Clean Power

Published on March 2nd, 2013 | by Giles Parkinson


Cut Off The Greenhouse Gas Emissions (Graph Of The Day)

March 2nd, 2013 by  

This article was originally published on RenewEconomy.

Addressing climate change is seen as the greatest challenge of our time – morally, industrially and financially. But are we making the problem too complex? Benoit Lebot, from the United National Development Program, certainly thinks so. He says we just need to cut fossil fuel use in half and plant more trees.

Lebot spoke this week at the 2nd Annual Australian summer study on Energy Efficiency and Decentralised Energy. He used this image of a filling bath tub to illustrate his point.

The world has agreed to limiting greenhouse gas emissions to 450 parts per million. It might have been better to cap them at 350ppm, but the world is already at 394ppm, and it currently has a big tap (actually composed of  billions of smaller ones) that is emitting 32 gigatonnes of Co2 equivalent a year. Natural carbon sinks and sequestration is taking out 15GT/Co2-e, and the gap is 17GT//Co2-e.

“The only way to stabilise greenhouse gas emission is to reduce the tap,” Lebot says. “Sure, plant some trees, but we have to reduce global greenhouse gas emissions by half. We are making things more complex than they are.”

Lebot says the level of greenhouse gases is determined by population, wealth, the amount of carbon in the energy system, and the efficiency of the energy system. The growth of the population and standards of living is inevitable, so the action plant needs to focus on the last two.

He proposes four wedges. The first two are a slight variation to the energy  efficiency narrative pushed by the likes of the International Energy Agency, because it includes a separate category of behaviour – changing the way we use the energy system.

This is combined with energy efficiency to create “energy conservation.” The other wedges are renewables and sequestration.

The complications come from deciding who should do what. As this graph to the    right shows, based on the amount of emissions per capita, the north (developed countries) should reduce their emissions by 80 per cent.

The south (developing countries), still need to grow their economies quickly, but in a more carbon constrained way than the north did.The south still has to cut emissions by 20 per cent.

Lebot’s concern is that delay simply makes the task harder. The most important thing is to accept size of effort that is needed. But this is something that politicians are reluctant to do.

The graph on the right shows the various trajectories. The red line illustrates a later start, requires more dramatic effort to make up for lost time.

“The more time we spend disagreeing, the harder the target,” Lebot says. ”When you start skiing, you never start on steepest slope.”

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About the Author

is the founding editor of, an Australian-based website that provides news and analysis on cleantech, carbon, and climate issues. Giles is based in Sydney and is watching the (slow, but quickening) transformation of Australia's energy grid with great interest.

  • Russell

    Nice to see it spelled out. Some things to add however about CO2 emissions and technology adoption.
    Its reasonable to believe that new technologies could not only make renewables competitive but much cheaper than fossil fuels. In that case, I expect rapid acceleration downwards of emissions to be entirely reasonable, and to happen equally in both developing and developed countries.

    In that case, the South may get much more than 20% just by following the lowest cost path. In that case, there wouldn’t ever be the case of emissions or CO2 levels stabilizing. Atmospheric levels would peak, then drop quite quickly and we wouldn’t ever get the temp that corresponds to that peak because of lag etc. This is called the transient climate response and I think it should be given more attention relative to achieving a stable atmospheric CO2 concentration, because there will be no stable CO2 level, it will peak, then drop quickly, perhaps even faster than it has risen if we suck CO2 from the air after we have stopped using fossil fuels.

  • With the feedback already “loaded’ into the system we need to be going for a lower goal sooner. A very simple graphic to explain a complex system. All it is missing is the fact that the drain is likely plugged a bit.

  • jonesey jonesey

    450 ppm, or 2 degrees C, would be a nightmare. Humanity will be devastated if we come anywhere close to it. We need to cut emissions much deeper and more quickly.

  • RobS

    Perfect, I have been looking for a simple explanation of this since your article on what our target should be for renewable energy penetration and people were saying we had to get to 120% and carry out major artificial sequestration otherwise CO2 levels will never stabilise. The reality is we only need to get emissions down below the ability of the natural carbon sinks to sequester carbon which according to this graphic is about 40% of current levels. Replacing 60% of emissions intensity with emissions free alternatives is far more achievable, the explosion going on in renewable technology is only going to accelerate.

    • Ronald Brakels

      If we cut greenhouse gas emissions by 60% we’d be a lot better off than we are now but stabilizing climate is not the same as stabilizing CO2 levels. If we cut emissions to a point where CO2 levels stabilize it means a lot of global warming will still occur. For one thing the oceans take a long time to warm up and they are currently protecting us from even higher temperatures, but as they warm that protection will decrease. Melting ice also has a similar effect, but there’s a limited amount of ice to melt. And CO2 sinks can become saturated and can depend on how much CO2 there is in the air. Roughly speaking we need to cut emissions by about 80% to avoid disaster, but as that doesn’t guarrantee avoiding disaster I think it might be a good idea to go carbon negative in the future. But that’s an issue for the future. When one is stuck in a hole, the first step is to stop digging.

      The people to avoid listening to are those who say since global warming has already occured it can’t be stopped there’s no point in doing anything. That is crazy talk:

    • Ross Chandler

      That’s predicated on the assumption that the natural sequestration will continue. With the risk of climate tipping points like the melting of permafrost it might be thrown into reverse.

      • RobS

        I agree, but the reverse is also possible, oceans previously too cold for significant algal growth could warm to the point of supporting blooms, and previously glaciated regions could become available for flora growth. I agree there are all sorts of tipping points and feedback cycles both positive and negative and where it will all end up is anyone’s guess. As a general rule I do think people underestimate the incredible homeostatic mechanisms of biological systems.

        • Ross Chandler

          I hope you’re right but I think it’s risky to assume a benign feedback allowing us to relax our ambitions for eliminating fossil fuels.

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