Emissions Nuclear Renewables

Six degrees of separation

earthhourHere is a piece I wrote that was published on 23 March 2009 in the Earth Hour special lift out of the Sydney Morning Herald and The Age.


If the planet is like an oven, it’s still possible to turn down the temperature, writes Barry Brook.

The number is 300 and the methods will be extraordinary. In 2007, a climate awareness campaign was launched by well-known environmental author Bill McKibben. It was coined, with the slogan “350 is the most important number on the planet”.

smhenviroThe figure refers to a target concentration of carbon dioxide (CO2) in the Earth’s atmosphere, in parts per million (ppm). This number was drawn from a recent study by a team of climate scientists, led by NASA’s Dr James Hansen. They showed that when long-term changes brought about by climate change are considered, the total global warming expected from a doubling of CO2 is about six degrees.

This is clearly of great concern, because even two degrees of warming could trigger irreversible melting of the Greenland and West Antarctic ice sheets and a rise in sea levels, a large expansion of tropical zones leading to persistent droughts in the mid latitudes (including southern Australia), and longer, hotter, more frequent heatwaves and associated hazards, such as bushfires. At anywhere approaching six degrees, it’s a completely transformed planet — a world hostile to most species.

So if we expect six degrees of planetary heating with a doubling of CO2, from 280 to 560 ppm, then the only way to avoid going over two degrees is to limit the rise of CO2 to about 350 ppm. Hence the slogan.

An obvious problem with this goal is that we are already over 350 — and skyrocketing. Current levels stand at 385 ppm and are rising about 2 ppm each year, due to industrial emissions (burning of coal, oil and gas) and land-use changes (deforestation).

Even without further acceleration in fossil-fuel use, this would take us to 470 ppm by 2050.

Yet global energy demand is expected to double by then and progressively less CO2 is being taken up by natural systems, as “carbon sinks” become saturated. So the hard reality is that we could be looking at 530 ppm by 2050 and a lot more in the following decades.

But there is another, more surprising, problem with 350. It’s the wrong number. While 350 ppm should give us a reasonable shot at avoiding more than two degrees of warming, that’s hardly a safe future to be aiming for. We need only to look at the impacts at less than one degree to know we’re already committed to some tough adaptation problems. These include more intense heatwaves, the rapid fall in Arctic summer sea ice, ongoing drought in Australia, sub-Saharan Africa and the western US, and the swift retreat of river-feeding mountain glaciers.

A target of 300 to 325 ppm CO2 — the levels of the 1950s — is necessary if we wish to cut additional warming and start to roll back the already damaging impacts. As such, 350 is not a target, it’s a signpost to a goal.

So we’re aiming at 350 but the real goal is 300 and we’re already at 385. Do we give up?

No. Think of it this way, if you turned your oven up to 180 degrees, left the thermostat on that setting for a few minutes then turned it back down, how hot would it be inside the oven? Hotter than before you turned on the gas, certainly, but it wouldn’t be close to 180. Because of inertia in the internal air and surface metals, it takes time to heat the oven. If you turn back that source of energy, the temperature drops again and never reaches the thermostat reading you had set.

So, too, with climate change. It takes time to heat the oceans and to melt ice. There are lags because of the amount of energy input it takes to heat these massive systems. If you turn back the source of heat — that is, reduce the amount of greenhouse gases trapping solar energy at the Earth’s surface — then you can prevent some of the warming you might otherwise have expected.

However, the higher we turn up the thermostat (that is, the more CO2 we release) and the longer we leave the oven on (time we take to cut emissions to zero), the closer the oven (Earth) is going to get to its final, thermostat-rated temperature (six degrees for a doubling of CO2).

Returning to 300 is possible but the actions required will be extraordinary. An emergency mode is needed, the likes of which we have not seen since World War II.

