Katy Hayden
HCOL 185
Brian Beckage
Coal Impacts on Global Climate
Beginning around the 1800’s, coal has been a major source of energy around the world.
Since then, the methods for extracting coal from the earth and using it have developed and had a major impact on the world in terms of energy use. However, this is not the only way the extraction and use of coal is impacting the world; it also effects the earth’s environment and climate in many ways. Mining itself releases a number of toxic chemicals, sulfur dioxide, nitrogen oxides, and hydrogen cyanide. It also produces methane, which carries a heavy weight in the long-term global climate. On top of that, the burning of coal for energy releases high levels of carbon dioxide, a greenhouse gas which plays a crucial role in climate change. Taking all these factors into account shows that the mining and use of coal is a major player in the changing climate.
The first step in harnessing coal’s energy is its extraction from the earth – the mining process. While the combustion of coal has a greater environmental impact than its mining, the latter generates a very important greenhouse gas: methane. The mining process releases methane in two different ways. First, it disrupts the coal within the coal seam through extensive fracture. Second, it opens pathways through the strata, or layers of sedimentary rock, through which the gas leaves the confines of the seam 1 . Undisturbed coal seams can contain up to about 23 m 3 of methane per ton of coal. Modern coal extraction methods are able to recover some of this methane to be used as an energy resource, but only about 50% of it 2 . This leaves
11.5 m 3 of methane escaping into the atmosphere for every ton of coal that is mined. Although

the amount of methane emitted in the process of utilizing coal is lower than that of carbon dioxide, it cannot be dismissed because it is about 25 times more effective at trapping heat, which is to say that over a 100-year period, its global warming potential is 25 times higher than that of CO
2
3 . Knowing this can shed light on how much potential coal has to raise the global temperature, but it is important to take into account the other factors that contribute to the temperature rise.
Once the coal has been extracted from the earth, it must be converted to energy through one of a variety of processes, such as gasification, liquefaction, and combustion.
Combustion is the most common process used to harness the energy of coal, as it produces electricity, which is the main use of coal 4 . This process creates most of the global warming potential that coal holds, because of the levels of carbon dioxide that it releases and the impact that carbon dioxide has on the climate. Each ton of coal that is burned produces 2.86 tons of carbon dioxide. For the amount of heat produced, this is 11% more carbon dioxide than is produced by oil, and 67% more than natural gas 4 . As the atmospheric concentration of carbon dioxide increases as more fuel is consumed, the global temperature will increase with it. Carbon dioxide does not absorb much short-wave radiation, i.e. sunlight radiating towards the earth, but it does absorb long-wave radiation, which is infrared or heat radiation. This means that sunlight reaches the earth unimpeded by carbon dioxide (though partially deflected by other factors), but as the infrared heat radiation travels away from the earth, a portion of it is absorbed by the carbon dioxide and re-radiated back towards the earth, causing the heat to be trapped and remain in the atmosphere.

As previously stated, 1 ton of coal produces 2.86 tons of carbon dioxide. It also produces roughly 22 gigajoules of energy, and as Figure
1 shows, it accounts for about 41% of the electricity generated for world use. For every
15 gigatons of carbon dioxide that are released into the atmosphere, there is an increase of 1 part per million (ppm) of CO
2
,
Figure 1 Total World Electricity Generation by Fuel (2009)
Source: IEA 2011 and a 50 ppm increase in CO2 constitutes a
1˚C increase in global temperature 5 . Current estimates suggest that approximately 903 billion tons of coal remain on earth, although with current technologies it will only be possible to extract 435 billion 6 . With this information, it is possible to estimate by how much coal can potentially increase the global temperature.
If all 435 billion tons of coal which current technology can extract from the earth is, in fact, extracted and combusted for electricity, 1244.1 billion tons of carbon dioxide will be produced. At 15 billion tons per 1 ppm increase, this level of carbon dioxide would cause an
82.94 ppm increase in the CO
2
levels of the atmosphere. With a 1˚C increase for every 50 ppm,
82.94 ppm would cause a 1.66˚C increase in global temperature. This, however, is under the conditions that all of the carbon dioxide emitted reached the atmosphere. This is not the case.
There are many sources that sequester carbon, or capture it and store it over long periods of time, so that it does not remain in the atmosphere. It is difficult to determine just how much carbon is sequestered in total, but oceans are the largest carbon sinks, absorbing over a quarter of anthropogenic carbon emissions 7 . This means that at least 311 billion tons of CO
2
will be

