Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.

Settings

Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup

Settings


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe


Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...



Username
Password
New? Register here
Forgot your password?

Latest Posts

Archives

A residential lifetime

Posted on 1 April 2010 by Doug Mackie

Guest blog post by Doug Mackie

One argument against accelerating global warming is that carbon dioxide has a short residence time in the atmosphere. The claim goes like this:

(A) Predictions for the Global Warming Potential (GWP) by the IPCC express the warming effect CO2 has over several time scales; 20, 100 and 500 years.
(B) But CO2 has only a 5 year life time in the atmosphere.
(C) Therefore CO2 cannot cause the long term warming predicted by the IPCC.

This claim is false. (A) is true. (B) is also true. But B is irrelevant and misleading so it does not follow that C is therefore true.

The claim hinges on what life time means. To understand this, we have to first understand what a box model is: In an environmental context, systems are often described by simplified box models. A simple example (from school days) of the water cycle would have just 3 boxes: clouds, rivers, and the ocean.

A representation of the carbon cycle (ignore the numbers for now) would look like this one from NASA.

In the IPCC 4th Assessment Report glossary, "lifetime" has several related meanings. The most relevant one is:

“Turnover time (T) (also called global atmospheric lifetime) is the ratio of the mass M of a reservoir (e.g., a gaseous compound in the atmosphere) and the total rate of removal S from the reservoir: T = M / S. For each removal process, separate turnover times can be defined. In soil carbon biology, this is referred to as Mean Residence Time.”

In other words, life time is the average time an individual particle spends in a given box. It is calculated as the size of box (reservoir) divided by the overall rate of flow into (or out of) a box. The IPCC Third Assessment Report 4.1.4 gives more details.

In the carbon cycle diagram above, there are two sets of numbers. The black numbers are the size, in gigatonnes of carbon (GtC), of the box. The purple numbers are the fluxes (or rate of flow) to and from a box in gigatonnes of carbon per year (Gt/y).

A little quick counting shows that about 200 Gt C leaves and enters the atmosphere each year. As a first approximation then, given the reservoir size of 750 Gt, we can work out that the residence time of a given molecule of CO2 is 750 Gt C / 200 Gt C y-1 = about 3-4 years. (However, careful counting up of the sources (supply) and sinks (removal) shows that there is a net imbalance; carbon in the atmosphere is increasing by about 3.3 Gt per year).

It is true that an individual molecule of CO2 has a short residence time in the atmosphere. However, in most cases when a molecule of CO2 leaves the atmosphere it is simply swapping places with one in the ocean. Thus, the warming potential of CO2 has very little to do with the residence time of CO2.

What really governs the warming potential is how long the extra CO2 remains in the atmosphere. CO2 is essentially chemically inert in the atmosphere and is only removed by biological uptake and by dissolving into the ocean. Biological uptake (with the exception of fossil fuel formation) is carbon neutral: Every tree that grows will eventually die and decompose, thereby releasing CO2. (Yes, there are maybe some gains to be made from reforestation but they are probably minor compared to fossil fuel releases).

Dissolution of CO2 into the oceans is fast but the problem is that the top of the ocean is “getting full” and the bottleneck is thus the transfer of carbon from surface waters to the deep ocean. This transfer largely occurs by the slow ocean basin circulation and turn over. This turnover takes 500-1000ish years. Therefore a time scale for CO2 warming potential out as far as 500 years is entirely reasonable (See IPCC 4th Assessment Report Section 2.10).

This post was written by Doug Mackie, a research fellow in the department of chemistry at the University of Otago.

0 0

Printable Version  |  Link to this page

Comments

Prev  1  2  

Comments 51 to 85 out of 85:

  1. GC, I think someone could write an interesting science fiction novel, entailing a plot wherein inhabitants of a planet with insufficient greenhouse gases are facing an ice age and discover (a hero is forced to jump through hoops to enlighten his fellows, natch) enormous hydrocarbon reserves, sufficient if extracted and burnt to bring things into balance. Evildoers attempt to thwart the plan by suggesting that these hydrocarbons are instead used to manufacture something called "Polyware", storage containers for mountains of excess food, but are ultimately thwarted. The hero basks in warmth and affection at the end of the book. But that's science fiction, as I said. The situation we face is unfortunately the opposite, but we could still sequester hydrocarbons in actual Tupperware(tm) if we chose and in this version of the plot the folks recommending the combustion method do not play the role of protagonists.
    0 0
  2. #34 John Russell (Sorry to anyone who has already read this comment: This is a repost. I am a potty mouth and John has made me delete bad words from the original. Where they are not being depleted by agriculture or deforestation the world's soils are all constantly deepening. No. This is false. As I said: with the exception of fossil fuel formation the carbon cycle is efficient at recycling carbon. Where precisely do you think significant accumulation is occurring? Please read TAR and AR4 on the subject of soils. There are certainly uncertainties but there is no way that soils can sequester a significant portion of fossil fuel emissions. My solution: Take a few unpopular low lying cities and flood them. Grow trees there. When mature, bulldoze the trees and repeat. It is essential to maintain anerobic conditions to promote peat/coal formation. Re the CO2 lifetime. I think the discussion tends to over-complicate a simple concept. The claim made by denialists is that CO2 has a short residence time and thus, they claim, cannot possibly cause warming over the 500 year timeframe discussed by IPCC. That is male cow excrement (can you guess what the offending word was?). Pure and simple. Through ignorance, malice, or both the denialists confuse lifetime with residence time. You go on to paraphrase my argument (that residence time is irrelevant) so I am not sure what your point is.
    0 0
  3. Johnd @50 Would the Urban Heat Island effect also qualify as a driver of water vapour? It certainly is measurable and widespread. This too is veering away from lifetime/residence time. However I shall indulge you, though without emoticons I am not sure you are serious. Do you mean to ask: “Do cities produce enough extra water vapour have the potential to control/change climate to a significant extent compared to extra water vapour in the atmosphere from general global increase in temperature”? If that is what you meant then no. The AR4 FAQ 1.1, 1.3. 2.1 and 3.2, and the main text they point to, answer this comprehensively and there is no point me pasting the text here. The issue is radiative forcing
    0 0
  4. Doug Mackie @ 53, thank you for indulging me. What I am asking is whether the billions? trillions? of tonnes, and ever increasing, thermal mass of manmade infrastructure has as much effect of storing heat energy as atmospheric CO2, thus also providing radiative forcing. The residential lifetime of such structures would generally exceed that of atmospheric CO2. Just a simple example to illustrate. Most brick, stone or concrete structures are built inside out with the thermal mass on the outside, insulated from the inside. When a structure is built with the thermal mass on the inside it modifies the internal climate due to the thermal mass both absorbing and dissipating heat energy albeit on a small scale. However structures built with the thermal mass on the outside have been built all over the planet on a massive scale and the effect is measurable as the UHI effect which is significant enough to perhaps inflate global average surface temperatures.
    0 0
  5. Doug Mackie @52. According to Wikipedia, (under the heading 'Soil Carbon') "over 2700 Gt of carbon is stored in soils worldwide, which is well above the combined total of atmosphere (780 Gt) or biomass (575 Gt), most of which is wood." I would say that counts as significant; don't you? I stand by my statement that natural biological processes -- if left alone by man (a critical qualification) -- will tend to build up the carbon content of the soil. I see this in my indigenous (to the UK) wet woodland year on year as rotting trees and leaves fall into the mud where only a few inches down it can become anoxic. Let's face it, this is how the fossil fuels formed in the first place. Note that I am not claiming that, left alone, soils can sequester all of our fossil fuel emissions -- can anything? -- but they do pull in the right direction. In Brazil I, personally, have witnessed deep, rich, soil full of organic matter being reduced to little more than sand within a decade or so, once it has been exposed by deforestation and turned over to agriculture. Forestation and even sustainable agricultural practices, if managed correctly, can sequester significant amounts of CO2. My point is that it can be more than just a temporary store while the trees/plants are growing, as your article suggests.
