If we want to contain global warming, then we need to constrain carbon dioxide emissions within an appropriate ecological budget. We now know what that budget is.

According to a paper published by Malte Meinshausen and colleagues in NATURE last week and reported in the Financial Times, the Earth’s cumulative carbon dioxide emissions budget for 2000-2050 is 1,000 gigatons.

This budget would limit global warming to no more than 2 degrees C — the target that scientists and politicians have agreed to work toward in the negotiations for a new global climate change treaty.

Two degrees of warming will have significant consequences for people and nature, but would avoid more catastrophic economic and ecological impacts that would likely accompany further warming (see my recent Cool Green Science post on the specific consequences).

So how are we doing in terms of spending within our budget? Not very well according to Mienshausen’s report. Between 2000 and 2006, cumulative global carbon dioxide emissions were about 234 gigatons, and we continue to emit 36.3 gigatons every year. At this pace, we will exhaust the 1,000 gigaton budget by 2027.

To get back on budget, we have a choice. We can continue emitting carbon dioxide at current rates and then abruptly stop when we hit our 1,000 gigaton limit in 2027. Or we can begin reducing emissions now and continue reducing emissions gradually so that our carbon dioxide budget lasts until 2050. Obviously, the latter would be the smarter course.

But there is temptation to continue our profligate carbon spending and to exceed our 1,000 gigaton budget. Since the start of the Industrial era, we have been drawing liberally from the enormous carbon bank accounts that Mother Nature stashed away in the form of fossil fuels. If we were to burn proven reserves, Meinshausen estimates that we would emit between 2,500 and 3,000 gigatons of carbon dioxide, making global warming of more than 2 degrees C a near certainty.

Mother Nature is not going to tell us what to do. Will we stay within our carbon dioxide budget on our own?  Or will we overspend and risk the consequences of more severe climate change?

(Image: Smokestack in Japan. Credit: papadont through a Creative Commons license.)

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  1. If the Nature Conservancy really wanted to maximize its carbon budget, reduce CO2 rapidly, contribute to the objective of energy independence and eliminate the further rape of forests, it would take a serious look at the benefits of industrial hemp.

    One acre of industrial hemp produces four times as much pulp for paper than an acre of trees. One acre of industrial hemp produces 500 gallons of gasoline.

    With your clout and resources you should be able to get “Mr. Change That Matters”
    to repeal the DEA’s irrational restrictions on the cultivation of industrial hemp, which is not narcotic.

    Even if industrial hemp costs a bit more to process its benefits far outweigh those costs because more than 20,000 products can be produced with industrial hemp; as many or more than with petroleum.

    Industrial hemp needs no pesticides or herbicides and far less water than cotton and corn. It can be cultivated on marginal land and restores the soil year after year grown in the same acreage. We have the soil bank and 500 million unplanted acres in the U.S. that do not compete with food acreage. Using only 20% of that acreage delivers fuel for all of our transportation needs, all of our needs for paper products, and produces no CO2.

    If you really care about the near term future, you have to pursue cultivation of industrial hemp.

  2. I agree. The Nature Conservancy could do a great justice by educating it’s supporters about the uses and benefits of Industrial Hemp. You could fill pages upon pages about the uses and benefits of this plant, which is NOT Marijuana! I am almost 40 years old and never new until this year that such a plant existed. All one should do is do a general search to read the countless articles written about this plant. If most countries are growing this crop and producing items such as food, building products, car parts and fuel, then wouldn’t it make sense to look at the benefits to us in America. After all we are the number one importers of Industrial Hemp. Why pay to ship it hear from all over the world, when our farmers can grow it right here. This plant absorbs and stores Carbon Dioxide during its growing cycle which happens to be only about 100 days. If one acre of Industrial Hemp can yield as much paper making material as 4 acres of trees, imagine how many forests could be saved. Please research and educate the public.

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