The Resilient Earth: Science, Global Warming and the Fate of Humanity

by Simmons, Allen

  Jean Baptiste Joseph Fourier was a French mathematician and physicist who is best known for the mathematical tool called a Fourier Series and its application to the problem of heat flow. He also invented the eponymous Fourier Transform, which figures prominently in modern infrared spectroscopy and astronomy.

  In 1827, Fourier published his theory that gases in the atmosphere might increase the surface temperature of Earth. He attributed this to interactions we now call the greenhouse effect. In his paper, he proposed the idea of planetary energy balance—that some sources warm a planet while heat is radiated away into space. Fourier recognized that Earth primarily gets energy from solar radiation, to which the atmosphere is transparent, and that geothermal heat contributes little to the energy balance. He theorized that a balance is reached between heat gain and heat loss, and that the atmosphere shifts the balance toward the higher temperatures by slowing the heat loss.

  Fourier stated that planets lost energy due to what he called “chaleur obscure” (“dark heat”). Fourier understood that the emission of dark heat increased with temperature, but the exact relationship was not discovered for fifty years. Today, Fourier's dark heat is called infrared (beyond red) radiation. The next link in the chain of discovery belongs to an Irishman.

  Illustration 52: John Tyndall (1820-1893), photo R. MacDonald.

  John Tyndall was born in Ireland, in 1820, the son of a local constable. Tyndall attended a common primary school and joined the Irish Ordnance Survey in 1839. Later, he did survey work in England and railway construction during the boom of the 1840s. In 1847, he taught mathematics at Queenwood College Hampshire. In 1848, Tyndall began studies in Germany and became one of the first British subjects to receive the new PhD at Marburg. Though he contributed to many fields, Tyndall's major scientific work was in atmospheric gases.209

  An accomplished mountaineer, Tyndall was fascinated by Louis Agassiz's daring proposal of ice ages, in which glaciers once covered enormous parts of the world (page 75). Looking for mechanisms to explain climate change, he established the absorptive power of clear aqueous vapour—water vapor. Tyndall's experiments showed that, in addition to water vapor, carbonic acid210 (H2CO3) can absorb a great deal of heat energy.211 He suggested this phenomenon was linked to changes in climate—changes that caused glaciers to advance and retreat.

  By this time, scientists knew that the atmosphere consisted of a number of distinct gases. A few, primarily nitrogen and oxygen, were plentiful, while others, notably water vapor and carbon dioxide, were present only in small amounts. The components of Earth's atmosphere are listed in Table 7.

  Table 7: Components of Earth's atmosphere.

  Correctly identifying water vapor as the strongest absorber of radiant heat, Tyndall marveled at the ability of transparent, colorless gases to trap heat. In his own words, he stressed the importance of water vapor in the atmosphere.

  “Aqueous vapour is a blanket more necessary to the vegetable life of England than clothing is to man. Remove for a single summer-night the aqueous vapour from the air which overspreads this country, and you would assuredly destroy every plant capable of being destroyed by a freezing temperature. The warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost.”212

  Where others speculated and theorized, Tyndall carefully planned and executed laboratory experiments, using equipment of his own design and construction. To take accurate measurements of the absorptive properties of various gases, he constructed the first spectrophotometer, shown in Illustration 53.

  Illustration 53: Tyndall's experimental apparatus, the first ratio spectrophotometer.

  Tyndall's experiments clearly demonstrated that trace atmospheric constituents were active absorbers of heat radiation, at least in the infrared. His meteorological and climatological speculations kept alive what was called the “hot-house theory,” and suggested to Svante Arrhenius (page 12) and others, that Earth's heat budget may be controlled by changes in the trace constituents of the atmosphere. Today, we know this is true.

  The Greenhouse Today

  The portion of solar radiation that is absorbed by Earth's surface, about 51%, is re-radiated at longer, infrared wave lengths. The so-called greenhouse gases, mainly water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), trap this infrared radiation, preventing it from leaving Earth quite so rapidly, as shown in Illustration 54. This is the source of the greenhouse effect.

