Right observation, wrong conclusion

Some time ago, I got an enthusiastic e-mail from a friend.

He told me he have had a compost heap at home
(Really a heap of leaves, not the neat thing you often find in a residential garden. It had been staying there for years, with just a slight decease in volume).
After having repeatedly listening to me talking of the benefits of adding char to compost and soils, he thought that he should give it a try. So he took some leftover barbeque char and put in the compost heap.

That was last autumn. He forgot everything until some weeks ago when he happened to stroll by. The heap had disappeared! Instead of the heap of semi-mouldered leaves, there was a much smaller heap of something rather looking like soil, with lots of earthworms in it. Plus the char.

Then he went to the computer and mailed me: --“ I am a believer …!”

-----------------------------------

In last week’s number of Science, (2 May), David Wardle, Marie-Charlotte Nilsson och Olle Zackrisson delivers an article: "Fire-Derived Charcoal Causes Loss of Forest Humus". They have done exactly the same observation, that charcoal increases soil meabolism, using a controlled measurement method during a ten-year long test. They used three types of 1 gram bags containing respectively charcoal, humus and humus + charcoal, letting them stay in the soil for up to ten years.

The investigation revealed that the reduction in weight of the bags containing both charcoal and humus was much larger than the bags containing only charcoal or only humus.
Just like my friend with the compost heap found out.

So long, so well. A fair conclusion would have been that the charcoal increases the soil metabolism. Not mentioned in the report, but the also found increased vegetation around the bag with humus + char.

Sadly, they did not stay with that. They also jumped to a conclusion where they claim that the increased microbial activity break down humus particles at a rate that counteracts the carbon sequestration effect of the carbon.

The latter conclusion, however, is wrong.
Since the humus particles would have been broken down later anyhow, a faster breakdown will not counteract the carbon sequestration made by the incorporation of carbon particles in soil.
Just like the compost heap of my friend; waiting some more years would have changed an un-charred heap into the same composted state as the one with char added.

The decomposition rate of the humus in the soil has nothing to do with the carbon sequestration capacity of the charcoal. This capacity is only influenced by the longevity of the charcoal in soil (which is many thousands of years)

Critical numbers: Where should Humanity Aim?

James Hansen and his associates are currently working with a manuscript called "Target Atmospheric CO2: Where Should Humanity Aim?", available in the link above.
In it, they conclude that, to be out of the immediate danger of tipping our life support system into a state where it no longer can be considered a life support system to us (the humanity), the carbon dioxide level in the atmosphere should be below 350 ppm.

The carbon dioxide level in the atmosphere is 385 ppm today.

This means that the atmosphere contains about 74 Gt too much carbon. Every year, about 7 Gt more is released. Say, as a thought experiment, that all emissions, 100%, are stopped within 20 years (don't ask me how), leading to a total breakdown of our current society. Even that would mean additional emissions of about 70 Gt more, leading to a CO2 concentration of 418 ppm (if the oceans don't suck up anything more, perhaps 400 ppm if they are friendly enough to do that).
CO2 levels like that would probably lead us far beyond several tipping points.
Even if not, the resulting climate would not feed the population, not to talk about the potential for floodings.

So, if disaster is threating whatever we do, should we give up?

No, since there is one more possibility: If the efforts to decrease emissions are combined with a massive sequestration of carbon, then it is possible to back away from the ominous carbon dioxide levels.
As the incorporation of plant charcoal in the soil obviously has a lot of benign effects (Google: Terra Preta ), increasing crops, reducing nutrient loses and so on, why shouldn't we start immediately?

The carbon numbers II

I have several times been asked about the amount of carbon existing in excess in the atmosphere, and the possibilities to remove it within reasonable time. Therefore, I will provide the figures as far as I know them, and the reasoning behind them.
If you can't stand numbers, stop reading here.

The global annual net primary production (NPP) varies, but is estimated to be between 70 and 100 Gt per year, by different sources. This is the annual biomass growth in the plant cover of the Earth. For ease of calculation, let's take 80 Gt as the number. Say that 50% of this is thin roots and leaves, not usable for charring. Remains 40 Gt C that is theoretically available for charring each year.
Assume furthermore that efforts to create charcoal for carbon sequestration results in an annual sequestration of 2 Gt C as charcoal. That would mean an addition of four tonnes of char per hectare globally, certainly a war-like effort. The global forest product production 2004 was abut 9.5 Gt (FAO), with a carbon content that can be estimated to 3.8 Gt C, so we are speaking of a herculean, warlike efforts in charring, about half the size of the global forest industry.
However, char can be made from not only forest products, but also straw and husks from agriculture, as well as forest products that are useless to the industry, which makes it at least theoretically possibie to reach a goal of 2 Gt. That is about 8.5% of the above figure of coarse biomass production.

