The CO2 Bathtub

Summary:  Previous postings have detailed the findings that a) even if humanity stops burning fossil fuels that produce atmospheric CO2, simply continuing to use existing facilities, such as power plants and automobiles, will add new CO2 to the atmosphere for several decades and lead to increased warming of the planet; and b) in reality, humanity’s demand for ever increasing amounts of energy will lead to much higher levels of atmospheric CO2 over the coming decades than at present.  In order to visualize this, here we imagine that the atmosphere is a bathtub containing CO2 at the present concentration.  We assess the factors that cause the bathtub to add more CO2 or that help drain it.  As noted, the bathtub will fill with more CO2 in coming decades. This model shows clearly that it is not enough merely to cut back on CO2 production, but that it is critical to cease completely the burning of fossil fuels for energy as soon as practical.

Introduction:  In earlier postings (Note 1)  we have discussed the current status of global warming  due to greenhouse gas (mainly carbon dioxide, CO2) accumulation.  Davis and coworkers (discussed here) have shown that even if installation of all new energy facilities worldwide that rely on fossil fuels were to abruptly stop right now, the continued emissions from existing facilities and machines would continue feeding new greenhouse gas into the atmosphere, leading to further global temperature rise.  In contrast to this limited hypothesis, Hoffert, in his commentary on the Davis article (presented here) , emphasizes the very dire situation that we will actually face in the future because of the accelerating addition of new CO2-emitting facilities.  Recent predictions of future global warming from the United Kingdom and the United Nations Intergovernmental Panel on Climate Change suggest that average global temperatures could rise 4 deg C (7 deg F) or more from today by the end of the century.  Such a drastic change in climate would lead to serious unfavorable effects on human populations around the world.

The CO2 Bathtub.  Suppose that the earth’s atmosphere is a bathtub, containing air with  CO2 at the present concentration of 390 parts per million (ppm; this means that out of 1 million molecules of all the gases in the atmosphere, 390 are CO2).  In this imaginary model, if the level of CO2 were to decrease the bathtub would be less full, and if the level of CO2 were to increase, it would ultimately overflow (see image below).  Thus, in this image, the bathtub represents the world’s CO2 level at the present time, and further represents the baseline for the additional CO2 accumulation anticipated by the climate scientists.  The CO2 bathtub at its present level also correlates with global warming (the planetary long-term average of measured temperatures) which is now about 0.7 deg C (1.3 deg F) above the average temperature that prevailed prior to the beginning of the industrial revolution, when the CO2 concentration was 280 ppm.

The Atmospheric CO2 Bathtub, showing pre-industrial (280) and current (390) CO2 levels.

Bathtubs are installed with faucets, delivering fresh water to the tub; and with drains that, when open, empty the contents of the bathtub.  In our imaginary bathtub, there is a “faucet”, made up of all the planetary processes that deliver new atmospheric CO2 into the bathtub.  There is also a “drain” that is partially “open”, such that some of the CO2 delivered into the atmospheric bathtub by the “faucet” is depleted.  In the previous posting we discussed the “virtuous cycle” of CO2 production and removal that was operating during the millennia before the onset of the industrial revolution.  This cycle operated with a dynamic equilibrium, maintaining the atmosphere, or in our present image, the bathtub, at the constant level of about 280 ppm CO2, or about 72% of its present level.  We will not consider the processes underlying this virtuous cycle any more here.  Rather, let’s mention the newer man-made processes that contribute to filling or emptying the bathtub. 

The Bathtub’s “Faucet”.  By far the largest contributor to the “faucet”, adding new atmospheric CO2, is the worldwide burning of fossil fuels for energy.  This energy provides mechanical motion in transportation vehicles of all kinds, including cars, trains and airplanes.  It is also used significantly in electrical appliances and apparatuses, and in heating and air conditioning of living and working spaces.  An additional contributor to the CO2 “faucet” is the large scale destruction of tropical forests, primarily by burning, to clear land for agricultural use or other purposes.  It’s important to note that this burning is on a scale that vastly exceeds the processes of dynamic CO2 equilibrium taking place in the primordial “virtuous” cycle.

The Bathtub’s “Drain”.  The major process “draining” atmospheric CO2 from our bathtub is the absorption, or dissolution, of atmospheric CO2 into the oceans of the planet.  A certain fraction of atmospheric CO2 dissolves into the oceans, but this process does not remove all the additional CO2 that we add by burning fossil fuels.  The absorption of CO2 into the waters of the oceans itself has detrimental environmental effects which will be discussed in future postings.   Another potential process that might contribute to “draining” atmospheric CO2 from the bathtub could be reforestation undertaken by humans.  This activity occurs in addition to the “virtuous” cycle of primordial times.  Its effect requires decades to become significant, however, since the planted trees have to grow to a size that would draw significant amounts CO2 out of the air.

