Frequently Asked Global Change Questions
This page lists global change questions that have been received at CDIAC and the answers that were provided to a diverse audience. If you have a question relating to carbon dioxide and global change and cannot find the answer you need here, you can "Ask Us a Question", and we will be glad to try to help you.
- Should we grow trees to remove carbon in the atmosphere?
- What are the present tropospheric concentrations, global warming potentials (100 year time horizon), and atmospheric lifetimes of CO2, CH4, N2O, CFC-11, CFC-12, CFC-113, CCl4, methyl chloroform, HCFC-22, sulphur hexafluoride, trifluoromethyl sulphur pentafluoride, perfluoroethane, and surface ozone?
- Where can I find information on the naming of halocarbons?
- Can you quantify the sources and sinks of the global carbon cycle?
- How much carbon is stored in the different ecosystems?
- In terms of mass, how much carbon does 1 part per million by volume of atmospheric CO2 represent?
- What percentage of the CO2 in the atmosphere has been produced by human beings through the burning of fossil fuels?
- How much carbon dioxide is produced from the combustion of 1000 cubic feet of natural gas?
- Why do some estimates of CO2 emissions seem to be about 3 1/2 times as large as others?
- Why is the sum of all national and regional CO2 emission estimates less than the global totals?
- Why do some smaller nations have larger per capita emission estimates than industrialized nations like the US?
- What is the greenhouse effect? Is it the same as the ozone hole issue?
- Should we be concerned with human breathing as a source of CO2?
- How does the oxygen cycle relate to the greenhouse effect and global warming?
- Is it possible to reduce CO2 emissions without cutting back on the burning of fossil fuels? In other words, can higher efficiency or better technology reduce the impact of the consumption of fossil fuels?
- How long does it take for the oceans and terrestrial biosphere to take up carbon after it is burned?
- How much CO2 is emitted as a result of my using specific electrical appliances?
- What are the conditions happening in certain countries that could upset or disturb the oxygen cycle?
- Why do certain compounds, such as carbon dioxide, absorb and emit infrared energy?
- What kinds of radiation pass through the atmosphere, and what kinds are absorbed?
- Why do clear winter nights tend to be colder than cloudy ones; and why is the daily temperature variation in the desert greater than that found in a moist environment?
- Is it possible to separate the carbon and oxygen from CO2 as is possible with other molecules?
- I am curious about the global warming potential of water vapor. Do you know if estimates are done of this in the same way as global warming potentials are calculated for other greenhouse gases? I am also interested in why no mention is ever made of the enhanced greenhouse effect caused by anthropogenic emissions of water vapor. Are the anthropogenic emissions not significant?
- Is there environmental impact/concern (greenhouse emissions) associated with technologies using CO2 (e.g. dry ice blasting, supercritical cleaning, painting, etc.,). If so, are there current or impending regulation specific to their use?
- Could you tell me, please, if I have 1 gallon of fuel in my car, how many (units?) of CO2 will be emitted? Is there any difference if the car 4 or 6 or 8 cylinders or in respect of horse power in percentage?
- How much CO2 do you get from combustion of fossil fuels? How can the mass of the CO2 be greater than the mass of the fuel burned?
- Is there any ONE person who discovered global warming? If not, what year was global warming discovered?
- Where can I find information on the use of liquefied carbon dioxide in the extraction of alkaloids from plant materials?
- Where can I obtain information on the properties of CO2?
- I would like to know whether or not significant amounts of soil organic matter (SOM) and freshly fallen litter in a forest ecosystem can be degraded ABIOTICALLY (i.e., through chemical or physical processes) and consequently generate CO2. In other words, can I consider that entire CO2 emitted from soil is derived from biological processes?
- I understand that atmospheric concentrations of CO2 are increasing, but when I look at a graph (for example, Keeling's Mauna Loa data), the curve is squiggly. For half of each year, the concentrations increases, and for the other half it decreases. What is the reason for this?
- How can I perform CO2 calculations of the carbon dioxide system in seawater?
- Are organizations elsewhere in the world studying technologies that could help us address the problem of global climate change?
