Greenhouse gases occur naturally in the atmosphere. They absorb part of the energy from the earth’s surface and from clouds, preventing heat from escaping into space. Without this so-called greenhouse effect, the earth would be a lot colder than it is. But since the Industrial Revolution, we have added sharply to the amount of carbon dioxide, methane and other greenhouse gases in the atmosphere. As a result, levels of carbon dioxide in the air have gone up from 288 to 395 parts per million. Such concentrations boost the greenhouse effect.
No other source of energy contributes as much to greenhouse gas emissions as coal. In 2014 it was responsible for emitting 14.2 gigatonnes of carbon dioxide. That is 44 per cent of all energy related carbon dioxide emissions, and more than one-quarter of all greenhouse gas emissions. The 35 biggest coal producers have been responsible for one-third of the global emissions since 1988. This was the year the Intergovernmental Panel on Climate Change was founded, and the Toronto climate conference requested governments to set targets for reducing their emissions.
The coal industry could no longer deny the harm its product was causing. Private companies, state-owned enterprises and government-run industries have made huge profits from producing and selling coal. But they have not been held accountable financially or legally for the loss and damage they have caused, and continue to cause, around the world. The majority of coal is burned to produce heat and electricity. That releases a lot of carbon dioxide, along with smaller quantities of methane and nitrous oxide. Different greenhouse gases have a different impact on the climate; converting them to a “carbon dioxide equivalent” measure makes them comparable. In general, generating electricity from coal damages the climate most; gas-powered plants emit only half as much carbon dioxide as modern coal-fired power stations.
The carbon footprint of coal is further enlarged by emissions of mine gas. This is created during the formation of the coal, and consists mainly of methane. In 2010, mines added the equivalent of another 500 million tonnes of carbon dioxide to the atmosphere. In addition, hard coal often has to be transported long distances. That involves energy and contributes to the climate damage. Burning coal, whether in a power station, furnace or stove, releases soot particles that also fuel the greenhouse effect. Mining and transporting lignite produce fewer emissions. But using it to generate electricity still harms the climate more than hard coal. This is because lignite is less compact. It contains less energy, so more has to be burned to produce the same amount of power.
There are already enough greenhouse gases in the atmosphere to raise the earth’s average surface temperature by 1.5 degrees Celsius. This figure should not be exceeded, because doing so would jeopardise lives and livelihoods in many parts of the world. If the temperature rises above that limit, the climate could cross a critical threshold. The West Antarctic ice cap might melt. Such temperature thresholds are known as climate “tipping points”. Beyond the tipping point, the climate would not return to its current state, but would undergo further changes that are impossible to predict.
At the climate change conference in the Mexican city of Cancun in 2010, the international community agreed to limit temperature change to 2 degrees Celsius above pre industrial levels. To have a 50 per cent chance of keeping under this limit, the carbon dioxide content of the atmosphere must be kept under 450 parts per million. That means that humanity must emit no more than 1,000 gigatonnes of carbon dioxide by 2050. That is possible only if 88 per cent of the currently confirmed coal reserves stay in the ground, along with one third of the mineral oil and half the natural gas reserves. Our consumption of coal will have to fall sharply, from 1.07 tonnes per person today to only 80 kilograms in 2050
Coal extraction has huge impacts on the environment. In open pit mining, which accounts for about 40 per cent of global coal production, the entire overburden has to be removed to reach the coal seams underneath. The landscape is completely destroyed. Communities are removed, plants and animals are eliminated, and the living soil is shovelled away. Excavators dig enormous craters, hundreds of metres deep.
The ecological consequences are similar across countries, though standards for mining, restoration and legal enforcement differ widely. Mining means digging up and shifting huge amounts of earth. In some types of soil, iron and sulphur compounds can oxidize to iron and sulphate when they come into contact with the air. After extraction ceases the groundwater levels rise again and sulphuric acid is produced. As a result, the flooded pits and groundwater acidify. Adding alkaline materials such as limestone can reduce the level of acidity but cannot prevent it completely. Pumps are used to lower the water table and prevent the pits from filling up with water. This has severe consequences for the groundwater. Keeping a mine dry disrupts the hydrology of the neighbouring areas, lowering the water table by as much as 550 metres dries up the springs that feed rivers, kills trees, desiccates wetlands and reduces biodiversity. This pumping, also called “mine dewatering”, would not only dry up wells, endangering drinking water supplies. It can take a hundred years for the groundwater level to regain its previous level.
Published in The Express Tribune, February 14th, 2017.
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