All the zero-carbon energy cards will need to be on the table — primarily advanced nuclear power but also renewables and geothermal sources and energy efficiency. We will need ways to pull extra CO2 out of the air through geological, chemical or biological engineering.

The response must be global and the solutions must work for all nations. Anything less and the thermostat will be set too high for too long. That’ll leave a future none of us will care to live in.

Barry Brook is Sir Hubert Wilkins chair of climate change and director of climate science at the University of Adelaide’s Environment Institute. He runs a blog at

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By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

26 replies on “Six degrees of separation”

As begun at the end of the Solar Fraud thread …

… carbon sequestration via alkiline earth silicates such as olovine and serpentine, as opposed to extracting CO2 from the atmosphere for liquid fuel synthesis …

Oh right. One gets tired of repeating oneself. Why don’t you do it? Or David B. Benson, since as I recall he has independently come to the same conclusion.

Alkaline, olivine.

Much of my alkaline earth silicate chattering is appended here.

(How fire can be domesticated)


Needed: One location for each major area that needs to be developed — for the discussion, for the science, for the financing, for the policy work.

Yeah, one for olivine/serpentine. Figure out how it’d work; figure out whose landscape gets used; figure out who’d pay.

One for convincing some company somewhere to try to get a Gen4 reactor permitted. Same thing.

And so on.

What can individuals contribute? Lives, fortunes, honor.
As and when available.

Right now we’ve got a mess of fragments and a maze of pointers. Good start.

I do see people each with their own enthusiasm getting past the stage of going from blog to blog talking them up.

How can these folks be encouraged to put it all in one place?

And can they be ready for the inevitable, when businesses move in, put the founder out to pasture, and take over their idea as something to really build?


Two problems Barry.
The thermostat analogy is logical but thermal inertia in the
system already will take a long time to be countered. Do we have the time.
Also – the biggest problem – the decisions are in the hands of politicians and it is clear already that they are treating it as a political problem. As Tim Flannery suggests, we need to get the world onto a ‘war footing’ and there is no sign of that. Even the opportunities provided by the financial disaster to shift to a ‘green energy structure’ are being avoided.


It’s strange how cyclones, firestorms and coral bleaching events don’t seem to galvanize people out of apathy. Therefore I think hard decisions will be postponed until the ‘war footing’ is tenable, in other words a matter of do or die. If there is no spare cash left by then something akin to war bonds and lotteries may be needed to raise capital. The only trouble is after the ‘war’ the IFR led recovery will be too late for many.

Re silicate weathering I doubt there is an easy path to lower net CO2. Near home an open cut has been dug in serpentine (looking for PGEs) using lots of greenhouse unfriendly diesel and ammonium nitrate. The exposed magnesium carbonate veins are dissolving out and will end up precipitated in mud I presume. We’re talking eons not decades.


Alkaline, olivine.

Thanks for the correction. It was a late night, and I typed in haste.

Oh right. One gets tired of repeating oneself. Why don’t you do it? Or David B. Benson, since as I recall he has independently come to the same conclusion.

I’m not opposed to the idea if it works. I’m all for a plethora of viable options, as long as aforementioned plethora doeas not result in paralysis.

But why did you respond to me in a different thread from the one in which I replied to you?

I would like to think that we are, in the end, on the same side.


Unfortunately, it would be very difficult for Australia’s electrical generation to become carbon negative in the short term. However, it would be easier in the medium term, say over the next five years. To achieve this I’d recommend an immediate $100 a ton carbon tax with its revenue equally distributed to all Australians. This tax can be increased as necessary to achieve carbon emission reduction goals.

A $100 a ton carbon tax would increase the price of electricity from coal and gas by about 3 cents and 1.9 cents a kilowatt-hour respectively. This would make low emission generating capacity much more competitive. It would result in a very large expansion of wind capacity and increase the amount of wind power the grid could economically support, as wind power would still be profitable even though the periods of time when strong winds combine with low demand to push the price of electricity towards zero would increase as its capacity expands.