- I would like to use a diagram, image, graph, table, or other materials from the CDIAC website. How can I obtain permission? Are there copyright restrictions?
- Can you suggest some education resources on global climate change?
It depends. View references of papers relating to forest management, biomass fuels, and CO2 emissions to the atmosphere.
See new document, Answers to ten frequently asked questions about bioenergy, carbon sinks and their role in global climate change, by Robert Matthews and Kimberly Robertson, prepared as part of IEA Bioenergy Task 38 (Greenhouse Gas Balances of Biomass and Bioenergy Systems).
Additional information on managing carbon through carbon sequestration is available on the DOE Office of Science Carbon Sequestration website.
Read a discussion of the global carbon cycle.
Note: GtC = gigatons of carbon and giga = 109
Find the latest carbon budget estimates. Source: Global Carbon Project
And, click here to see figures summarizing the global cycles of biologically active elements. Source: William S. Reeburgh, Professor Marine and Terrestrial Biogeochemistry, University of California.
Using 5.137 x 1018 kg as the mass of the atmosphere (Trenberth, 1981 JGR 86:5238-46), 1 ppmv of CO2= 2.13 Gt of carbon.
Anthropogenic CO2 comes from fossil fuel combustion, changes in land use (e.g., forest clearing), and cement manufacture. Houghton and Hackler have estimated land-use changes from 1850-2000, so it is convenient to use 1850 as our starting point for the following discussion. Atmospheric CO2 concentrations had not changed appreciably over the preceding 850 years (IPCC; The Scientific Basis) so it may be safely assumed that they would not have changed appreciably in the 150 years from 1850 to 2000 in the absence of human intervention.
In the following calculations, we will express atmospheric concentrations of CO2 in units of parts per million by volume (ppmv). Each ppmv represents 2.13 X1015 grams, or 2.13 petagrams of carbon (PgC) in the atmosphere. According to Houghton and Hackler, land-use changes from 1850-2000 resulted in a net transfer of 154 PgC to the atmosphere. During that same period, 282 PgC were released by combustion of fossil fuels, and 5.5 additional PgC were released to the atmosphere from cement manufacture. This adds up to 154 + 282 + 5.5 = 441.5 PgC, of which 282/444.1 = 64% is due to fossil-fuel combustion.
Atmospheric CO2 concentrations rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv, or 174 PgC. In other words, about 40% (174/441.5) of the additional carbon has remained in the atmosphere, while the remaining 60% has been transferred to the oceans and terrestrial biosphere.
The 369.5 ppmv of carbon in the atmosphere, in the form of CO2, translates into 787 PgC, of which 174 PgC has been added since 1850. From the second paragraph above, we see that 64% of that 174 PgC, or 111 PgC, can be attributed to fossil-fuel combustion. This represents about 14% (111/787) of the carbon in the atmosphere in the form of CO2.
If we start with 1000 cubic feet of natural gas (and assuming it is pure methane or CH4) at STP (standard temperature and pressure, i.e., temperature of 273°K = 0°C = 32°F and pressure of 1 atm = 14.7 psia = 760 torr), and burn it completely, here's what we come up with:
1 cubic foot (cf) = 0.0283165 cubic meters (m3)
and 1 m3 = 1000 liters (L)
so 1 cf = 28.31685 L
and 1000 cf = 28316.85 L
Since 1 mole of a gas occupies 22.4 L at STP, 28316.85 L of CH4 contains 28316.85/22.4 = 1264.145 moles of CH4 (each mole of CH4 = approx. 16 g)
If we burn CH4 completely, it follows this equation:
CH4 + 2O2 => CO2 + 2H20
That is, for each mole of methane we get one mole of carbon dioxide.
One mole of CO2 has a mass of approx. 44 g, so 1264.145 moles of CO2 has a mass of approx. 1264.145 x 44 or 55622.38 g
A pound is about equivalent to 454 g, so 55622.38 g is about equivalent to 55622.38/454 or 122 lb
That is, the complete combustion of 1000 cubic feet at STP of natural gas results in the production of about 122 lb of carbon dioxide.
