The Carbon Economy

One of my goals in my peak oil studies is to understand the whole system of planet+economy as best I can. I want to develop an informed opinion on what humanity's options are as it faces these interlocking crises-in-the-making. That's obviously an enormous task. The relevant disciplines include at least geology, petroleum engineering, economics, sociology, urban planning, international development, climatology, demography, political science, mining engineering, military strategy, archaeology, history, chemistry and chemical engineering, physics, statistics, biology, ecology, agricultural science, and electrical engineering. No-one can hope to master all these subjects to the point a specialist in them would know them.

And yet it seems to me that, while accepting this limitation, it's worthwhile for a few generalists such as myself to attempt to try to understand the situation as deeply as possible in all aspects; it may be that new ideas and insights can only come from deeply integrating a number of the important perspectives. Only time will tell.

In that spirit, I'm trying to understand the carbon cycle and in particular the current carbon flows in the economy. I have two goals - one is to better understand the debate over the viability of biofuels. The other is to better understand whether we have any real options over climate change other than just suffering the consequences of our collective fecklessness. Either way, I can never make any sense out of any debate like this until I start to understand the relative sizes of the flows involved, and the trends in them.

This post is the first in a series of (so far) four on the carbon cycle and carbon in the economy which I'll be putting out one per day this week (if I can finish them fast enough anyway).

Let's start by looking at the overall planetary carbon cycle, which is summarized in a nice graphic from the Wikipedia. (I also recommend the more detailed version in the 2001 IPCC report).

Earth's carbon cycle with stocks in Gt (Gigatonnes), and flows in Gigatonnes/year. Click to enlarge. Source: Wikipedia. Click to enlarge.

The black text represent the stocks of carbon in the system in gigatons (billions of metric tons/tonnes). To give you a feel, one gigaton of carbon is the amount of carbon in about 8-9 gigabarrels of oil. So when the world is currently producing about 30 Gb a year of oil, that is a little less than 3.5 Gt of carbon (just in the oil), most of which is released into the atmosphere in the form of CO2. (However, the quoted weight is just that of the carbon in the CO2, not the oxygen chemically bonded to it).

There are 750 Gigatons of carbon in the atmosphere, an enormous 39000 Gt or so in the ocean, about 610 Gt in vegetation, and another 1580 Gt in soils. Finally, there is a huge amount in the earth's crust.

Actually, the atmosphere is likely up to about 800 Gt now - the Wikipedia's numbers are a little out of date in this and a couple of other respects, as we'll see.

Anyway, the purple lines and numbers represent the flows in the system. We'll focus on the flows in and out of the atmosphere, as that's where our big problem is. Carbon leaves the atmosphere through two main routes, the ocean, and vegetation. The ocean exchanges about 90 Gt/year with the air, but there's a net sink of about 2 Gt/year. This is because humans have increased the CO2 concentration in the air, the ocean is not in equilibrium with it, and there's a net flow into the ocean (which should increase further as atmospheric concentration goes up further).

More interesting is the exchange with the biosphere. Plants absorb about 120 Gt of carbon/year and turn it into sugars via photosynthesis (and then onto other materials). This is the gross primary production of photosynthesis in the biosphere. Of this, the plants themselves burn about 60 Gt of carbon (in the form of sugars) to power their own operations, so that is released out into the atmosphere again immediately. The remaining 60Gt or so is called the net primary production. Almost all of the net primary production ends up going into the soil (a small amount passing through some animal on the way), but humans use and burn some of it. The soil releases back pretty much all of the carbon influx through the action of decay organisms. The (biosphere+soil) system as a whole is pretty much in equilibrium with the atmosphere, but not quite. According to the 2001 IPCC report), there is a net release overall of 0.2Gt/yr of carbon from the (biosphere+soil) because of the actions of humans (but there has been considerable uncertainty on this issue historically). Again, these numbers are a little out of date (more below).

Since 610 Gt is stored in the biosphere, about 20% of the carbon there turns over annually - this represents a weighted average of annual crops and weeds together with redwood and bristlecone pine tree trunks. The main net flow into the atmosphere is that 5.5 Gt/year in fossil fuel burning that the Wikipedia has. However, this next graph contains more accurate information with the trend over time:

Carbon emissions in Gt/year 1850-2004. Click to enlarge. Source: ORNL through 2002. 2003-2004 were estimated by scaling the 2002 numbers by the appropriate percentage increases in coal, oil, and natural gas from the BP annual production numbers.

As you can see, we are at 8Gt/year now, and climbing fast. I started with this graph that goes back all the way to 1850 so you can get a sense for how much of the emissions have been since 1950. I also want to draw attention to the fact that this net flow is not yet enormous compared to the exchanges in the system - eg it's significantly smaller than the 120 Gt that runs through the biosphere each year (although as we shall see, it's quite a bit larger than the amount of carbon entering the economy from the biosphere currently). Let's now focus in just on the timeframe since 1960:

Carbon emissions in Gt/year 1960-2004. Click to enlarge. Source: ORNL through 2002. 2003-2004 were estimated by scaling the 2002 numbers by the appropriate percentage increases in coal, oil, and natural gas from the BP annual production numbers.

The big uptick in Chinese coal production is very clear after 2000, and the big run-up in oil production from 2002-mid 2005 adds to it. As you can see, the implementation of the Kyoto protocol is not having a dramatic effect on the overall world emissions yet - the trend is going exactly in the other direction. We'll take up Kyoto further in a future post.

Before we move onto looking at how much impact this has on the atmosphere, let's briefly discuss how we might extrapolate this into the future. Obviously, peak oil is going to have an effect on the oil piece of the picture. However, since I currently favor the slow squeeze idea, I think that, while there might be a significant transitional reduction in carbon emissions due to peak oil, over the decades-long timescale we'll see the carbon emissions continue to grow. Initially, natural gas will take up some slack, but the big issue is this:

Ten countries with the largest 2004 coal reserves, in Gt of coal. Click to enlarge. Source: BP.

As you can see, with 1000 Gt of coal reserves (which is probably somewhere in the range of 600-800 Gt of carbon), we can keep up a high rate of emissions for a long time to come. And then there's the tar sands, Orinoco belt oil, oil shale, 3000 Gt of coal under the North Sea, etc. These sources are capital intensive, so they cannot be exploited quickly. But slow declines in oil production will allow them to be brought online as alternatives. And at a minimum, I think we have to assume that the Chinese can keep up a healthy rate of growth in their coal production (running at 10% annually recently). Furthermore, to the extent coal displaces oil, coal has more carbon per Joule of energy than oil. As many of us have studied, energy usage is very price inelastic and tends to have income elasticity close to one - so it grows with GDP and it takes an awful lot of price to change it much. Similarly, this inelasticity corresponds to enormous political resistance to reducing fossil fuel usage.

All in all, keeping it simple, I'm just going to assume that we can linearly extrapolate the trend of the last 45 years into the future for a "business-as-usual" scenario where the world make no effective attempt at emissions control. I've also put in an exponential extrapolation, and the line that would happen if the world could keep fossil fuel emissions constant at the 2004 value.

Carbon emissions in Gt/year 1960-2004, together with linear, exponential, and constant extrapolations through 2050. Click to enlarge. Source: ORNL through 2002. 2003-2004 were estimated by scaling the 2002 numbers by the appropriate percentage increases in coal, oil, and natural gas from the BP annual production numbers.

Obviously, there is a great deal of uncertainty here, but the linear extrapolation is probably as good as any other. At any rate, the area under that purple curve is significantly less than the world's existing coal reserves alone, never mind the alternative hydrocarbons. So there's no physical barrier to humanity releasing this much carbon. The exponential curve would use up all the existing reserves of coal by 2050, so we'd be mining for coal under the ocean. Hence it's probably a very generous upper bound on what the economy could actually do. Similarly, the constant (blue) line seems quite hard to square with the implications of Chinese cement production. The global economy is not on track to control emissions like this any time soon.

The effect of burning this stuff is as follows:

Annual average concentration of CO2 in the atmosphere since 1959 as measured by Keeling et al in Mauna Loa, Hawaii. Graph is not zero-scaled. Click to enlarge. Source: Keeling via ORNL.

Now, the mass of the atmosphere, according to the Wikipedia again is 5.1 million gigatons, and almost all of that is well-mixed on the relevant timescales. So we can take those measured percentages, and convert them into a net uptake of carbon by the atmosphere. (If any reader should decide to check my calculations here, remember that the ppm numbers are by volume, and you have to correct for CO2 having higher molecular weight than the other species in the atmosphere, and you only want the tonnage of carbon, not CO2).

So then I get this graph. The green line is the fossil carbon emissions, the plum line is the net addition to the atmosphere according to the CO2 measurements, and the blue line is inferred difference - the sink of CO2 because the atmosphere is out of equilibrium with the other components of the system (together, possibly, with any net effect of humans on the biosphere).

Carbon emissions in Gt/year 1960-2004, together with net increase in carbon in the atmosphere, and the implied "sink" of carbon via all other processes. Click to enlarge. Source: carbon emissions from ORNL through 2002. 2003-2004 were estimated by scaling the 2002 numbers by the appropriate percentage increases in coal, oil, and natural gas from the BP annual production numbers. Annual average concentration of CO2 in the atmosphere as measured by Keeling et al in Mauna Loa, Hawaii via ORNL.

