A trillion tonnes of carbon

Previously, I described how Andrew Weaver used different estimates of how sensitive the Earth’s climate is to greenhouse gasses to determine how many total emissions humanity can have without causing more than 2°C of warming. The 2°C figure is commonly cited as the level of warming that is unambiguously ‘dangerous’ – either because of the harm it would do directly or because warming to that point would kick off positive feedbacks that would then make the planet hotter still.

A new site simplifies this analysis, arguing only that: “If we are to limit global warming caused by carbon dioxide emissions to less than 2°C, widely regarded as necessary to avoid dangerous climate change, we need to limit total cumulative emissions to less (possibly much less) than” one trillion tonnes of carbon (equivalent to 3.67 trillion tonnes of CO2). This is probably too high an estimate, given that the IPCC estimates climate sensitivity to be between 3.6°C and 4.5°C. At the low end, that means we need to cap total emissions below 0.661 trillion tonnes of carbon; at the high end, the limit would be 0.484 trillion tonnes. The website estimates that our emissions to date are around 0.555 trillion tonnes.

In the event that actual climate sensitivity is a high but possible 8°C, cumulative emissions of just 0.163 trillion tonnes of carbon would be enough to produce 2°C of warming.

Still, ‘trillionth tonne’ is an accessible concept and it is interesting to watch the numbers update in real time. One especially interesting figure is this one: “We would not release the trillionth tonne if emissions were to start falling immediately and indefinitely at…” At present, their estimate is about 2.1% per year. A higher rate of reduction is necessary if the trillion tonne figure proves overly high.

Author: Milan

In the spring of 2005, I graduated from the University of British Columbia with a degree in International Relations and a general focus in the area of environmental politics. In the fall of 2005, I began reading for an M.Phil in IR at Wadham College, Oxford. Outside school, I am very interested in photography, writing, and the outdoors. I am writing this blog to keep in touch with friends and family around the world, provide a more personal view of graduate student life in Oxford, and pass on some lessons I've learned here.

13 thoughts on “A trillion tonnes of carbon”

  1. Note that Canada’s Athabasca Oil Sands are estimated to contain about 1.7 trillion barrels of oil.

    Forget about the emissions associated with mining and upgrading, for now.

    This site estimates that emissions from one barrel of oil are at least 0.317 tonnes of CO2 – equivalent to 0.0864 tonnes of carbon.

    As such, burning all of that oil would produce something in the realm of 0.15 trillion tonnes of carbon. If the trillion tonne cumulative total and 555 billion tonne total to date are correct, that means burning up all of the oi sands would represent about 34% of humanity’s total allowable emissions between now and the end of time.

    Of course, it isn’t economical to extract every last barrel of that oil. Even so, this rough calculation gives a sense of just how much climate change the oil sands of Alberta could generate.

  2. Oh, and if the climate really will warm by 8°C for each doubling of atmospheric CO2 (the high but possible estimate above), burning all of the oil sands would alone be sufficient to increase mean global temperatures by 2°C.

  3. Of course, we will fill in most of that circle burning coal. The oil sands will be useful, but not necessary, for breaching 1 trillion tonnes.

    Indeed, if we run out of conventional oil and replace it with liquid fuels made from coal, it could be even worse than fully exploiting the oil sands.

  4. Wikipedia says that: “With modern unconventional oil production technology, at least 10% of these deposits, or about 170 billion barrels (27×10^9 m3) were considered to be economically recoverable at 2006 prices, making Canada’s total oil reserves the second largest in the world, after Saudi Arabia’s.”

    Extracting only 10% of the oil sands would obviously be 1/10th as bad as the scenario above.

  5. Apparently, the world as a whole contains 909 billion tonnes of “proved recoverable coal reserves.”

    Also, “[c]omplete combustion of 1 short ton (2,000 pounds) of this coal will generate about 5,720 pounds (2.86 short tons) of carbon dioxide.”

    That means burning all the coal would generate about 2.6 trillion tonnes of carbon dioxide.

  6. Yes, coal is the enemy of the human race.

    Still, it is worth remembering that potential emissions from the oil sands are sufficient to have a notable impact on a planetary scale. By themselves, they could contribute more to total human emissions than Canada’s share of the population justifies, and of course Canadians will be emitting in other ways at the same time.

  7. Most oil sands production is intended for export. Surely the buyers bear some of the responsibility, as well.

    Canada is like a crack-addicted crack dealer with a huge supply of crack. While it might be virtuous to not sell all of it, some of the responsibility for the harm that accompanies its sale and use lies with the other addicts.

  8. Yes, the buyers are also morally responsible.

    That being said, if Canada had the fortitude to cut off the supply, we might be able to prevent a lot of suffering in future generations.

    If all fossil fuel producers imposed a carbon price – set at the net present value of the level of social harm to all future generations – on all fossil fuels extracted for dometic use or export, we could go a long way towards cutting emissions to zero.

  9. Burning fossil fuels costs the U.S. $120 billion a year — not counting mercury or climate impacts!

    “The report estimates dollar values for several major components of these costs. The damages the committee was able to quantify were an estimated $120 billion in the U.S. in 2005, a number that reflects primarily health damages from air pollution associated with electricity generation and motor vehicle transportation. The figure does not include damages from climate change, harm to ecosystems, effects of some air pollutants such as mercury, and risks to national security, which the report examines but does not monetize.”

  10. Do you think politicians will ever be courageous enough to do something like that? Especially politicians whose hearts are still in Alberta?

  11. From The Times
    November 4, 2009
    It’s a dirty business — the new gold rush that is blackening Canada’s name

    Canada faces a dilemma as it prepares for next month’s UN climate summit in Copenhagen. It wants to present itself as environmentally responsible but also wants the profits from the tar sands, which cover an area of Alberta’s natural coniferous forest larger than England.

    The sands contain 174 billion barrels of proven reserves, the world’s second-largest reserves after Saudi Arabia. With improved techniques, Canada hopes to extract between 315 billion and 1.7 trillion barrels.

    A Co-operative Bank study calculated that, even if all other carbon dioxide emissions stopped, fully exploiting the tar sands would still tip the world into catastrophic climate change by raising global temperatures more than 2C above pre-industrial levels. Extracting each barrel of crude from the sticky mass of sand, clay and bitumen produces two to three times as much CO2 as drilling for a barrel of conventional oil. The tar sands boom faltered a year ago as the oil price fell below the $60 a barrel at which the extraction process is profitable. Now, with oil at about $80 a barrel, hundreds of fortune seekers arrive each day in Fort McMurray, the oil equivalent of a gold rush town.

  12. “Amidst continued discussions on targets — whether to stabilize atmospheric carbon dioxide concentrations at 450 or 350 parts per million, and whether peaking global emissions by 2015 or 2020 will be enough to avoid catastrophic warming — a group of scientists suggested it would be easier to concentrate on one nice round number.

    The number? One trillion tonnes. That’s the limit we should place on our cumulative carbon dioxide emissions if we are to have a reasonable chance of avoiding warming above 2 °C, said Myles Allen of the University of Oxford and colleagues (Nature 348, 1163; 2009).

    Given that we’ve already released more than half a trillion tonnes since the year 1750, we have only another half-trillion tonnes to play around with. At current emissions rates, we’ll reach that number in 40 years.

    Politically, the trillion-tonne approach raises the risk that decision-makers will continue to put off action, reasoning that there’s no hurry as long as we stop before the trillionth tonne. But Allen and co-authors say the cumulative approach emphasizes that there is a hard limit to emissions and that the more we delay, the more drastic the action we will have to take as the trillion-tonne mark looms nearer.”

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