Of course, the mass of the methane in 1000 cubic feet will vary if the temperature and pressure are NOT as assumed above, and this will affect the mass of CO2 produced. According to the Ideal Gas Law:
PV = nRT where P = pressure V = volume n = moles of gas T = temperature R = constant (0.08206 L atm/mole K or 62.36 L torr/mole K) at STP, 1000 cf contains n = PV/RT moles of methane = (1 atm)(28316.85 L)/(0.08206 L atm/mole K)(273°K) = 1264 moles CH4 (the value given in the example above)
In the energy industry, however, 1 standard cubic foot (scf) of natural gas is defined at 60°F (= 15.6°C = 288.6°K) and 14.7 psia, rather than at STP (Handbook of Formulae, Equations and Conversion Factors for the Energy Professional, JOB Publications, Tallahassee, FL;). Solving again at this higher (relative to STP) temperature, we get:
n = (1 atm)(28316.85 L)/(0.08206 L atm/mole K)(288.6°K) = 1196 moles CH4
That is, at the higher temperature, a given volume of gas will contain fewer moles, and less mass. Going again through the calculation for CO2 emitted, but using the value of 1196 moles of CH4, results in an answer of approximately 115 lb of carbon dioxide.
When looking at CO2 emissions estimates, it is important to look at the units in which they are expressed. The numbers are sometimes expressed as mass of CO2 but are listed in all of our estimates only in terms of the mass of the C (carbon). Because C cycles through the atmosphere, oceans, plants, fuels, etc. and changes the ways in which it is combined with other elements, it is often easier to keep track only of the flows of carbon. Emissions expressed in units of C can be easily converted to emissions in CO2 units by adjusting for the mass of the attached oxygen atoms, that is by multiplying by the ratios of the molecular weights, 44/12, or 3.67.
The difference between the sum of the individual countries (or regions) and the global estimates is generally less than 5%. There are four primary reasons for this.
- global totals include emissions from bunker fuels whereas these are not included in national (or regional) totals. Bunker fuels are fuels used by ships and aircraft in international transportation,
- global totals include estimates for the oxidation of non-fuel hydrocarbon products (e.g., asphalt, lubricants, petroleum waxes, etc.) whereas national totals do not,
- national totals include annual changes in fuel stocks whereas the global total does not, and
- due to statistical differences in the international statistics, the sum of exports from all exporters is not identical to the sum of all imports by all importers.
Often it is difficult to attribute emissions to a source. Many small island nations have military bases that are used for re-fueling or have large tourist industries. Who do you assign the emissions to; the US whose military planes are re-fueling on the Wake Island with aviation and jet fuel or the Wake Island? The accounting practices used within the UN Energy Statistics Database assign this fuel consumption to the Wake Island thus elevating the Wake Island's per capita estimate. The same is true for tourist nations like Aruba who are assigned the fuels used in the commercial planes carrying tourists back to their native countries. Although this distorts the per capita emission estimates it makes it easier from an accounting standpoint than trying to trace each plane or ship to its final destination. One should be cautious in using only the per capita CO2 emission estimates.
No, they are two different (but related) issues.The greenhouse effect issue concerns the warming of the lower part of the atmosphere, the troposphere (the layer in which temperature drops with height; it is about 10-15 kilometers thick, varying with latitude and season), by increasing concentrations of the so-called greenhouse gases (carbon dioxide, methane, nitrous oxide, ozone, and others) in the troposphere. This warming occurs because the greenhouse gases, while they are transparent to incoming solar radiation, absorb infrared (heat) radiation from the Earth that would otherwise escape from the atmosphere into space; the greenhouse gases then re-radiate some of this heat back towards the surface of the Earth.
The ozone hole issue concerns the loss of ozone in the upper part of the atmosphere, the stratosphere, resulting from increasing concentrations of certain halogenated hydrocarbons (such as chlorinated fluorocarbons, known as CFCs). Through a series of chemical reactions in the stratosphere, the halogenated hydrocarbons destroy ozone in the stratosphere. This is of concern because the ozone blocks incoming ultraviolet radiation from the Sun, and portions of the ultraviolet radiation spectrum have been found to have adverse biological effects.