Notice that the sink is a significant offsetter of the fossil fuel emissions, but is quite volatile year-to-year. This makes sense if you think about the fact that there's big exchanges in the system. Eg. 120 Gt/year of carbon fixation by plants is offset by a similar amount of carbon release due to respiration by plants, animals, and microorganisms in the soil. It doesn't seem hard to believe that fluctuations in weather, etc, could cause that system to be different than its average by a few percent either way in any given year. Likewise, CO2 exchange with the ocean must involve deep upwelling waters with low concentrations of CO2 taking on more carbon, and CO2 rich water giving up carbon to winds that had crossed rural areas and lost carbon to plants. The vagaries of currents and weather could cause significant fluctuations in this also.

In the graph, it rather looks to me as though the overall volatility in the absorption of CO2 is increasing over time.

Now this net sink of carbon has spawned an enormous scientific literature trying to measure, study, model, and project it. I am going to cheerfully short-circuit that literature and develop a simple planetary-engineering rule-of-thumb for it instead. I hypothesize overall that the annual sink of carbon into the non-atmosphere components of the system should be roughly proportional to the difference between the current atmospheric concentration of CO2 and the pre-industrial value for CO2. This is because that flow represents the atmosphere re-equilibriating with slowly-changing components of the system, such as the ocean (which takes O(1000yr) to turn over), tree trunks, deep layers of soil, etc.

If we plot the annual sink of carbon versus the excess of CO2concentration over and above 270ppm (which gives a slightly better fit than the generally accepted value of 280ppm), we get:

Excess of annual average concentration of CO2 above 270ppm (left scale), and inferred annual sink of carbon in Gt/year (right scale). Click to enlarge.

The annual sink value, although noisy, has a definite linear trend to it (eg a quadratic fit lies very close to the linear fit), and when plotted on suitable scales, the two align nicely. This suggests that for every 100ppm additional of CO2, we will get another 3 Gt/year of additional sink. Now, no doubt this linearity will break down at some point. Thus the extrapolation, like all extrapolations, has its dangers. However, I doubt that modeling all the individual and poorly understood components of the sink will lead to a very reliable extrapolation either - when you add together lots of uncertain things, the result is usually a great deal of uncertainty.

Anyway, if you buy that, we can put together the extrapolated carbon emissions, partially compensated by the growing sink, and project CO2 out to mid-century:

Annual average concentration of CO2 in the atmosphere since 1959 as measured by Keeling et al in Mauna Loa, Hawaii, together with model projections. Click to enlarge. Source: Keeling via ORNL.

My preferred linear baseline case is the plum line, and you can contrast that to the brown exponential emissions growth and the blue constant emissions at the 2004 level. Obviously the result contains the uncertainties that we just reviewed - will carbon emissions really grow approximately linearly, and is the rule-of-thumb for the sink adequate. However, the thing is visually plausible, and will serve as our baseline for further consideration in future posts.

What I would draw attention to right now is this. We are now about 100ppm over the pre-industrial value. We will hit 200ppm above the pre-industrial value in the late 2040s in in the linear model. We could view this value as some kind of approximate indicator of the driving force behind "weather problems" - mountain glaciers all melting, increased storm activity, record heatwaves, etc. So during the expected lifetime of anyone here under about 35-40, that driving force is going to double. Whether the system is likely to respond linearly to that is another day's subject.

Next I will talk about how much we should worry about these levels of CO2. After that we'll have a look at the Kyoto protocol and its likely impact, and then we'll begin looking at how much of the 60 Gt/year of net primary productivity for carbon in biomass makes it into the economy, and where it goes. I have some interesting graphs of the total weight of matter the world economy processes each year as context for that.

This is a very impressive post.
Might I add that if you have 4 of these, I think a book is on the way on this subject alone.
There is also another force that we must worry about regarding climate change, what is happening under the earth's crust.  These 2 forces will cause some serious havoc. (I guess it's already starting)
I agree Stuart. You should write a book. Or at least some vehicle for TODers to financially support your great work here. :)
The links below outline the likely effects of the ~50% of anthrophogenic CO2 absorbed by the worlds oceans.
- 22 pages, with an error on the last page "increasing pH" should be "decreasing pH" (point 1), mainly graphical.
- much the same info but in 5 pages of text.

Note that pH is a logarithmic scale ( a "p" function in chemistry = -log [], where [] = concentration )

I would be dubious about accepting coal reserves totals. China used up 2 billion tons of coal last year, yet its reserves reported stayed the same. Deja vue? The same happened with the US. That is not say there is a lot of coal underground
I now understand all the hoopla around the acidification of the oceans.  The idea that the oceanic carbon sink is buffering the massive and rapid release of carbon that was effectvely removed from the biosphere some hubdreds of millions of years ago is scary.  Does anyone recall doing titration labs in high school(or later)? I may have to be corrected here, but does a buffering solution (the ocean pH 8.2)not accept a certain amount of acid with little change and then suddenly become acid itself?  That is why we call it a buffer right?

So hot or not, more CO2 = more oceanic uptake = more carbonic acid = acid oceans?  Or is there some suspicion that the uptake will slow if the pH of the oceans start to drop? I'm gonna find out here.

Thanks for this post Stuart.  Though I'm a bit dazzled by the analysis, identifying a difference between the preindustrial carbon levels and those of today is crucial.  I have often tried to explain to the curious the difference between short cycle and fossil carbon.  Too few people understand the different climatological impact of burning wood versus burning coal or oil.

We are launching ourselves into the upside of a carbon cycle that spans many millions of years.  This carbon enrichment of the biosphere is the atmospheric reenactment of a time in which humanity did not exist.

Also a good article here from NASA about phytoplankton and hurricanes

Just more checks and balances that the earth has.  As hurricanes increase it stirs up the ocean causing more phytoplankton to bloom.
Phytoplankton is where half our Oxy comes from.  Now I see why all this talk about biofuels coming from algae, is so big.

Now I see why all this talk about biofuels coming from algae, is so big.

Problems with Algae:

  1. De-wetting the oil-algae
  2. Energy/materials needed to contain the growing algae  (including the land set aside)
  3. Most of the 'cost effective' projects are using CO2 output from some other burning hydrocarbon event going on.

I was 'excited' by algae - until I looked into the need for non CO2 feedstocks, location and energy investment needed to make the algae holding areas.  

Then I became less excited.

Some of that hoopla surrounds the finding that a small drop in pH will prevent some marine organisms from producing a shell.  Lower pH being more favourable to the dissolution of carbonates, the shell seems to dissolve faster than it is produced.
Good point.  I read that article also and did a little investigation of my own.

Here is a great article that describes what you are talking about.

The Chart on Page 11 says it all.
Maybe SS can spiff if up a bit.

Coal follows also a Hubbert curve. It seems quite likely that world coal production is also peaking in relatively near future, may be in 10 - 20 years. China can no way keep up its production growth of nearly 10% for long - this might mean 1 to 5 years. So the global carbon flow will probably diminish significantly during the next 50 years. We can expect that almost all of the carbon in the fossile fuels reserves will be used eventually, but at slower rate and during very long time frame. So the question is, what will this mean for carbon amounts in the atmosphere and oceans.

This is a very good point.  In reality we ought to be looking at coal reserves on a country by country basis, and trying to get a feel for how accurate those numbers are.

You also have the same problem with coal as you do with oil - namely you can get light sweet crude, and heavy sour crude.  With coal, you can get low-sulphur or high-sulphur.  The low-sulphur is in high demand right now, but we will run out of that sooner.

Yes, and let's not forget that much of China's coal is the high sulfur kind.  On a visit to Xingdao, where they make the beer, about ten years ago, I was taken up a track to a hill with a view overlooking the city.  We travelled the last part on foot because the road had come to an end.  It was October, the start of the heating season, and I remember the burning in my eyes, the sulfur taste in my mouth and the effect on my lungs much better than the view.

Along with the GHG effects, we might also pause to remember sulfur emissions and acid rain at some point.

Sulfur may be the least of their worries.  Millions of people suffer arsenic poisoning in China, due to coal with high arsenic content.  Flouride poisoning is also a problem.
And, the largest source of mercury emissions in America is...a coal fired power plant!
Could we be in for a new website called, ?  Maybe we will need a whole bunch of websites for every other mineral like and maybe

It looks like every non-renewable resource is subject...

When the Vikings landed in Iceland over 1100 years ago, they found a land with ~30% forests (a shrubby Icelandic birch) and another 10% with shrub (<10 m tall) willow & birch "forest".  All useless for sheep grazing ! And a good source of charcoal.  By the early 1900s Iceland had less than 1% forest cover and an estimated 6 billion metric tonnes of carbon had been released.

Since then an aggressive tree planting program (~5 million/year in recent years) has been in place and 4% forest cover is within sight.

Reforesting much of Iceland (sheep farming is highly protected and is still uneconomic) with larger and faster growing trees has the potential to reverse/slow down global warming by a year or so (over the better part of a cantury).

That is my goal and I & others* have found a leverage point, introducing higher value trees** that have been overlooked in earlier surveys.  The American chestnut (no blight in Iceland) and Sugar Pine (world's largest pine tree, from 3,000 m in Southern California) have been introduced so far with my help.

I am the only nonIcelandic member of the Tree Growing Club in Iceland, Trjáklúbbur.

* Humans are more motivated to plant trees if they can make money than if they are motivated just by love of nature, etc.

Globally, increased carbon capture can be part of the solution.

I love your effort. It's corny but true - Think Global, Act Local!
an american aluminium company is building a dam for a smelter in Iceland, move the nasty stuff abroad?

local or not Icelandic people are asking people to come from all over the world for an "eco defence camp"


Stop the Icelandic government and Alcoa destroying Europe's last remaining wilderness for an aluminium plant!
Be aware of the `master plan' to `develop' Iceland's beautiful nature into a heavy industry hell servicing the greed of aluminium corporations!
It has already started. The Kárahnjúkar dam project in the Icelandic highlands is well under way... But it can be stopped!

