Yesterday, I posted that the total budget of fossil fuel emissions we can ever emit is 1 trillion tonnes of Carbon. And that we’ve burnt through about half of that since the dawn of industrialization. Today, I read in the Guardian that existing oil reserves may have been deliberately overestimated by the International Energy Agency. George Monbiot explains how frightening this could be, given the likely impact of lower oil supplies on food production. Madeleine Bunting equates the reluctance to discuss this with the head-in-the-sand attitude that preceded last year’s financial crisis. Looks like the more pessimistic of the peak oil folks may have had it right all along.
None of these articles however makes the link to climate change (Monbiot only mentions it in passing in response to comments). So, which problem is bigger, peak oil or climate change? Does one cancel out the other? Should I stop worrying about the trillionth tonne, if the oil simply doesn’t exist to get there?
A back of the envelope calculation tells me that more than half of the world’s estimated remaining reserves of fossil fuels have to stay buried in the ground if we are to stay within a trillion tonnes. Here’s the numbers:
- Oil: The Energy Watch Group estimates there are 854 Gb (gigabarrels) of oil left, while industry official figures put it at well over 1200Gb). Let’s split the difference and say 1,000Gb (1×10^12). Jim Bliss calculates that each barrel of crude oil releases about 100kg of carbon. That gives us 0.1 trillion tonnes of Carbon from oil.
- Coal: Wikipedia tells us there are just under 1 trillion tonnes of proved recoverable coal reserves, and that coal has a carbon intensity of about 0.8, so that gives us 0.8 trillion tonnes of Carbon from coal.
- Natural Gas: The US EIA gives the world’s natural gas reserves as about somewhat over 6,000 trillion cubic feet, which converts to about 170 trillion cubic meters. Each cubic meter gives about 0.5kg Carbon, so we have 85 trillion kg, or 0.08 trillion tonnes of Carbon from gas.
That all adds up to about 1 trillion tonnes of carbon from estimated fossil fuel reserves, the vast majority of which is coal. If we want a 50:50 chance of staying below 2ºC temperature rise, we can only burn half this much over the next few centuries. If we want better odds, say a 1-in-4 chance of exceeding 2ºC, we can only burn a quarter of it.
Conclusion: More than one half of all remaining fossil fuel reserves must remain unused. So peak oil and peak coal won’t save us. I would even go so far as to say that the peak oil folks are only about half as worried as they should be!