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Taking a hard look at climate change and its causes

Whenever one reads articles on climate change and its causes carbon dioxide (CO2) is cited as the main culprit. But is this really the main greenhouse gas? Seldom are the other greenhouse gases mentioned. In this article I will be investigating ALL of the known greenhouse gases and their relative contributions to global warming and climate change. But first of all we must have a clear understanding of what is exactly meant by global warming, climate change and what greenhouse gases are.

What is global warming?

Global warming (also called the greenhouse effect) describes the gradual increase of the air temperature in the earth's lower atmosphere. Why is global warming called the greenhouse effect? Greenhouses are not common in Africa, so don't be surprised if you have never seen one! They are used mainly in the cooler northern hemisphere to grow vegetables and flowers.

A greenhouse is made entirely of glass. When sunlight (shortwave radiation) strikes the glass, most of it passes through and warms up the plants, soil and air inside the greenhouse. As these objects warm up they give off heat, but these heat waves have a much longer wavelength than the incoming rays from the sun. This longwave radiation cannot easily pass through glass, it is re-radiated into the greenhouse, causing everything in it to heat up.

Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation, which trap heat that would otherwise escape from Earth. This is a type of greenhouse effect.

Is global warming, caused by human activity, even remotely plausible?

Earth's climate is mostly influenced by the first 9 kilometres or so of the atmosphere which contains most of the matter making up the atmosphere. This is really a very thin layer if you think about it. In the book The End of Nature, author Bill McKibbin tells of walking three miles to from his cabin in the Adirondack's to buy food. Afterwards, he realized that on this short journey he had travelled a distance equal to that of the layer of the atmosphere where almost all the action of our climate is contained. In fact, if you were to view Earth from space, the principle part of the atmosphere would only be about as thick as the skin on an onion! Realizing this makes it more plausible to suppose that human beings can change the climate. A look at the amount of greenhouse gases we are spewing into the atmosphere (see below), makes it even more plausible.

Is the Temperature Really Changing?

What are the Greenhouse Gases?

The most significant greenhouse gas is actually water vapour, not something produced directly by humankind in significant amounts. However, there are a number of other gases that are directly attributable to human activities that play a significant role as greenhouse gases and therefore contribute significantly to global warming and climate change. These are carbon dioxide (CO2), methane and nitrous-oxides and even slight increases in atmospheric levels of these gases can cause a substantial increase in atmospheric temperature.

Why is this? There are two reasons: First, although the concentrations of these gases are not nearly as large as that of oxygen and nitrogen (the main constituents of the atmosphere), neither oxygen or nitrogen are greenhouse gases. This is because neither has more than two atoms per molecule (i.e. their molecular forms are O2 and N2, respectively), and so they lack the internal vibrational modes that molecules with more than two atoms have. Water and the greenhouse gases, for example, all have these "internal vibrational modes", and these vibrational modes can absorb and re-radiate infra-red radiation, which causes the greenhouse effect.

Now, let's take a look at the effects that the various greenhouse gases have in the atmosphere.

Yes! As everyone has heard from the media, recent years have consistently been the warmest in hundreds and possibly thousands of years. But that might be a temporary fluctuation, right? To see that it probably isn't, the next graph shows the average temperature in the Northern Hemisphere as determined from many sources, carefully combined, such as tree rings, corals, human records, etc.

Carbon-dioxide (CO2)

CO2 tends to remain in the atmosphere for a very long time (time scales in the hundreds of years). Water vapour, on the other hand, can easily condense or evaporate, depending on local conditions. Water vapour levels therefore tend to adjust quickly to the prevailing conditions, such that the energy flows from the Sun and re-radiation from the Earth achieve a balance. CO2 tends to remain fairly constant and therefore behave as a controlling factor, rather than a reacting factor. More CO2 means that the balance occurs at higher temperatures than water vapour levels.

Human beings have increased the CO2 concentration in the atmosphere by about thirty percent, which is an extremely significant increase, even on inter-glacial time-scales. It is believed that human beings are responsible for this because the increase is almost perfectly correlated with increases in fossil fuel combustion, and also due other evidence, such as changes in the ratios of different carbon isotopes in atmospheric CO2 that are consistent with "anthropogenic" (human caused) emissions. The simple fact is, that under "business as usual" conditions, we'll soon reach carbon dioxide concentrations that haven't been seen on Earth in the last 50 million years.

Combustion of Fossil Fuels, for electricity generation, transportation, and heating, and also the manufacture of cement, all result in the total worldwide emission of about 22 billion tons of carbon dioxide into the atmosphere each year. About a third of this comes from electricity generation, and another third from transportation, and a third from all other sources.

This enormous input of CO2 is causing the atmospheric levels of CO2 to rise dramatically. The following graph shows the CO2 levels over the past 160 thousand years (the upper curve, with units indicated on the right hand side of the graph). The current level, and projected increase over the next hundred years if we do not curb emissions, are also shown (the part of the curve which goes way up high, to the right of the current level, is the projected CO2 rise). The projected increase in CO2 is very startling and disturbing. Changes in the Earth's average surface temperature are also shown (the lower curve, with units on the left). Note that it parallels the CO2 level curve very well.

These graphs show a very discernible warming trend, starting in about 1900. It might seem a bit surprising that warming started as early as 1900. How is this possible? The reason is that the increase in carbon dioxide

actually began in 1800, following the deforestation of much of Northeastern American and other forested parts of the world. The sharp upswing in emissions during the industrial revolution further added to this, leading to a significantly increased carbon dioxide level even by 1900. 

Thus, we see that Global Warming is not something far off in the future - in fact it predates almost every living human being today.


Methane is a chemical compound with the chemical formula CH4. It is the simplest alkane, the main component of natural gas, and probably the most abundant organic compound on Earth.