The greenhouse effect and ozone hole issues are, however, related. For example, CFCs are involved in both issues: CFCs, in addition to destroying stratosphere ozone, are also greenhouse gases. It has traditionally been thought there is not much mixing of the troposphere and stratosphere. But there is recent evidence of transport of stratospheric ozone into the troposphere (see "Ozone-rich transients in the upper equatorial Atlantic troposphere," by Suhre et al., Nature , Vol. 388, 14 August 1997, pages 661-663, and the related discussion paper, "Ozone clouds over the Atlantic," by Crutzen and Lawrence, on pages 625-626 in the same issue of Nature ). So ozone depletion in the stratosphere could result in reduced concentrations of this greenhouse gas in the troposphere. Conversely, global climate change could also affect ozone depletion through changes in stratospheric temperature and water vapor (see "The effect of climate change on ozone depletion through changes in stratospheric water vapour," by Kirk-Davidoff et al., Nature, Vol. 402, 25 November 1999, pages 399-401).
No. While people do exhale carbon dioxide (the rate is approximately 1 kg per day, and it depends strongly on the person's activity level), this carbon dioxide includes carbon that was originally taken out of the carbon dioxide in the air by plants through photosynthesis - whether you eat the plants directly or animals that eat the plants. Thus, there is a closed loop, with no net addition to the atmosphere. Of course, the agriculture, food processing, and marketing industries use energy (in many cases based on the combustion of fossil fuels), but their emissions of carbon dioxide are captured in our estimates as emissions from solid, liquid, or gaseous fuels.
With recent developments it is now feasible to measure variations in the oxygen content of the atmosphere at the parts per million (ppm) level. Regular measurements of changes in atmospheric oxygen (O2) are currently being made at a number of locations around the world using two independent techniques, one based on interferometry and one based on stable isotope mass spectroscopy. Oxygen measurements can inform us about fundamental aspects of the global carbon cycle. Oxygen is generated by green plants in photosynthesis and converted to carbon dioxide (CO2) in animal and human respiration. Carbon dioxide is the greenhouse gas of most concern due to its abundance in the atmosphere (~ 360 ppm) and anthropogenic sources. Variations in atmospheric O2 are controlled largely by fluxes of carbon (e.g., photosynthesis and respiration CO2 + H2O <=> CH2O + O2).
For further reading, we suggest:
- Keeling, R.F., D.A. Najjar, M.L. Bender, P.P. Tans. 1993. What Atmospheric Oxygen Measurements Can Tell Us About The Global Carbon Cycle. Global Biogeochemical Cycles 7:37-67.
- Moore, B. III, and B.H. Braswell. 1994. The lifetime of excess atmospheric carbon dioxide. Global Biogeochemical Cycles 8:23-38.
- Keeling, R.F. and S.R. Shertz. 1992. Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle. Nature 358:723-727.
- Broecker, W. and J.P.Severinghaus. 1992. Diminishing Oxygen. Nature 358:710-711.
Fossil fuels are basically carbon and hydrogen. When fossil fuels are burned the carbon is oxidized to produce carbon dioxide and the hydrogen is oxidized to water. During these reactions heat is released, which is why we burn the fossil fuels in the first place. There are all kinds of issues involved in the efficiency with which the heat is used to provide services for mankind, but basically, if you burn fossil fuels - you get carbon dioxide (and water, but we don't care about the water). People have debated ways to collect the carbon dioxide, and what you would do with it if you did collect it, but to collect it requires a significant portion of the energy (heat) that you got by burning the fossil fuel in the first place. That is, it is very expensive to collect the carbon dioxide and it is still not very clear what you would do with it - lots of it. I think that many people envision that carbon dioxide is like sulfur dioxide in that it is a pollutant the comes along with burning coal and that if we had better technology or more care, we could eliminate it. This is simply not true, if you burn coal, you get carbon dioxide as a necessary and unavoidable product. Like I say, there is a fair amount of literature now on ways to collect and dispose of carbon dioxide, but you really can't burn fossil fuels without getting it.
