While all fossil fuels are contributing to the accumulation of carbon dioxide in the atmosphere, coal stands apart as really problematic, not just because of its CO2 emissions today (see chart, global emissions in millions of tonnes CO2 vs. time), but because of the vast reserves waiting to be used and the tendency for an emerging economy to lock its energy system into it. Global energy emissions I recently came across data relating to the potential coal resource base in just one country, Botswana, which is estimated at some 200 billion tonnes. Current recoverable reserves are of course a fraction of this amount, but just for some perspective, 200 billion tonnes of coal once used would add well over 100 billion tonnes of carbon to the atmosphere and therefore shift the cumulative total from the current 580 billion tonnes carbon to nearly 700 billion tonnes carbon; and that is just from Botswana. […]