Methane is a relatively potent greenhouse gas. The concentration of methane in the Earth's atmosphere in 1998, expressed as a mole fraction, was 1745 nmol/mol (parts per billion, ppb), up from 700 nmol/mol in 1750. By 2008, however, global methane levels, which had stayed mostly flat since 1998, had risen to 1,800 nmol/mol.

In 2010, methane levels in the Arctic were measured at 1850 nmol/mol, a level over twice as high as at any time in the previous 400,000 years. Historically, methane concentrations in the world's atmosphere have ranged between 300 and 400 nmol/mol during glacial periods commonly known as ice ages, and between 600 to 700 nmol/mol during the warm interglacial periods. It has a high global warming potential: 72 times that of carbon dioxide over 20 years, and 25 times over 100 years, and the levels are rising.

Methane in the Earth's atmosphere is an important greenhouse gas with a global warming potential of 25 compared to CO2 over a 100-year period (although accepted figures probably represents an underestimate). This means that a methane emission will have 25 times the effect on temperature of a carbon dioxide emission of the same mass over the following 100 years. Methane has a large effect for a brief period (a net lifetime of 8.4 years in the atmosphere), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20 year time period is 72. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases (these gases don't include water vapour which is by far the largest component of the greenhouse effect). Usually, excess methane from landfills and other natural producers of methane is burned so CO2 is released into the atmosphere instead of methane, because methane is a more effective greenhouse gas. Recently, methane emitted from coal mines has been successfully utilized to generate electricity.

Nitrous oxide

Nitrous oxide (N2O) is produced by both natural and human-related sources. Primary human-related sources of N2O are agricultural soil management, animal manure management, sewage treatment, mobile and stationary combustion of fossil fuel, adipic acid production, and nitric acid production. Nitrous oxide is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests.

Nitrous oxide emission levels from a source can vary significantly from one country or region to another, depending on many factors such as industrial and agricultural production characteristics, combustion technologies, waste management practices, and climate. For example, heavy utilization of synthetic nitrogen fertilizers in crop production typically results in significantly more N2O emissions from agricultural soils than that occurring from less intensive, low-tillage techniques. Also, the presence or absence of control devices on combustion sources, such as catalytic converters on automobiles, can have a significant affect on the level of N2O emissions from these types of sources.

Nitrous oxide gives rise to NO (nitric oxide) on reaction with oxygen atoms, and this NO in turn reacts with ozone. As a result, it is the main naturally occurring regulator of stratospheric ozone. It is also a major greenhouse gas and air pollutant. Considered over a 100-year period, it has 298 times more impact 'per unit weight' (Global warming potential) than carbon dioxide.

Other greenhouse gases

In addition to the main greenhouse gases listed above, other greenhouse gases include water vapour, ozone, sulphur hexafluoride, hydrofluorocarbons, nitrogen trifluoride and perfluorocarbons.

The gases do not play a significant role in that their contribution to global warming is small and, consequently, I will not be taking them into consideration when proposing possible solutions to the climate change problems that we face.

Carbon dioxide equivalent (CDE) and Equivalent carbon dioxide (or 'CO2e') are two related but distinct measures for describing how much global warming a given type and amount of greenhouse gas may cause, using the functionally equivalent amount or concentration of carbon dioxide (CO2) as the reference.

Carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO2 that would have the same global warming potential (GWP), when measured over a specified timescale (generally, 100 years). Carbon dioxide equivalency thus reflects the time-integrated radiative forcing of a quantity of emissions or rate of greenhouse gas emission — a flow into the atmosphere — rather than the instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere described by CO2e.

The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the GWP of the gas. The following units are commonly used:

  • By the UN climate change panel IPCC: billion metric tonnes of CO2 equivalent (GtCO2eq).

  • In industry: million metric tonnes of carbon dioxide equivalents (MMTCDE).

  • For vehicles: g of carbon dioxide equivalents / km (gCDE/km).

For example, the GWP for methane over 100 years is 25 and for nitrous oxide 298. This means that emissions of 1 million metric tonnes of methane and nitrous oxide respectively is equivalent to emissions of 25 and 298 million metric tonnes of carbon dioxide.

These are useful measures if we are to compare the relative effects that the greenhouse gases have on global warming.

Carbon dioxide has a variable atmospheric lifetime, and cannot be specified precisely. The atmospheric lifetime of CO2 is estimated to be of the order of 30–95 years. This figure accounts for CO2 molecules being removed from the atmosphere by mixing into the ocean, photosynthesis, and a few other processes. However, this excludes the balancing fluxes of CO2 into the atmosphere from the geological reservoirs, which have slower characteristic rates. While more than half of the CO2 emitted is currently removed from the atmosphere within a century, some fraction (about 20%) of emitted CO2 remains in the atmosphere for many thousands of years.

The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale. Thus, if a gas has a high radiative forcing but also a short lifetime, it will have a large GWP on a 20 year scale but a small one on a 100 year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase with the time-scale considered. Carbon dioxide is defined to have a GWP of 1 over all time periods.

Methane has an atmospheric lifetime of 12 ± 3 years and a GWP of 72 over 20 years, 25 over 100 years and 7.6 over 500 years. The decrease in GWP at longer times is because methane is degraded to water and CO2 through chemical reactions in the atmosphere.

The GWP of the various greenhouse gases is compared to carbon dioxide in the following table:

Gas name

Chemical formula

Lifetime in years

GWP for 20 years

GWP for 100 years

Carbon dioxide


>100 years





12 years



Nitrous oxide


114 years





100 years

11 000

10 900



12 years

5 160

1 810



50 000 years

5 210

7 390



10 000 years

8 630

12 200

Sulphur hexafluoride


3 200 years

16 300

22 800

Nitrogen trifluoride


740 years

12 300

17 200

Table 1: Comparison of major greenhouse gases and their lifespans.