    0 0
  6. doug_bostrom (#51), My post that John deleted related directly to your point. I will try again after pausing to show that this post is "on topic". On this thread we are discussing the "Residence Time" of CO2 in the atmosphere, so it seems relevant to consider whether mankind can affect this in any way. Most of us accept the idea that CO2 concentrations are in fact rising owing to human activity. The sequestration issue is the other side of the same coin. Can mankind reduce CO2 concentrations? In my opinion the answer is clearly YES and there are plenty of strategies for doing so that I would support. Doug's idea of storing non-perishable food in Tupperware is probably the best of all. Governments should provide incentives to farmers to produce non-perishable food mountains instead of the perishable "Butter Mountains" and "Wine Lakes" created by the European Economic Community. This will help reduce the horrific famines that will occur during the next "1816" (The Year Without a Summer). This is not science fiction; enlightened governments have used this strategy all the way back to biblical times. It used to be called "Building Granaries" rather than "Sequestration". Where can one find a Hammurabi in this modern world?
    0 0
  7. Water vapor will respond to, and amplify any change in temperature, (although with the proviso that to amplify an upward change, there must be a source of water vapor). I would *suspect* that there is enough water vapor emitted in a city in exhaust and respiration for that to work.(**) However, while the UHI is locally important, averaged over the planet's surface it is tiny compared to the CO2 forcing. (**) There's a lot of other things going on with a city though. It's not just a heat island, it's a pollution island. Ground level ozone, aromatic hydrocarbons, NOx, ... you'd have to ask an atmospheric chemist specializing in such matters if those have any effect on urban humidity.
    0 0
  8. Apologies. My #57 was in response to #50, which I now see was also answered at #53. Heh, considerable similarity in points made - scientific understanding is consistent. To add value, I'll respond to #54. Thermal mass of anything on land is tiny compared to the thermal mass of the ocean. Also, adding thermal mass in some location while holding other factors the same will in general produce a moderation of temperature extremes, e.g. warmer nights and cooler days. The UHI has very little to do with thermal mass, and very much to do with albedo. Blacktop, dark roofs, and the three dimensional topography of buildings make a city a much better absorber of sunlight than natural landscapes are.
    0 0
  9. @55 John R. Yes, on very long time scales, there has been a net flow of carbon *through* the soil into fossil fuels. But that flow rate is very low. Other than that, what the soil takes up, it gives back (or else all the carbon would wind up in the soil, which obviously hasn't happened). So, while the woods near you may be building soil, there are other places in the world where soils are shrinking. Absent man, soil would be in pretty good equilibrium, except for that tiny net flow to fossil fuels. You are right that the size of the soil carbon reservoir is larger than that of the air (and smaller than that of the ocean). As long as near-equilibrium is maintained, that doesn't matter. However, one very possible concern is that because of human interference, the soil reservoir will shrink, pushing carbon into the air. Specifically, deforestation in tropical to temperate regions, and warming of soil/permafrost in subarctic regions are processes that have the potential for a significant transfer of carbon from the soil to the air.
    0 0
  10. "the UHI effect which is significant enough to perhaps inflate global average surface temperatures" There is no credible evidence for this. The trends for urban areas aren't significantly different from rural areas. See this post, which references the papers listed below. http://www.skepticalscience.com/urban-heat-island-effect.htm http://pubs.giss.nasa.gov/docs/2001/2001_Hansen_etal.pdf http://www.ncdc.noaa.gov/oa/wmo/ccl/rural-urban.pdf http://journals.ametsoc.org/doi/abs/10.1175/JCLI3730.1 http://www.agu.org/pubs/crossref/2008/2008JD009916.shtml GC, your irrational fear mongering with things like the earlier "pestilence" (already adressed) or that new "horrific famine" is getting tiresome. It seriously undermines your argument, whatever that is. That kind of gross exaggeration, completely divorced from reality, is fine in tabloids or clumsy attempts at manipulating the public. Take it to that kind of forum.
    0 0
  11. Philippe Chantreau @60, some recent analysis of USA surface temperatures by Dr. Roy Spencer (http://www.drroyspencer.com/category/blogarticle/) suggests that there is sufficient doubt and perhaps significant difference that warrants closer examination to accurately quantify the UHI effect. As a matter of interest, and to put it into perspective, is there any data that indicates the total weight of manmade structures world wide that would qualify as thermal mass? GFW @58. Are not albedo and thermal mass merely different sides of the same coin especially when dealing with the UHI effect?