  The case for anthropogenic global warming is based on human generated greenhouse gases. These gases build up in the atmosphere, increasing greenhouse warming. The primary culprit in this scenario is CO2, the second most plentiful greenhouse gas in the atmosphere after water vapor.

  Because it is well-know that mankind pumps billions of tons of CO2 into the air each year, it is easy to lay the blame for global warming squarely on human activity. As a result of the tremendous world-wide consumption of fossil fuels, the amount of CO2 in the atmosphere has increased over the past century and continues to rise at a rate of about 1 part per million (ppm) per year.

  Illustration 54: Solar radiation striking Earth and the Greenhouse Effect, source USGS.

  Most anthropogenic CO2, some 79%, is produced from burning fossil fuels; coal, oil, and natural gas. Electricity generation accounts for 41% and transportation accounts for 22%.213 There are other minor industrial sources for CO2 and other greenhouse gases as well, but fossil fuels account for the lion's share of human greenhouse gas emissions (see Illustration 55).

  The contributions of other greenhouse gases to global warming are usually glossed over because they complicate the story (i.e. CO2 causes global warming, Man causes CO2). When we talk about the causes of climate change in detail, the effects of the other greenhouse gases will be analyzed. For the purpose of discussion, we will continue under the assumption that CO2 is the main source of greenhouse warming even though it makes up only 0.038% of the atmosphere.

  Illustration 55 Sources of greenhouse gases.

  Predicted world CO2 emissions through the year 2030 are listed in the table in Illustration 56. Notice that the majority of future increases will come from developing countries (Non-OECD) which have an average annual change of 3.0%, while the developed countries will only increase by 1.1%. This is one of the main problems with trying to freeze global CO2 emissions. Developing nations are still building their economies and have not yet stabilized their emissions levels.

  The United States and other developed countries show a lesser increase in CO2 emission rates than developing countries. Even though most of the projected future increase come from developing nations, the Kyoto Protocol mostly exempts developing countries from emissions reduction obligations. The treaty requires developed countries, and only developed countries, to return their greenhouse gas emissions to 1990 levels.

  Illustration 56: Predicted world CO2 emissions. Source DOE.

  Developing countries have surpassed the developed countries in tons of CO2 emissions. Still, the Kyoto Protocol Treaty wants the United States and other industrialized countries to return to emissions levels of 3,000 million tons, while developing countries, like India and China get a free pass to raise their emissions to 4,000 million tons. Quoting from Harvard Magazine regarding Kyoto, “Harvard scientists and economists who study climate change express almost universal criticism of the accord, which they fault as economically inefficient, unobjective, inequitable, and—worst of all—ineffective.”214 Is it so strange the US and Australia did not sign the Kyoto Treaty?

  Note that Illustration 56 shows emissions by total weight, in metric tons of CO2. IPCC figures are given in carbon equivalent units (CEUs). Carbon equivalent units are based on the carbon content of a gas, 27% in the case of CO2. Using CEUs makes it easier when comparing carbon emissions in the form of other gases, like methane, and the amounts of carbon stored in plants and rock. To convert the Department Of Energy (DOE) numbers to the IPCC numbe
rs, multiply by 0.27.

  A graphical view of the same emissions trend, using carbon equivalent data, can be seen in Illustration 57. Again, notice the rise of emissions from developing countries, and the projected displacement of the developed nations as the world's largest emitters. A review of this data raises the question: Does pumping 6,500 million tons of carbon in the form of CO2, into the atmosphere every year, create a problem? It sounds like it could, but is 6,500 million tons a large amount when all factors are considered?

  Illustration 57 Predicted CO2 emissions until 2025 in millions of tons.

  In order to understand the magnitude of the problem we need to know how much carbon is in circulation, and to do that, we need to understand more about carbon dioxide and the carbon cycle.