Aside from purely human-produced synthetic halocarbons, most greenhouse gases have both natural and human-caused sources. During the pre-industrial Holocene period, concentrations of existing gases were roughly constant. In the industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and the clearing of forests.

The 2007 Fourth Assessment Report compiled by the IPCC (AR4) noted that "changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system", and concluded that "increases in anthropogenic (resulting from human activities) greenhouse gas concentrations is very likely to have caused most of the increases in global average temperatures since the mid-20th century". In AR4, "most of" is defined as more than 50%.


Pre-industrial level

Current level

Carbon dioxide

280 ppm  

394 ppm


700 ppb

1745 ppb

Nitrous oxide

270 ppb  

314 ppb

Table 2: Comparison of the main greenhouse gases showing their increase since pre-industrial times.

Ice cores provide us with evidence for the variation in greenhouse gas concentrations over the past 800,000 years. Both CO2 and CH4 vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature. Direct data does not exist for periods earlier than those represented in the ice core record, a record which indicates CO2 mole fractions staying within a range of between 180 ppm and 280 ppm throughout the last 800,000 years, until the increase of the last 250 years. However, various proxies and modelling suggests larger variations in past epochs; 500 million years ago CO2 levels were likely 10 times higher than now. Indeed higher CO2 concentrations are thought to have prevailed throughout most of the Phanerozoic period, with concentrations four to six times current concentrations during the Mesozoic era, and ten to fifteen times current concentrations during the early Palaeozoic era until the middle of the Devonian period, about 400 Ma. The spread of land plants is thought to have reduced CO2 concentrations during the late Devonian, and plant activities as both sources and sinks of CO2 have since been important in providing stabilising feedbacks. Earlier still, a 200-million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 Ma, by a colossal volcanic out-gassing which raised the CO2 concentration of the atmosphere abruptly to 12%, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day. This episode marked the close of the Precambrian eon, and was succeeded by the generally warmer conditions of the Phanerozoic, during which multicellular animal and plant life evolved. No volcanic carbon dioxide emission of comparable scale has occurred since. In the modern era, emissions to the atmosphere from volcanoes are only about 1% of emissions from human sources.

Searching for solutions

In our search for solutions to the greenhouse gas problem we should consider the following questions:

  • What are the human induced origins of the greenhouse gases?

  • Which greenhouse gases have the most impact on global warming?

  • What will the monetary costs of implementing possible solutions be?

  • Which reduction in greenhouse gas emissions will have the quickest effect?

You will note that I have omitted the natural origins of the gases because we have almost no control over natural processes.

Human induced origins of greenhouse gases

Since about 1750 human activity has increased the concentration of carbon dioxide and other greenhouse gases. Measured atmospheric concentrations of carbon dioxide are currently 100 ppm higher than pre-industrial levels. Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity, but over periods longer than a few years natural sources are closely balanced by natural sinks, mainly photosynthesis of carbon compounds by plants and marine plankton. As a result of this balance, the atmospheric mole fraction of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era.

It is likely that anthropogenic (human-caused) warming, such as that due to elevated greenhouse gas levels, has had a discernible influence on many physical and biological systems. Warming is projected to affect various issues such as freshwater resources, industry, food and health.

The main sources of greenhouse gases due to human activity are:

  • Burning of fossil fuels and deforestation leading to higher carbon dioxide concentrations in the air.

  • Land use change (mainly deforestation in the tropics) account for up to one third of total anthropogenic CO2 emissions.

  • Livestock enteric fermentation and manure management, paddy rice farming, land use and wetland changes, pipeline losses, and covered vented landfill emissions leading to higher methane atmospheric concentrations. Many of the newer style fully vented septic systems that enhance and target the fermentation process also are sources of atmospheric methane.

  • Use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing processes.

  • Agricultural activities, including the use of fertilizers, that lead to higher nitrous oxide (N2O) concentrations.

Greenhouse gases that have the greatest impact on climate change

For many years the focus on gases that have the most impact on climate change has been focussed on carbon dioxide and its emission from power generation plants, industry and transportation. In fact most recent scientific papers have been mainly solely concerned with carbon dioxide emissions and proposals for the reductions in CO2 emissions. I feel, however, that this focus has been ill-informed and I will now give my reasons for this.

If we refer to the atmospheric lifespan of the main greenhouse gases listed in Table 1, we will observe that carbon dioxide has a lifespan of >100 years in the atmosphere and that it will take thousands of years for it to be completely dissipated. In other words, even if we manage to reduce the emissions of carbon dioxide drastically within our lifetimes, it will take over 100 years (some scientists even mention 200 years) before the effect will be discernible.

Methane, on the other hand, has an atmospheric lifespan of only 12 years. Consequently, if the methane emissions can be drastically reduced, we would start feeling the effect of the reduction, or elimination, of global warming within a fairly short time. A much better proposition!

Nitrous oxide has an atmospheric lifespan of 114 years. However, it is much more potent as a greenhouse gas than either carbon dioxide or methane.

The other greenhouse gases exist only in very small quantities.

Costs of implementing solutions to global warming

Most international concern has been for the reduction of carbon dioxide emissions. While these concerns are, indeed, admirable, they are far from realistic. It has been estimated that, should governments be able to enforce carbon-dioxide emissions by 20% over the next twenty years, the cost to the world's taxpayers (they will be the ones who have to pay) will be in the order of trillions of dollars! Moreover, these suffering taxpayers will be unable to benefit from this tax within their lifetimes and they will have to live, or perish, from the side-effects of the increase in global temperatures. So the concentration on reducing carbon-dioxide emissions on their own is totally uneconomic.

If we cannot afford to reduce global warming in our lifetimes by reducing carbon-dioxide emissions, is there an alternative option? Fortunately, there is!

