saying that this is what “knowledgeable people” believe. Well, the knowledgeable people I know realize this “climate change” fraud for what it is worth.


  2. bleikind

    Mr. Tomlinson,
    I’m afraid that the “knowledgeable people” you know have misinformed you.
    Here’s how climate scientists and other researchers know that carbon dioxide is a key “control knob” for the Earth’s temperature. They have known this since Svante Arrhenius published research on the greenhouse effect in the 1890s. .

    The greenhouse effect is not a new phenomenon caused by human fossil fuel use. It is a natural effect, and is the reason why the Earth’s average surface temperature is about 60 F instead of 20 F, which is what it would be if there were no water vapor or carbon dioxide in the atmosphere.
    The basic idea is this: The flow of energy into the Earth must balance for the temperature to be stable. The flow in, of course, comes from the Sun. The flow out comes from the Earth and appears in the far infrared. The atmosphere is transparent to most of the Sun’s radiation, which is in the visible and near infrared. But the atmosphere absorbs and re-emits substantial parts of the Earth’s upward flowing far infrared radiation. Water vapor and carbon dioxide absorb upward moving far infrared radiation and re-emit it in all directions. This reduces the amount flowing to space. Therefore, the Earth has to increase the amount of upward flowing radiation leaving its surface until the flow outward equals the flow inward from the Sun. To increase its radiation, the Earth’s surface temperature must increase. That is, the globe must warm.
    Natural fluctuations in the amounts of water vapor and carbon dioxide in the atmosphere produce fluctuations in the Earth’s surface temperature, as when there have been massive volcanic eruptions.
    Thus actual knowledgeable people, and not your “knowledgeable people” know from fundamental principles, the 1st Law of Thermodynamics, and the detailed properties of water and carbon dioxide, that carbon dioxide is a key “control knob.”



    • Bernard,
      There is an important difference between the work of Svante Arrhenius and the earth’s surface/atmosphere. Namely, Arrhenius’s laboratory was in thermal equilibrium whereas the earth and its atmosphere was not — never was and never will be. Therefore, Arrhenius could read and report the temperature and pressure of his gases whereas it makes no sense to even talk about a single temperature or H2O vapor pressure of the earth’s atmosphere. Hence, most of those physical chemistry laws with which we have become familiar (including the Clausius-Clapeyron equation) do not apply on the global scale because they assume thermal equilibrium. These laws, however, can be applied locally over a region small enough to be characterized by a single temperature and pressure, which makes them an excellent for meteorologists. But to extend them to a global scale is mathematically invalid. Therefore, while Arrhenius may have made some great contributions to our understanding of the greenhouse effect, his conclusions apply only to the laboratory and not the entire atmosphere.


  3. Bernard,
    There is an important difference between the work of Svante Arrhenius and the earth’s surface/atmosphere. Namely, Arrhenius’s laboratory was in thermal equilibrium whereas the earth and its atmosphere was not — never was and never will be. Therefore, Arrhenius could read and report the temperature and pressure of his gases whereas it makes no sense to even talk about a single temperature or H2O vapor pressure of the earth’s atmosphere. Hence, most of those physical chemistry laws with which we have become familiar (including the Clausius-Clapeyron equation) do not apply on the global scale because they assume thermal equilibrium. These laws, however, can be applied locally over a region small enough to be characterized by a single temperature and pressure, which makes them an excellent for meteorologists. But to extend them to a global scale is mathematically invalid. Therefore, while Arrhenius may have made some great contributions to our understanding of the greenhouse effect, his conclusions apply only to the laboratory and not the entire atmosphere.