    0 0
  12. johnd, surface temperature measurements are off topic. If you want to continue discussing that, you should do so on the appropriate thread: Temp record is unreliable. (I suggest you read that posting and the existing comments on it first.)
    0 0
  13. Tom @62. Thanks, I had read that discussion some time ago, but I see that it has had some recent additions. I'll post the link I provided above onto that discussion as it is more recent than any of the postings there.
    0 0
  14. Johnd @54 Huh? Sorry, I seem to be especially obtuse lately. Do you mean to ask if: Given that there is so much concrete etc with a lot of thermal inertia then will the concrete soak up a lot of the excess heat that would otherwise warm the atmosphere? And/or will the slow release of such stored heat alter the climate? The answer is simple and can be phrased as a question: “Why are wine cellars cellars?” Hint #1: What should you wear in a desert at night? Hint #2: Compared to concrete, what is the heat capacity of water? Or soil? Or sand? How much of each is there on earth?
    0 0
  15. John Russel @55 Yes, reforestation can be a help. BUT ask this question: How much of the current “extra” CO2 in the atmosphere is due to deforestation and/or soil degradation and how much is due to fossil fuel burning? The answer is that reforestation and reforming soils will help but it will never be a significant contribution to reducing atmospheric CO2 UNLESS we have some way of reforming fossil fuels faster than we are burning them. Your example about Brazilian soils is especially informative. The reason more and more forest is slashed and burned is that rain forests have poor, shallow soils that depend on a short residence time of carbon. That is, they depend on high turnover of leaf litter etc to support high biomass. They do not have deep reserves of buried organic matter and once the biomass is removed and you can take only a few seasons of crops (grain and/or cows fed on the grain) before the soils are exhausted.
    0 0
  16. Philippe Chantreau (#60), You really need to be more aware of recent history. Just to get you started, I recommend the following video by the "History Channel". It does not take sides in the Alarmist/Denier debate but it explains climate change over the last 1,000 years in an interesting way. Enjoy: http://www.veoh.com/browse/videos/category/educational/watch/v158890018kQaxQaK Getting back to the residence time of CO2 in the atmosphere, do you see this as something that mankind can influence or would you leave it up to nature? The FACE experiment (NASA/Duke university) showed that the rate of sequestration by trees is affected by CO2 concentrations. If such effects are significant the relevant time constants could be much shorter than those suggested at the top of this thread. On another thread, Tom Dayton has pointed out that the growth spurt in loblolly pines caused by elevated concentrations of CO2 tends to be short lived owing to limitations in other nutrients such as nitrogen. However, it is likely that higher CO2 concentrations will favour plants that can acquire nitrogen directly from the atmosphere (e.g legumes), especially if agricultural incentives are in place. Imagine "Bean Mountains" as well as wheat and rice mountains. Throw in Olive oil lakes and maybe we can cook up something tasty and nutritious when the next Tambora blows its top.
    0 0
  17. Doug Mackie @64. I'm not trying to take this off topic, is there a more appropriate thread for this line of thought? However to respond to your comments, it is the relative effect of 10 Gt of concrete added to the earths surface as infrastructure globally each year against the 3.3 Gt of CO2 added to the atmosphere each year that I was hoping to have quantified.
    0 0
  18. gallopingcamel @66. Similar FACE experiments growing wheat in Victoria resulted in improved growth and yields with improved utilisation of moisture but protein % were slightly down due to nitrogen limitations. I'm not sure whether the increased yield, + 17%, meant that each plant still maintained the same nitrogen uptake . From what I recall the total protein yield of each plant was the same or even more but did not match the increase in wheat yield. It is a natural fact of cropping that often protein % rises when wheat yields fall and vice versa.
    0 0
  19. johnd, how about taking that topic over to "It’s land use"?
    0 0
  20. gallopingcamel and johnd, I believe your comments on plants belong not on this thread, but on "CO2 is not a pollutant".
    0 0
  21. In my final reply to this off topic line of questioning: 1A)You have a ref for your concrete figure? 1B) Do you know how concrete is made? 2) Why don’t concrete structures continue to get hotter and go china syndrome? (Hint: Clausius) 3) My earlier comments were to invite you to suggest how the heat retained by conrete compares to the heat retained by the oceans and/or soil and/or deserts and/or rocks. You did not respond.
    0 0