With over 800 billion metric tons of carbon in the atmosphere and an annual exchange with the biosphere and oceans equal to around 200 billion metric tons, an average atom of carbon spends only about 4 years in the atmosphere before it goes into the oceans or the terrestrial biosphere. We can think of this as the average residence time for a carbon atom in the atmosphere. However, the oceans and terrestrial biosphere not only take up carbon from the atmosphere (e.g., absorption by the oceans and photosynthesis by plants) but they also give it back (e.g., emission from oceans and respiration by animals). That is, most of these carbon atoms are “recycled” so the atmosphere is not entirely rid of them. The time it takes for a carbon atom to make it out of this recycling system and to get into the deep ocean is about 100 years.
The figure below, provided by Ken Caldiera of the Carnegie Institution for Science, shows how an instantaneous doubling of pre-industrial carbon dioxide (from 280 parts per million to 560 parts per million) would be removed from the atmosphere-biosphere system. About 50% of the added CO2 would be removed after about 200 years and about 80% of it would be removed after about 1000 years, but complete removal of the remaining 20% to the deep ocean and carbonate rocks would have to rely on geological processes operating over much longer time periods.
In general, as of 2010, an average of about 1.4 lb (0.63 kg) of carbon dioxide (CO2) is emitted to the atmosphere per kilowatt-hour (kW-h) of electricity delivered to a customer in the United States. This includes electricity consumed to run the generating plant, and electricity lost in lines and transformers on the way from the generating plant to your toaster. Actual emissions per kW-h generated can vary, from virtually zero* (e.g., for hydropower) to around 2.4 lb per kW-h for a coal-fired power plant. Within that range, the value will depend on the mix of energy sources providing the electricity.
A good source of information for particular regions within the United States is given by EPA at http://cfpub.epa.gov/egridweb/ghg.cfm. These numbers are in units of lbs. per megawatt hour so you would divide by 1000 to get lbs/kilowatt-hour. Those figures apply to electricity leaving a generating plant, but do not count electricity losses in lines and transformers on the way to your house (transmission and delivery losses). To roughly account for these losses, multiply the numbers given by 1.07, as per Annual Energy Review.
The energy (kW-h) and dollar costs for many specific types of appliances are given at http://www.energysavers.gov/your_home/appliances/index.cfm/mytopic=10040
*Carbon emitted as a result of constructing a generating facility, from vehicles needed to maintain the facility, etc. are sometimes included in the accounting, so that carbon emitted from a hydropower facility, for example, would be very small but not exactly zero.
The first person to quantitatively investigate variations in atmospheric oxygen, and their relation to the global oxygen cycle is Dr. Ralph Keeling of Scripps Institution of Oceanography. The Web link (http://scrippso2.ucsd.edu) provides information on his work. Given that oxygen is produced by vegetation, it might be argued that humankind has the greatest influence on the oxygen cycle by means of alterations in the world's vegetation (e.g., deforestation, effects of increasing atmospheric CO2 on photosynthesis).
Certain wavelengths of infrared radiation moving upward from the earth are absorbed by molecules consisting of 3 or more atoms, such as carbon dioxide, in the atmosphere. The absorbed energy causes these molecules to go into excited modes of vibration until they get rid of the absorbed energy. One way to get rid of the energy is to emit infrared radiation, some of which will be radiated back down towards the earth.
For an animation of the vibrational modes of the CO2 molecule, see
Molecules can become excited in other ways than vibration; some excited modes of molecules involve rotation, but the wavelengths that affect molecules that way are usually in the far infrared, beyond those wavelengths in which most of the earth’s energy is radiated. Shorter wavelengths can also excite electrons within molecules, or even strip electrons away. These wavelengths are typically in ultraviolet parts of the spectrum.