Yes, let us stop green, renewable energy, with EXTREMELY high lifetime EROI and instead burn more natural gas to run aluminum smelters in Qatar and elsewhere.

Karahnjukar (I have been there) is being built where a natural ice/rock dam existed about 10,000 years ago.  Remnants of the sedimentary silt left at the bottom of that ancient reservior are still left and can be clearly seen going up the valley at the same elevation.

"Unspoiled wilderness" ?  I will quote an offical of the Icelandic Forest Service, "Iceland is an unspoilt as a strip mine.  Our forefathers and mothers cut down every tree in sight, introduced grazing animals and decimated the environment.  They created the only blowing sand boreal desert.  Add to this the lasting effects of massive volcanic explosions & eruptions and the glacier advances that scrubbed the landscape clean of anything living every Ice Age and we did no worse than nature.  This "unspoilt nature" is just PR lies by the Tourist Bureau".

Greenland has far more wildnerness left than Iceland.  And then there is Spitzbergen and other Artic islands.

Aluminium is a key material to build cars and all kind of wehicles with less weight and thus less fuel consumption. Aluminium and aluminium oxide is not toxic, there is no harm in getting aluminium oxide everywhere, it already is everywhere. Aluminium do in manny applications not require any surface treatment or they can be made in an enviromentally friendly way as a thicker oxide layer. Aluminium is easy to extrude and machine. Aluminium cans, containers etc are light and energy saving in transportation. Aluminium is often used for conducting electricity thus saving copper who also has a poisonous oxide. Aluminium is an exelent roofing material. Aluminium is one of the easiest metals to smelt for reuse.

Aluminium is one of the most sustainable metals, perhaps the most sustainable metal. We realy can not get too much of the stuff, massive ammounts of aluminium would be a blessing for future generations.  The only problem with aluminium is that it require enourmous ammounts of electricity for its original manufacturing.

I hope those greedy corporations make an enourmous profit and invest it in even more aluminium works in areas with abundant hydro och geothermal power.

I suggest that the next death blow for the Icelandic scenery is more trees.
Stupid humans to change things to make the world better...

When the Vikings landed in Iceland over 1100 years ago, they found a land with ~30% forests (a shrubby Icelandic birch) and another 10% with shrub (<10 m tall) willow & birch "forest".  All useless for sheep grazing ! And a good source of charcoal.  By the early 1900s Iceland had less than 1% forest cover and an estimated 6 billion metric tonnes of carbon had been released.

Since then an aggressive tree planting program (~5 million/year in recent years) has been in place and 4% forest cover is within sight.

Reforesting much of Iceland (sheep farming is highly protected and is still uneconomic) with larger and faster growing trees has the potential to reverse/slow down global warming by a year or so (over the better part of a cantury).

That is my goal and I & others* have found a leverage point, introducing higher value trees** that have been overlooked in earlier surveys.  The American chestnut (no blight in Iceland) and Sugar Pine (world's largest pine tree, from 3,000 m in Southern California) have been introduced so far with my help.

* I am the only nonIcelandic member of the Tree Growing Club in Iceland, Trjáklúbbur.

** Humans are more motivated to plant trees if they can make money than if they are motivated just by love of nature, etc.

Globally, increased carbon capture can be part of the solution.

An impressive set of figures and
graphs that give am excellent
basic understanding of what it is
all about, but there are many
complicating factors that make a
definitive analysis almost

The mere fact that we are adding an extra
7 or 8 billion tonnes of carbon to
the atmosphere every year should in
itself be cause for alarm. When
that gas dissolves in water it forms
a weak acid H2CO3, which depresses
the pH to as low as pH5.5. That may
not sound too terrible, but it is
sufficient to wreck the chemical
balance that permits corals and
shellfish to deposit their
structures. Even more disturbing,
many plankton are rather pH
sensitive and we risk annihilating
the organisms at the base of the
ocean food chain.

Another particularly scary phenomenon
is the release of carbon dioxide and
methane from permafrost that is
thawing. This is clearly a self-
reinforcing phenomenon that can easily
lead to runaway global warming
-abrupt climate change- that could raise hte average temperaure of the planet by as much
as 8 or 10 C in a matter of a
decade or so.

Disturbance of the metahane-ice
clathrates that are deposited on
ocean floors will almost certainly
have a similar effect.

Finally, there is the totally
unknown aspect of how elevated
temperatures and elevated CO2
levels will affect the uptake of
CO2 by plants. Although many
scientists blitely assumed that
higher temperatures and higher COr
levels would increase photosynthesis
this may not necessarily be so. In
particular, if higher tempertures
result in lower moisture content of
soil, plants stop transpiting and
photosynthesis comes to a halt.
There have been reports of reduced
rice harvests that have been directly
attributed to global warming...
sorry I don't have the link.
Everything tell me we should be
applying the Precautonary Principle
to everything we do.

The report of an extended drought
in the Amazon in the latter part
of 2005 should have sent alarm
bells ringing around the world,
since if the Amazon stops absorbing
carbon dioxide and starts releasing
it, we are likely to be toast in a

Very interesting post Stuart. I look forward for the follow up.
Just behind TOD as ever! the BBC has a relevant article at giving the results of a new report. This quotes target levels for CO2 in the atmosphere of 400 - 450 ppm to give "only" a 2 degree rise but goes on to say that 500+ is more realistic as an outcome. Good to see this in MSM but the minister spoils it by referring to 1,000 years timescale at which point most will switch off and carry on as usual. I suspect, and Stuart's analysis may infer, that the timescale is a great deal shorter than that.
We're going up at 2 ppm/year and we're at 380 right now.  I'd say we're going to blow past 450 in a lot less than 1000 years.
I infer that you did not mean to imply that you were unaware of the difference in meaning between "infer" and "imply", but you did.
Bravo!  Only to be found at TOD.

Published on 17 Jan 2006 by Fortune. Archived on 19 Jan 2006.

Cloudy with a chance of chaos
by Eugene Linden

A disturbing consensus is emerging among the scientists who study global warming: Climate change may bring more violent swings than they ever thought, and it may set in sooner.


If you ever decide to have a day or two of downtime, you might enjoy Roy Rappaport's "Pigs for the Ancestors". It's about measuring energy as it is harvested, or displaced, by humans. In this case, the humans are a primitive society, who channel solar into their herds of pigs. The social traditions and mythologies that direct the activity <leveraging energy> are fascinating.

I just came over to read this (excellent summary, Stuart) after reading more news of anti-science activities related to global warming over at "science blogs"

Taking one step back, and looking at the global human response to this problem, it doesn't look good.  While it will be interesting to look at Kyoto & etc., here's what I currently expect:

A sufficient global concensus for effective action won't come until the environmental effects are painfully obvious.  (The fact that they aren't obvious enough now is cause for extreme pessimism.)  Given that, I think we have to blue sky what a global mobilization (on things like tree planting and carbon sequestration) would do at some late stage.

Either we can play catch-up at some point, or we'll have to ride it out (whatever the heck that comes to mean).

It's totally unlikely that anything will be done about climate change or peak oil until it is too late.  People are getting wealthy with things the way they are; they are going to do anything to prevent change that might cost them money.  As a matter of fact, the worse the future looks the more incentive they will have to increase their wealth.  Money is a great insulator from hardship.
Yeah, and to my knowledge no one has ever dreamed up an effective way to reclaim significant amounts of CO2 from the atmosphere.  We play at Kyoto, and the dream that we might halt the increase ...

Right now it looks like we are not going to halt the increase (remember yesterday's stories of China's concrete and coal expansion?) ... and we're short a "plan b."

Maybe we have different definitions of "significant amounts", but I recently read about an interesting CO2 reclamation scheme from an unlikely source: Allan Nation's "Quality Pasture: How to Create It, Manage It & Profit from It". I'm in the midst of moving so the book has been packed, and it's not in the teaser at Amazon, but my recollection is that increasing the amount of organic matter in the top few inches of all the world's aerable land by 1% would nullify the increase in CO2 concentrations. 1% isn't a particularly lofty goal. I'm aiming for 2% on the land that we're buying.

For much of the world's tired fields, this would not only help with climate change, but vastly improve the soil's productive capacity. The methods of raising organic matter are very simple: Minimize tilling, leave agricultural waste (straw, for example) on the field. Switching cattle production back to a grazing centered approach would do a great deal of good too. One can go as far as growing a crop just for the purposes of knocking it down to stay on the field to contribute organic matter to the soil (and shade out weeds, and conserve soil moisture, and reduce soil erosion).

I can look up the exact statement in a couple of days and stick it in the next open thread.

Of course, I just don't think this, or any promising actions, will be implemented for the usual reasons (ignorance, short-term greed, ...).

There are some farmers in Vermont doing work / workshops on this subject.  Try googling Cimarron Farm.
If this turns out to be correct (and I don't have reasons not to believe it) this is a much better way to go, IMO.

I'd suggest that we accept an international treaty instead of Kyoto, according to which at least 20% of the areable land of each country each year must be subject to such treatment. Instead of carbon emissions we will start trading "carbon absorbtions" based on areable land treated. Of course this will put an end to the biofuel madness and we'll step directly for electric transportation (also a step in the right direction IMO).

BTW, my evolutionist's explanation of this is that we have a natural (and normally healthy) bias toward short term worries.  In the african savanna, why worry about what's going to happen ten years from now?  Worry about staying alive for the day, and at the outside, the season.

Our base wiring favors short term concerns.  Without an internal mechanism for longer timescales, we have to try to patch one together with the general cognative machinery ... and we see how well that works.