sequestered into the oceans, dropping the atmospheric increase to 62.21 ppm and the global temperature increase to 1.24˚C. Unfortunately, it is not adequate to rely on the oceans to fix the problem for a variety of reasons. First, they only reduce the potential climate change by
0.42˚C, still leaving the impact of carbon from coal at a significant level. Second, allowing these levels of carbon to be sequestered into the oceans causes other problems for marine biological ecosystems in turn, such as pH reduction, carbonate dissolution, and the smothering of various living systems 8 . Finally, the oceans cannot be continually relied on to sequester the carbon produced by humans and by coal production because new research suggests that their ability to absorb atmospheric CO
2
may be declining. As the temperature of the oceans rise with the atmospheric temperatures, they can hold less carbon dioxide, which means more will be left in the atmosphere causing temperatures to rise further, creating a positive feedback loop 9 .
Although more research needs to be done in this area, if correct these findings could mean that the impact of coal-produced carbon on global temperature would rise towards 1.66˚C again.
NASA scientists in 2006 determined that global warming of more than 1˚C relative to the global temperature in 2000 will constitute a “dangerous” warming in terms of sea level effects and species extermination, but now it has become clear that it will be extremely difficult, if not altogether impossible to stop warming of this level, so the generally accepted goal has become to keep warming under 2˚C 10 . As shown, the coal reserves currently available to the world now have the potential to cause up to 75% of this warming solely from carbon emissions, although it will not be immediate. Table 1 shows the levels of world coal consumption for the years 2007-
2010. In 2007 the world consumed 7.02 billion tons of coal, and in 2010, 7.99 billion. The average change was a 4.5% increase each year. At this rate of increase, the 435 billion tons of

Year 2007
Table 1: World Coal Consumption 11
2008 2009 2010
Coal consumption
(billion tons)
7.02 7.33 7.32 7.99
% Change --- +4.4% -0.1% +9.2% remaining available coal could last until the year 2036. The world may not, therefore, see the
1.24˚ rise in temperature until that time, but this means that it may only be 24 years until the impacts of ‘dangerous’ global warming as stated by James Hansen et al, such as sea level rise and extinction of species, occurs. However, if the world were to hypothetically keep its coal consumption levels at a constant rate for the next 5 years and then decline by merely 1% per year, the current coal reserves could hold out until 2075.
There is an alternative scenario to the world reducing its coal use, one that holds a negative result for the goal of staying below 1˚ of global warming. In the 24 years before the current available coal reserves run out, it is possible that new technologies will be developed that allow the extraction of more of the 468 billion tons of coal which are not currently available. If this was to happen and coal consumption remained at its current rate of growth, it would take only until 2049, a mere additional 13 years, to use up these resources and release the carbon dioxide impacts on the climate. In addition, the impacts would be greater. While utilizing the 435 billion currently available tons would cause between a 1.24 and 1.66˚ increase in temperature, using the full 903 billion tons would have a much greater effect. Even if the oceans continue to absorb at least a quarter of the carbon dioxide put into the atmosphere, utilizing all of the 903 billion tons of coal would result in a 2.58˚C increase in temperature. This is well above the 1˚ of ‘dangerous’ global warming as a result of solely the carbon dioxide released by coal – not taking into account the other ways coal contributes to climate change,

such as methane and trace gases. While coal is one of the largest sources of worldwide anthropogenic carbon dioxide 4 , it is not the only source, and there would be other contributors raising the 2.58˚ change.
Coal has been a source of power since the Industrial Revolution, growing in demand until today it constitutes 40% of all electricity produced around the world. Its consumption rates are still growing, and this will inevitably have an impact on the world’s climate. It is one of the greatest contributors to anthropogenic atmospheric carbon dioxide, which is a greenhouse gas with one of the highest impacts on global temperature. If world consumption continues growing at the rate is has been, the 435 billion tons of remaining available coal will last less than a quarter of a century. By that point the coal could have already contributed up to 1.66˚ of global warming, which is higher than the ‘safe’ levels of warming. If the world decreases its coal consumption and finds another resource for generating electricity, the coal reserves can last longer and the temperature change could be staved off for a while. Alternatively, technologies could be developed to recover more of the remaining coal on earth in order to generate more electricity – this solution would more than double the amount of temperature change. In either scenario, the worldwide utilization of coal will have a significant impact on the global climate.

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