The Current Level in the Bathtub.  At the present time, the “level” in our imaginary bathtub is not staying steady, but rather is rising in the tub.  The people of the world are burning so much fossil fuel that the level of atmospheric CO2 is rising by about 2 ppm per year, corresponding to about 0.5% per year, even though the “draining” processes remove part of the added gas.

The Future Level in the Bathtub.  As noted in the Introduction, Davis, Caldeira and Matthews, Science Vol. 329, pp. 1330-3, 2010; see Note 2 and see also http://warmgloblog.blogspot.com/2010/09/todays-co2-emitting-devices-add-to.html) have shown hypothetically that even if installation of all new energy facilities worldwide that rely on fossil fuels were to abruptly stop right now, the level of atmospheric CO2 in our imagined “bathtub” would continue to rise, in view of the continued emissions from existing facilities and apparatuses.  This would continue to lead to further global temperature rise for several decades.  Only as the presently installed base of fossil fuel facilities and apparatuses ages and is removed from service would these processes level off and the level in the “bathtub” begin to fall.

In reality, however, we know that new facilities that consume fossil fuels are constantly being added to the energy economy. The United Kingdom National Weather Service (Met Office) reported in 2009 that CO2 emissions are proceeding at a higher rate than was thought only a few years earlier.  In other words, not only is the current level in our “bathtub” increasing at about 0.5% per year, but the rate of rising of the level is most likely going to increase for the indefinite future.  Very briefly, this can be ascribed to increased demand for energy in developed countries of the world, and to the addition of vast new portions of the global population to the demand for energy-requiring apparatuses and living conditions, populations that earlier had minimal demands for energy.  Indeed, the Met Office predicts that the global average temperature could be 4 deg C (7 deg F) higher than today (note: 4.7 deg C higher than preindustrial revolution times) by 2100, using a “high-end emissions scenario”.  The level in our atmospheric “bathtub” is foreseen as rising continuously into the future, with no pattern currently in view that eases the increase, or the rate of increase, of the bathtub’s level.

We Must Level Off the Bathtub As Soon As Possible.  Our imagined bathtub shows clearly that the world’s peoples have to stop the level of atmospheric CO2 from rising any further as soon as possible, because each increase in the bathtub’s level correlates with additional global temperature rise.  This simple picture makes it very clear that it is not sufficient simply to slow the rate of burning fossil fuels, because all this will do is slow the rate of rising of the bathtub’s level.  What is really needed is to approach the situation imagined by Davis and coworkers, i.e., not building any new fossil fuel-burning facilities right away.  As described above, even this drastic requirement still results in having the level in our bathtub continue rising for several decades before leveling off.  In our model the bathtub is equipped with both a faucet and a drain.  The scenarios of Davis and coworkers, and of the Met Office, are concerned primarily with the faucet.  In fact, there is little technology currently available, other than reforestation, that has the effect of “opening” the drain more than it is now.  It is for this reason that global warming scientists stress the critical need for reducing the burning of fossil fuels to zero as soon as possible.

Note 1. http://warmgloblog.blogspot.com/2010/09/todays-co2-emitting-devices-add-to.html;

http://warmgloblog.blogspot.com/2010/10/we-need-to-achieve-alternativesustainab.html;    http://warmgloblog.blogspot.com/2010/10/why-we-need-massive-effort-for.html.

Note 2.  Abstract available online free, or the full article for a fee or through personal or institutional subscription.  Many public libraries, and university libraries open to the public, receive the journal.

What’s Needed: An Alternative Energy “Moon Landing Project”

Note:  This posting discusses a commentary by Hoffert on the article by Davis and coworkers which was the subject of the posting immediately preceding this one.

Summary:  The world-wide transportation, space heating and electric generating installations currently in use will continue to produce new atmospheric CO2 emissions  (the main greenhouse gas) throughout their useful lifetimes, adding to global warming.  New installations yet to be built will produce even more CO2 emissions in the coming decades. 

In the previous posting, the analysis of Davis and coworkers is described.  They imagine that as of today we abruptly cease to manufacture new cars, planes, furnaces and air conditioning, and stop commissioning new electric power plants.  They show that even so existing facilities would add enough new atmospheric CO2 that the global mean temperature would likely rise by about another 0.6 deg C (1.1 deg F) from today’s level by 50 years from now.