Stuart. You are truly gifted. While I understand what you wrote and could probably replicate it eventually, the SPEED and clarity that you are cranking out is of a 5 star analyst.(or 6).

My initial thoughts after reading this is: we're going to be having alot more 'degree cooling days' than 'degree heating days'. Perhaps that theme is already occuring in the natural gas markets as the historical wide spread between winter months and summer months has flattened dramatically.


It would be interesting to include in this analysis any estimates of the contribution made to global carbon by methane hydrates released via permafrost destruction. I recall seeing a report on the amount of methane released to the atmosphere via permafrost destruction at Prudhoe Bay, (Colette?), do not have a reference.

The amount of methane released to the atmosphere exceeded oil production by a factor of 20  (I recall). Since permafrost destruction is a circumpolar problem and methane hydrates are common in this environment perhaps a very large source of atmospheric carbon is being ignored

Here's the RealClimate page on that:

I'd note that the picture above showing carbon flows is current rather than projected.  To keep things apples-to-apples, we'd really want to know the current rate of permafrost and hydrate melt/release.  I don't think anyone knows.

Oddly, the methane concentration has stalled out just as all those permafrost stories hit the press:

Source: Wikipedia

If a substantial fraction of those emissions were from gas pipeline leaks, the recent hike in gas prices would have created strong incentives to repair them.
Excellent work as usual, Stuart.

I looked up the Joint Global Ocean Flux last year, curious about the oceans' place in the carbon cycle, and see that it has not been funded since about 2003 or so. They have published a lot of raw data, but I haven't seen many studies of it ...

Also I see Kevin mentions methane as a cause for concern; with the Gulf Stream, well with the whole thermohaline circulation system being disturbed, methane hydrates which have been kept frozen by cold bottom currents from the poles may begin to melt, and that process will likely be catastrophic rather than linear. A couple of questions come to mind:

  1. how much methane is really down there?
  2. can any of you physical chemists explain what the measure  of 'greenhousiness' is for a gas, and how we'd estimate that property from IR spectra, etc?
Highly recommended recent book on this subject:  THIN ICE by Mark Bowen.  Gives an engaging account of the history of the subject, the personalities involved, where the science has been and is going, and the implication of climate change past and future. A great read for folks who visit this site.

Here is an interesting note on the big energy balance picture of the climate by one of the leading climate scientists, Jim Hansen.

There is a wealth of info at this NASA site if you want to wade though it - much having to do with the best climate models available at present.


Meant to post a link:

Joint Global Ocean Flux Study
Great post Stuart.  

Clearly man is increasing the carbon emissions over background.  This is now not disputable, the way it was a decade or so ago.  Two points with this.

  1.  Are the emissions self reinforcing?  As you stated there is a lot of carbon in the ground as peat, organic matter and frozen tundra.  Prairies used to be carbon sinks they are now farm fields and net releasers of organic carbon.  Ditto for tundra that is thawing.  Centuries of trapped carbon is being released in forms other than oil.

  2.  What data set says we need large carbon increase (compared to total world amounts) to have negative effects on life?  Small changes in temperature can have lethal effects on species.  That we have been able to pump a measurable surplus of carbon into the environment, in this complex a system is quite alarming.  Ecosystems tend to run at equilibrium and it is usually hard to alter the system due to the enormous energies invovlved.

Point 2 is often used by business and conservatives to say the problem is not worth worrying about.  I think we should be cautious on minimizing our impact on the carbon cycle at this point.  Saying it is only a small percentage of the total is a value judgement and not based on cause and effect.
For that matter nobody's ever exposed humans to 400 ppm CO2 long term before.  Short term effects start showing up at 1500 ppm; it wouldn't be impossible that there are long term toxic effects at lower concentrations.  Maybe we're all losing IQ points even as we type.
I bet indoor levels have been higher than that, as long as there have been "indoors" ;-)

Remember, they use mountain top measures (as in the Mauna Loa graph above) because there is such huge variation in terrestrial environments.

Searching now:

Widory and Javoy (2003) measured CO2 concentrations and carbon isotope abundances in air samples collected from various locations in Paris, France (its streets, gardens, etc.), its suburbs and the surrounding open countryside, as well as from vehicles, heating sources, power stations, etc., and from laboratories and classrooms where the human component of the urban CO2 dome would be expected to be dominant.  They found that the near-surface atmospheric CO2 concentration throughout the surrounding countryside averaged 415 ± 9 ppm, while values in the city sometimes reached as high as 950 ppm.  These higher values were driven primarily by vehicular exhaust, as the authors report that "road traffic is the main contributor and, in particular, vehicles using unleaded gasoline (~90% of the total)."  In enclosed spaces, however, the CO2 derived from human respiration dominated.  In a 150-m3 classroom containing 20 students for a period of four hours, for example, the CO2 concentration rose as high as 4630 ppm, which "corresponds well," in their words, "to an average individual respiration flux of 5 l/min containing ~3.7% CO2."

Does that mean that the more people taking that final exam the lower my score? ;-)

Only if you were downwind.
But, on the upside, it should reduce panic attacks--like making everybody re-inhale from a brown paper bag, all the time.
Trying to calculate the net carbon addition to the atmosphere every year is a little harder than it sounds. CO2 levels are quite variables on a seasonal basis, as this diagram of measured CO2 levels shows:

Given this drastic variability, you have to average it over a whole year and then subtract one year from the next in order to get the net addition. It is no wonder that there is a lot of noise in this measurement, since the raw data is clearly highly variable. I don't know if it is right to attribute this noise to genuine variability in atmospheric sinks or if it is purely measurement error.

there is virtually NO variablity in the above graph - there is some seasonal phenomenon that looks completely predictable. (Each peak and trough is the same distance)
Putting on my chemistry hat for a second (I worked for a time in medical and evironmental monitoring), I'd limit the term "measurement error" to "given a sample of air, did I get the true CO2 level in that sample."  I'd expect that kind of measurement error to be vanishingly small.  Actually the sawtooth pattern indicates that, because a measurement error would unlikely be so regular.

No, what we've got is the interesting phenomenum that air blowing over the top of a mountaintop shows a seasonal variation in CO2 concentration.

As I understand it, this sawtooth curve is a northern hemisphere phenomenon.  CO2 concentration falls in the summer due to CO2 uptake by plants and it rises in the winter from plant decay and from extra carbon usage for heating.  Air mixture between northern and southern hemispheres is somewhat slow (takes more than a year), so the southern hemisphere has a different shape of sawtooth.  Mixing is fast enough, however, that the average concentration in both hemispheres is  about the same.
I think mixing is far faster than one year, considering the speed of winds. It's just that the northern hemisphere has much more "weight" and dominates the process.
No, its not a local phenomenon neither a measurment error.

Worldwide annual concentration of C02 peaks in the end of the winter and drops until the end of the summer. Reason: photosynthesis, the northern hemisphere has much more biomass and in northern hemisphere summer and spring the vegetation blossoms and absorbs CO2, while in the winter you get the opposite process (loss of biomass).

What I meant by "mountaintop" was not to imply locality, but rather the opposite, of course.  Air blowing across an isolated peak, especially a mid-oceanic peak, is going to be a sum of influences elsewhere.  They have quite the interesting list of monitoring locations ... Easter Island & etc.

And I just thought I'd pause after narrowing the "measurement" question and let the others pick it up, as you have done.

 ".....I hypothesize overall that the annual sink of carbon into the non-atmosphere components of the system should be roughly proportional to the difference between the current atmospheric concentration of CO2 and the pre-industrial value for CO2. This is because that flow represents the atmosphere re-equilibriating with slowly-changing components of the system, such as the ocean (which takes O(1000yr) to turn over), tree trunks, deep layers of soil, etc......"

I'm not sure I understand the rationale for this hypothesis.

 Are you saying the the rate of CO2 uptake by the oceans, etc. is more or less linearly proportional to the increase in atmospheric CO2? Maybe; maybe not.

While the CO2 dissolved in the oceans (where it reacts with the water to instantly dissociate into hydrogen ions and bicarbonate ions) will increase as the oceans start coming into a new equilibrium with the atmosphere, there are so many factors affecting where that equilibrium point is and how fast the system will readjust that I don't think you can make such a blanket assumption. The chemistry of this whole thing is extremely complex and subtle. Furthermore, increased CO2 in rainwater will cause increase weathering of minerals, and that in turn will affect the chemistry of the whole system. And it's not just about chemistry but also about physical transport, as affected by wind, currents, photsynthesis, and at least a dozen other things.

I strongly suspect that with respect to CO2, the atmosphere and the ocean will probably never get back into complete equilibrium as along as we continue pumping the huge amount of CO2 into the atmosphere. In other words, it will always be out of balance, with the ocean trying to catch up with the atmosphere.  I'd venture that if all man-made CO2 were to cease tomorrow, we wouldn't return to pre-industrial-era atmospheric CO2 for a long, long time.

Finally, to address a concern raised by another poster, I wouldn't worry about the oceans running out of buffering capacity and experience a sudden drop in pH. The reason is the when CO2 is dissolved in water as H2CO3 (so-called 'carbonic acid'), the pH may lower slightly but the total alkalinity of the water-carbon system does not change. The reason (somewhat simplified) is that for ever H+ ion added, there is also a corresponding HCO3- (bicarbonate) ion added. Furthermore, a slighly lowered pH will cause more CaCO3 deposits to dissolve, thus releasing more alkalinity. So, I wouldn't worry about the affect on ocean CO2 chemistry all that much (at least not for now).