Methane, which has a short lifespan in the atmosphere, and the greatest effect on global warming (as we shall see later in the article) can be controlled at minimal cost provided that the human population of the world can be persuaded to co-operate. Furthermore, the people of the world would be able to feel the improvements within 12 to 20 years – some scientific writers have even estimated that we would begin to feel the effects within a mere 8 years! A far better proposition.

Nitrous oxides are mainly emitted from artificial fertilizers that are used in agriculture. The reduction of nitrous oxide emissions would have to go hand-in-hand with the reduction in the use of artificial fertilizers and a switch to organic farming methods. Fortunately, nitrous oxides have a limited effect on global climate change.

Livestock is the major source of global warming

Livestock production is a major source of greenhouse gas emissions. In addition vast tracts of land are required for their grazing and for animal food production.

It has become fashionable to believe that the burning of fossil fuels are the main cause of climate change. However, as Robert Goodland and Jeff Anhang have determined and published in their paper “Livestock and Climate Change” (Worldwatch, November/December 2009), the role that the raising of livestock, and the supply chain, for meat production have on the emission of greenhouse gases has been vastly underestimated as a source of greenhouse gases.

Indeed, we should take cognisance of the fact that oil, natural gas, and especially coal are major sources of human-caused emissions of carbon dioxide (CO2) and other greenhouse gases.

But Goodland and Anhang believe that the life cycle and supply chain of domesticated animals raised for food has been vastly underestimated as a source of greenhouse gases, and in fact they account for at least half of all human-caused greenhouse gases. If this argument is correct, it implies that replacing livestock products with better alternatives would be the best strategy for reversing climate change. In fact, this approach would have far more rapid effects on greenhouse gas emissions and their atmospheric concentrations — and thus on the rate that the climate is warming — than actions to replace fossil fuels with renewable energy.

Livestock’s Long Shadow, the widely-cited 2006 report by the United Nations Food and Agriculture Organization (FAO), estimates that 7,516 million metric tons per year of CO2 equivalents (CO2e), or 18% of annual worldwide greenhouse gas emissions, are attributable to cattle, buffalo, sheep, goats, camels, horses, pigs, and poultry.

That amount would easily qualify livestock for a hard look in the search for ways to address climate change. But Goodland and Anhang's analysis shows that livestock and their by-products actually account for at least 32,564 million tons of CO2e per year, or more than 51% of annual worldwide greenhouse gas emissions. They base their argument against the FAO estimate on the following facts:

  • The FAO’s estimate of 7,516 million tons of CO2e per year attributable to livestock, an amount established by adding up greenhouse gas emissions involved in clearing land to graze livestock and grow feed, keeping livestock alive, processing and transporting the end products.

  • Goodland and Anhang show that 25,048 million tons of CO2e attributable to livestock have been under-counted or overlooked; of that subtotal, 3,000 million tons are misallocated and 22,048 million tons are entirely uncounted.

  • When uncounted tons are added to the global inventory of atmospheric greenhouse gases, that inventory rises from 41,755 million tons to 63,803 million tons.

  • FAO’s 7,516 million tons of CO2e attributable to livestock then decline from 18% of worldwide greenhouse gases to 11.8%.

Let's take a closer look at each category of uncounted or misallocated greenhouse gas emissions.

Breathing. The FAO excludes livestock respiration from its estimate, with the following argument:

Respiration by livestock is not a net source of CO2…. Emissions from livestock respiration are part of a rapidly cycling biological system, where the plant matter consumed was itself created through the conversion of atmospheric CO2 into organic compounds. Since the emitted and absorbed quantities are considered to be equivalent, livestock respiration is not considered to be a net source under the Kyoto Protocol. Indeed, since part of the carbon consumed is stored in the live tissue of the growing animal, a growing global herd could even be considered a carbon sink. The standing stock livestock biomass increased significantly over the last decades…. This continuing growth…could be considered as a carbon sequestration process (roughly estimated at 1 or 2 million tons of carbon per year).”

This is a flawed way of looking at the matter. Examining the sequestration claim first: Sequestration properly refers to extraction of CO2 from the atmosphere and its burial in a vault or a stable compound from which it cannot escape over a long period of time. Even if one considers the standing mass of livestock to be a carbon sink, by the FAO’s own estimate of the amount of carbon stored in livestock is trivial compared to the amount stored in forest cleared to create space for growing feed for and grazing livestock.

More to the point, livestock (like motor vehicles) are a human invention and convenience, not part of pre-human

times, and a molecule of CO2 exhaled by livestock is no more natural than one from a motor vehicle tailpipe. Moreover, while over time an equilibrium of CO2 may exist between the amount respired by animals and the amount photosynthesised by plants, that equilibrium has never been static. Today, tens of billions more livestock are exhaling CO2 than in pre-industrial times, while Earth’s photosynthetic capacity (its capacity to keep carbon out of the atmosphere by absorbing it in plant mass) has declined sharply as forests have been cleared. (Meanwhile, of course, we add more carbon to the air by burning fossil fuels, further overwhelming the carbon absorption system.)

The FAO asserts that livestock respiration is not listed as a recognized source of greenhouse gases under the Kyoto Protocol, although in fact the Protocol does list CO2 with no exception, and “other” is included as a catch-all category. For clarity, it should be listed separately in whatever protocol replaces Kyoto. It is tempting to exclude one or another anthropogenic source of emissions from carbon accounting — according to one’s own interests — on the grounds that it is offset by photosynthesis.

But, if it is legitimate to count as greenhouse gas sources fossil-fuel-driven motor vehicles, trains and ships, which hundreds of millions of people do not drive, then it is equally legitimate to count livestock respiration. Little or no livestock product is consumed by hundreds of millions of humans, and no livestock respiration (unlike human respiration) is needed for human survival. By keeping greenhouse gases attributable to livestock respiration off greenhouse gas balance sheets, it is predictable that they will not be managed and their quantity will increase — as in fact is happening.