Radiatively active gases absorb specific wavelengths of radiation. Very little radiation is absorbed in the visible wavelengths, between about 0.4 and 0.75 micrometers. Therefore, we can see the visible reflection of sunlight from the moon, and astronauts can see physical features of the earth, through the entire atmosphere. However, an infrared camera sensing radiation between 5 and 8 micrometers would not detect physical features even a few kilometers away, even on a day that would be considered clear in the visible wavelengths. This is because water vapor is "opaque" in many infrared wavelengths, including 5 to 8 micrometers, and there is water vapor in the atmosphere even when there are no clouds.
Solar radiation includes ultraviolet, visible, and infrared wavelengths. Fortunately for us and other living things, most of the ultraviolet radiation (wavelengths shorter than visible) from the sun is picked off in the high atmosphere. This highly energetic radiation can strip electrons from atoms, causing the ionosphere and its associated phenomena such as aurora and the variations in your radio's ability to pick up distant broadcasting stations. Chemical reactions involving ozone formation and depletion in the middle and high stratosphere also pick off a lot of ultraviolet radiation, thereby preventing it from reaching the surface and causing skin cancers. Some of the infrared radiation in the solar spectrum is absorbed by atmospheric gases, mostly water vapor. The differentiation between solar radiation and visible light is not always made in meteorology textbooks, so students sometimes come away thinking that the "solar radiation" absorbed by the atmosphere is in visible spectrum; instead, it is mostly in the ultraviolet and infrared.
The earth emits radiation in the infrared, mostly between about 5 and 50 micrometers. Water vapor absorbs strongly between 5 and 8 micrometers, and above 20 micrometers. Water vapor and carbon dioxide absorb radiation between about 13 and 20 micrometers. Most wavelengths between about 8 and 13 micrometers can pass through the atmosphere. The main effect of increasing atmospheric carbon dioxide would be to increase absorption of wavelengths near 13 micrometers.
Clouds absorb a lot of outgoing (infrared) radiation, and re-radiate it back down to earth. On nights when clouds are sparse or nonexistent, much less radiation comes back to us and more goes through the atmosphere out to space. This partly explains the large amount of radiative cooling at night in deserts, where clouds are sparse or nonexistent.
A related factor of frequently underrated importance is condensation of water vapor as mist, dew, or even frost. As vapor molecules lose energy and condense to the liquid or solid state, that energy is added to the surrounding air, a process which retards any temperature decrease by radiation. Formation of dew or frost will thus retard nighttime cooling, and this is more likely to happen in climates where the relative humidity is generally high.
Finally, in many deserts, the thermal conductivity of the (dry) soil is really small, especially in a sandy desert where the soil particles are relatively large and there is a lot of space for air in between. In addition, with little or no water to evaporate, evaporative cooling is minimal. There is also little vegetation to provide shading. This all leads to a hot surface, but not much transport of heat into the subsurface. When the sun goes down, that hot surface radiates a lot of energy away very quickly and relatively little heat is conducted upward to keep the surface warm. The result is low surface temperatures in the early morning hours. This reduced “thermal inertia” of a desert surface partly explains the wider day-night variations in temperature of a desert as compared to an agricultural area, for example.
The problem in separating the carbon and oxygen from CO2 is that CO2 is a VERY stable molecule, because of the bonds that hold the carbon and oxygen together, and it takes a lot of energy to separate them. Most schemes being considered now involve conversion to liquid or solids. One present concept for capturing CO2, such as from flue gases of boilers, involves chemical reaction with MEA (monoethanol amine). Other techniques include physical absorption; chemical reaction to methanol, polymers and copolymers, aromatic carboxylic acid, or urea; and reaction in plant photosynthetic systems (or synthetic versions thereof). Overcoming energetic hurdles is a major challenge; if the energy needed to drive these reactions comes from burning of fossil fuels, there may not be an overall gain. One aspect of the current research is the use of catalysts to promote the reactions. (In green plants, of course, chlorophyll is such a catalyst!) One area of current research is looking at using cellular components to imitate photosynthesis on an industrial scale. For example, see http://www.ornl.gov/ornl94/looking.html which describes research of the Chemical Technology Division at Oak Ridge National Laboratory.