  Carbon Dioxide

  Carbon dioxide, CO2, is one of the gases found naturally in Earth's atmosphere. It was first identified by Joseph Black, a Scottish chemist and physician, in 1750. A simple molecule, CO2, consists of one atom of carbon and two atoms of oxygen joined together with double bonds.

  Illustration 58: A CO2 molecule. The carbon atom is in the center.

  Under normal terrestrial temperatures and pressures, CO2 is a slightly toxic, odorless, colorless gas with a slightly acidic taste. When present in concentrations greater than 5% by volume, it can be dangerous to human health. Air, with a carbon dioxide content of more than 10%, will extinguish an open flame and can be life-threatening by causing asphyxiation. Such high concentrations may build up in silos, wells, and sewers, so this is not an idle warning.

  Fortunately, CO2 is uniformly distributed throughout the atmosphere at a concentration of only 0.038% or 380 ppm (parts per million). Though this sounds like a very small portion of the atmosphere, and it is, CO2 is still the most abundant of the greenhouse gases, with the exception of highly variable water vapor (H2O).

  Water vapor is present in the atmosphere at an average concentration of 1%, but that amount varies widely, from 0-4%. If you have ever been in the American South during the summer, you have probably felt the greenhouse effect first hand. In the summer, even well inland, the heat of a southern day lingers well into the night, clinging like a hot, moist towel to the land. This is water vapor in action, retaining the heat that would otherwise escape into space.

  Contrast this with nights in the desert southwest. Death Valley is one of the hottest places on Earth,215 with daytime temperatures routinely reaching 122°F (50°C) during the summer. Located in the state of California near the Nevada border, Death Valley is also one of the driest places on Earth, receiving only 2 inches (5 cm) of rain each year216 . From the rock-splitting heat of the day, temperatures drop below freezing at night under clear cloudless desert skies.

  Water vapor also affects the climate by participating in energy transfer between the ocean and the atmosphere. It affects energy absorption from the Sun by forming clouds which trap heat under some conditions and reflect radiation under others. Combine water vapor's complex environmental interactions with the fact that water covers 70% of Earth's surface, and it seems implausible to identify H2O as the cause of the current dilemma. Because of these complexities, CO2 is usually treated as the most abundant greenhouse gas and prime suspect in the global warming crisis. H2O is just too complicated.

  CO2 finds commercial uses in beverage carbonation, fire extinguishers, as a refrigerant, and many other applications.217 Dry ice is CO2 in its solid form, which only exists at temperatures below -108°F (-78°C). Dry ice is often used to keep perishable items frozen during shipment, like mail order steaks from Omaha. In the United States, 10.89 billion pounds of carbon dioxide were produced by the chemical industry in 1995, ranking it 22nd on the list of top chemicals produced.

  Because of the low concentration of carbon dioxide in the atmosphere, it is not practical to obtain the gas by extracting it from air. Most commercial carbon dioxide is produced as a by-product of other processes, such as manufacturing ammonia or the production of ethanol by fermentation. CO can also be made as a primary product by burning coke or other carbon-containing fuels.

  In addition to being a component of the atmosphere, carbon dioxide also dissolves in the water of the oceans. At room temperature, the solubility of carbon dioxide is about 55 in3 per quart (900 cm3 per liter) of water. When absorbed by water, carbon dioxide exists in many forms but most of it remains as dissolved gas.

  The Carbon Cycle

  Carbon is the fourth most abundant element in the universe, accounting for ~4.6% of all normal matter. But it is not nearly as common on Earth where the lithosphere (Earth's crust) is only 0.032% carbon by weight. In comparison, oxygen and silicon make up 45.2% and 29.4% of Earth's surface rocks, respectively.218 Given the relative scarcity of carbon on Earth, it may seem surprising that carbon is so abundant in living things. But there are good chemical reasons our planet is full of carbon-based life-forms.

  Carbon is a very versatile element. An atom of carbon is capable of forming links, called chemical bonds, with up to four other atoms at a time. Forming bonds with itself or other elements, carbon can create an incredible number of different molecules. Compared with bonds formed by other elements, carbon bonds are not that hard to break. This allows carbon to react quickly with other elements. Carbon makes a good building block for life because it can form multiple bonds and do so quickly. But, why carbon, to the exclusion of all other elements?