With a $100 a ton carbon tax, many things would become cheaper to burn than coal and gas, so biomass would be used in some existing fossil fuel plants. Fortunately Australia has the capacity to replace a significant portion of its coal and gas use with biomass. The decline of the sheep and cattle industries that would result from the carbon tax should free up land that could be used for biomass production. A small percentage of carbon in solid biomass is trapped as ash when it is burned, so the process would be slightly carbon negative.

At $100 a ton, several carbon sequestration methods should become profitable. For example it should be worthwhile to add char to soil in many areas to improve agricultural productivity.

Efficiency measures and demand management would help. A shift towards charging consumers minute-by-minute wholesale prices multiplied by a factor that pays for transmission costs, would encourage efficiency and allow a greater amount of intermittent energy to be supplied to the grid. It would also make it cost effective for many people to use smart appliances that have a greater portion of their power use during periods of low electricity prices.

While the electricity generation could be made carbon negative in five years, making the transportation sector carbon negative is more difficult and might take twice as long and much higher carbon taxes.


A couple of factors:

(1) The CO2-equivalent values are higher by ~ 50 ppm due to methane, i.e. the present level is close to ~ 440 ppm CO2-equivalent.

(2) Due to positive feedback processes, including carbon gas release from the biosphere and warming water and methane leakage from bogs, permafrost and shallow sediments, no CO2 value (300, 350 or 400 ppm) can be assumed to remain “stable” or “fixed”. Further, ice melt/warm water interaction and albedo change result in further polar warming, affecting the rest of the globe, in turn resulting in further release of carbon gases.

It is the magnitude of carbon and ice/water feedbacks which explain the glacial terminations (Roe, 2004; Hansen et al., 2008).

Untile recently the sensitivity of the atmosphere and the role of feedbacks have been grossly underestimated, with implications for current climate change and potential tipping points.


Andrew, not quite. Yes, there are various other GHG that raise the CO2-e, but there are also aerosols that lower it. Current CO2-e — that being ‘felt’ by the climate system — is around 375-380 ppm. At present, when speaking about CO2 or CO2-e, you end up talking about the same climate forcing effect. If we end up reducing aerosols, then of course we must also reduce the non-CO2 GHG +ve forcing agents too.

We can safely assume that 280 ppm does not kickstart the feedbacks to which you refer. Thus I think an extra 20ppm above that is a reasonably ‘safe’ target. 350 might be okay too — but that seems to be the point at which the Arctic sea ice started its downwards trend to eventual oblivion.


Peter Wherret died this week.
He is largely remembered for his infatuation with driving cars. I remember him more for his series on ABC TV 20 years ago (The Drive for Power). It was a set of 30 minute programmes on energy resources. I especially liked the fact that he gave equal prominence to CONSERVATION as a resource.
It is readily available, everyone can be involved and not only does it not cost anything, it actually saves money!
While we struggle to find alternatives for coal – nuclear, solar, geothermal etc. – the quickest way to actually making an impact is surely CONSERVATION. The global financial mess is demonstrating this to some extent and insulating homes as well as phasing out incandescent lamps will also help, but we might really need a well thought out and properly integrated conservation programme. This is supposed to be the point of an ETS but if the scheme as proposed is going to compensate everyone, it is hard to see much conservation actually occurring.


Well, at 288 ppm CO2 (I don’t know the methane level) in 1850 CE the Little Ice Age came to a end as the Swiss glaciers stopped growing. By 315 ppm CO2 (ditto methane) in 1958 CE, Swiss glaciers were melting back, in retreat at about 4 m/yr; also, Greenland started, just started, melting.

So 325 ppm seems too high to me.
RIght around 300 ppm is maybe optimal.


Regarding enhanced mineral weathering.