Carbon dioxide from livestock respiration accounts for 21% of anthropogenic greenhouse gases worldwide, according to a 2005 estimate by British physicist Alan Calverd. He did not provide the weight of this CO2, but it works out to about 8,769 million tons. Calverd’s estimate is the only original estimate of its type, but because it involves only one variable (the total mass of all livestock, as all but cold-blooded farmed fish exhale roughly the same amount of CO2 per kilogram), all calculations of CO2 from the respiration of a given weight of livestock would be about the same. Calverd’s estimate did not account for the fact that CO2 from livestock respiration is excluded from global greenhouse gas inventories. It also did not account for the greenhouse gases newly attributed to livestock in Greenland and Anhang's analysis. After adding all relevant greenhouse gases to global greenhouse gas inventories, the percentage of greenhouse gases attributable to livestock respiration drops from 21% to 13.7%.


There is now a global shortage of grassland, and the only practical way more livestock and feed can be produced is by destroying natural forest. Growth in markets for livestock products is greatest in developing countries, where rainforest normally stores at least 200 tons of carbon per hectare. Where forest is replaced by moderately degraded grassland, the tonnage of carbon stored per hectare is reduced to 8.

On average, each hectare of grazing land supports no more than one head of cattle, whose carbon content is a fraction of a ton. In comparison, over 200 tons of carbon per hectare may be released within a short time after forest and other vegetation are cut, burned, or chewed. From the soil beneath, another 200 tons per hectare may be released, with yet more greenhouse gases from livestock respiration and excretions. Thus, livestock of all types provide minuscule carbon “piggy-banks” to replace huge carbon stores in soils and forests. But if the production of livestock or crops is ended, then forest will often regenerate. The main focus in efforts to mitigate greenhouse gases has been on reducing emissions, while — despite its ability to mitigate greenhouse gases quickly and cheaply — vast amounts of potential carbon absorption by trees has been foregone.

Brazil has the world's largest cattle farming herd and vast areas of the Amazon rainforest are being cleared for pastures and animal feed crop production.

The FAO counts emissions attributable to changes in land use due to the introduction of livestock, but only the relatively small amount of greenhouse gases from the annual changes. Strangely, it does not count the much larger amount of annual greenhouse gas reductions from photosynthesis that are foregone by using 26 percent of land worldwide for grazing livestock and 33 percent of arable land for growing feed, rather than allowing it to regenerate forest. By itself, leaving a significant amount of tropical land used for grazing livestock and growing feed to regenerate as forest could potentially mitigate as much as half (or even more) of all anthropogenic greenhouse gases. A key reason why this is not happening is that reclaiming land used for grazing livestock and growing feed is not yet a priority; on the contrary, feed production and grazing have been fast expanding into forest areas.

Or suppose that land used for grazing livestock and growing feed were used instead for growing

crops to be converted more directly to food for humans and to biofuels. Those fuels could replace

one-half of the coal used worldwide, which is responsible for about 3,340 million tons of CO2e

emissions every year. That tonnage represents 8 percent of greenhouse gases in worldwide greenhouse gas inventories that omit the additional greenhouse gases assessed by this article, or 5.6 percent of greenhouse gases worldwide when the greenhouse gases assessed in this article are included. If biomass feedstocks are chosen and processed carefully, then biofuels can yield 80 percent less greenhouse gases per unit of energy compared to coal. Therefore, the extra emissions resulting from using land for livestock and feed can be estimated to be 2,672 million tons of CO2e, or 4.2 percent of annual greenhouse gas emissions worldwide.

Considering these two plausible scenarios, at least 4.2 percent of worldwide greenhouse gases should be counted as emissions attributable to greenhouse gas reductions foregone by using land to graze livestock and grow feed.


According to the FAO, 37 percent of human induced methane comes from livestock. Although methane is a far more potent greenhouse gas than CO2, its half-life in the atmosphere is only about 8 years, versus at least 100 years for CO2. As a result, a significant reduction in livestock raised worldwide would reduce greenhouse gases relatively quickly compared with measures involving renewable energy and energy efficiency.

The capacity of greenhouse gases to trap heat in the atmosphere is described in terms of their global warming potential (GWP), which compares their warming potency to that of CO2 (with a GWP set at 1). The new widely accepted figure for the GWP of methane is 25 using a 100-year time-frame — but it is 72 using a 20-year time-frame, which is more appropriate because of both the large effect that methane reductions can have within 20 years and the serious climate disruption expected within 20 years if no significant reduction of greenhouse gases is achieved. The Intergovernmental Panel on Climate Change (IPCC) supports using a 20-year time-frame for methane.

The FAO estimates that livestock accounted for 103 million tons of methane emissions in 2004 through enteric fermentation and manure management, equivalent to 2,369 million tons of CO2e. This is 3.7 percent of worldwide greenhouse gases using, as FAO does, the outdated GWP of 23. Using a GWP of 72, livestock methane is responsible for 7,416 million tons of CO2e or 11.6 percent of worldwide greenhouse gases. So using the appropriate time-frame of 20 years instead of 100 years for methane raises the total amount of greenhouse gases attributable to livestock products by 5,047 million tons of CO2e or 7.9 percentage points. (Further work is needed to recalibrate methane emissions other than those attributable to livestock products using a 20-year time-frame.)

Other sources.

Four additional categories of greenhouse gases adding up to at least 5,560 million tons of CO2e (8.7 percent of greenhouse gas emissions) have been overlooked or under-counted by the FAO and uncounted in the existing inventory of worldwide greenhouse gases:

  • First, Livestock’s Long Shadow cites 2002 FAO statistics as the key source for its 18-percent estimate. From 2002 to 2009, the tonnage of livestock products worldwide increased by 12 percent, which must yield a proportional increase in greenhouse gas emissions. Through extrapolation from the FAO’s estimate as well as Goodland and Anhang's, they calculate that the increase in livestock products worldwide from 2002 to 2009 accounts for about 2,560 million tons of CO2e, or 4.0 percent of greenhouse gas emissions.