  Illustration 59: Gases in Earth's Atmosphere. Source Wikipedia.com.

  One row below carbon, in the periodic table of elements, lies silicon—carbon's heavier and more plentiful twin. Silicon also forms four bonds, but they are stronger than carbon bonds. As a result, silicon compounds tend to be less reactive than carbon compounds. But sometimes, when silicon is substituted for carbon, the resulting molecules are unstable.219

  Silicon is an essential element in biology, though only tiny traces of it are required by animals. In 1893, James Emerson Reynolds, a British chemist, speculated that the heat stability of silicon compounds might allow life to exist at very high temperature.220 Silicon life-forms have been a staple of science fiction ever since. On Earth, there are no silicon-based life-forms—according to NASA's Astrobiology Institute, “silicon simply doesn’t have the moves.”221

  Silicon's real problem is that it bonds too tightly with oxygen. When we breath, carbon is oxidized forming the gas carbon dioxide. When silicon combines with oxygen it forms a solid, called silicate (SiO4-4), in which each silicon atom is surrounded by four oxygen atoms. Silicate anions connect to each other by sharing oxygen atoms, forming crystals. A gas is easy to exhale, a solid is much harder to dispose of. For this and other reasons, life chose carbon and, by extension, CO2.

  Life extracts carbon from the environment in order to build organic molecules (molecules based on carbon). Organic molecules can assume a bewildering number of shapes: rings, long chains, multi-ring chains, and folded sheets to name a few. Carbohydrates (starches and sugars), lipids (fats), nucleic acids (DNA and RNA), and proteins are all based on carbon. Carbon is the stuff of life.

  There are two large pools of terrestrial carbon; geologic carbon stored in rock and fossil fuel deposits, and biologic carbon stored in living things or “in play” in the atmosphere and oceans. The source of both types of stored carbon is life. Over billions of years, uncountable billions of living things have collected carbon; growing, eating, breathing, reproducing and finally, dying. Most of this carbon came from Earth's primitive atmosphere in the form of carbon dioxide, which has steadily decreased over time.

  Through a number of different living processes, vast amounts of carbon are now trapped in Earth's crust in the form of sedimentary rocks; limestone, dolomite, and chalk. This type of storage, or sink, accounts for the majority of carbon on Earth, 66,000,000 to 100,000,000 billion metric tons222 (gigatons or Gt).

  As seen in Table 8, fossil fuel deposits, the other major type of geologic carbon, accounts for a paltry 4,000 Gt. The important difference between geologic and
biologic carbon sinks is that geologic carbon is out of short term circulation. It is only released by slow processes, such as volcanism,223 degassing,224 and rock weathering, which can take millions of years. At least that was true before Man started digging up fossil fuels and burning them.

  The other carbon sinks shown in Table 8, the oceans, soil, atmosphere, and plants, all participate in what is called the carbon cycle of life. This carbon is involved with life over the short term.

  Table 8: Amount of carbon stored in sinks. Source Dr. Michael Pidwirny225 .

  Carbon is constantly cycling between the atmosphere, the oceans, and living matter. Plants take in atmospheric CO2 in order to grow. When the plants die and decay, the carbon returns to the biosphere. When animals eat plants, some of the carbon becomes incorporated into the living tissues of the consumer. Part is released as gases, byproducts of digestion, and the rest becomes organic waste. Other organisms break down the organic waste as it becomes mixed with the soil.

  Eventually all animals die and, regardless of whether they are eaten or decompose, the carbon in their bodies eventually gets returned to the biosphere. In this way, carbon passes through Earth's biota ultimately ending up in either the ocean or the atmosphere. The major exchange paths, along with the amounts exchanged in gigatons, are shown in Illustration 60.

  Illustration 60: The carbon cycle of life. Source IPCC.