As David Spratt explained recently, the Australian Government is keen to boost its carbon mitigation credentials by claiming we are doing our part to avoid dangerous climate change. Australia’s current target — 5 to 25% reductions by 2020 on 2000 emissions levels, and a 60% reduction by 2050, sounds decent enough and will require transformative changes in energy use if it is to be achieved. Other developed countries have similar targets — Obama’s aim for the USA, for instance, is to get back to 1990 levels by 2020 and 80% lower by 2050.
We’re doing our bit, perhaps. But is this bit enough, or fair, or feasible, given the need for strong global cooperation and Australia’s current rejection of the nuclear energy option? No, no and no.
The problem with our emissions reduction target boils down to historical and current inequities. Let’s consider the year 2000 baseline — in that year, human-caused CO2e emissions were about 34 billion tonnes (Gt). For a world population of 6.5 billion people, that’s about 5.2 t per annum for each and every man, woman and child on the planet. What is Australia’s per captia emissions, relative to that world average? At about 25 t, it’s around 5 times larger. Other countries in the developed world range from about the same (USA, Canada) through to about half (UK, Germany) or even a third (France and Sweden — go those nukes and hydro!). As you can imagine, the developing world’s average is far lower — about 4 t for China, 2 t for India, 1 t for Bangladesh, etc.
Okay, I’m going to switch units on us now. For reasons of convenience that will become apparent in a moment, let’s re-express these figures in terms of carbon (C) alone. To do this, we can (roughly) divide the above figures by 3.66 (i.e., 44/12, being the molecular weight of carbon+oxygen+oxygen divided by that of carbon alone) — I’m subsuming methane, nitrous oxide, CFCs etc. in this approximation. So we have 9.3 GtC for the world in 2000 at a per capita rate of 1.4 tC and Australia at 6.8 tC.
Now, in a recent issue of Nature, there were a number of useful papers which explored the idea of total global carbon budgets. David Adam from The Guardian has done a good write-up of them here, and George Monbiot has reviewed the implications of their results for fossil fuel use, asking what it means in terms of how much coal, oil and gas we can afford to burn (answer: we can afford to burn only 33 to 61% of known [proven + provable] fossil fuel reserves between now and eternity). In essence, to have a 50% chance of avoiding 2C of global warming above pre-industrial levels (already a difficult challenge for adaptation), humanity can afford to emit only 310 GtC between 2009 and 2049, and a maximum of 400 to 500 GtC at any time between now and the point at which humans leave the planet (in whatever way this occurs). For a ‘good’ (>75%) chance of avoiding +2C, the carbon budget tightens to 190 GtC between 2009 and 2049.
Let’s assume the human collective throws caution to the wind (hey that’s a good bet based on current policies), and we shoot for that 50% chance of avoiding +2C. Under this scenario, we’ve got a 40 year carbon budget of 310 GtC, or about 7.75 GtC per year. If we were to lock emissions at 2000 levels, we’d get to 372 GtC, which already breaks the budget — and emissions have been growing by a few percent each year since that date, so we’ll be well over at this rate. Next, let’s assume that we instead peak in 2015 at 11.7 GtC (based on 2% growth from 2000 to 2008, 1% growth from 2009 to 2015) and then cause global emissions to decline at 1% pa from 2016 to 2019, 4% pa from 2020 to 2030, and 3% pa thereafter. This scenario assumes that we make the big inroads in the decade 2020 to 2030 (emissions in 2030 = 7.2 GtC) after ‘building momentum’ during the decade 2010 to 2019 (emissions in 2019 = 11.2 GtC), and it manages to stay within our 40-year budget of 310 GtC. The result is global emissions in 2050 being 4 GtC, or a per capita rate (assuming a population that has stabilised at around 9.5 billion people — mid-range UN projection) of 0.42 tC per annum. That’s a global carbon emissions reduction of 57% in 2050 compared to 2000 levels — almost spot on the Australian target of 60%!
Trouble is, Australia’s emissions were 6.8 tC per capita in 2000. If we are to contract to the global average by 2050 of 0.42 tC per person per annum, we’ll need to reduce our emissions by 94%. Not 60%, which is the current policy. This of course presumes that a global climate agreement emerges from the principle of shared and differentiated responsibility; akin to a contraction-and-convergence approach. Whilst I acknowledge that a C&C agreement is highly unlikely in its purest form, I still suspect that if we are indeed to achieve a peak CO2e concentration of 450 ppm (or lower), it will be on the basis of some agreement that is closer to C&C than anything resembling a full retention of historical advantages — which is what the current Australian policy implicitly assumes.
Of course if you want a 75% chance of avoiding +2C, the figures become tighter (about 80% global reduction by 2050 and 97% for Australia). If you take into account slow feedbacks, which imply a climate sensitivity that is higher than the mid-range estimate of 3C, or conclude that +2C is too much global warming, then the permitted carbon budget contracts still further — this is why Hansen and others are talking seriously about negative net emissions (with the help from geoengineering) well before 2100.
The bottom line: Australia’s target of 60% reduction by 2050 is not supportable on the basis of climate science, and should be rejected. A reduction of around 95% by 2050 implies a total decarbonisation of our electricity, construction, manufacturing and commercial sectors and transportation system, and a huge reduction in our agricultural sector. It will require something like this:
1. Early improvements in energy efficiency and conservation, and a substantial expansion of our use of renewable energy.
2. Large-scale adoption of nuclear power (around 75 to 100 GW will probably be required by 2050) based on fast spectrum and thorium reactors.
3. Metal-fuelled vehicles [combusting boron or aluminium in pure oxygen] (and perhaps a useful contribution of battery electric vehicles).
4. Plasma torches for municipal solid waste recycling.
5. Halt to deforestation (land clearing) and improvement in soil carbon retention.
6. Reduction in livestock methane emissions (probably by a combination of reduced stock and genetic engineering of methanogens).
All difficult, but all possible. My mantra is this: let’s be completely honest about facing up to both the carbon targets required and the means required to achieve them. The challenge, in terms of emissions reduction, is enormous. Given the magnitude of this extraordinary task, the means to get there will be only remotely possible if nuclear power plays a major role. If you are anti-nuclear, get over it, unless you are willing to leave a wrecked climate system as your legacy.