  • Second, the FAO and others have documented frequent under-counting in official statistics of both pastoral and industrial livestock. Livestock’s Long Shadow not only uses no correction factor for such under-counting, but in some sections actually uses lower numbers than appear in FAO statistics and elsewhere. For example, Livestock’s Long Shadow reports that 33.0 million tons of poultry were produced worldwide in 2002, while FAO’s Food Outlook of April 2003 reports that 72.9 million tons of poultry were produced worldwide in 2002. The report also states that 21.7 billion head of livestock were raised worldwide in 2002, while many non-governmental organizations report that about 50 billion head of livestock were raised each year in the early 2000s. If the true number is closer to 50 billion than to 21.7 billion, then the percentage of greenhouse gases worldwide attributable to under-counting in official livestock statistics would likely be over 10 percent.

  • Third, the FAO uses citations for various aspects of greenhouse gases attributable to livestock dating back to such years as 1964, 1982, 1993, 1999, and 2001. Emissions today would be much higher.

  • Fourth, the FAO cites Minnesota as a rich source of data. But if these data are generalized to the world then they understate true values, as operations in Minnesota are more efficient than operations in most developing countries where the livestock sector is growing fastest.

Finally, Goodland and Anhang believe that the FAO has overlooked some emissions that have been counted under sectors other than livestock. These emissions add up to at least 3,000 million tons of CO2e, or 4.7 percent of greenhouse gas emissions worldwide.

  • Uncounted, Overlooked, and Misallocated Livestock-related GHG Emissions (T

Annual GHG emissions (CO2e), million tonnes

Percentage of
worldwide total

FAO estimate



Uncounted in current GHG inventories

1. Overlooked respiration by livestock



2. Overlooked land use



3. Undercounted methane



4. Other four categories (see text)






Misallocated in current GHG inventories

5. Three categories (see text)



Total GHGs attributable to livestock products



* FAO starting percentage is decreased from 18% since total emissions are greater.

First, the FAO states that “livestock-related deforestation as reported from, for example, Argentina is excluded” from its greenhouse gas accounting.

Second, the FAO omits farmed fish from its definition of livestock and so fails to count greenhouse gases from their life cycle and supply chain. It also omits greenhouse gas emissions from portions of the construction and operation of marine and land-based industries dedicated to handling marine organisms destined to feed livestock (up to half the annual catch of marine organisms).

Lastly, the FAO leaves uncounted the substantially higher amount of greenhouse gases attributable to each of the following aspects of livestock products versus alternatives to livestock products:

  • Fluorocarbons (needed for cooling livestock products much more than alternatives), which have a global warming potential up to several thousand times higher than that of CO2.

  • Cooking, which typically entails higher temperatures and longer periods for meat than alternatives, and in developing countries entails large amounts of charcoal (which reduces carbon absorption by consuming trees) and kerosene, each of which emits high levels of greenhouse gases.

  • Disposal of inevitably large amounts of liquid waste from livestock, and waste livestock products in the form of bone, fat, and spoiled products, all of which emit high amounts of greenhouse gases when disposed in landfills, incinerators, and waterways.

  • Production, distribution, and disposal of by-products, such as leather, feathers, skin, and fur, and their packaging.

  • Production, distribution, and disposal of packaging used for livestock products, which for sanitary reasons is much more extensive than for alternatives to livestock products.

  • Carbon-intensive medical treatment of millions of cases worldwide of zoonotic illnesses (such as swine flu) and chronic degenerative illnesses (such as coronary heart disease, cancers, diabetes, and hypertension leading to strokes) linked to the consumption of livestock products. Full accounting of greenhouse gases attributable to livestock products would cover portions of the construction and operation of pharmaceutical and medical industries used to treat these illnesses.

A key risk factor for climate change is the growth of the human population, conservatively projected to be roughly 35 percent between 2006 and 2050. In the same period, the FAO projects that the number of livestock worldwide will double, so livestock-related greenhouse gas emissions would also approximately double (or rise slightly less if all the FAO’s recommendations were fully implemented), while it is widely expected that greenhouse gases from other industries will drop. This would make the amount of livestock-related emissions even more unacceptable than today’s perilous levels. It also means that an effective strategy must involve replacing livestock products with better alternatives, rather than substituting one meat product with another that has a somewhat lower carbon footprint.

A substantial body of theory, beliefs, and even vested interests has been built up around the idea of slowing climate change through renewable energy and energy efficiency. However, after many years of international climate talks and practical efforts, only relatively modest amounts of renewable energy and energy efficiency have been developed (along with more nuclear- and fossil-energy infrastructure). Greenhouse gas emissions have increased since the Kyoto Protocol was signed in 1992 and climate change has accelerated. However desirable, even major progress in displacing non-renewable energy would not obviate substantial action to reduce the huge amounts of livestock-related greenhouse gas emissions.

Action to replace livestock products not only can achieve quick reductions in atmospheric greenhouse gases, but can also reverse the ongoing world food and water crises. Were the recommendations described below followed, at least a 25-percent reduction in livestock products worldwide could be achieved between now and 2017, the end of the commitment period discussed at the United Nations’ climate conference in Copenhagen in December 2009. This would yield at minimum a 12.5-percent reduction in global anthropogenic greenhouse gas emissions, which by itself would be almost as much reduction as is generally expected to be negotiated in Copenhagen.

Because of the urgency of slowing climate change, Goodland and Anhang believe that recommending change directly to industry and the public will be more effective than recommending policy changes to governments, which may or may not eventually lead to change in industry. This is true even though industry and investors normally thrive when they are responsive to customers and shareholders in the short term, while climate seems to pose long-term risks.