Hoffert, in a commentary on the work of Davis and coworkers, emphasizes that the global warming threat is far more dire than this.  Even 5-10 year old estimates of CO2 emissions and consequent temperature rise are now recognized as seriously underestimating the actual global production by new CO2-producing facilities.  He concludes that major technological and political initiatives will be needed to restrict atmospheric CO2 levels to levels deemed acceptable in order to keep global warming within constrained limits over the next 50 years.

Introduction.  The world’s nations already have enormous numbers of cars, airplanes, power generating plants, and heating and cooling facilities installed throughout their economies.  Yet as a consequence of globalization and human aspiration, there is strong pressure to add large numbers of even more such facilities and items.  These new additions to global CO2-producing capacity constitute a critical danger exacerbating global warming.

Accounting only for existing installations, atmospheric CO2 will increase in the next 50 years.  In the September 10, 2010 issue of Science, Davis, Caldeira and Matthews (Vol. 329, p. 1330-3 ; see Note 1) report an analysis in which they imagine that no new CO2-generating facilities are added in the next 50 years. 

Their analysis predicts that the global concentration of atmospheric CO2 will increase from the present 390 parts per million (ppm; parts by volume of CO2 gas per million parts by volume of air total), to a predicted maximum of about 412 ppm at about 2037.  (A sense of how much CO2 is produced by burning one tankful of gasoline, or one thankful a week for a year, can be seen here.)  After 2037 the predicted CO2 concentration falls slightly to about 408 ppm by 2060.

Global temperature is predicted to rise from its present level in the next 50 years.  Davis and coworkers predict that as a result of this increased atmospheric CO2 the average global temperature will rise over the next 50 years, reaching 1.3 deg C (2.3 deg F) above the average preindustrial temperature by 2060.  This is higher than the current average global temperature of about 0.7 deg C (1.3 deg F) above the average preindustrial temperature.

Overall assessment of global warming.  In the same issue of Science independent commentary by Hoffert (Vol. 329, p. 1292-4; see Note 1) on the Davis article assesses just how difficult it will actually be to reduce CO2 emissions.  He cites the recent book by J. Hansen, a pioneer in climate research and an early proponent of reducing global CO2 emissions (Note 2), as representing a commonly agreed limit of 450 ppm for atmospheric CO2, which is expected to limit global temperatures to 2 deg C (3.6 deg F) above pre-industrial levels.  Hoffert concludes that significant world-wide efforts will have to be undertaken to achieve the limitations proposed by Hansen.  This is all the more so because estimates of future CO2 production and resulting global warming put forth five or more years ago are proving today to have been woefully inadequate, as explained below.

Past assessments of “Business As Usual” CO2 emissions are seriously deficient.  Hoffert cites an analysis by Pacala and Socolow from 2004 (Science, Vol 305, p. 968 (2004) (see Note 1), which builds on a baseline of projected emissions termed “Business as Usual” (BAU; see the graphic below).  In the left part of the graphic, up to year 2010, the red line shows actual production of worldwide CO2 emissions from burning fossil fuels.  In business as usual, it is supposed that future CO2 emissions continue as the straight red line




Adapted from Hoffert (Science). “Gt CO2” or “gtCO2” stands for gigatons of CO2, where 1 gigaton is 1 billion tons, and 1 ton is a metric ton, 1000 kg, or about 2200 lbs.  In the vertical scales on the left, please ignore the inner scale, and focus on the outer scale giving fossil fuel emissions in gtCO2/year. © American Association for the Advancement of Science.  Presentation of this Figure here is believed to comply with the "Fair Use" limitations (sections 107 and 108) of US Copyright law.

extension of the trend beginning at  2010, up to the year 2060.  As Hoffert points out, part of the BAU assumption relies on preserving the earlier advantage gained in the efficiency of energy production, with respect to CO2 emissions, by shifting from coal and oil (which require burning of relatively larger amounts of fuel) to natural gas (which produces more energy while emitting less CO2).  The BAU model adds a total of 175 Gt CO2 by the year 2060, shown in the graphic by the gray triangle.

