Global coal consumption is set to remain steady in absolute terms through the middle of the century, even as its relative share of total energy consumption declines in favour of oil, gas and renewables.
Continued coal combustion is one reason why policymakers are not on track to achieve their target of limiting the rise in global temperatures to well below 2 degrees above pre-industrial levels.
Coal is projected to be the slowest growing primary energy source over the next three decades, with its share of total primary energy consumption expected to decline to just 20 per cent by 2050 from 27 per cent in 2015.
But in absolute terms, global coal consumption is still projected to be around 165 quadrillion British thermal units (BTUs) in 2050 up from 158 quadrillion BTUs in 2015, according to the U.S. Energy Information Administration.
Rising consumption in India and other developing economies is expected to offset reduced combustion in the United States and China ("International Energy Outlook", U.S. Energy Information Administration, 2017).
Long-term projections have proved notoriously inaccurate in the past because they are sensitive to small changes in the assumptions underlying the model, so any effort at future-gazing should be treated with caution.
But the projections show how the impact of rising populations and prosperity in developing economies is likely to drive an enormous increase in total energy demand which will continue to support absolute coal consumption.
The persistence of high levels of coal consumption for many decades is consistent with earlier energy transitions in which incumbent and emerging energy sources and technologies co-existed for long periods.
Energy historians have identified a "grand energy transition" in which human and animal muscle power has been successively replaced by wind and water mills, wood burning, coal and more recently oil and gas.
The same transition can be identified at micro-level for services such as lighting, where tallow candles were gradually replaced by stearin candles, kerosene lamps, gas lighting, incandescent electric bulbs and now light-emitting diodes.
By making energy services such as heating, lighting, transportation and power dramatically cheaper, energy transitions have encouraged an enormous increase in total energy consumption ("Heat, power and light: revolutions in energy services", Fouquet, 2008).
In the United States, for example, wood burning continued growing for several decades, even as coal emerged as the fastest growing and eventually dominant energy source in the second half of the nineteenth century.
Use of fuelwood continued to grow in absolute terms until 1875-1880 even as it declined per capita and as a percentage of total energy consumption continuously from the 1840s ("Fuelwood used in the United States", U.S. Department of Agriculture, 1942).
Despite its increasing importance, coal consumption did not finally overtake wood as the dominant source of energy until 1885-1890 ("Energy in the American economy 1850-1975", Resources for the Future, 1960).
Coal itself was not replaced by oil as the dominant source of energy in the United States until 1955, almost a century after the petroleum revolution began with the first modern wells drilled in Pennsylvania.
In Britain, the railways, which relied on steam, stimulated rather than replaced horse-drawn vehicles for decades because passengers and freight relied on horse-drawn carriages and carts to get to and from the rail stations.
The use of horses, primarily for short journeys, continued to increase into the 1910s, long after the railways had come to dominate long-distance travel in the 1850s ("The transport revolution from 1770", Bagwell, 1974).
In both Britain and the United States, surging demand for lighting provided a growing market for gas and kerosene lamps long after the introduction of the incandescent light bulb ("Burning to serve", Goodall, 1999).
LEGACY ENERGY SOURCES
The lesson from history is that energy transitions take a long time (usually many decades) and in the early and mid-stages the new energy source/technology tends to add to rather than displace the older one.
The United States was still using more fuelwood in the 1910s than it had in the 1840s - even though wood had been clearly overtaken by coal and to a lesser extent petroleum as an energy source.
But at a macro-level major transition take much longer with legacy energy sources and technologies lingering for perhaps 50-100 years.
(With inputs from agencies.)