Livestock-related greenhouse gases could be managed by governments through the imposition of carbon taxes (despite opposition from the livestock industry), in which case leaders in the food industry and investors would search for opportunities that such carbon taxes would help create. In fact, they might seek to benefit from such opportunities even in the absence of carbon taxes because livestock-related greenhouse gas emissions are a grave risk to the food industry itself. Disruptive climate events are forecast to threaten developed markets increasingly, and to result in even more harm to emerging markets, where the food industry is otherwise forecast to achieve its greatest growth.

Opportunities for food companies

An individual food company has at least three incentives to respond to the risks and opportunities applicable to the food industry at large. The first incentive is that individual food companies already suffer from disruptive climate events, so a company’s self-interest might well be served by acting to slow climate change. In affected areas, disruptive climate events can be expected to degrade not only the food industry’s markets, but also its infrastructure and its ability to operate. For example, all these risks played out in the New Orleans area in 2005 following Hurricane Katrina,when Whole Foods Market, Inc. reported US$16.5million in losses that year due to the closure of its damaged stores in the New Orleans area, loss of sales, and renovations at the damaged stores. Such risks will be aggravated by extreme climate events in the future, which are expected to occur with increasing frequency and intensity worldwide.

A second incentive stems from the likelihood, once the current economic crisis is resolved, that demand for oil will rise to levels impossible to meet because of a terminal decline in production (the “peak oil” phenomenon). Petroleum’s price will spike so high as to bring about the collapse of many parts of today’s economy. Livestock products would take an extra hit because every gram of biofuel from crops that can possibly be produced to replace conventional fuel likely will be produced — and thereby diverted from livestock — in efforts to stave off disaster. It has been predicted from within both the livestock and financial sectors that peak oil could bring about

the collapse of the livestock sector within a few years. To be ahead of the competition in that scenario is another reason for leaders in the food industry to immediately begin replacing livestock products with better alternatives.

A third incentive is that a food company can produce and market alternatives to livestock products that taste similar, but are easier to cook, less expensive, healthier, and so are better than livestock products. These alternatives are analogues to livestock products such as soy- and seitan (wheat gluten) beef, chicken, and pork; and soy- and rice milk, cheese, and ice cream.

Sales in the United States alone of soy analogues totalled $1.9 billion in 2007, up from $1.7 billion in 2005, according to the Soyfoods Association of North America. In comparison, sales in the United States of meat products (including poultry) topped $100 billion in 2007. This 1.9 to 100 ratio suggests much room for growth in sales of meat and dairy analogues. Meat and dairy analogues are already sold throughout the developing world, and as in the United States sales have increased in recent years. So efforts to increase sales of these products in developing countries do not have to wait for similar efforts to succeed in the developed world first. Worldwide, the market for meat and dairy analogues is potentially almost as big as the market for livestock products.

Large organic-food companies might find these opportunities especially appealing. Such companies could establish subsidiaries to sell meat and dairy analogues, possibly exclusive of meat or dairy products. They could significantly scale up production and sales of analogues within a few years at a reasonable capital cost and with an attractive return on investment. And because meat and dairy analogues are produced without the greenhouse gas-intensive processes used in raising livestock — such as animals’ CO2 and methane emissions, and usage of land for growing feed and grazing livestock — the analogues clearly generate a small fraction of the greenhouse gases attributable to livestock products. So additional revenues might be captured from the sale of carbon credits for the reduction in greenhouse gas emissions achieved by analogues versus livestock products.

Analogues are just as nutritious as meat products, and in some cases, even more tasty when properly cooked and prepared.

Analogues are most indistinguishable from meat and dairy products when they are chopped, breaded, sauced, spiced, or otherwise processed, so among the least risky strategies might be for a company subsidiary to build a chain of fast-food outlets featuring soy burgers, soy chicken products, s
andwiches made with various meat analogue products, and/or soy ice cream. If the chain’s growth were rapid, then other food companies would be tempted to copy from the first mover.

If production of meat and dairy analogues is significantly increased, then their costs will decline — a key advantage for at least as long as the present economic recession in many countries persists. Cost reductions will follow from economies of scale and increased competition among analogue producers, as well as because the primary feedstock for bio-diesel is soy oil. Meeting the significantly higher forecast demand for biodiesel will yield surpluses of soy meal, which is not only a by-product of soy oil but a raw material for many meat and dairy analogues. Surpluses in stocks of soy meal may drive down its price significantly.

For consumers who do not like meat and dairy analogues, protein-rich legumes and grains are readily available alternatives.

Another option might be artificial meat cultivated in laboratories from cells originating from livestock, sometimes called “in vitro” meat. Some experiments have been done and patents registered, but production and possible commercialization are several years off and it will be awhile before it is known whether in vitro-meat might compete with analogues in cost and taste as well as health and environmental impacts.


To achieve the growth discussed above will require a significant investment in marketing, especially since meat and dairy analogues will be new to many consumers. A successful campaign

would avoid negative themes and stress positive ones. For instance, recommending that meat not be eaten one day per week suggests deprivation. Instead, the campaign should pitch the theme of eating all week long a line of food products that is tasty, easy to prepare, and includes a “superfood,” such as soy, that will enrich their lives. When people hear appealing messages about food, they listen particularly for words that evoke comfort, familiarity, happiness, ease, speed, low price, and popularity. Consequently, several other themes should be tapped to build an effective marketing campaign: By replacing livestock products with analogues, consumers can take a single powerful action collectively to mitigate most greenhouse gases worldwide. Labelling analogues with certified claims of the amount of greenhouse gases averted can give them a significant edge.

Analogues are less expensive, less wasteful, easier to cook, and healthier than livestock products.

Meat and dairy analogues can be positioned as clearly superior to livestock products, thus appealing to the same consumer urges that drive purchases of other analogue products, such as Rolex knockoffs.