However, since 2004, Hoffert points out that the above shift has halted.  This is especially so because the commissioning of large numbers of coal-fired power plants in China, India and the U. S has reversed the earlier efficiencies.  As a result recent CO2 emissions have been significantly higher than those assumed by Pacala and Socolow.  This is shown schematically in the graphic by the steeper turquoise line starting at 2010, and adding the total additional CO2 emissions by 2060 as the orange colored triangle, which is estimated to be worth about 450 Gt CO2.   Further, as a result of this worsening situation installing sustainable or alternative power generation, yet to be developed and placed in service, as proposed by Pacala and Socolow would not succeed to keep CO2 production below the 450 ppm limit proposed by Hansen.  Thus, as estimated by Hoffert, the current scenario (turquoise line) requires far more extensive installation of sustainable or alternative power sources than Pacala and Socolow proposed in 2004.

In stark contrast to these increasing CO2 scenarios, the “aging out” of fossil fuel technologies assessed by Davis and coworkers presented a trend of decreasing CO2 emissions (see the yellow line in the graphic).  Since this trend obviously will not occur, Hoffert evaluates the negative consequence of this failure as “175 more Gt CO2” in the graphic, coded by the orange line and the pale yellow triangle.  Adding up all these needs for compensating all the CO2 emissions by the year 2060 yields a total of 625 Gt CO2, the furthest right vertical arrow in the graphic.  The compensation must be derived from alternative or sustainable energy production that does not emit any atmospheric CO2.

Conclusion.  Many more power generating plants, automobiles, and home heating and cooling capabilities that produce CO2 are likely to be built over the next 50 years.  This is because many areas of the world are only now passing from “undeveloped” to “developing” status, and currently developing countries are adding to demand for these devices and installations as well.  These factors, and others, underlie the trend toward accelerating CO2 emissions shown by the turquoise line in the graphic above. 

It is imperative to undertake the worldwide installation of alternative and sustainable energy sources that do not release atmospheric CO2.  In Hoffert’s view this requires “programs with the scale and urgency of the Manhattan atom bomb project. One goal should be to develop technologies that can … eventually provide [the required] power by mid-century…from ‘clean coal’ and from nuclear and renewable technologies.”  The massive injection of federal support for the Manhattan Project, and for the program to land a man on the moon, effectively achieved their objectives.  Otherwise severe global consequences of excessive warming are predicted to occur.

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Note 1. Abstract available online free, or the full article for a fee or through personal or institutional subscription.  Many public libraries, and university libraries open to the public, receive the journal.

Note 2. J. Hansen, Storms of my Grandchildren, Bloomsbury, New York, 2009.

 

Today’s CO2-Emitting Devices Add to Tomorrow’s Global Warming

Note:  This posting discusses an article by Davis and coworkers.  The posting immediately following this one discusses a commentary by Hoffert on the Davis article.

Summary:  The world-wide transportation, space heating and electric generating installations currently in use will continue to produce new CO2 (greenhouse gas) emissions for decades, adding to global warming.  Imagine that as of today we abruptly cease to manufacture new cars, planes, furnaces and air conditioning, and stop commissioning new electric power plants.  Even so, existing facilities and apparatuses, given their expected service times, would add sufficient new CO2 to the atmosphere    that the global mean temperature would likely rise about another 0.6 deg C (1.1 deg F) from today’s level by 50 years from now.  In actual fact, however, addition of new fossil fuel-burning facilities will not cease, and indeed will greatly expand, making global warming even worse.  Accordingly it is imperative to transform the world’s energy economy to one that relies mainly on alternative and sustainable energy sources and on devices adapted to use them.

Introduction.  The world’s nations already have enormous numbers of cars, airplanes, power generating plants, and heating and cooling facilities installed throughout their economies.  Yet as a consequence of globalization and human aspiration, there is a desire, if not a need, to add even more such facilities and items, probably increasing their numbers by large factors in the remainder of this century.  These new additions to global CO2-producing capacity constitute a critical danger exacerbating global warming.

Atmospheric CO2 will increase in the next 50 years due to existing installations.  In the September 10, 2010 issue of Science, Davis, Caldeira and Matthews (Vol. 329, p. 1330-3; see Note 1) report an analysis in which they imagine that no new CO2-generating facilities are added in the next 50 years.  They assess the future production of atmospheric CO2 (committed CO2) and its effect on global temperature from only CO2-producing equipment already in place.  This assessment was carried out using available data for world-wide fixed sources (e.g. power plants, residences and work places) and transportation equipment. They use a commonly accepted global climate model to make their projections.

Their analysis predicts that the global concentration of atmospheric CO2 will increase from the present 390 parts per million (ppm; parts by volume of CO2 gas per million parts by  volume of air total), to a predicted maximum of about 412 ppm at about 2037.  (A sense of how much CO2 is produced by burning one tankful of gasoline can be seen here.)  After 2037 the predicted CO2 concentration falls slightly to about 408 ppm by 2060. (See Fig. 1C from Davis and coworkers below). 