Henry's law (developed in 1803 by the physical chemist William Henry) holds that the "escaping tendency" of a gas is proportional to its concentration, i.e., P=kX where X is the mole fraction.  If the rate of CO2 transfer from air to water is proportional to its escaping tendency, and if the solutions are "ideal", this is a good assumption.
Researchers at the U of Washington School of Oceanography are studying the effects of atmospheric CO2 increases on the oceans. As I recall, one area of concern is that a slight reduction in pH markedly increases the solubility of calcium carbonate, the key component of phytoplankton skeletons. I believe they published a paper in Science in 2005 on this issue. A recent synopsis of this issue is:

The Acid Ocean - the Other Problem with CO2 Emission

Interesting link!

It further reinforces my belief that as long as we pump CO2 into the ocean at the enormous rate we are, the equilibrium between the ocean and atmosphere will never be fully reestablished, because the ocean will always be lagging due to the long time it takes for things to balance out. It all seems to be very mass-transfer limited.

I would agree that even very tiny pH changes can have a profound effect on the marine biota, and I didn't mean to downplay its importance. My only point was that the ocean will probably not see a really large pH spike due to increased CO2 in the atmosphere.

If these concerns about increased CO2 in the ocean are valid, then what does that say about some of these schemes to 'sequester' CO2 from power plants by pumping it into the ocean?  (Maybe I'm missing something, but that has always struck me as a totally hair-brained idea anyway.)

I remember reading that one very uncertain variable is the degree of mixing of the ocean's topmost layer with the bulk ocean water.  The story I remember is that the top thousand feet doesn't mix very rapidly with deep water.  Hence, the interaction of ocean and atmosphere is limited to the surface possibly slowing ocean absorption of CO2 from the air.

Of course, local upwelling and sinking occurs (Greenland, Antarctica, Peru) but the bulk mixing is still slow.

The first diagram Stuart shows, the carbon cycle picture from Wikipedia, has carbon fluxes between the deep ocean and shallow water of 90-100 Gt/yr, comparable in magnitude to the 90 Gt/yr fluxes between the ocean and the atmosphere. If this is correct then the surface water is connected to the deep ocean about as well as it is to the atmosphere, and we would not expect CO2 impacts to be limited to the surface.

Of course, the deep ocean holds far more carbon (because it is so much bigger in volume, I guess) so it would be affected relatively less by a given quantity of increased carbon input.

Halfin, that doesn't follow at all. Look at the amount of CO2 in the ocean--orders of magnitude more than 100 Gt/yr. The disparity in magnitudes between quantity and transport indicates that the flow between shallow and deep ocean is probably quite small. It was stated several times in other comments that there's about a thousand-year turnover of the oceans.

This means that it will take a while for the CO2 that's absorbed on the surface to get to the deep ocean. So the surface will be able to hold less, and its chemistry will be affected more.


The point is that the flux between the atmosphere and the surface ocean is about the same as the flux between the surface and the deep ocean (both 90-100 Gt/yr). If you're going to say that the surface is disconnected from the deep ocean, then you also have to say that the surface is disconnected from the atmosphere.
The IPCC version linked above shows only about 40Gt of exchange between the shallow ocean and the deep ocean. I shouldn't think it's a very easy number to measure.
I'm not saying that surface and deep ocean are disconnected. I am saying that they may take a long time to equilibrate.

You wrote: "If this is correct then the surface water is connected to the deep ocean about as well as it is to the atmosphere, and we would not expect CO2 impacts to be limited to the surface."

Suppose that it takes 10 years for CO2 to get from the top of the surface water to the bottom of the surface water. Meanwhile, 90 Gt are crossing the surface/deep boundary every year. Thirty years after you transfer extra CO2 from the atmosphere, it works its way through the mass of water containing the 1,020 Gt listed for "surface ocean," and then it can start transferring to the deep ocean.

So for ten years, that CO2 has been concentrated in the surface water, not absorbed by the deep water. So we should expect that CO2 will affect the surface water more strongly than it would if it were immediately dispersed throughout the whole ocean.

Of course, after the delay, it will indeed reach the deep ocean, and have an effect there too. But as long as the system is out of equilibrium, we should expect CO2 to have more effect in the surface than in the deep ocean.

When I first read your post, I thought you were suggesting that the CO2 would immediately be shared among surface and deep ocean. That would be incorrect. But if you were instead saying that the CO2 will eventually get to the deep ocean, then I'll agree with that.


I admit that I don't know much on this topic - I don't know exactly where the boundary is between "surface" and "deep" water, and whether there is any physical meaning to that boundary, or if it is just an arbitrary depth.

I would seem reasonable to me that the surface ocean would be relatively well mixed because of wind and wave action. So I don't see it taking 30 years for CO2 to percolate from the top to the bottom of this so-called surface region. But at this point I am just speculating, as I think you are as well, so perhaps we should wait for more authoritative information.

The ocean thermocline is real and does affect mixing. The vast majority of ocean water lies beneath it and does not mix readily with surface water. See here:
Yes, I suspect the oceans are such a complex system that we will never be able to fully quantify what is really going on.  All we can hope to do is to more or less define the boundary envelope in which things are likely to happen.  I think that with such a complex system as the chemistry and mass transport between the atmosphere and the oceans, many things are literally indeterminant. Trying to rigorously model something like that may keep many graduate students busy for a long time, but I think that in the long run it is an exercise in futility.
Nice post, Stuart.

Re: "However, I doubt that modeling all the individual and poorly understood components of the sink will lead to a very reliable extrapolation either - when you add together lots of uncertain things, the result is usually a great deal of uncertainty."

I appreciate the need to make some simplifying assumptions and so I just thought I would make some comments on whether they are correct. As you already know, we can't expect the Earth's carbon sinks to remain "roughly proportional to the difference between the current atmospheric concentration of CO2 and the pre-industrial value for CO2" in the future. This is due to postitive feedbacks that have deleterious effects in so far as humans have altered the carbon cycle as it has operated in the Holocene. Here's a few remarks on that.

Let's look at an authoritative paper on all these "poorly understood components". From The Oceanic Sink for Anthropogenic CO2 by Christopher L. Sabine,1* Richard A. Feely,1 Nicolas Gruber, et. al.

Note: Pg = Petragram = 1 billion tons
Click to enlarge

As you alluded to, the error bars are high. This is especially true for land use. Here's a nice paper on that subject, Land use effects on terrestrial carbon sources and sinks. The conclusion of Sabine, speaks to the future of the oceanic carbon sink [emphasis added].

There is a potential for both positive and negative feedbacks between the ocean and atmosphere, including changes in both the physics (e.g., circulation, stratification) and biology (e.g., export production, calcification) of the ocean. These processes are still not well understood. On the time scales of decades to centuries, however, most of the known chemical feedbacks are positive. If the surface ocean pCO2 concentrations continue to increase in proportion with the atmospheric CO2 increase, a doubling of atmospheric CO2 from preindustrial levels will result in a 30% decrease in carbonate ion concentration and a 60% increase in hydrogen ion concentration. As the carbonate ion concentration decreases, the Revelle factor increases and the ocean's ability to absorb more CO2 from the atmosphere is diminished. The impact of this acidification can already be observed today and could have ramifications for the biological feedbacks in the future. If indeed the net feedbacks are primarily positive, the required socioeconomic strategies to stabilize CO2 in the future will be much more stringent than in the absence of such feedbacks. Future studies of the carbon system in the oceans should be designed to identify and quantitatively assess these feedback mechanisms to provide input to models that will determine the ocean's future role as a sink for anthropogenic CO2.
As for the terrestrial carbon sink, some climate models (that include a carbon cycle) actually project that the Amazon will become a source, not a sink, by mid-century. This is due to changes in land use and burning. The same thing is going on in the rainforests of southeast Asia (Indonesia). Rainforests are micro-climates which basically means they create their own weather. Changes due to landuse changes or severe drought conditions (perhaps brought on by conditions in the Pacific) affect the rainforest carbon sinks in a positive feedback. The less forest, the less carbon absorbed, the more released. The same type of process is at work in the high latitudes of the Northern Hemisphere. Already, we note that the Siberian and Alaskan permafrost is melting down, releasing both CO2 and methane into the atmosphere whereas these GHGs had been sequestered in those soils at least since the previous glacial maximum. Note the large numbers (measured in petragrams) due to land use in the included graphic. Nobody really knows what's going on with the Earth's terrestrial carbon sinks but climate scientists are starting to get that anxious feeling in the pit of the stomach. See Land Won't Soak Up Carbon Indefinitely. Also see Sinks for Anthropogenic Carbon for a good overview. Finally, for the really brave, try Terrestrial Carbon Sinks -- Uncertain Explanations.

The bottom line is that there are almost certainly positive feedbacks at work in the carbon cycle having to do with land use, saturation of the ocean's ability to absorb carbon and the ongoing warming itself. None of these are likely to be good news.

best, Dave

A whole series of excellent questions.  I would like to point out that some of these have been asked by others for quite some time.  During the period 1972-1974 my summer job was at an agricultural field lab, keeping a variety of microclimatology measurement equipment functioning.  One of the studies that the big brains were involved in was essentially "Where the hell is all the carbon dioxide?"  Even at that time, some people realized that the amount released into the atmosphere since the beginning of the industrial revolution should have raised the ppm numbers by more than had occurred.

IIRC, the results of that work suggested that it wasn't going into North American cropland, and it wasn't going into tropical rain forests, but it might be going into the oceans.  At least one theory was that microscopic organisms were fixing carbon in some fashion and carrying it to the sea bottom when they died -- a theory that still does not seem to have been settled.  I wasn't all that interested in the "big picture" at that time; I got paid to make sure the diffuse radiometer was properly aligned, not to think about carbon sequestration :^)


Some years ago I read about Iron being used to increase the growth of plankton. I just did a search and found

It seems that Iron is a limiting factor and so I suppose the idea is to add iron to the seawater, increasing plankton and the ability of the oceans to become a carbon sink. Obviously the mission of a "non-profit" organization.

