How Much Should We Leave in the Ground?

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The Guardian/UK

How Much Should We Leave in the Ground?

The two papers on carbon emissions published in Nature last week were ground-breaking: they show us how much carbon dioxide we can produce if we're to have a reasonable chance of preventing two degrees of global warming. It's a completely different approach from the UN's and national governments'. They set targets for reductions by a certain date but have nothing to say about the total amount of carbon we can release.

One of the papers, by Myles Allen and others(1), suggests that we can burn, at most, another 400-500 billion tonnes of carbon at any time between now and the extinction of humanity if we want to avoid two degrees of warming. The other, by Malte Meinshausen and others(2), suggests that producing 1000 billion tonnes of CO2 between 2000-2050 would give us a 25% chance of exceeding two degrees. That's a lot less than Allen's estimate, as one tonne of carbon produces 3.667 tonnes of CO2 when it's burnt: 1000 billion tonnes of CO2 arises from 273 billion tonnes of carbon.

But let's err on the side of valour and use Allen's figures. Moreover, let's disregard all other greenhouse gases (which, he suggests, should reduce the total CO2 budget to under 400 billion tonnes). How does his maximum allowance of carbon compare with known reserves of fossil fuel?

Let me make two things clear before I make this calculation. First, reserves are not the same as resources. A resource is the total amount of a mineral found in the earth's crust. A reserve is the part of the resource which has been identified, quantified and is cost-effective to exploit. In most cases this is likely to be a small percentage of the total resource.


According to the World Energy Council:

global reserves of coal amount to 848 billion tonnes(3)


global reserves of crude oil are 162 billion tonnes(5)






848 x 0.746 = 633


177,000 x 0.00049 = 87


162 x 0.605 = 98



Or, using Meinshausen's figure, we can burn only 33% between now and 2050. Sorry - 33% minus however much we have burnt between 2000 and today.


The test of all governments' commitment to stopping climate breakdown is this: whether they are prepared to impose a limit on the use of the reserves already discovered, and a permanent moratorium on prospecting for new reserves. Otherwise it's all hot air.













George Monbiot

George Monbiot is the author of the best selling books The Age of Consent: a manifesto for a new world order and Captive State: the corporate takeover of Britain. He writes a weekly column for the Guardian newspaper. Visit his website at

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