Gt CO2 stands for gigatons of CO2, where 1 gigaton is 1 billion tons, and 1 ton is a metric ton, 1000 kg, or about 2200 lbs.  In Figs. 1A and 1B the number for each colored band is the total committed Gt CO2 for that band. 

© American Association for the Advancement of Science.  Presentation of this Figure  here is believed to comply with the "Fair Use" limitations (sections 107 and 108) of US Copyright law.



In greater detail, the incremental increase in CO2 concentration in the atmosphere year by year starts out high, as all the facilities and equipment are active. (See Figs. 1A (graphed according to energy sector)  and 1B (graphed according to country/region) from Davis and coworkers).   Year by year as installations reach the ends of their predicted lifetimes and are taken out of service (based on historical useful lifetimes of comparable equipment) the annual increments diminish more or less in a straight line, falling to no further increment by about 2046 (i.e., 36 years from now).  These increments are superimposed on a baseline of CO2 annual additions that remain essentially constant throughout the 50 year span arising from “non-energy” sources, which are exemplified by cement and steel manufacture, and agriculture.  For this reason the annual CO2 increments never fall to zero. 

Global temperature is predicted to rise from its present level in the next 50 years.  Davis and coworkers depict the current average global temperature as being about 0.7 deg C (1.3 deg F) higher than it was in preindustrial times.  They predict that as a result of the increased atmospheric CO2 concentration arising from existing installations (Fig. 1C above) the average global temperature rises slowly over the next 50 years, reaching 1.3 deg C (2.3 deg F) above average preindustrial temperature by 2060. (See Fig. 1D above). 

Further detail: Predicted upper and lower bounds.  In Fig. 1, predicted upper and lower bounds to the changes shown are given by the dashed lines in Figs. 1A and 1B, and by the red and blue lines, respectively, in Figs. 1C and 1D.  These are based on higher and lower assumed production levels for CO2 than used in the median analysis.

Significance for global warming.  Davis and coworkers show that existing CO2-producing installations and devices lead to seemingly modest further increases in atmospheric CO2 levels and predicted further global temperature increases.  There is no comfort in these findings, however (see the next blog posting describing the article by Hoffert).  First, these predictions are due only to existing facilities.  There is no doubt that many more power generating plants, automobiles, and home heating and cooling capabilities that produce CO2 will be built over the 50 years covered.  This is because many areas of the world are only now passing from “undeveloped” to “developing” status, and currently developing countries are adding to demand for these devices and installations as well.  Second, as Davis and coworkers point out, other activities that lead to more burning of fossil fuels were not analyzed, but are significant.  These include transportation fuel distribution infrastructure, and highway development.

Conclusion. Davis and coworkers conclude “satisfying growing demand for energy without producing CO2 emissions will require truly extraordinary development and deployment of carbon-free sources of energy, perhaps 30 TW [terawatts, or trillion watts] by 2050 [citations omitted]. Yet avoiding key impacts of climate change depends on the success of efforts to overcome infrastructural inertia and commission a new generation of devices that can provide energy and transport services without releasing CO2 to the atmosphere.”

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Note 1. Available online for a fee or through personal or institutional subscription.  Many public libraries, and university libraries open to the public, receive the journal.

Light And Heat – The Greenhouse Effect

Summary:  Global warming is attributed to a greenhouse effect occurring in the atmosphere as a result of the accumulation of excess amounts of carbon dioxide, methane, nitrogen oxides and other “greenhouse gases”.  Sound methods of objective scientific investigation have shown that the excess levels of these gases is due to human activity, namely, the burning of fossil fuels that produce CO2 on combustion.  This blog posting provides an explanation of the greenhouse effect in general, and shows why carbon dioxide is a greenhouse gas.  A brief discussion is presented in the paragraphs immediately following.  Expanded explanations are found in the Notes further below that are referenced in the discussion.

The Greenhouse Effect.  The greenhouse effect refers to the fact that a glass greenhouse (or a car interior) maintains a warmer temperature inside the greenhouse than outside when the sun shines on it.  This happens because glass is transparent to sunlight, permitting the sun’s light to reach the inside of the greenhouse.  Some of the heat released by the incident sunlight is trapped by the glass, retaining much of the heat inside the greenhouse.

Colored objects convert visible light to heat. Whenever light from the sun strikes a colored object on the face of the earth, the object absorbs some of that light (see Note 1).  All light is actually a form of energy.  The energy in visible light that is absorbed by the colored object is re-emitted as heat energy, invisible to the human eye, called infrared radiation (see Note 2).