I thought this was a really neat idea as well, but apparently later news is less positive:

I hope they can find a slow/safe level of iron/mineral seeding.

Suffice it to say that (eyeballing it from Stuart's numbers) when we dump a ton of carbon into the atmosphere in the form of CO2, about 40% of it fairly quickly ends up somewhere else.  I, for one, would like to know whether it's going somewhere relatively innocuous -- eg, silt in the bottom of deep oceans -- or somewhere that might be worse than having it in the atmosphere.

Note to Stuart: You build a variety of interesting small data sets, and you are meticulous about sourcing them, but you don't always pose the analysis quite the way I would like.  Is there any chance that we could get you to make those sets available somewhere convenient?  I know I'm just being lazy, but if it's easy to do...

"In the graph, it rather looks to me as though the overall volatility in the absorption of CO2 is increasing over time."

Now that you mention it, it really does look that way. A lot. And that's over just a few decades! I repeat: That increase in volatility took only a few decades to develop!

Anything that can change a global mechanism that drastically in that short a time needs to be understood. If the carbon sink is a function of the weather, then this would seem to be proof that the weather is getting more extreme. If it's a function of ocean currents, then there's proof that ocean currents are changing. And so on.

Can we get more historical data on this? Can you quantify the degree of volatility? If you are the first to notice this, you should publish your observation.

Several posters here have recently mentioned one or another graph as the first time they've been scared. I won't be scared quite yet, until it's understood a little better, but this could be the one that scares me.


While talking about capacity of oceans to absorb CO2, don't forget the impact of coal burning. Coal releases both mercury and silver, both of which are highly toxic to marine invertebrates.

The amount of silver in the North Pacific apparently isn't toxic, but the first article mentions concerns about "hot spots" of greater concentration.


Excellent - looking forward to the next installment.

Something about the graph "Carbon emissions in Gt/year 1960-2004, together with net increase in carbon in the atmosphere" had a vaguely familiar look to it...

The graph at seems to match the peaks for the applicable years extremely well

It doesn't seem hard to believe that fluctuations in weather, etc, could cause that system to be different than its average by a few percent either way in any given year.

Indeed not.


The carbon cycle - and the economy for that matter - is a (somewhat) stable complex system far from equilibrium.  Thus understanding the whole system of planet+economy is going to involve non-linear analysis, attractors, phase space, fractals, dissipative structures, bifurcation points, etc.
I just want to add an important caveat to this entire discussion thread. The carbon cycle is a theoretical construct--it is a model. How humans are altering that process must be incorporated into the model. For example, it is not really understood why CO2 levels rose and fell (lag or lead, but most likely lag) as the ice ages of the last 800 kya occurred. So, there is no predictive theory that explains why CO2 levels in the atmosphere were about 190 ppmv (parts per million by volume) in the atmosphere at the times of the glacial maximums and about 270/280 ppmv during the interglacial periods--like the one we're in, which is called the Holocene. (Just for informational purposes, the Pleistocene from about 1.6 mya to about 10 kya--the Holocene--together are called the Quaternary. Prior to that, at the so-called K/T boundary at about 65 mya when the non-avian dinosaurs bit the dust, the "T" stands for Tertiary in the geological timescale--(65 to 1.6 mya). The "K" stands for Cretaceous, the last period of the dinosaurs--the "K" is from the German--don't ask. Furthermore, CO2 levels derived from very rough paleoclimate proxy data indicate that CO2 levels (ppmv) in the atmosphere have been falling since at least the Eocene/Oligocene boundary (about 35 mya) and the present level (380/ppmv) has probably not been seen since the early Miocene about 22 to 24/mya. Just so you know where we're at in the Earth's history.

mya = million years ago, kya = thousands years ago.

This might give you all an insight into the special circumstances we find ourselves in now. There is no known analogue to the special circumstances we find ourselves in now in the paleoclimate record as known in Geological Time. None.

So, you can see why some climate scientists, especially those who have looked at abrupt climate change, are not able to sleep well at night.

Seems counterintuitive that the CO2 levels would be DOWN during glacial periods and up during the warm spells.  Since plants are the dominant life form one would think that their CO2 uptake would decrease the CO2 during warm spells.  But, then again, warmer water apparently takes up less CO2 and the ocean is a big CO2 sink.

All this seems futile given the size of the problems and the obvious fact that there is no agency on earth with authority to limit the use of coal, oil and methane.  One shudders to think what kind of agency WOULD have such authority.  We may yet have even more German words - Chinese more likely.

For better for worse, price will have to do since money is the only authority with sufficient reach.

TOD is primarily about oil.  Climate issues are obviously very important but may be a bit off topic.  I think of the TOD constituency as a band of individuals from  many walks of life mulling over oil related issues while warming our hands by an internet mediated campfire.  Climate is obviously related to oil but it's actually more a superset than a subset.  Once the topic shifts to climate we find oil just one piece of the puzzle.  I think TOD should keep its oil focus.  There is nothing to prevent spinning off a website related to the oil/climate connection.

Given that your concerns about climate change are real, what exactly do you propose as a response other than a great gnashing of teeth and refrains of, "We're f%%ked, we're REALLY f%&ked!"

I get tired of listening to Kunstler and the apocalypticons rant and rave.  It's  both repetitive and a real downer.

If you are right and climate change is the real elephant in the room (and you probably are right about that), there's nothing much we fleas can do about it.  Even limiting carbon combustion may be too little too late.  Once these cycles get started they tend to run to completion due to positive feedback loops.  The earth has seen many changes of climate and life has managed to hang on.

Perhaps we should simply sit back and watch what happens realizing that, much as it may damage our fragile egos, this is a Greek tragedy in the most real sense:  the inexorable working of things.  I personally lay the blame for our situation at Aristotle's door with his creation of logical thinking.  Logic allows the forebrain to separate itself from the world.  But, as we see, the rules of logic, even augmented by statistics, can't model the complexity of life with enough accuracy to allow predictive control of things like an Amazon rainforest.

Furthermore, and even more important, underneath this thin glaze of rationality we remain emotionally similar to chimps.  Man is not a rational animal.  The civilization we inhabit encourages a certain limited kind of rationality while feeding the lurking animal Monday night football.  We may think the animal sleeps but scratch the surface and look at your own behavior -  how many times does your actual behavior violate what you rationally think is in your best interest?

So pretending that we are rational animals capable of stepping back and sacrificing our material comforts to achieve a stable climate, borders on absurd.  In the first place we would never know that it worked even if it did.  In the second place we would likely sacrifice our comfort for the next ten to twenty years and discover we're past the tipping point.  Methane would be dumping into the atmosphere from the far north.  How in hell do you tell people to give up la dolce vita on such long odds?  You don't.

I think your criticism of Stuart is misplaced.  Of course there is no model for the current situation.  I find it fascinating to watch him try and model the world even knowing it's probably futile.  I think trying to make sense of things using the tools at hand is a noble effort no matter what the outcome, don't you?

CO2 is a strange gas, it is more soluble in cold water than in warm water, hence the bubbles as one's champagne warms up in the glass. That may explain at least a part of the counter-intuitive reduction of atmospheric CO2 in glacial periods. Also tundra areas seem to lock in CO2 and methane, beware them melting! Animals exude CO2 (and methane), the animal population will likely reduce during glacial periods.

I disagree strongly about TOD sticking exclusively to a narrow oil focus. Climate change and some aspects of economics are intimately enmeshed with the peak oil problem.

Re: "I think your criticism of Stuart is misplaced..."

Hold on there, partner, I didn't criticize Stuart at all! I was just emphasizing a point I think he had made in his figure illustrating the carbon cycle as it is presently understood. That model will be changing over time due to human interference and that was another point I was trying to make.

Please don't miscontrue what I said, LJR.

Mea culpa.  I stand corrected.
TOD is primarily about oil.  Climate issues are obviously very important but may be a bit off topic.

I would like to see a wiki, drawing on a number of existing blogging communities (TheOilDrum, RealClimate, WorldChanging), which set out to brainstorm an agenda similar to that of the "alternative to Kyoto" which met in Sydney, Australia recently. (The "work plan" of AP6, the Asia-Pacific Partnership on Clean Development and Climate, can be seen here.)

The agenda of such a site, as I imagine it, would be both factual and normative. There would be an attempt to hammer out a consensual understanding of the facts regarding climate, economics, and politics; and an exploration of future scenarios, policy options, and technologies. Wikipedia, with the talk pages that accompany every article, shows how a consensus document can coexist with threaded discussion.

Most ambitiously, one might hope that such a site would be more than a means for a self-selected group of people to improve their understanding of the situation, and that it might actually enter into dialogue with its institutional counterparts (e.g. the AP6, and whoever administers the new AEI). But that may overestimate the contributions that ad-hoc net-forums like wikis can make...

Feeling compelled to take the bait: There are a number of individuals around that we could single out as having created enormous bad effects on the environment and climate change. Personally, I'd go for folks like James Watt, Otto Diesel, John D. Rockefeller, Henry Ford, Alfred Sloan, Andrew Carnegie, and many more. But Aristotle! Isn't that a bit harsh?

If you look way back in human history, everywhere humans have gone, large-scale extinctions and environmental damage have followed. It was occurring far before Aristotle opined on anything. It was probably occurring before we had effective language skills. Call it id, greed, or whatever--humans have always been bad for the environment. Aristotle may have given us the tools to rationalize our behavior after the fact, but he didn't cause our transgressions.