The International Energy Agency's Greenhouse Gas R&D Programme has many activities in the area of separation and sequestration of CO2 - see their website (http://www.ieagreen.org.uk/).
The best answer to this question at this time is found in Chapter 2 (Changes in Atmospheric Constituents and in Radiative Forcing) of the Intergovernmental Panel on Climate Change (IPCC), Working Group 1 Report: The Physical Basis of Climate Change, and is as follows:
Water vapour is the most abundant and important greenhouse gas in the atmosphere. However, human activities have only a small direct influence on the amount of atmospheric water vapour. Indirectly, humans have the potential to affect water vapour substantially by changing climate. For example, a warmer atmosphere contains more water vapour. Human activities also influence water vapour through methane (CH4) emissions, because CH4 undergoes chemical destruction in the stratosphere, producing a small amount of water vapour.
Also, see additional entries in this IPCC chapter that refer to "water vapour".
"Most of the CO2 used in these kinds of applications is recovered from processes like fermentation and it is either CO2 that it is being extracted from the atmosphere by plants or CO2 that would have been released from fossil fuel burning anyhow. In essence it passes through this kind of use rather than being emitted immediately and there is no extra CO2 produced".
A good estimate is that you will discharge 19.6 pounds of CO2 from burning 1 gallon of gasoline. This does not depend on the power or configuration of the engine but depends only on the chemistry of the fuel. Of course if the car gets more miles per gallon of gasoline, you will get less CO2 per unit of service rendered (that is, less CO2 per mile traveled).
The U.S. Department of Energy and the U.S. Environmental Protection Agency recently launched a new Fuel Economy Web Site designed to help the public factor energy efficiency into their car buying decisions. This site offers information on the connection between fuel economy, advanced technology, and the environment.
Let us illustrate with the combustion of natural gas (methane).
C = carbon, atomic weight approximately 12
H = hydrogen, atomic weight approximately 1
O = oxygen, atomic weight approximately 16
CH4 = methane, molecular weight approximately 16
O2 = molecular oxygen, molecular weight approximately 32
CO2 = carbon dioxide, molecular weight approximately 44
H2O = water, molecular weight approximately 18
For combustion of methane
CH4 + 2O2 = CO2 + 2H2O
So, combustion of 16 mass units (grams, pounds, whatever) of methane produces 44 mass units of carbon dioxide and 36 mass units of water while consuming 64 mass units of oxygen.
The first person to have quantitatively predicted a change in surface temperature resulting from increases in atmospheric carbon dioxide is generally acknowledged as Svante Arrhenius, in 1896.
As far back as the 1930’s Guy Callendar investigated carbon dioxide concentrations in the atmosphere and indicated that increases were indeed occurring. Proof came in the 1960s when precise measurements began by Charles David Keeling in 1957 showed a steady increase at remote stations, indicating the global nature of the increases. By the 1990s, it was widely accepted that the Earth's surface air temperature had warmed over the past century, and that increasing concentrations of carbon dioxide in the atmosphere were an important contributor to this warming.
Climate changes, warming and cooling, have been occurring throughout geologic history. In general, climatologists accept 30-year trends as indicative that something has changed in the mechanisms that influence climate. There have been two such warming periods in the last 100 years, one from 1910 to 1940 and one from 1970 through 2000, separated by a period of cooling. Most climatologists now believe that increasing concentrations of greenhouse gases (e.g., carbon dioxide) in the atmosphere have become a strong enough influence to have been primarily responsible for the most recent warming.
Arrhenius, Svante. 1896. On the influence of carbonic acid in the air upon the temperature of the ground. Philosophical Magazine and Journal of Science. Series V, Volume 41, no. 251 (April), pages 237-276.
Fleming, James Rodger. 2007. The Callendar Effect. Published by the American Meteorological Society.
Kaiser, J. 1996. Supercritical Solvent Comes Into Its Own. Science. Vol. 274. p. 2013.
Earliest quantitative measurements indicate that decomposition can be entirely attributed to biological processes.
