Five gigatonne globe

∑ 5 Gt CO2e

[Update: 22 January 2009] Some of the information in the post below is inaccurate. Namely, it implies that some level of continuous emissions is compatible with climate stabilization. In fact, stabilizing climate required humanity to have zero net emissions in the long term. For more about this, see this post.

As discussed before, credible estimates of the carbon absorbing capacity of the biosphere are around five billion tonnes (five trillion kilograms) per year of carbon dioxide equivalent.

The graphic above is probably far too nerdy to have popular appeal – and it is possible the numerical figure will need revision – but it does strike me as a concise expression of what needs to be tackled.

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.

28 thoughts on “Five gigatonne globe”

  1. According to Wikipedia, global emissions are 27,245,758 tonnes. That means they must be cut by over 80% to reach stabilization.

    The top five emitters, with values:

    United States: 6,049,435 tonnes
    China: 5,010,170 tonnes
    European Union: 3,115,125 tonnes
    Russia: 1,524,993 tonnes
    India: 1,342,962 tonnes

  2. The first symbol is an upper-case Sigma: a Greek letter. It represents summation.

    The remainder is just an abbreviated form of five billion tonnes of emissions, measured in carbon dioxide equivalent.

    I was trying to express the stabilization target as concisely as possible.

  3. Adapting to climate change: Now is the time to act

    Special to Globe and Mail Update

    October 15, 2007 at 1:47 AM EDT

    In recent months, global awareness on the risks associated with climate change has shifted drastically. Few would now dare to argue against the view that climate change does and will present an enormous humanitarian challenge. Even if progress was made in reducing the emissions of greenhouse gases, we should not forget that weather patterns have already changed, global temperatures have already risen and, above all, climate change is already taking a heavy human toll around the globe.

  4. The tar sands
    Canada’s version of liquid coal
    Posted by Joseph Romm at 7:27 PM on 11 Oct 2007

    Canada has about as much recoverable oil in its tar sands as Saudi Arabia has conventional oil. They should leave most of it in the ground.

  5. “If the royalties on the tar sands were allowed to rise to anywhere near the normal levels for oil-around 40%, not 1% — the entire industry would cease to be. The profit would vanish, simple as that. “

  6. Climate equity: Andrew Pendleton
    On how to divvy up responsibility for climate change

    “This is the climate equity challenge, and it must now be set in the context of largely non-negotiable global emissions reductions on the order of 80 percent by 2050. As an organisation that advocates on behalf of the world’s poorest communities, Christian Aid supports the least risky and therefore most stringent pathway to decarbonisation. Therefore, step one in defining climate equity is to set a global carbon budget, within which all countries, industrialised and developing, have a legal obligation to remain.”

    Pendleton leads the climate change policy work at Christian Aid.

  7. Michael Meacher, the former UK Environment Secretary, sets a stringent timeline:

    “Moreover, even this seemingly unreachable 60% cut by 2050 is still nowhere near enough. The
    latest science indicates that a cut of no less than 90% is necessary by the much earlier date
    of 2030 if we are to keep carbon concentrations in the atmosphere below 430 parts per million.
    The significance of this threshold is that above this level we may not be able to prevent some of
    the potentially catastrophic feedback processes from kicking in: such as the dieback of the
    Amazon rainforest, the release of billions of tons of methane hydrates from the ocean floor, or the
    collapse of the Greenland and Antarctica ice sheets. After that, nature takes over and the
    biosphere becomes the primary producer of carbon. The global warming process takes on a
    momentum of its own, beyond our control” (Meacher 2007).

    Many of the works surveyed in this report express this urgent view, and argue that atmospheric
    greenhouse gases should be reduced from the current level of 430ppm to 350-400pmm CO2e
    (Meinshausen 2005, Retallack 2005, Harvey 2006a), requiring further emission cuts to near zero.
    Britain’s Environment minister David Miliband says “essentially, by 2050 we need all activities
    outside agriculture to be near zero carbon emitting if we are to stop carbon dioxide levels in the
    atmosphere growing” (Miliband 2006).

  8. When the science tells us that, to have a high probability of holding total warming (since pre-industrial) to 2C degrees — a widely endorsed maximum, but by no means a “safe” one — global emissions must peak somewhere around 2015? When the more we overshoot 2C the faster we’ll need to pull down post-peak emissions, if, that is, we want to keep the warming to “manageable” levels? When, to quote John Holdren’s bitterly precise summary, “We already know the future, and it’s some combination of mitigation, adaptation, and suffering”?

  9. Wildfires turning northern forests into carbon-dioxide sources

    A group of U.S. researchers have found that wildfires — fuelled by climate change — may be turning boreal forests into sources of carbon dioxide.

    The boreal forests — found in northern Canada, Alaska, Siberia, China, Scandinavia and elsewhere — make up the second largest type of forest in the world behind the tropical rainforest.

    Scientists have historically believed that the boreal forests act as a carbon sink, as trees absorb carbon emissions and reduce them in the atmosphere.

    But new research from the University of Wisconsin-Madison, published in the Nov. 1 issue of the journal Nature, has found that the forests may be emitting more carbon than they are absorbing.