But it's always great to add another villain to the list. And I love the "internet-mediated campfire" image.

Thanks for including flaring on the chart. All the talk about natural gas recently left me wondering how much had gone up in smoke.
A few important points that need

methane is very much more active than
carbon dioxide as a greenhouse gas
-it is all to do with bond energies
 - and is about 22 times as active
per molecule. The reason we focus
on CO2 is that the concentration of
CO2 is so much higher.

methane in the air oxidises to
carbon dioxide when it passed
through a flame or when lightning
passes through air. It should not
build to excessive levels in the
atmosphere unless there is a
catastrophic release (as per major
disturbance of methane trapped in
tundra, bogs etc, that may have
taken tens of thousands of years to
accumulate, or release from methane-
ice on the sea bed.

It is suggested that the massive
extinction event that occured 55
milion years ago was caused by a
large volcanic system erupting
under a major oil field, thereby
vaporising the hydrocarbons
and oxidising them; the sudden
increase in carbon dioxide and
methane content of the air was
enough to trigger an 8C rise in
average temperature, wiping out
95% of living things.

By continuing to add carbon dioxide
to the atmosphere and pushing the
Earth's systems to the point of
positive feedback, we are probably
creating a situation that will lead
to a similar abrupt climate change
(increase in average temperature of
5-10C in a decade) and similar
mass extinction event.

This is not the kind of analysis
any politician like to hear, nor
the kind of discussion any mainstream
media like to publish, hence we get
the rather preposterous 'sometime in
the next 1,000 years' phraseology,
rather than some time in the next
100 years (or even worse of course,
some time in the next 10 years).

The Precautionary Principle tells
us that unless we know it is safe,
we should not do it. Our economy
operates on the basis that we
should keep doing it until it is
no longer possible to do so. That
is the really scary part. Once is is no loner possible to keep adding carbon, we will have gone well past the triggering point for abrupt
climate change (we may have already
passed it  -we do not know).
it= unconstrained addition of
carbon dioxide to the atmosphere
in this case, but PP should apply
to most aspects of our lives.

The irony here is that Peak Oil may
save us from abrupt climate change, by forcinga  reduction in emissions.
But PO may also trigger unrestained
use of coal and bring abrupt
climate change faster than ever.

Just an observation, especially for those of you against nuclear power plants. There has been one meltdown in the entire history of nuclear power. The two times the U.S. used nuclear weapons for war put far more radiation into the atmosphere. (However I know this is slightly irrelevent)
Here's a great new factoid. If there really is as much carbon burned as that graph suggests, over 2,000 lbs of C-14 (radioactive, undergoes beta-decay) are produced annually. Gee, now I know why everyone has cancer.
-Stop the Iran war-
C-14 has a half-life of 5730 years.  It is produced by cosmic-ray bombardment of N-14.  Coal, oil and gas are very old; there is essentially no C-14 in them.

Uranium, thorium and decay products are a different story.

You are correct, however my comment depends on two points.
First, I know the percent abundance is not even a thousandth of a percent, but when one talks about 8 gigatons of material, that fraction of a percent becomes significant. My post was to illustrate that point.
Second, even if all that was burned was C-12, as you point out, C-12 is made into C-14 in the upper atmosphere. Consequently, if we are burning 8 gigatons of C-12 per year, that would put plenty of carbon atoms in the upper atmosphere to be struck by cosmic rays, which would still increase the C-14 levels.
-Stop the Iran war-
No, nitrogen is made to C-14 in the upper atmosphere.
when one talks about 8 gigatons of material, that fraction of a percent becomes significant.

The coal and oil have been sitting for at least 500 million years.  500 million years is roughly 8500 half-lives of C-14.  Each 10 half-lives is roughly a factor of 1000, so the original C-14 quantity has been reduced by a factor of ten-to-the-2550th-power.  Even if you started with 8 gigatonnes of pure C-14, it would all have decayed by now.

Never underestimate an exponential process.

I'm not religious even though I was raised Methodist.  However, it struck me while reading this post that the Garden of Eden parable applies.  We have lived in an age of innocence believing in fairy tales such as the "invisible hand."  But if we are to survive as a science-based secular society the time of testing is at hand.  We are soiling our nest and running out of food.  If we can collectively meet these twin challenges of global warming and resource depletion in a rational manner, we will truly demonstrate that there's something new under the sun.  I refer to solutions that allow us to keep the truly valuable and hard won scientific knowledge of our world and use it to help achieve homeostasis.  Our childhood is over.  We must manage this world we live in with vigor, intelligence and competence.  Our collective life depends on it.

Successful solutions must arise out of collective action.  TOD is a crucial part of that by providing an open forum for civil scientific discourse - good minds from a variety of disciplines come together here to discuss our possibilities.  It is my observation that TOD participants are economists, oil folks, geologists, professors, farmers, retirees, business executives and perhaps even a lawyer or two.  And the list grows daily.

It's really quite exciting when I step back and look at what's happening here.  This seems close in spirit to the town hall meetings in New England at the beginning of our country.  Perhaps just a tad more scientific.  More like the wonderful scientific clubs of 18th and 19th century Europe.

What I find most appealing is the rock solid civility and genuine kindness of spirit that pervades these posts.  It is clear that our moderators put a lot of their time and thought into providing a tableau of topics that illuminate and help direct our conversations into productive channels. Stuart's post on the carbon cycle is a perfect example.  I'm aware that the carbon petagram numbers Stuart has used may be off by an order of magnitude - but that's merely a technicality.  Stuart's quest is helping me learn how to think about this problem numerically.  And, unlike carbon scientists, his post is not filled with opaque scientific jargon.

While there is no guarantee rationality will pull us out of the maelstrom, I far prefer it to the shrill apocalyptic approach.  Sufficient unto the day is the evil thereof.  Let us survey our world with a cool, calm eye and assess our possibilities.

I fancy this is the kind of conversation that would give Garrett Hardin, that tough-minded and brilliant ecologist, great hope.  I found his "Filters Against Folly" to be one of the best books I've ever read.  We must think with both words and numbers. Finally we ask "and then what?"

There are no easy answers.

The test can not be taken again if we fail.

The test will not be graded on a curve.

Well, considering my posts here--which were made to convey some knowledge to augment Stuart's excellent effort--and the lack of any response whatsoever to them--I guess I might as well not typed them up at all.

Which is why I never actually post (but will occasionally comment) on climate change issues at TOD. As always, I recommend Real Climate. But, I still hope to read Start's continuing series on the subject because I will find it interesting and in the end it is a much bigger subject than maintaining our pathetically shortlived affluent lifestyles based on fossil fuels addiction.

Does that sound bitter? You bet.

I recommend that TOD energy enthusiasts get themselves acquainted PDQ (pretty damn quick) with climate change issues as caused by fossil fuel emissions. Then maybe we wouldn't see so many pie-in-the-sky solutions to our problems (like CTL--coal to liquids or Canadian tar sands or Venezuelan heavy oil/bitumen) that don't change the Big Climate Change Elephant In The Room that nobody cares to acknowledge.

I'd expect that the readers here are the "early adopters" on both Peak Oil and Global Warming, and have all made at least some attempt at increased energy (and CO2) efficiency.

(Heck, I sit here in a cold house as I type this.)

I saw the "million years" post and didn't feel a need to responed.  Sometimes "no response" equals "ack."

I continue to see PO and GW as "population response" problems, and my feeling is that "early adopters" can only push so far.  They (we) will be seen as strange by the majority until (if or when) some magic condition occurs.

I mean look at GM's "SUV shock" ... did that happen because we convinced everyone that PO/GW was around the corner ... or did $3 gas do more than we ever could?

Stepping back, and pretending to be a martian observer - I think we're screwed unless (if or when) we are fortunate enough that some "shock" wakes everybody up.  It is my (maybe cycnical) opinion that fringe ideas do not change majority minds.

I think that a lot of us have a pretty strong certitude that things like converting to all nuclear or all renewables in the next two decades has zero chance of happening.  Construction and installation would have to jump 1000% practically overnight and that's just not possible.  As I understand it the U.S. his already close to maxed out on wind power installation and solar installation because of a shortage of manufacturing capacity.  Also the corporations and the governments with the multibillion resources required show no inclination to spend it.

The world will not willingly cut its consumption of energy, IMO.  They will instead demand of their governments cheap energy, if for no other reason that that is the only proven way to a good standard of living.  As long as there are people that say that an energy crisis or global warming does not exist, a majority of the population will believe them because it's easier.

You can build concentrating solar peaking power in the southwest, releasing hydroelectric power now used for peaking to be used for intermittancy gap filling for wind power. The extra solar and wind would about equal nuclear, and would essentially replace our depleting natural gas.
That's probably what's going to happen, that and coal based power and synfuel plants. Oh, and some nukes. Probably the crappy PWRs we have right now.
Unless technology changes and we go and do something completely unexpected like cold fusion or whatever.
Dave, I appreciated your posts above.  As a non-scientist, until I got to them I was thinking "I wonder what the folks at RealClimate would have to say about this discussion?" and was contemplating an email or a post there to alert them to Stuart's series and invite comments.  When I read your posts I realized that we had climate expertise right here at hand.  Thanks, and please keep it up.
Liz, I appreciate your kind remarks but I have nothing like the expertise of those Real Climate guys. But I've done some reading.
Don't assume that no response means no readers. I follow your RealClimate links. Looks like we're in trouble. But those articles say it more eloquently than I could, so I don't comment.


Well, Dave, I appreciate your posts.

I've been swamped with work and family and "off-line" life.