    Liked by 1 person

    • bleikind

      Mr. Tomlinson,
      I believe that Svante Arrhenius was, for the most part, a theoretical scientist. His ideas about what he called the hot-house effect arose from the observations and measurements of others.
      He did not create a “hot-house” in his laboratory and figure out why they kept their interior warmer than their surroundings. Indeed, hot-houses, glass enclosed volumes, work for two main reasons. Incoming visible radiation from the Sun passes inward through the transparent glass, but the radiated infrared energy from the house’s interior cannot pass outward through the glass. Hot-houses also work by stopping convection. Winds do not blow past and cool the plants, and the warm air does not rise away from the plants drawing in cooler surrounding air.
      Arrhenius showed, using measurements of CO2 and H2O infrared absorption made by others, that those gases take the role of the glass in a hot house.
      His model, created as equations, that he and his assistants had to solve or estimate by hand were much simpler than today’s models. His model of the atmosphere designed to elucidate the effect of CO2 and H2O did not consider the role of convection in transporting energy upward through the atmosphere. He knew, of course, about convection. But he intended his model to illustrate the effect of those two gases. Today’s weather and climate models take convection and other effects into account along with those of CO2 and H2O.
      These modern models, and all modern scientific thought confirm Arrhenius’ insights.
      Climate scientists know that the physical and chemical properties of the atmosphere, oceans, and continents change from second to second, from one altitude to the next, from one latitude to the next, between day and night, from one season to another, and from year to year. The technical term that they use to describe these changes is the weather. That is why they take averages of things. Climate scientists research the long-term and large-scale variations in the key properties of the atmosphere and oceans.
      Consider the temperature. The global average surface temperature cited by climate researchers is an average over the many time and space scales I mentioned. The same could be done for pressure, water content, and any other important property. As you know, normal human body temperature is about 37 C (or 98.6 F). Human body temperature varies throughout the body, cool at the skin, high in working muscles, and throughout the day, lower in the morning, higher in the late afternoon. According to your argument about the meaning of temperature, the concept of human body temperature would be meaningless.
      In equilibrium thermodynamics, a closed system with no energy or material flowing in or out will eventually reach a stable state in which no changes occur. This is an equilibrium. The Earth, for the purposes of meteorologists and climate researchers is not a closed system. Energy flows into the system from the Sun primarily in the visible and near infrared regions of the spectrum, and energy flows out of the system from the Earth’s surface and atmosphere in the far infrared. As you say, this is not an equilibrium, it is a stationary state, for most purposes.
      The flow of energy through the Earth’s environment is stationary over long scales, but it does change. Thus, researchers today believe that tiny roughly periodic changes in the Earth’s orbit over thousands of years lead to changes in the incoming flow of radiation from the Sun. The averaged properties of the Earth’s environment adjust to this, warming or cooling. This is thought to be a key cause of ice ages.
      The flow of energy through the Earth’s environment also depends upon the properties of that environment. For example, snow reflects some of the Sun’s radiation back into space. Less snow, in the summer, or from a warming climate, means less radiation going back into space. Less sea ice in the Arctic or Antarctic means less reflected into space and more absorbed by the polar seas. (The official term for this property is the albedo.)
      Another property of the atmosphere that is stationary for many purposes but that changes for natural and human-caused reasons is the CO2 content. You could think of this property as changing the insulation that the atmosphere provides to the surface. Since pre-industrial times, humans have changed the CO2 content of the atmosphere from about 280 parts per million to more than 400 parts per million. In my opinion, those who deny that the climate is warming have the burden of proof to explain why adding significant insulation does not cause the surface to warm.
      Look at the famous Keeling curve. (Look at my blog post, Global Warming VII — Carbon Dioxide History , for example.) You will see, in addition to the decades-long slightly concave upward swoop, that the CO2 concentration at the Mauna Loa Observatory shows seasonal wiggles. According to your criticism of global temperature averages, researchers should not use this data to represent properties of the atmosphere over continents, near urban areas, or close to volcanoes. What they do, rather than follow your advice to abandon their efforts, is to check whether these other factors significantly change their conclusions, and take these variations into account where necessary.
      Scientists use equilibrium thermodynamics when the systems they study are in or near to equilibrium, and they use non-equilibrium thermodynamics when they deal with energy flows. Climate science is an applied branch of non-equilibrium thermodynamics and non-linear fluid mechanics.