Jim Hansen and Pushker Kharecha of NASA Goddard Institute for Space Studies have pointed out some faults in my calculations in the following paragraph, why I below present it in the revised form :
The carbon dioxide "cloud" is presently about 475 Gt too large (counted as accumulted emissions of C, carbon). Due to buffering from seas and other ecosystems, the atmosphere only contain 220 Gt of carbon The number is the difference between the atmospheric content in pre-industrial time (280 ppm) and that of today (384 ppm). (Of this figure, about 33% is from deforestation). (Figures from Richard A Houghton, Woods Hole Research Center, one of the IPCC guys, and Jim Hansen/Pushker Kharecha of NASA) Imagine that you could take all this away and convert it into charcoal. That amount would add about 955 tonnes of char per hectare agricultural land globally. This wll give the soils a carbon content f about 25%, not very far from the Terra Preta soils. But with the above efforts, 2 Gt p.a., it would take about two hundred years to reach that point.

The global carbon dioxide effluents of today are equivalent of about 7 Gt C. Assume, for a moment, that the people and their leaders around the world will face the imminent danger of a sudden and irreversible climate change and decide to do everything possible to avoid it. They decide to start the above sequestration combined with a sudden braking in carbon emissions, e.g. an 85% reduction in 25 years, leveling out on roughly 1 Gt C per annum, leading to a net sequestration of about 1 Gt C per annum.
Then, given that the reduction is even over time, one could expect that the carbon dioxide cloud could start reversing after about 18 years.

I hope sincerely, that that is not too late.

The carbon numbers

I have several times been asked about the amount of carbon existing in excess in the atmosphere, and the possibilities to remove it within reasonable time. Therefore, I will provide the figures as far as I know them, and the reasoning behind them.
If you can't stand numbers, stop reading here.

The global annual net primary production (NPP) varies, but is estimated to be between 70 and 100 Gt per year, by different sources. This is the annual biomass growth in the plant cover of the Earth. For ease of calculation, let's take 80 Gt as the number. Say that 50% of this is thin roots and leaves, not usable for charring. Remains 40 Gt C that is theoretically available for charring each year.
Assume furthermore that efforts to create charcoal for carbon sequestration results in an annual sequestration of 2 Gt C as charcoal. The global forest product production 2004 was abut 9.5 Gt (FAO), with a carbon content that can be estimated to 3.8 Gt C, so we are speaking of a herculean, warlike efforts in charring, about half the size of the global forest industry.
However, char can be made from not only forest products, but also straw and husks from agriculture, as well as forest products that are useless to the industry, which gives us a large possibility to reach a goal of 2 Gt. Which is about 8.5% of the above figure of coarse biomass production.

The carbon dioxide "cloud" is presently about 475 Gt too large (counted as C, carbon). The number is the difference between the atmospheric content in pre-industrial time (280 ppm) and that of today. (Of this figure, about 33% is from deforestation). (Figures from Richard A Houghton, Woods Hole Research Center, one of the IPCC guys.)
Imagine that you could take this amount away and convert it into charcoal. That amount would add about 95 kg char per hectare agricultural land globally. 38 bags of barbecue char. Not very much . But with the above efforts, 2 Gt p.a., it would take more than three hundred years to reach that point.

The global carbon dioxide effluents of today are equivalent of about 7 Gt C. Assume, for a moment, that the people and their leaders around the world will face the imminent danger of a sudden and irreversible climate change and decide to do everything possible to avoid it. They decide to start the above sequestration combined with a sudden braking in carbon emissions, e.g. an 85% reduction in 25 years, leveling out on roughly 1 Gt C per annum, leading to a net sequestration of about 1 Gt C per annum.
Then, given that the reduction is even over time, one could expect that the carbon dioxide cloud could start reversing after about 18 years.
I hope sincerely, that that is not too late.