  22. Johnd, I'm surprised. I gave a list of scientific references. You cite a blog post. Any real scientific work in that blog post? Sorry, I have barely enough time to keep up with SkepSci, so I'm not going to Spencer's blog. If there is anything substantial there (i.e. published), you can cite or link it. I think Doug Mackie summarizes a number of good points in hos post 71. GC, I am not sure exactly what you are trying to say and that's not my point. I don't care for language including "horrific", "pestilence" and what not. It's amusing for a while, then it becomes annoying. This site's focus is the existing science on a certain subject. Grandiloquence and theatrical effects do not add to the discussion.
    0 0
  23. Shows what gallopingcamel knows. I was in fact referring to the point in Earth's history when dinosaurs dominated every single ecological niche on the planet. A time before the evolution of grass & the crops which were developed from said grass species. In truth of fact, it is far, far easier to guard against cold-via technology-than it is against heat. For instance, as long as we have access to fuel/energy, we'll always be able to generate sufficient warmth to grow crops & live quite comfortably, & you can always add additional layers to your clothing if it gets too cold. The same cannot be said for extreme warmth, where plants wither & die & where water may well become exceedingly scarce. So, given the choice between a Warmer World & a colder world, I know which I'd pick-no matter how much the Fossil Fuel Lobby tries to convince us otherwise.
    0 0
  24. Philippe (#72), My points have to do with influencing the CO2 "Residence Time" in the atmosphere. In particular there are some sequestration strategies that make sense. Many sequestration methods proposed create useless materials thereby destroying wealth, whereas growing food or wood contributes to prosperity. I can't put it much plainer than that. Can I count on your support? Did you look at the History Channel video (#66)?
    0 0
  25. Marcus (#73), "For instance, as long as we have access to fuel/energy, we'll always be able to generate sufficient warmth to grow crops & live quite comfortably, & you can always add additional layers to your clothing if it gets too cold." Maybe Tom Dayton can point me to the appropriate thread for discussing this very interesting speculation. If not, I look forward to the subject coming up on some future thread.
    0 0
  26. Doug Mackie @55 Thanks for your response. I have emailed a colleague who is a leading soil scientist for his comment. I'll let you know his response on this thread as soon as I hear back. You're right about tropical soils: the temperature ensures there are high levels of microbial activity which break down organic matter very rapidly. However we should also consider the immense areas of tundra in the high latitudes where soil accretes at around 1mm per year. I agree completely that human activity -- to use a cynical expression -- is more than a match for natural sequestration processes. The reason I was a rather critical of your original statement was that I don't wish to discourage people from planting trees; it's an essential part of dealing with the problems we face -- that and the fact I have 100 acres of young trees growing even as I write. One does one's best to do the right thing when so many other people appear not to care about the future.
    0 0
  27. John Russell @76 Nor do I wish to disuade people from tree planting. However, I read over 900 public submissions made to 3 successive Select Committees considering an Emissions Trading Scheme (ETS) in New Zealand. It was curious to see how many people from the forestry industry took issue with the Kyoto rule that tree carbon is considered released when the trees are harvested. (*) The foresters claimed they could keep growing and cutting trees for ever and keep getting new credits. My point was that in most situations reforestation is a one time credit. A one time credit worth having but still a one time credit. If you can dig a deep pit and throw your cut down pines in there so they don't rot for a few thousand years it will give us a bit of breathing space. (But still won't address ocean acidification when they eventually do rot). * One submission said that since you didin't hear the CO2 hissing out the cut stump it was proof that CO2 was not relaeased from cut down trees. Judging by the rest of that submissioin, I'd say they meant that sincerely).
    0 0
  28. GC "I can't put it much plainer than that." Indeed, and that's a significant progress compared to the horrific- pestilence type of formulation. I conclude that we are in agreement on the better ways to word an argument.
    0 0
  29. Doug Mackie: 77 I see now where you're coming from if your vision of woodland/forest is the monoculture cash crop of pines which are rased and replanted every 30 years or so -- as also are oil palm plantations. That's the current reality of most commercial forestry, enabled by the ready availability of cheap diesel. I'm talking about woodland management of indigenous trees which are coppiced and thus highly sustainable and, I would claim, a net carbon sink. That's the only sort of tree-planting I wish to promote.
