Graph of the Day - Why solving climate change is simple | RenewEconomy

Graph of the Day – Why solving climate change is simple

The challenge to address climate change often appears overwhelming. But are we trying to make it too complicated? Let’s imagine a bathtub filling with water. We need to turn off the tap and take out the plug.


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.

Screen Shot 2013-02-28 at 7.15.38 PM

“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.”

Screen Shot 2013-02-28 at 11.40.38 PM

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.

graph of the day

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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  1. Ben Elliston 8 years ago

    The late Stephen Schneider also used a bathtub analogy to explain GHG concentrations. It is an excellent one.

  2. Danial Ahchow 8 years ago

    I think this is just highlighting how difficult of an issue this is. Its hard enough for one country (Australia) to get its people and politicians on the same page, let alone the whole world!

    That said, it seems that Australia (at least) is reducing its energy consumption, or is that just media hype?

    • Chris Fraser 8 years ago

      Thankfully its not just media hype. Those countries that are investing in demand-side management are reducing their energy consumption. That and about 2GW of rooftop solar in Australia knocking out the afternoon peak. Those reductions are very measurable and thus cause the Coalition much angst.

    • concerned 8 years ago

      Danial,the reduction is about the slowing of the economy.No real growth.

    • Martin 8 years ago

      Not quite
      Unfortunately “Reducing energy consumption” is not the same as reducing GHGs. There is data to suggest a decrease in direct release of GHG’s from within Australia, but overall energy consumption has actually continued to rise. How come? Solar panels supplying the additional energy. It’s a small step in the right direction of course, not really due to a change in habits.

      Rapid GHG reductions in europe however do stem extensively from change in habits. Recessions do tend to work wonders in that regard!

      Further to the previous point, if we were to think GHG’s in a wholistic way, similar to how carbon footprints are calculated, then overall GHG release caused by Australians is in fact rocketing. We cant really stick our heads in the sand and pretend we have no responsibility for, not power to reduce GHG’s released in foreign manufacture of goods that we import.
      I’m not even going try and straighten out the spin we are shovelled about the vast volumes of coal we export.

  3. David Woodgrove 8 years ago

    Yep – the bathtub is a great analogy.
    A recent report also grabbed my attention and was simple to understand and went something like this….(was it a IPCC or World Bank report, and have I got it right?)…..

    To cap temp rises to a pre-run away scenario, we can only emit 500 another Giga Tonnes of CO2e. But there are already 2,500 G Tonnes of emissions soon to come from burning the coal, gas and oil under current mining leases.

    ….can we use coal as a soil supplement or making mud bricks rather than burning it?

  4. Craig 8 years ago

    I really think simple visual models help the majority, who are largely untrained in hard science, actually understand complex systems, and this is a beauty….

  5. Terry Wall 8 years ago

    As I tweeted just this morning:

    Neither geo-engineering or the Pope will stop rising temperatures. But planting trees and bio-char can, while adding food and water.

    Technology will I believe, deal to the expansion and continuation of carbon emissions. It is already well on the road and heaps of new break throughs are in final testing.
    This will not be enough I suspect, in stopping a very uncomfortable ride for humanity.

    So the CALL MUST GO OUT to all citizens to plant trees. The role of Governments should be restricted to allocation of appropriate land and it is all appropriate the current war footing that we should declare! Plus they should put in place clear rules and transparent monitoring of those who contribute in large enough areas to warrant reward through an emissions trading desk.

    OK, so let us get on with it.

    • Tim 8 years ago

      Maybe the Pope could help a lot. Encouraging contraception and small family sizes would be a good start.

      • Terry Wall 8 years ago

        Yes Tim, I guess if you think about it hard enough, the Pope could have such an influence, but it would be too little too late. Providing free and ongoing contraception alongside food aid would be more beneficial and having worked in East African droughts, a lot more appreciated.

  6. Jonathan Maddox 8 years ago

    Unfortunately the picture is missing the Rube Goldberg machine that dumps a whole lot of extra “water” (nobody knows quite how much) into the “tub” when it gets sufficiently warm : positive feedback mechanisms such as permafrost methane emissions and ice-cap albedo reduction.

    • Giles Parkinson 8 years ago

      I think Benoit would agree with both jonathon and suthnsun, but it’s about simplicity. He hasn’t for instance, allowed for what happens if Gina and Clive jump into the bath.

  7. suthnsun 8 years ago

    To my mind the graphic and accompanying sums are ‘gilding the lily’. We already have sufficient (excess) acidity in the ocean so around 11 Gt CO2 per year should not be going there (so should not be counted as a natural sink). We also have a full load of Methane Hydrates in the oceans which we desperately don’t want to be released. In addition we have 16 or 17 Gt increased loading of CO2 in the atmosphere every year for the last 10 years and already a precipitately high levels of CO2.
    So the sum is simple, we need to stop 28Gt CO2 p.a. from being released in the first place and we are currently emitting around 35 Gt globally . Hence we have a 7Gt allowance or roughly 1 tonne per capita.
    Whatever the history has been, we have to face the reality of the current situation and the sums dictate that at 7 tonnes per capita for China they need to cut by 85%, at 28 tonnes per capita for Australia we need to cut by more than 95% . .. etc.
    The situation is so dire from a risk perspective that we need to educate vigorously and urgently and act forcefully and coherently. Obfuscation and delaying action is in no one’s long term interest.

  8. Egor 8 years ago

    A simplified call for action is good but delivering that action is far from simple. Yes we can easily achieve 20% with efficiency gains and this is happenning. The next 20% is harder and the next 20% very hard. I am an advocate of biochar but like soil carbon what can be practically delivered is only very small fraction of simplified calculation.
    If you have tried to substantially cut your own footprint(including transport)you will know that once beyond the early gains you reach a choice between curtailing lifestyle or big investments with very long payoff periods. The reality is that this is going to hurt in costs of climate impacts or costs of emissions reduction and probably both. Until people are broadly prepared to pay or reduce consumption do not expect major emmision reductions.

    • Terry Wall 8 years ago

      That is a common response Egor but I would counter in this way:

      People on the land are very resourceful, accustomed to risk and decision making. Offer them an alternative way of earning a dollar with a well managed and honest Emission Trading Desk and you will be flabbergasted at how quickly they will destock (pay off debt) areas of their properties and plant faster growing trees using contour ripping and the like.
      Most are aware that much grazing land is over grazed and needs a rest. Most love the land they live on and they will readily help it heal, and do us all a great favour at the same time. They know that it takes trees to initiate rain and yes they need the rain.

  9. Andree L'Estrange 8 years ago

    I am so pleased to see bEnoit making this simple point! the work on reducing climate change effects needs to stop being splintered and become one united gavel to hit the Main Nail, which is reduction of fossil fuel use. The more united and focussed we are on that goal, the more likely it is to cross political lines…

    • Terry Wall 8 years ago

      Absolutely Andree, your comments hit the nail on head.

      The world NOW needs transparent and energetic leadership. As Al Gore says in his latest read “The Future” I think we are going to have to rely on a new form of change: The internet just might have the power to to rip the scabs off the democracy killing influence of corporations and their lobbyist minions. Without any understanding of the big picture this narrow minded abomination of capitalism has to be bought under control to give hope of change from above.

      At the same time, humanity has the power to change this imbalance, by pursuing active avoidance of companies that continue to f..k the world over. Make you healthier as well!

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