Is coal burning the biggest contributor to climate change?
During a discussion this week about the legacy of the UK’s coal industry, I wondered aloud whether coal emissions were the biggest contributor to the world’s current excess of atmospheric carbon dioxide.
Coal has obviously played a huge role in our current crisis. Humanity has been burning coal in industrial quantities for longer than we’ve been burning similar amounts of oil and gas. And when burnt in power plants, coal emits about twice as much CO2 per unit of energy as gas.
But I did have a hunch that the rapid increases of oil and gas extraction since the mid-20th century might mean that coal’s contribution would now be outweighed by those other fossil fuels.
No one in the meeting could say for sure. And some later web searches didn’t turn up anything definitive. So I thought I’d crunch some numbers myself.
I found some global time-series emissions data from Our World in Data. And CarbonBrief offered some good analysis on which countries are historically responsible for climate change.
That analysis used data from 1850, about when the industrial revolution really started to take off. Carbon dioxide persists in the atmosphere for centuries so, tonne for tonne, those Victorian emissions are contributing to current warming just as much as last year’s.
By plugging the world numbers into Excel, it’s easy to plot annual emissions from coal, oil and gas.
Coal started early, but its annual emissions were passed by oil in the mid-1960s. Then, thanks primarily to quick’n’dirty coal-fired industrialisation in China and India, coal took the lead again at the start of this century.
Total emissions
But it’s the cumulative totals I want.
Carbon Brief’s analysis found that humans are responsible for over 2,600 gigatonnes of carbon dioxide emissions since 1850. Over two thirds of that came straight from our fossil fuel use.
Around 845 gigatonnes, or just under a third of the total, are from burning coal. Around 50 gigatonnes of historic coal emissions are from the UK, so we punched above our weight there.
Oil is meanwhile responsible for some 638 gigatonnes, and gas 276 gigatonnes.
But we usually treat the oil and gas industry as a single thing, so let’s add those totals together.
So my hunch was right – the oil and gas industry has produced more carbon dioxide emissions than the coal industry. The difference isn’t as much as I thought it might be, though.
And of course, the oil and gas sector’s total contribution to global warming is even higher than this simple analysis suggests. It’s also responsible for high emissions of other greenhouse gases – especially methane, which doesn’t linger in the atmosphere for as long as CO2, but has a much higher warming effect while it’s there.
Meanwhile, recent research from the International Energy Authority shows that coal demand is expected to fall again due to competition from more affordable sources including renewables and nuclear. But while we might be approaching a peak in total global emissions, the IEA also reports that gas demand is still growing.
Coal is undeniably filthy stuff, and the UK’s done well to take it out of the energy mix (decades after dismantling the domestic mining industry). The sooner that other countries get off coal, the better. But relatively speaking, it maybe isn’t quite the blackest of villains.