Greenhouses trap some of the heat radiation. In a greenhouse, as we noted, the glass lets the sunlight through.  Plants, soil and other objects in the greenhouse absorb the sunlight, and re-radiate heat energy as a result.  If these objects were in the open, the heat would radiate out into the atmosphere.  But in a greenhouse, the glass panes actually absorb a part of the heat radiation and don’t let it radiate back out.  The glass traps the heat inside the greenhouse, keeping all its contents warmer than the outside air.

Greenhouse gases trap heat in the earth’s atmosphere. Greenhouse gases such as carbon dioxide (CO2) in the earth’s atmosphere work in exactly the same way.  They are transparent to visible sunlight, but absorb some of the heat radiation in the infrared portion of the spectrum, retaining the heat within the atmosphere and emitting some of it back to the surface (see the graphic below, and Notes 3 and 4).

http://www.hotindienews.com/2010/05/19/1023923

Rising CO2 levels result in global warming. Over the course of the eons during which CO2 concentrations were constant in the atmosphere, temperatures were within a range that permitted life forms to develop and branch out on our planet.  But now, in a relatively short period on the geologic time scale, man-made CO2 arising from the burning of fossil fuels  is being added to the atmosphere.  Climate scientists are finding that the greenhouse effect of the added CO2 is increasing, making global temperatures warmer.  This effect has been most pronounced over the past 50 or so years, and especially so in the recent two decades.  The graphic below shows superimposed measurements of CO2 concentrations in the air and global temperatures from 1880 to 2004. 



http://oceanworld.tamu.edu/resources/oceanography-book/evidenceforwarming.htm



It’s quite apparent that the two trends are fully correlated with each other, showing that it is highly likely that the higher CO2 concentration is directly responsible for the warming trend because of the greenhouse effect.

Other gases are also greenhouse gases.  Among the most significant is methane, the gas of natural gas (see Note 5). 

Conclusion: From this discussion we understand how atmospheric CO2, methane and certain other gases behave as greenhouse gases, and that the greenhouse effect is increasing as we burn more fossil fuels and release more and more CO2 into the atmosphere.  The greenhouse effect is leading to global warming.  Thus it should be a high priority for all of humanity to minimize the burning of fossil fuels, and to develop programs that combat the effects of the higher amounts of CO2 already present.

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NOTES

Note 1. We all know that white objects absorb little or no sunlight.  But consider the light from the sun that does strike an object.  Sunlight is made up partly of visible light of all the colors of the rainbow, from violet all the way to red; this is called the visible spectrum.  This is also seen when light passes through, for example, a crystal chandelier or a glass prism, displaying the rainbow spectrum.  This is shown in the graphic below.

Dispersion of visible light by a prism

Objects we perceive as having color, such as a green leaf, or the orange color of autumn leaves, absorb some of the colors in sunlight but reflect back the remaining colors (see the graphic below).   

 

Greenhouse0-mrnice.nl

Chlorophylls and carotenoids are the pigments in green leaves that give them their color.  The chlorophylls a and b in the leaf absorb the violet-blue and red ends of the spectrum, reflecting back the unabsorbed greens and yellows (the higher the line, the more light of that color of the spectrum is absorbed).  These unabsorbed greens and yellows are the colors we see.  The carotenoids absorb the bluish and greenish parts of the spectrum and reflect back the oranges and reds, which are the colors we see in autumn.  Black objects appear black because they absorb all the colors of the visible spectrum; we should consider the black to be actually the absence of any light whatsoever.  The visible light absorbed is radiated back as heat, or infrared light (see Note 2).

Note 2. It’s known from physics that light is actually a transmission of energy.  The energy absorbed  by colored objects (Note 1) is converted to a different part of the energy spectrum, the infrared spectrum (infra means below, meaning below the  red light of the visible spectrum), which is felt as heat.  The light contained in the visible, or rainbow, spectrum is not heat energy in and of itself.  Rather, colored objects feel warm in sunlight because of the conversion to heat, or infrared radiation (see the graphic below, showing the infrared portion in the spectrum of light radiation).  Black objects absorb the most light and so feel the warmest, while light shades absorb considerably less and don’t feel warm in the sun. 



Portions of the spectrum including the infrared and visible portions.