Bali: the lose of the losers

Today, the Bali meeting to combat global warming is still not over, but however the ultimate outcome, one thing is to be said for sure: Because they focus on emission reductions only, they will not offset global warming.
Naturally (sad to say) the statesmen will not be able to agree. Vested interests prevail.
But.
Assume, quite hypothetically of course, that they concur of the utmost severeness of the problem and agree on, and stick to, a 90% decrease of the emissions of carbon dioxide during the nearest 15 years, starting today.
Even such an effort would give the atmosphere an additional amount of 20 Gt carbon dioxide, assuming the annual emissions of today is 7 Gt.
Even this amount might lead to abrupt climate changes. And we must do everything possible to avoid that. (Read Mark Lynas 'Six degrees')

So, even if the politicians stand together and make bold decisions, we all will probably lose.

So what to do? Pray the last prayer, take farewell of our closest, let the musicians play "Nearer, My God, to Thee" ?

No. There is a further possibility. If we combine a radical reduction of emissions with a strenuous effort in carbon sequestration with charcoal, say of 2 Gt annually (see below), then the actual amount of atmospheric carbon dioxide will start to diminish within 7-10 years, and we might get off with nothing more than the fright (and more fertile soils).

Otherwise, we might all loose.

How much space do you need?

For some years ago, I was asked the above question by one of my students.
Like most scientists, I started to answer: -- "That depends ... "
Then, I realized that it actually was a rather appropriate answer.
If you are talking about sitting space, it is not the same as what you need for producing your food demand for a year, or for making a good climate for your and your fellow creatures.
It is actually a series of spaces, each depending on the function of the next.
The attached picture attempts to give a notion of that.

The figure is clickable, if you have problems with reading the texts.

The reasoning is quite obvious. You need more space to produce food than you need to sit at the dinner table. And you need more processes and space to maintain a healthy atmosphere than you need to breath (although that area is a quite large, considering the 90 sq. m. inner area of your lungs).

The picture is just a rough outline, just attempting to draw attention to the different spaces needed for our life support, and our dependence of them. But it can also be seen as an attempt to bring figures to the global carrying capacity, with or without fossil fuels. Since the surface area of the planet Earth is estimated to around 150,000,000 km², the figure on the sketch would indicate that the carrying capacity for 'climate production' is exceeded at 7.5 billion people, given our current lifestyle.
It is certainly not sure that the use of fossil fuels will eternally increase the carrying capacity of the globe.
Perhaps the opposite.

A new way to tell the same thing

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L19703, doi:10.1029/2007GL031018, 2007

Received 15 June 2007; accepted 7 September 2007; published 6 October 2007.

Long term climate implications of 2050 emission reduction targets

Andrew J. Weaver
School of Earth and Ocean Science, University of Victoria, Victoria, British Columbia, Canada
Kirsten Zickfeld
School of Earth and Ocean Science, University of Victoria, Victoria, British Columbia, Canada
Alvaro Montenegro
School of Earth and Ocean Science, University of Victoria, Victoria, British Columbia, Canada
Michael Eby
School of Earth and Ocean Science, University of Victoria, Victoria, British Columbia, Canada

Abstract
A coupled atmosphere-ocean-carbon cycle model is used to examine the long term climate implications of various 2050 greenhouse gas emission reduction targets. All emission targets considered with less than 60% global reduction by 2050 break the 2.0°C threshold warming this century, a number that some have argued represents an upper bound on manageable climate warming. Even when emissions are stabilized at 90% below present levels at 2050, this 2.0°C threshold is eventually broken. Our results suggest that if a 2.0°C warming is to be avoided, direct CO₂ capture from the air, together with subsequent sequestration, would eventually have to be introduced in addition to sustained 90% global carbon emissions reductions by 2050.

(My italics)

As I said in the blog of 28/10, (why it needs two..) , it is not enough with reductions. More efficient measures need to be done. Only an extreme reduction of the effluents of greenhouse gases plus a strenuous sequestration effort might do the job.

Sequestration is easy, good for the soil, and might be profitable, so why not do it?

A small company, Purity, making kettles for water heating and purification, has taken up the idea: They calculate how much carbon dioxide emissions the making of their product generate and will contract a group of farmers in Ethiopia to make and bury charcoal to improve their soils under the supervision of an independent company. After that, Purity can claim that their products are carbon negative! (Since more carbon is buried than actually is released.)

Something for the big oil companies to take after?

Or buy carbon emission permissions... from a person who actually buried the same amount of carbon as charcoal!