      • I’m afraid CO2 is not the best “insulation” for the atmosphere as indicated by the cooling trend that occurred between the early 1940s and 1970s. In fact the fear of global cooling persisted into the late 1970s. During this entire cooling period, however, CO2 levels continued to rise as they did throughout the entire 20th century. This indicates to me that, all else being equal, the earth may well be cooler without CO2, but there are other factors much more important in determining earth’s temperature. What worries me much more than the greenhouse warming resulting from anthropogenic CO2 emissions is how our government and others (including the UN) are going to react to this “crisis”. We simply cannot afford any more economy-crippling taxes and regulations that our last president tried to impose on us. Fortunately, it appears our current president and EPA director are working to undo the damage.


  4. Mr. Tomlinson,
    No one claims that CO2 is the best insulation or the only one. Water vapor is a more important greenhouse gas, for example. It happens, however, that CO2 is the control knob that humans have rotated to the right and are continuing to turn.
    Researchers believe, based on substantial evidence, that the cooling you cite was the result of increased atmospheric aerosols, which are one of the other factors that influence the extent to which incoming solar radiation reaches the surface. These aerosols increased as industrial production returned to normal and then grew after World War II, and they increased because of several major volcanic eruptions. World-wide efforts in the 1960s and 1970s to reduce poisonous pollution from coal burning led to a decrease in aerosols and an increase in solar energy reaching the Earth’s surface. Once these aerosols lessened, CO2 induced warming resumed.

    As for your political and economic concerns, economists call costs that one economic actor imposes on others an externality. For example, a manufacturer who takes clean water from a river to use in production, and then returns the contaminated water to the river is imposing costs on downstream water users. They must spend to clean up the water before they use it. The water-polluting upstream manufacturer imposes costs upon downstream manufacturers who require clean water.Economists usually prescribe taxes on the polluter with revenues used to clean up the dirty river water or regulations to require that the polluter clean up the water. These government interventions are necessary because the polluter’s products do not reflect the actual costs of their production, a market failure.
    President Obama, and presidents going back to Richard Nixon, who created the EPA, have been putting in place sensible regulations to protect Americans health.
    EPA Administrator Pruitt, an industry shill and known enemy of the EPA’s mission, is systematically working to destroy the EPA. He is pushing out public-spirited knowledgeable scientists and replacing them with polluters.
    Regulations that require coal mine owners to provide safe working conditions for their miners and to protect nearby streams and rivers, and regulations that power plants that burn coal not spew acid rain causing sulfur dioxide, low levels of mercury and radioactive uranium, and micro-particles of soot into the atmosphere have significant and measurable benefits to our health and the health of the environment. They are not the cause of the decline of employment in the coal industry, which economists tell us arises from increasing mechanization and competition from less expensive fuels such as natural gas.
    Delusional Donald Trump, who has asserted that global warming is a hoax perpetrated by the Chinese to destroy American business, will cause great harm, not just to the citizens of the United States, but to all humans living today and to come.

    Liked by 1 person

    • What you pointed out about aerosols increasing from human industry and volcanic eruptions demonstrates my point. There are factors other than CO2 that affect earth temperatures just as much or more. These aerosols caused a net cooling trend for about 30 years despite increased CO2 levels during those times. It is probably the sun, however, that is the most important driver of temperatures. The “warming hiatus” noted by the IPCC in 2005 was well correlated with a drop in solar activity that started within the first few years of the 21st century.


  5. bleikind

    Mr. Tomlinson,
    No one asserts that CO2 is the only, or even the most important, factor that contributes to the Earth’s climate or temperature. Indeed, you are correct that the Sun is the most important factor. Climate scientists investigate both the sizes and changes in the various factors when they assess changes in the climate. It happens to be the case, that humans have grabbed the CO2 control knob and are turning it strongly to the right, increasing CO2 levels to ones not seen for millions of years.
    There has been no hiatus in global warming. Variations in the Earth’s global average surface temperature are larger than the annual change in the underlying temperature trend caused by warming. In addition to aerosols, produced by volcanoes and humans burning fossil fuels, there are also fluctuations in ocean currents and temperatures known popularly as El Nino that contribute to short term global temperature fluctuations. It happens that 1998, a strong El Nino year, produced a record high average global surface temperature. For several years after this as the El Nino weakened, temperatures did not exceed 1998. Each of the last three years, 2014, 2015, and 2016 have exceeded 1998, each setting a new record. This year looks as if it will again set a new record.
    While global warming deniers declared that the Earth was now cooling, global warming continued unabated. Indeed, most of the increasing heat energy goes into the world’s oceans.
    I’d like to put a graph here in this comment, but WordPress doesn’t let me. So I am going to add a paragraph and the chart at the end of my original blog post. Please take a look.