Note 3. Over the lifetime of the earth, as life forms emerged and spread, over more than a billion years, the earth’s atmosphere accumulated a certain level of carbon dioxide partly as a result of metabolism of carbon compounds by the living beings.  Through the eons that carbon dioxide has been recycled out of the atmosphere partly by photosynthesis, which re-incorporated it back into plant matter, or biomass.  In the history of the earth, these balancing processes maintained the carbon dioxide level relatively constant within certain limits of variation, such that up to the beginning of the industrial revolution the amount of carbon dioxide in the atmosphere was about 280 parts per million (ppm).  Today however, as a result of man’s burning fossil fuels for energy, the CO2 concentration is now about 380 ppm, and growing.

Note 4. Why is CO2 a greenhouse gas?  Most molecules behave as if they have a “color” in the part of the unseen light spectrum that transmits heat.  This is called the infrared spectrum (see the graphic in Note 2).  Different molecules have different “colors” in the infrared part of the spectrum, just like different substances having different colors to our eyes in the visible spectrum (such as the chlorophylls and carotenoids in the graphic in Note 1).  Atmospheric CO2, while permitting the visible light of sunlight to pass unimpeded through the air to the ground, does have an infrared “color”, and partially absorbs heat radiated back into the atmosphere from the surface of the earth after colored objects have absorbed sunlight (see the graphic below; here absorbed infrared radiation is indicated in the downward troughs, and transmitted or unabsorbed light is shown by the flat portions at the top). 

The absorbed infrared radiation is re-released in all directions, including back into the atmosphere and down to the earth’s surface.  The heat absorbed by the CO2 would otherwise radiate without hindrance into outer space.  Thus atmospheric CO2 retains a portion of the heat ultimately provided by sunlight via the re-radiation of heat from the earth’s surface.  This retained heat keeps the atmospheric temperature somewhat warmer than it otherwise would be.  In this way CO2 and other greenhouse gases act just as the glass in a greenhouse does. 

Note 5. Methane has an infrared “color” that is much stronger than that of CO2.  Molecule for molecule, methane is about 25-40 more effective in absorbing heat than is CO2.  For this reason, scientists working on global warming are very concerned about methane, although its concentration in air is less than 1% of the concentration of CO2.  This is why there’s an interest in reducing the amount of methane arising from dairy cows and other domesticated animals that chew the cud.  The bacteria in the rumen of these animals produce large amounts of methane that are belched out by the animals.  Methane is also sequestered as a solid crystalline ice hydrate in arctic tundras.  This methane originated from the decay of organic matter in the tundra’s vegetation.  As the tundra melts due to global warming, large amounts of methane are melted out of the hydrate crystals and released into the atmosphere, which contributes to warming even more.  This is one way that global warming is accelerating its own progress on Earth.

Invisible Energy

Summary: Since CO2 is odorless and colorless, we cannot grasp how much of this greenhouse gas we generate in our daily activities. Here, I present some graphics and descriptions that easily permit such an understanding. An inevitable conclusion is that we must all strive to minimize our activities that contribute to the accumulation of CO2 and other greenhouse gases.


Why does a large fraction of the American public deny the truth of global warming? Well, for one thing, what is out of sight is out of mind. We heat our homes with gas or oil that we do not see. Once in a while, if we look inside the furnace, we’ll marvel at the beauty of the cool blue flame. But we have no sense of how much gas is actually flowing, or how much oil we’re actually consuming. So we, the warmed citizens of this country, can’t appreciate how much of that fossil fuel is actually being burned to CO2 gas and released into the atmosphere.


Likewise, we consume electricity in our homes for lighting, powering appliances, for air conditioning in the summer, and in some cases for space heating instead of gas or oil heating mentioned above. Here too, even more so, we as consumers are fully and effectively shielded from the vast amount of carbon based fuels burned to produce the electricity we use. Almost all electric power in the US is produced from coal and natural gas. Who among us has any sense of the vast tonnage of coal, or the millions of cu. ft. of gas, that are burned (with relatively poor efficiency) to generate that power? Electricity is delivered to us through wires hidden from view inside the walls of our houses, and of course we can’t count the electrons coursing through those wires to our homes as we go about our daily routines.


Third, gasoline- or diesel-fueled transportation effectively conceals any sense of consumption of liquid. We pump an invisible liquid through an opaque hose into an unseen gas tank, that mystical internal storage compartment in our cars, trucks and buses. But we really can’t grasp how much we’re pumping in, or how much it weighs. Gas stations aren’t equipped with auto scales so that we could actually measure the weight of gasoline added by filling up. Further, we have no sense of how much CO2 is actually produced when that weighty liquid is burned to CO2 and released into the atmosphere. So there’s no sense of the CO2 burden we’re imposing on the atmosphere with every fill-up at the gas station. And of course, that CO2 vapor is colorless and odorless, so we don’t sense the final product of our transportation consumption either.