SHANKS, R. E., and J. S. OLSON. 1961. First-year breakdown of leaf litter in southern Appalachian forests. Science 134(3473):194-195.
OLSON, J. S. 1963. Energy storage and the balance of producers and decomposers in ecological systems. Ecology 44(2):322-331.
There may be some photo-oxidation but it is likely to be minor. For a more modern treatment (but largely based on the model develobet over 30 years ago by Olson) see:
Bosatta, E. and Agren, G.I. 1985. Theoretical analysis of decomposition of heterogeneous substrates. Soil Biology and Biochemistry 17:601-610.
Bosatta, E. and Agren, G.I. 1995. The power and reactive continuum models as particular cases of the q-theory of organic matter dynamics. Geochemica et Cosmochimica Acta 59:3833-3835.
Agren, G.I. and Bosatta, E. 1996. Theoretical Ecosystem Ecology. Cambridge University Press.
The variations within each year are the result of the annual cycles of photosynthesis and respiration. Photosynthesis, in which plants take up carbon dioxide from the atmosphere and release oxygen, dominates during the warmer part of the year. Respiration, by which plants and animals take up oxygen and release carbon dioxide, occurs all the time but dominates during the colder part of the year. Overall, then, atmospheric carbon dioxide decreases during the growing season and increases during the rest of the year. Because the seasons in the northern and southern hemispheres are opposite, carbon dioxide in the atmosphere is decreasing in the northern hemisphere summer while increasing at the same time in the southern hemisphere winter, and vice versa. The magnitude of this cycle is strongest nearer the poles and approaches zero towards the Equator, where it reverses sign. The cycle is more pronounced in the northern hemisphere (which has relatively more land mass and terrestrial vegetation) than in the southern hemisphere (which is more dominated by oceans).
The Program Developed for CO2 System Calculations (ORNL/CDIAC-105), recently released by Ernie Lewis, Department of Applied Science, Brookhaven National Laboratory, and Doug Wallace, Abteilung Meereschemie, Institut fuer Meereskunde, was developed to help calculate inorganic carbon speciation in seawater.
This program, CO2SYS, performs calculations relating parameters of the carbon dioxide system in seawater and freshwater by using two of the four measurable parameters of the CO2 system [total alkalinity (TA), total inorganic CO2 (TCO2), pH, and either fugacity (fCO2) or partial pressure of CO2 (pCO2)] to calculate the other two parameters at a set of input conditions (temperature and pressure) and a set of output conditions chosen by the user.
Yes, quite a few. For example:
Research Institute of Innovative Technology for the Earth (RITE) (http://www.rite.or.jp/English/E-home-frame.html) in Japan was founded in 1990 as a "research hub ... for the development of innovative environmental technologies and the broadening of the range of CO2 sinks."
GREENTIE, the Greenhouse Gas Technology Information Exchange, (http://www.greentie.org/) an initiative of the International Energy Agency (IEA) and the Organisation for Economic Cooperation and Development (OECD), was established in 1993 "to improve the awareness of, and facilitate the access to, suppliers and experts of `clean technologies', particularly technologies that help mitigate the emissions of greenhouse gases."
CADDETT (http://www.caddet-re.org/), the IEA/OECD Centre for the Analysis and Dissemination of Demonstrated Energy Technologies, "provides an international information network to help managers, engineers, architects, and researchers find out about the energy-saving techniques that have worked in other countries."
ScientecMatrix (http://www.scientecmatrix.com) is "a community of over 1000 scientists and technologists working on subjects as diverse as clean energy production from waste."
All of the reports, graphics, data, and other information on the CDIAC website are freely and publicly available without copyright restrictions. However as a professional courtesy, we ask that the original data source be acknowledged. Suggested citations appear at the bottom of the Web page for each data set. If the citation is unclear, simply contact CDIAC through our Web form. Please identify the URL of the Web page in which the information or graphic appears.
These educational links on global climate change were chosen because we have found them useful in responding to those with inquiring minds. These links will take the user outside of CDIAC, and are by no means comprehensive. We are not responsible for the content or intent of these outside links.