    • I’m afraid there is strong evidence that most of your statements in this comment are based on “corrected” (ie. falsified) temperature data. Several indisputable facts point in that direction. As you probably remember, NOAA presented a paper by Thomas R. Karl et. al. in 2015 which basically rewrote the entire temperature record from 1880 onward, allegedly to help eliminate data “biases”. On several occasions, NASA did similar doctoring of their data. How can they possibly know if their adjusted data in any more accurate that the original readings taken over 100 years ago? Nowadays, however, you can’t go to the NOAA or NASA websites and pull up data for the year 1995 and expect to get actual measurements taken in 1995. Instead, you will get “corrected” data that was probably calculated sometime after 2010. If you want 1995 data taken in 1995, you will need to go the NASA archives, assuming they still exist. Since most climate researchers are not aware of this, they use the currently posted NASA and NOAA data without question. If you ask them “Where is the data that convinced the IPCC we are in a warming hiatus?”, they will probably respond with “WHAT warming hiatus?” since the new “corrected” data eliminates all level and downward temperature trends. Unfortunately, our government agencies have become extremely deceitful in this manner. Is this any way to do science?

      Suppose one of your graduate students gathered data for his/her thesis, and then “corrected” that data to fit the original hypothesis. Would you or your university accept that thesis? If not, then please don’t expect me, the Trump administration, nor the American people in general to buy these NASA/NOAA arguments when they would most likely be used to justify economy destroying carbon taxes and regulations.


  6. Pingback: The Carbon Dioxide Control Knob Discussion I | two heads are better

  7. Pingback: Global Warming Control Knob Discussion II | two heads are better

  8. Pingback: The Carbon Dioxide Control Knob Discussion III | two heads are better

  9. Pingback: The Carbon Dioxide Control Knob Discussion IV | two heads are better

  10. bleikind

    Mr. Tomlinson,
    You are thoroughly informed about global warming denier debating points. Unfortunately, these arguments or assertions are misleading or mistaken. Your argument also falsely impugns the integrity not just of the climate scientists involved, but of the scientific enterprise.
    NOAA, NASA, and the British Hadley group do not “doctor” their data. They all adjust and correct it however. You can read a description of what they do here:
    No climate conspiracy: NOAA temperature adjustments bring data closer to pristine
    This is written by a climate scientist involved in the research and published in the Guardian.
    Thorough, not thoroughly fabricated: The truth about global temperature data: How thermometer and satellite data is adjusted and why it must be done.
    This is written by a scientist who is also a science journalist.
    Explainer: How data adjustments affect global temperature records.
    This one is written by one of the climate scientists involved in the global temperature research.

    You are correct that the scientists go back to the original raw data records and recalculate corrections as more data become available. The corrected data sets are labeled, for example, HADCRUT1, HADCRUT2, and so on.

    You are mistaken that climate scientists are unaware of this, and you are mistaken that the original raw data sets are not available. Here you can find the raw data that researchers used to produce HADCRUT4. The raw data for the NASA and NOAA datasets are also available and easy to find.
    The new corrected data does not “eliminate all level and downward temperature trends.” Indeed, comparing a century’s data, the corrected data reduces the warming between the first half of the 20th century and the second half. Here’s the data for you to see for yourself.
    I’ve put this graph above as an addition to the original blog post.

    Also, I have moved this series of comments and replies to new blog posts: Carbon Dioxide Control Knob I, II, III, IV, and V, which you can read here. I did this to bring my blog’s readers’ attention to these discussions.
    Start here: . Please make any addition comments to these new posts.


  11. Pingback: Carbon Dioxide Control Knob Discussion V | two heads are better

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