Here’s a simple illustration intended to help us grasp how much CO2 we actually release when driving a car. Suppose your car is representative, and takes about 15 gallons of gasoline to fill up the tank. When you do so, you’ve added about 84 pounds of gasoline liquid (see the first figure, below).

Weighing a tankful gas in your car on a fulcrum balance.

When burned in your engine (and after the exhaust passes through the catalytic converter of the car) you’ve produced about 260 pounds of CO2. (You’ve also produced some water vapor, but that’s not significant for our discussion about the greenhouse gas effect.) CO2 can be liquefied by applying extra pressure and cooling it; as a liquid these 260 pounds would measure about 69 gal. If that were kept in an on-board pressurized tank, it would have to be much larger than the gas tank that you filled at the pump.


But in reality, without compression and cooling CO2 is a gas. These 69 gal. of liquid CO2 would actually occupy about 16,400 gal. of gaseous volume, if that volume contained the pure CO2 and no other components of air (see the second figure, further below). But in today’s atmosphere, the distributed concentration of CO2 in the air is about 360 parts per million (ppm), meaning that in 1 million gallons, for example, of air volume, 360 gallons would be CO2 (thus, 360 ppm) and the remainder would be the other components of our atmosphere, such as nitrogen, oxygen and water vapor. So if we now equilibrate the 16,400 gallons of CO2 vapor from burning our tankful of gas into the atmosphere, and considering a cubic volume, this CO2 would be distributed into a cube about 180 feet on a side. For comparison, most mature trees are about 60-80 feet tall (see the second figure); and a building this tall would have 12-18 stories.

Virtual cube 180 feet on a side showing the volume that would be occupied by liquid CO2,
by the same amount of pure CO2 gas, and by distributed skunk-odor-linked CO2
produced by burning one tankful of gasoline.  A mature tree is shown for comparison.

Now, suppose we could attach the smelly molecule that skunks emit to every CO2 molecule. The result of burning 15 gallons of gasoline from one fill-up at the gas station would produce a cube of skunk-smelling gas that is 180 feet on side. In fact the smelly odor of skunks is a very strong odorant; usually we can detect a few ppm in the air. So if you entered this virtual cube, with skunk odor at the 360 ppm concentration that characterizes atmospheric CO2, you would be overwhelmed, and might even start feeling sick!

If you fill up your tank once a week for 1 year, you could envision lining up these cubes end-to-end. In that 1 year period, you’d be making a rectangular volume that is 180 feet wide, 180 feet tall, and almost 9,500 feet long. Thus, with our imaginary skunk-smelling CO2, you’d create a strongly skunk-smelling rectangular volume that is almost 2 miles long at the end of 1 year of driving.

This detailed illustration covers only our transportation usage of fossil fuels. But our other energy needs mentioned at the beginning of this article obviously also contribute to producing atmospheric CO2, so comparable volumes of gas, and in our illustration, skunk-smelling gas, would be produced by each one of those sources over the course of a year. The numbers will differ, but the general effect for each contributing source will be the same. Enormous volumes of equilibrated carbon dioxide are produced by each one of us as we go about our daily activities.

Global production of atmospheric CO2.  This illustration needs to be multiplied by the number of people in the U.S., or rather, since global warming is indeed a world-wide phenomenon, multiplied by the total contributions from all the people in the world. In general, our fossil fuel consumption is increasing with time, both because the population in general is increasing, and because in developing countries the per capita consumption of fossil fuels is increasing dramatically. So it’s useful to imagine our skunk-smelling CO2 gas covering this virtual earth, and growing stronger in odor every year. Indeed, we, the global population of humans, are currently adding 2 ppm of CO2 to the atmosphere every year.

The world’s CO2 burden is like a bathtub with a drain and a faucet. If we add water to this bathtub with a strong stream but open the drain only a little, it’s evident that the level of water in the tub will keep on rising. It’s the same with the CO2 in the atmosphere. There’s not much place for the added CO2 to go to in order to exit the atmosphere (except the oceans), and by our activities we keep adding CO2 to it, more than the oceans can absorb.

Conclusion. From this illustration, it’s clear that each one of us is contributing to the worsening of global warming with each energy-dependent activity that we undertake. We all have to go about our daily routines thinking of ways to reduce the burning of fossil fuels in the maintenance of our life styles. There really is no other answer to the problem that increasing atmospheric CO2 exacerbates global warming.