In developing countries, where per-capita meat and dairy consumption is lower than in developed countries, consumers often see meat and dairy products as part of a better diet and a better life, and have not yet been informed about their adverse impacts. Yet meat and dairy analogues can yield even better outcomes, particularly if they are marketed with such intent.

As shown by the track record of green businesses, the most appropriate target of the campaign would be environmentalists, on the basis that eating meat and dairy analogues is the best way to combat climate change. They can be expected to spread such messages to other people, and may press for analogues to be served at meetings they attend and for the greenhouse gases thereby avoided to be well publicized.

Probably most susceptible to messages about new foods and fast foods are children, who are prone to act on advertising, having less-ingrained habits than adults, and often seek to catch the wave of a new trend. Parents often join in eating a fast food meal or other food product that their children insist be bought for them. At the same time, children are being increasingly educated on climate change in school, and are searching for activities that allow them to experiment with what they have learned. Yet they are major targets when it comes to marketing livestock products, despite the grievously high climate risk of those products. To correct this, consideration should be given to changing applicable standards for marketing to children. In any event, marketing meat and dairy analogues to children should be a priority.

In addition, food companies can market meat and dairy analogues through strategic alliances with other companies. They can engage with schools, governments, and non-governmental organizations. Environmentalists with relevant skills can be called upon to conduct ongoing, comprehensive tracking of greenhouse gases attributable to livestock products and analogues. Politicians and celebrities can be enlisted to make public pitches for consumers to choose alternatives to livestock products.

Goodland and Anhang recommend that when grocers plan displays and set slotting fees (for favourable shelf placement), they consider the benefits of displaying analogues side by side with meat and dairy products. This would expose analogues to many consumers who may not otherwise be exposed to them, and thereby facilitate an increase in their sales. It would permit the achievement of good sales results that normally occur when consumers are shown multiple forms of a product on the same shelf. Where analogues cost less than meat products, displaying one beside the other may have an enhanced benefit for grocers. That is, if consumers find in a side-by-side comparison that analogues are cheaper than livestock products, then side-by-side placement may help grocers keep up their overall sales volumes in an economic downturn.

Sources of Investment

A company with a sound plan for increasing sales of meat or dairy analogues is likely to find sufficient commercial financing available from investors seeking investment opportunities that promise to help slow climate change. It may also find concessional financing through development finance institutions and “climate funds.” But it may need to raise awareness among investors unfamiliar with meat and dairy analogues.

Investors can be shown that it is in their self-interest to avoid new investments in the production of meat and dairy products and to seek investments in analogues instead. Compared with power and transportation projects, analogue projects can be implemented quickly, with relatively low levels

of incremental investment, larger amounts of greenhouse gases mitigated for the same amount of investment, and faster returns on investment.

Investments in minimizing and mitigating greenhouse gases most often focus on renewable energy in the transportation and power sectors. However, renewable-energy infrastructure has both long and complex product-development cycles and capital-intensive requirements. Converting vehicle fleets and power plants is forecast to cost trillions of dollars, and to require political will and consensus that do not appear close at hand. Even if money and politics were up to the task, such solutions are expected to take more than a decade to implement fully, by which time the tipping point may long since have been passed for irreversible climate disruption.

Most commercial banks, some export-credit agencies, and even some equity funds have adopted the Equator Principles, by which they commit to complying with a set of rigorous environmental and social performance standards for investment projects in developing countries. If those standards were to frown upon investments in large-scale livestock projects, then a company with a meat or dairy analogue project would be well positioned to attract investments.

Benefit Package

Meat and dairy analogue projects will not only slow climate change but also help ease the global food crisis, as it takes a much smaller quantity of crops to produce any given number of calories in the form of an analogue than a livestock product.

Analogues would also alleviate the global water crisis, as the huge amounts of water necessary for livestock production would be freed up. Health and nutritional outcomes among consumers would be better than from livestock products.

Analogue projects would be more labour intensive than livestock projects, so would create both more jobs and more skilled jobs. They would also avert the harmful labour practices found in the livestock sector (but not in analogue production), including slave labour in some areas such as the Amazon forest region.

Workers producing livestock products can easily be retrained to produce analogues.

Of course, some livestock will continue to be raised, especially where they are important in mixed farming systems. They may also be important where raising livestock is one of the few ways for poor rural populations to create assets and earn income. However, that is increasingly less common, as the dramatic growth in recent years in the use of computers, mobile communications, mobile banking, micro-finance, and off-grid electricity has created a multitude of new opportunities for poor rural communities.

For many years, advocacy of alternatives to livestock products has been based on arguments

about nutrition and health, compassion for animals, and environmental issues other than carbon intensity. These arguments have mostly been ignored and the consumption of livestock products worldwide has increased, leading some to believe that such advocacy may never succeed. Even urging governments to mandate reductions in livestock production on grounds of climate change may prove ineffective because of the food industry’s own large lobbying capacity. But if the business case for meat and dairy analogues is clear, then those who normally would lobby governments can appeal directly to leaders in the food industry,who may welcome them as champions. The business risks of analogue projects would be similar to those in most other food manufacturing projects, but the risks would be mitigated by the fact that much of the necessary infrastructure (such as for growing and processing grains) already exists.

The key change would be a significant reduction in livestock products. Industry-led or supply-led growth has been successful in other industries, such as the computer and mobile-phone industries, which suggests that it can be successful with meat and dairy analogues. Generally, the food industry worldwide has a very sophisticated marketing capacity, making high growth from marketing new food products practically a norm — even before one considers the extra lift that might be achieved from interest in slowing climate change.

The risks of business as usual outweigh the risks of change. The case for change is no longer only a public policy or an ethical case, but is now also a business case. We believe it is the best available business case among all industries to reverse climate change quickly.