    0 0
  30. Phillippe (#78), I will choose my words more carefully! Several folks are discussing the production of timber and that is another great strategy for sequestration. Are we headed for consensus on something?
    0 0
  31. There is no doubt that vegetation is a great way to take a hold of all that carbon. That's how it was stored in the first place. As others have mentioned, the problem is to not only store, but actually remove that carbon from the cycle. It would be, in fact, low tech and possibly low impact geo-engineering. Problem is, it's not so easy to do that from vegetation because it implies that the vegetation will neither burn nor rot. The remarkable thing that happened in the carboniferous was the storage of immense quantities of vegetation in anoxic conditions. Now all that carbon/hydrogen is getting back to the oxygen with a vengeance, thanks to us. If we want to get anywhere close to the kind of quantitative result we need, we're going to have to use, reuse and recycle ad-infinitum every scrap of wood we produce, and produce vast quantities of it. Feasible but difficult and perhaps energy intensive too. There is no silver bullet. We're looking here at a solution requiring: massive land use changes, infrastructure changes, attitude changes (getting back to using wood for all sorts of applications). Not to mention that the displaced industries will fight with their usual methods (i.e. the current climate disinformation, tobacco campaigns, lead paint campaigns, etc). It will also involve some strain on the world's economy. It's not a bad idea and I'm not opposed to it in principle but it will be every bit as hard as reducing emissions.
    0 0
  32. Many trees, from Sequoias to Olives can survive thousands of years when we let them. Even if we harvest the trees for lumber that wood can have a long lifetime, especially high quality woods. Instead of incentives for food and timber production we have provided incentives for farmers to produce ethanol from corn as an additive for gasoline, so the carbon absorbed is soon released back into the atmosphere. It is hard to see much benefit from this idea while the disadvantages have become increasingly obvious, including poorer vehicle performance, higher food prices and the pollution of water ways. Phillipe mentions the lobbyists who pressure governments into making bad public policies. The ethanol in gasoline idea is a notable example of that; it can be traced directly to ADM (Archer, Daniels, Midland). To influence the residence time for CO2 in the atmosphere we need to implement better solutions than the ones tried so far. I agree with John Russell (#76) when he says humans can overwhelm the natural processes that sequester carbon; it is important that we make good choices. As Phillipe Chantreau points out, it is not going to be easy but this might be something you could persuade "Deniers" to support. I would also point out that it does less harm to the world's economy to produce valuable goods (non-perishable foods and high quality timber) than goods that are useless or perishable. Probably the worst kind of public policy is the all too common practice (USA & EEC) of paying farmers to grow nothing at all.
    0 0
  33. The main problem with this is quantitative. I'm not sure it makes any quantitative sense. It took millions of years of natural processes to store all the CH we are now burning. How many years of these processes do we roll back in just 1 year of coal/oil burning? How much vegetation is necessary to store 1 year's worth of emissions? How much land does that require? How can all that vegetation been prevented from releasing its carbon? I don't think that any idea like that is viable if not accompanied by emissions reduction.
    0 0
  34. #84 Philippe Chantreau at 16:01 PM on 7 April, 2010 How much vegetation is necessary to store 1 year's worth of emissions? How much land does that require? The carbon stored in plant biomass is about 8 kg/m2 both in grasslands and forests. The carbon released to the atmosphere is some 8 × 1012 kg annually. Therefore you would need 1012 m2 which translates to 387000 sq miles (larger than Texas).
    0 0
  35. Clarification re #84 The only way for this idea to work is to convert low carbon density land to high carbon density land. Hence we are talking about taking a large area of desert and turning it into a forest. Every year. And never cutting it down. Box 3.2 of TAR explains the “maximum impacts of reforestation and deforestation on atmospheric CO2” using a simple spherical cow calculation: Emissions to date ~500 PgC and increasing. Total reforestation sucks up ~200 PgC maximum. (re actual calculation in #84: The exact values for carbon content of large areas is difficult to nail down and Table 3.2 of TAR gives somewhat higher carbon densities but I agree that the point is that forestation would need to increase each year - just to keep pace).
    0 0

Prev  1  2  

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.



The Consensus Project Website

THE ESCALATOR

(free to republish)


© Copyright 2022 John Cook
Home | Translations | About Us | Privacy | Contact Us