  10. Report: Carbon Removal Has Little Impact

    According to the new U.S. study, North America released 1,856 million metric tons of carbon into the air in 2003 — 85 percent from the United States, 9 percent from Canada and 6 percent from Mexico.

    At the same time, growing vegetation and other sources took in about 500 million metric tons of carbon.

    This is the first net carbon report for the region, said Tony King, lead researcher on the report and chief scientist at Oak Ridge National Laboratory.

  11. Evidence is fast mounting that time is running out for nations to unite in a credible response to climate change. The International Energy Agency said last week that energy-related emissions of carbon dioxide are set to grow from 27 gigatonnes in 2005 to 42 gigatonnes by 2030 — a rise of 56%. Other estimates project even higher growth, and also reveal, alarmingly, that ‘carbon intensity’ — the level of carbon emissions required to sustain a given level of economic activity — is actually growing again.


  12. “It’s not enough that we do our best; sometimes we have to do what’s required.”

    -Winston Churchill

  13. Nature 451, 297-298 (17 January 2008) | doi:10.1038/nature06593; Published online 16 January 2008

    A steep road to climate stabilization

    Pierre Friedlingstein

    The only way to stabilize Earth’s climate is to stabilize the concentration of greenhouse gases in the atmosphere, but future changes in the carbon cycle might make this more difficult than has been thought.

    “Industrialized countries are currently focusing on ‘climate mitigation’ policies that, when implemented, will result in reduced emission of greenhouse gases. It was recently proposed that by 2020 each of these countries should reduce emissions to 60–75% of the amount that they emitted in 1990; and by 2050, to 25–50% of 1990 levels. However, no such agreement was reached at the last UN Framework Convention on Climate Change Conference of Parties, held in Bali in December 2007. Nevertheless, these proposals, if acted on soon, are good news. But, to paraphrase Neil Armstrong, that’s one giant leap for policy-makers, but one small step for the global environment…

    From a glance at the global carbon cycle, it is clear that this reduction will not come close to stabilizing the concentration of greenhouse gases in the atmosphere. At present, deforestation and the combustion of fossil fuels release almost 10 billion tonnes of carbon into the atmosphere each year in the form of CO2 — the main greenhouse gas. Of this amount, about 4.5 billion tonnes accumulate in the atmosphere, and the rest is absorbed by the ocean and by land-based ecosystem. To stabilize atmospheric CO2 at the current concentration, emissions would need to be reduced to the amount that is taken up by the ocean and land — about 5.5 billion tonnes, which equates to an immediate 45% reduction in global emissions of CO2. This roughly matches the objective proposed for the industrialized countries for 2050, by which time considerably more CO2 will have accumulated in the atmosphere…

    In fact, climate stabilization might be even more complex. Recent observations and simulations indicate that the current uptake of atmospheric CO2 might be adversely affected by climate change. Careful measurements of the airborne proportion of anthropogenic emissions (that is, the proportion that remains in the atmosphere) show a small increasing trend in the past 50 years. Therefore, the proportion of anthropogenic CO2 absorbed by the ocean and the land is becoming smaller. The Southern Ocean might be responsible for this reduction, because changes in ocean-surface winds seem to have decreased the amount of CO2 taken up by surface waters in this region in recent years.

  14. “This environmentally concerned view needs to be taken up and followed through by a succession of post-Kyoto regulations in the coming decades that lead to larger and larger reductions in greenhouse-gas emissions and eventually to stabilization of Earth’s climate in a state that is safe for society and the environment. There is, unfortunately, no mystery: to stabilize climate, the concentration of greenhouse gases in the atmosphere must be stabilized, and to do so — given the limited capacity of the natural environment to absorb these gases — anthropogenic emissions will eventually need to be reduced to zero.”

  15. ‘Stabilizing climate requires near-zero emissions’
    A new climate science paper calls for dramatic action

    Avoiding climate catastrophe will probably require going to near-zero net emissions of greenhouse gases this century. That is the conclusion of a new paper in Geophysical Research Letters (subs. req’d) co-authored by one of my favorite climate scientists, Ken Caldeira, whose papers always merit attention. Here is the abstract:

    Current international climate mitigation efforts aim to stabilize levels of greenhouse gases in the atmosphere. However, human-induced climate warming will continue for many centuries, even after atmospheric CO2 levels are stabilized. In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires near-zero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures. As a consequence, any future anthropogenic emissions will commit the climate system to warming that is essentially irreversible on centennial timescales.

  16. The fraction of CO2 remaining in the air, after emission by fossil fuel burning, declines rapidly at first, but 1/3 remains in the air after a century and 1/5 after a millennium (Atmos. Chem. Phys. 7, 2287-2312, 2007).

  17. Here is an updated version of this graphic.

    Instead of calling for global emissions of five gigatonnes or less, it calls for an end to the changing concentration of carbon dioxide in the atmosphere. A graphic referring to zero change in the mean annual energy balance of the planet would be more accurate, but I don’t know how to express that idea concisely.

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