In situ peridotite weathering:

It may be that the only substantial cost is shipping flue gas to the chosen (near-surficial) rocks. Unfortunately, flue gas is only about 14% carbon dioxide, so this isn’t as inexpensive per tonne of CO2 as it might seem. Still, I don’t know of a better idea which could be adopted on the scale required.

The only environmental cost, AFAIK, is that the disposal site will swell up rather considerably.


David B. I think the better idea is not to generate the CO2 in the first place.

Recent TV showed an oil and gas company (Conoco) claiming an offset by paying aborigines to regularly set fire to scrub. The theory was this practice emits less CO2 than irregular wildfires caused by lightning for example. I’m unconvinced. The whole CO2 absorption issue is getting far fetched and in my opinion borders on fraud if there are financial benefits.

I say forget all alleged forms of enhanced CO2 capture and let earthbound carbon stay there.


There is a map of CO2-hungry silicates’ occurrence in North America here.

‘Finrod’ said,

I’m not opposed to the idea if it works. I’m all for a plethora of viable options, as long as aforementioned plethora doeas not result in paralysis.

But why did you respond to me in a different thread from the one in which I replied to you?

I would like to think that we are, in the end, on the same side.

We’re definitely on the same side in re fossil fuel replacement. Perhaps we disagree on what to do about all the fossil fuel ash already in the air, and destined yet to go there despite us. Do you have some reason to think Mg_(2-2x)Fe_2xSiO4 dispersal wouldn’t work significantly better than any other method? We know particles small enough to take a few hours to fall a few kilometres through air react plenty quick enough: one to four years for zero ‘x’, otherwise faster.

That other thread was a long-in-the-tooth solar power thread. CO2 downsnatching seemed more on-topic here.

(B: a better energy carrier than H2?)


I sketched out a plan for capturing 1% of the excess carbon emitted in 2007, 100 MtC. I’ll use half of your Nullarbor Plain to grow algae in tanks at an assumed 10 t C/ha/yr, closed loop (except water) via the abstract formula

CO2(air) + 2H2O –>
O2(air) + (CH4 + CO2)(captured)

separate the methane from the acid gas to obtain 387 MtCO2 ready for sequestration and 533 MtCH4 = 743 Mm^3 CH4. That’s far more than is necessary to run the process using sea water, so the rest goes to market. To set in perspective, according IEA 2006 statistics, 80×10^(-9) of world prodcution of natural gas.

Suitable nearby ultramafic rocks occur in Weat Australia (nothern interior) and massive amounts of it in Papua New Guinea, enough and more to weather out all of the excess carbon added so far, about 500 GtC.

THe saleable product from this enterprise include brine for extraction of mineral salts, methane and some form of excess carbon dioxide removal fee (if anybody is paying that). I don’t know what the ROI might be, but it might make some money. Any takers there in Oz?


A very clear and useful article, Barry, but how can you support nuclear energy? The waste and security issues alone pose incredible challenges to the safe use of this technology, and uranium is itself a finite resource.

I’ll have a look at your posts on the nuclear option, but for the moment I’m very much persuaded by the arguments put forward by Professor Ian Lowe in his Quarterly Essay, ‘Reaction Time’. I also still have an image burnt in my head from a photo my father took at the end of the Second World War – it shows a human image burnt into the steps of a building in Hiroshima a year after the atomic bomb.


If you take the time to read the posts on IFR and maybe read Tom Blees book “Prescription for the planet” you will find that your misgivings are addressed and answered. You can also listen to some radio interviews by Tom and others which will clarify new gen nuclearin an easy format. To access these click on Barry’s previous post entitled “Fast Reactor Radio” which provides the links.
I, too, was stridently anti-nuclear, but have been converted, and am convinced the we will need this technology, along with renewables, to save ourselves from the climate change holocaust ahead, if we don’t act decisively.The planet will go on, in some form, without us!


Wasn’t suggesting yours was “strident”- however, if a “strident” opposition to new nuclear can be overcome, as in my case, your rational views against are almost sure to be persuaded. Great that yoou have an open mind!Happy reading!