Also, I'm trying to absorb info on other threads and some other sites.  But, yes, climate change is a big deal and my guess is that we will be overtaken by an enevironmental tsunami that will dwarf our geopolitical bickering and our haggling over just how much oil is left, EROEI of alternatives, and specific nuances of the application of HL to various places.

Even so, I think that Stuart S. is right to note that many of us are trying to integrate data and analysis as best we can.

Many of us are taking action as you know.

Keep posting, I for one chime in when I can and when I suspect that I contribute.

-- bathed in petroleum and the effluence of coal burning, nuclear weapons testing and use, and Lord knows what other goodies -- beggar

Well said Dave. Global warming is
the elephant in the room and
every day that passes it's getting
a little bigger and a little angrier.

I am going to fly a kite here and put
it to the group that September 2006
will mark a turning point for the US
and probably for humanity.

Remembering the horrendous damage
that Katrina, Rita and Wilma caused,
and noting that the CO2 level in the
atmosphere rose by a biggest amount
in recorded history through 2005,
(up 2.2ppm in the first ten months),
we should surely anticipate even
greater damage than last year in
the coming [Northern] summer of

Note also that September 2005 saw
the smallest area of sea ice in
the Arctic, the culmination of a
several-year sequence. Logic would tell us that the meltdown will be greeater this year
and that disturbances to normality
will be greater.    

And I concur absolutely with your
comments regarding pie-in-the-sky
solutions to peak poil, such as
converting coal into liquid fuels,
in ordrer to keep the system going
just a little bit longer.

At some stage those who do not
curently accept that pratically
everything we do adds to the
problem, rather than reducing the
problem, will be forced into such
acceptance of reality.

I will cite the dropping of water
onto forest fires by helicopters as
a classic example of short term
thinking that adds to the long
term problem  -using a fast
depleting resource and generating
harmful emissions in order to solve
an immediate problem that is
almost certainly exacerbated by
consumption of oil and release of
emissions into the atmosphere.

As an observation that will
undoubtedly upset many, I will
add that I oten personally find
engineers the most difficult
'scientists' to deal with, because
they always seem to think that
there is a technical fix to every
problem. I am not sure whether it
is that kind of mind that takes
up engineering, or whether that
attitude develops as a
consequence of engineering training.  

Good thoughts.  And another very interesting post.  
Carbon/Global warming and peak oil certainly dovetail in terms of calling out for solutions that will enable some creature comforts going forward.  I would love to hear about real-live existing companies (not just Rocky Mountian Institute think tanks) that are making money promoting conservation technologies.  Right, the market does not price externalities well, but there must be so much low-hanging fruit in terms of our overall energy usage that enterprising folks could do well by doing good and get us off of this trajectory.  I work in the capital markets, and investors will fund anything that can make a buck with a good story around it.  And nothing seems to be quite so sustainable (or credible) as a company making a buck.  What does the collective wisdom of TOD see in terms of emerging conservation technologies?  I think we are all dying to support them!
(kevin, formatting issue:  would you mind not inserting breaks so that your text flows to the column width like everyone else's?  Just use breaks between paragraphs.  It's easier to read that way.)
IME, people do that when the formatting of the page is too wide for their screens/font size.  They are forced to scroll back and forth to read, and try to "fix" it by inserting hard breaks in their own posts.
Users can change their comment text box width by altering their 'Interface preferences' (link in the user box in the upper right hand corner of TOD pages, or here). On the form, there is a field called 'Text box width'. Make number smaller, and click 'Save preferences'. See if that helps.
I have adjusted the character width from the
preset 60, to 100, as suggested, so this is
just a test to see how that works out. I must
say it was frustrating to be typing away and
having the text disappear off the right of the
sceen so quickly, then having to hit 'enter' to
view what I had written  -hence the unintended
breaks. Thanks for the tip.  
Actually, you're supposed to make the number smaller, not larger.
Sounds like you're using an old browser where text doesn't word-wrap in the text-input box. That would be a huge pain. Making the box smaller won't help. Make it very big, and you still have line breaks, and then if your comment is squeezed tighter than the box, it looks really ugly.

The problem is that lack of word-wrap, which most of us don't have to deal with. As I type this, I only hit "enter" at the end of each paragraph.

Get Firefox ( and then get the Adblock extension and learn to use it. You'll have a much nicer Internet experience. (Adblock is wonderful--I see maybe three flashing ads on my screen in a day's surfing.)


What do you any of you think of the reverse greenhouse effect caused by an interaction of monsoon rains and the Himalayian mountains?

"As the Himalayas grew, huge amounts of rock were exposed to the elements. The heavy monsoon rains combined with carbon dioxide in the air and eroded the rock. Could this process called chemical weathering take so much carbon dioxide out of the atmosphere that global temperatures would drop enough to trigger an ice age?"

I want to make one belated comment on the general issue of global warming and the future.

My understanding is that most of the impact of global warming is in the relatively far future, decades away, in the latter half of the 21st century. Some small effects are being noticed now, changes in growing seasons, changes in animal and plant distributions, but nothing major. There has been 1 paper I think claiming to see an increase in hurricane strength but there are many papers that show just the opposite.

Given this fact, and given our great uncertainty about the course of the future, I tend to discount damage that is so far off. There are many things, both good and bad, that could happen between now and then which would make global warming much less of an issue than it now appears.

One obvious possibility which I am sure Peak Oil believers will have thought of is that we might run out of oil and fall into a permanent worldwide depression. In this scenario, even though we have coal and other energy resources (tar sands, methane hydrates?), we are not able to muster the infrastructure to put those into widespread use as we have today with oil, and so we revert to a low-energy society, with or without a dieoff. Obviously, with such a catastrophic outcome, carbon emissions will be greatly reduced and the impact of global warming in the 2050-2100 time frame will be much less.

A more optimistic scenario has us successfully switching away from oil and continuing the long-term trend of economic, technological and scientific growth. In this version, which I see as the business-as-usual model, the world of 2050 is far richer and more capable than the world today. They may have many technological tools to deal with global warming and its problems that we cannot even envision from our current perspective. Maybe nanotech or biotech will let them evolve an organism or machine that can efficiently remove carbon from the atmosphere, or maybe some kind of shield can be constructed in space to reduce sunlight hitting the earth. Of course this sounds like science fiction today, but on the assumption of continued scientific growth, we have to use science fiction to envision the world 50 or 100 years from now.

The point is that so many things can happen, good or bad, that it is almost impossible to judge how great an impact today's carbon emissions will have. By the time they will have built up enough to be a problem, the world will very likely be quite different from today. We can't begin to judge how bad a problem our current carbon emissions will turn out to be.

The way economists model such uncertainty is by discounting future costs based on an interest rate. If we use a rate of 5%, then costs 50 years in the future get discounted by about a factor of 10; and costs 100 years in the future get discounted by about a factor of 100. This provides a basis for judging whether a proposed mitigation strategy makes economic sense. If it is designed to help against problems 50 years from now, it needs to cost 10 times less than the problems it fixes; and if it is designed against problems 100 years from now, it has to cost 100 times less. At this point I don't think there are many proposals on the table that satisfy this stringent cost/benefit analysis.

Halfin wrote ". . . most of the impact of global warming is in the relatively far future, decades away, in the latter half of the 21st century. Some small effects are being noticed now, changes in growing seasons, changes in animal and plant distributions, but nothing major."

Actually, what appears to be a fairly subtle effect (e.g, small temperature rise) can have (actually has had) a surprisingly big impact. Basically (if I recall the seminar correctly), since the 1920's April 1 snowpacks in the mountains of the Colombia River system have declined some 50% and, at the current rate of temperature increase, are projected to decline another 50% in some 20 years. Paradoxically, precipitation increased 15% in the same period but it essentially ran off. The hydrologist said the river system managers will shortly have the choice of managing river flows for salmon, for hydropower or for irrigation water but only one of the three because that disappearing snowpack has essentially been the water storage system. He added that even if it were publically acceptable, the river system structure is such that this storage capacity could not be replaced by raising existing dams or constructing new ones. Currently the river system supports both significant irrigated agriculture (Snake River plain in   Idaho, Columbia Basin in Washington) and significant hydropower production. Salmon recovery is a major public issue.

Climate Impacts on Washington's Hydropower, Water Supply, Forests, Fish, and Agriculture <>

This work is being done by the Climate Impact Group of the Center for Science in the Earth System at the U of Washington <>

Halfin, I was going to write you a long diatribe / explantion but it would not help. Let me give you an analogy instead: if it takes 5 miles to turn a tanker through 90 degrees it takes 100+ years to change the climate so.

I have a criticism too, it is unwise, and incorrect, to apply apparent economic truths (or fictions, sorry for that jibe) to other sciences.

Strangely I think those things you perceive as plausible 'sci-fi' possibilities are our best hope! But that is sadly because i fear those you seem to think may be realistic are in loud cuckoo land.

Perhaps we should arrange an audio chat, i would enjoy.

typo correction: loud cuckoo -> cloud cuckoo, lol
"[We might] revert to a low-energy society, with or without a dieoff. Obviously, with such a catastrophic outcome, carbon emissions will be greatly reduced and the impact of global warming in the 2050-2100 time frame will be much less."

Halfright (sorry, couldn't resist), it's true that carbon emissions would be reduced. But particulate emissions, which cool the earth, would also be reduced, and particulates leave the atmosphere very quickly. So in this scenario, global warming would hit quite hard, quite quickly.


"Maybe nanotech or biotech will let them evolve an organism or machine that can efficiently remove carbon from the atmosphere ..."

Actually, it's been done. It's called a plant. And it works fine to sequester carbon until the plant dies. After that, rotting or burning it releases the carbon, and we're back to square zero ...