Basic Fossil Fuel Facts (extracts from various letters written by Dr James Hansen to government authorities across the world explaining the need to put a moratorium on new coal and phase out existing coal without CCS)
The role of coal in global warming is clarified by a small number of well-documented facts

Figure 1 shows the fraction of fossil fuel carbon dioxide (CO2) emissions that remains in the air over time. One-third of the CO2 is still in the air after 100 years, and one-fifth is still in the air after 1000 years.

Oil slightly exceeds coal as a source of CO2 emissions today, as shown in Figure 2a. [IPCC = Intergovernmental Panel on Climate Change; WEC = World Energy Council]
But, because of the long atmospheric lifetime of past emissions, fully half of the excess CO2 in the air today (from fossil fuels), relative to pre-industrial times, is from coal (Figure 2b).

Moreover, coal use is now increasing, while oil production has stagnated. Oil production will peak and will be constrained by available resources earlier than will coal production.


Figure 3 shows reported fossil fuel reserves and resources (estimated undiscovered deposits).
Reserves are hotly debated and may be exaggerated, but we know that enough oil and gas remain to take global warming close to, if not into, the realm of dangerous climate effects.

Oil will not determine future climate change. Coal will.

Coal and unconventional fossil fuels such as tar shale contain enough carbon to produce a vastly different planet, a more dangerous and desolate planet, from the one on which civilization developed, a planet without Arctic sea ice, with crumbling ice sheets that ensure sea level catastrophes for our children and grandchildren, with shifting climate zones that cause great hardship for the world’s poor and drive countless species to extinction, and with intensified hydrologic extremes that cause increased drought and wildfires but also stronger rain, floods, and storms.

Oil and coal uses differ fundamentally. Oil is burned primarily in small sources, in vehicles where it is impractical to capture the CO2 emissions. Available oil reserves will be exploited eventually, regardless of efficiency standards on vehicles, and the CO2 will be emitted to the atmosphere. The climate effect of oil is nearly independent of how fast we burn the oil, because much of the CO2 remains in the air for centuries. [It is nevertheless important to improve efficiency of oil use, because that buys us time to develop technologies and fuels for the post-oil era, and high efficiency surely will be needed in the post-oil era.]

Avoiding dangerous atmospheric CO2 levels requires curtailment of CO2 emissions from coal. Atmospheric CO2 can be stabilized by phasing out coal use except where the CO2 is captured and sequestered, as is feasible at power plants. Indeed, agreement to phase out coal use except where the CO2 is captured is 80% of the solution to the global warming crisis. Of course, it is a tall order, as coal is now the world’s largest source of electrical energy. Over the next few decades those coal plants must be closed or made to capture their CO2 emissions. Yet it is a doable task. Compare that task, for example, with the efforts and sacrifices that went into World War II.