I’ve read Ian’s “Reaction Time”. His arguments against nuclear power are lightly documented, not based on new technology, and suffer from a number of logical flaws. I have great respect for Ian on many matters, but with regards to nuclear power and what it can do to alter our climate trajectory, we are at opposite poles.

I agree that Hiroshima was a tragedy. But this is not relevant to whether the future is powered by atomic energy. Indeed, a hard nosed analysis suggests that the number of lives lost is not even the persuasive argument, given that the casualties estimated for Operation Coronet and Olympic, if they had needed to proceed, was far worse:

A study done for Secretary of War Henry Stimson’s staff by William Shockley estimated that conquering Japan would cost 1.7 to 4 million American casualties, including 400,000 to 800,000 fatalities, and five to ten million Japanese fatalities. The key assumption was large-scale participation by civilians in the defense of Japan

This is by no means an argument for nuclear weapons — and today’s stockpile nuclear weapons could inflict far more deaths than any conventional war. But that wasn’t true at the time of Hiroshima, which is another reason why it is not a relevant example today. And another reason to dismantle today’s weapons stockpile and burn up the plutonium in fast reactors such that it is never again a problem for us.


Supplementary to the good responses Lewin-Hill has already received, this,

I also still have an image burnt in my head from a photo my father took at the end of the Second World War – it shows a human image burnt into the steps of a building in Hiroshima a year after the atomic bomb.

refers to a bomb that had no connection to any nuclear reactor of any kind.

If the CP1 experiment under Stagg field had never been done, Hiroshima or a city like it would have burned just the same, and if someday all the cities on Earth are powered exclusively by wind turbines, every city will still, and forever*, be under that threat.

— G.R.L. Cowan
Internal combustion made continent

* OK, not strictly forever, but for many hundreds of millions of years.

Let one half-life of 238-U go by and the Sun will probably still be stirring up wind, but natural uranium’s 235-U atom fraction will have diminished, because one of 238-U’s half-lives is 6.348 of its, to 0.018 percent from its present 0.72 percent.

So wind-powered clandestine separation of this now much smaller trace will be much harder. Perhaps as hard as the membrane-diffusion enrichment that was done to get the material for the Hiroshima bomb.


The following letter informed in part by Professor Barry Brook’s excellent article is being variously sent to climate activists, media and governments around Australia and around the World re Australia-based and its 300 ppm CO2 target for a safe planet (as opposed to the 350 ppm target of the US-based

Dear Sir/Madam,

Positive feedback effects from man-made global warming are accelerating climatic disruption, increasing the threat to humanity and decreasing the time for effective action to save the planet.

Major examples include the albedo flip involving replacement of light-reflecting sea ice with dark, light-absorbing ocean in the Arctic and Antarctic; the ticking methane bomb involving CO2-driven global warming causing tundra melting and release of methane that is 21 times worse than CO2 as a greenhouse gas on a 100 year scale; increased storm intensity causing loss of the Southern Ocean as a major CO2 sink; and present climatic disruption causing destruction of major forest carbon sinks due to greatly increased forest fire extent and insect herbivore population explosion.

Just as the latest scientific discoveries have supplanted IPCC predictions of 2007 (e.g. the Arctic summer sea ice is now predicted to completely go by 2013 rather than in 2100) so climate activism is also being rendered out of date. Thus US-based advocates reduction of atmospheric CO2 from the present 387 ppm to 350 ppm based on the upper estimate from NASA’s Dr James Hansen in 2007.

However now Australia-based urges a goal of 300 ppm atmospheric CO2 for a safe planet, informed by the latest from Dr Hansen and many other top climate scientists – notably, Australia’s Professor Barry Brook who says “The number is 300” and that “350. It’s the wrong number” (see: ).

Dr Gideon Polya

Macleod, Melbourne, Victoria 3085, Australia


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