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Unforced variations 3

Filed under: — group @ 21 October 2010

Here’s an open thread for various climate science related discussions, to prevent more off-topic clutter everywhere else. We have some good posts coming up, but if you want to discuss something you read in the media, saw in a press release or just wanted to ask about, this is the time.

Some interesting things we’ve seen recently include discussions on the epistimology of climate modelling, Andy Dessler’s adventures in debate land and his new paper on water vapour trends, and a review of trends in the Columbia glacier. Have at it.

Addendum: Kevin McKinney has beaten us to the mention of this, but another recent article of importance is a thorough review of the state of knowledge of drought, past and future, by Dai.  The article is open access here.

573 Responses to “Unforced variations 3”

  1. 301

    270 Barton Paul Levenson

    Rather than accept certain death of mankind, how about working on a way to capture CO2 without imposing heavy burdens on those that produce electricity?

    I like to imagine that there has been some progress with discussions here at realclimate on a water-forest project. Maybe someone has some more information on China’s progress along these lines.

  2. 302
    Anonymous Coward says:

    Dear Jim Bullis,
    And the macroeconomic evidence for “cost of manufacturing determines competitiveness” in the real world is what exactly? For “increased sales enables expansion of employment” you can at least find macro evidence for a correlation (if not for the causation you posit). Your original conclusion does not follow from your axioms by the way.
    There’s no point in having a discussion alright. I noticed already. But there would be a point in substantiating these gratuitous assertions. If you’re unwilling, someone has to point out that you’re making it up as you go along. Denying the physics of the climate or the economics of mitigation has about the same effect. But one is easier to pull off on RC than the other…

  3. 303
    David B. Benson says:

    Lisa Boucher @295 — Fairly earlier on in this thread there are sev eral good comments about models, ending with
    https://www.realclimate.org/index.php/archives/2010/10/unforced-variations-3-2/comment-page-5/#comment-189329

  4. 304
    Ray Ladbury says:

    Susan Anderson,
    If we’d done something like this 40 years ago in response to the Oil crisis, it might have worked. Even if we had done it 20 years ago when the science of CO2 and the atmosphere became clear, it would have stood a chance.

    Now after 30 years of delay and complacency, we are playing catchup, and even with the most remarkable innovation, it will take significant cuts and severe conservation to buy enough time to deploy any new technologies. The initiative seems to be equivalent of a politician saying, “We’ve appointed a committee to study that!” It has more to do with camouflaging inaction than taking action.

  5. 305
    Patrick 027 says:

    Re HenryP – re my 167,181

    What are the implications for global average forcings?

    We could start by dividing the SW forcings by 2.4 – the angle of the sun also matters (how much is absorbed in the stratosphere vs troposphere vs surface, how much is backscattered by air) but an intermediate angle is used in that paper so it might be close to the global average effect.)

    Then there is the issue of using MLS conditions, which would affect the LW forcings.

    After that, their is the issue of clouds, which affects both SW and LW forcings.

    Clouds, especially low level clouds, will tend to reduce the surface LW forcing changes. Clouds, especially high level clouds, will tend to reduce the upper level LW forcing changes. This is because clouds block some of the radiation that would otherwise be available to block, and replace that with some radiation that would otherwise have come from gases. Clouds would reduce the stratospheric cooling that could occur by reducing the upward LW flux at the tropopause; thus, clouds should make the TOM and 200 mb forcings more similar.

    Clouds reduce solar heating that would otherwise occur beneath them, but do themselves absorb some solar radiation. They also reflect some radiation back upward, which can increase solar heating above them somewhat (if the relevant wavelengths were not already completely absorbed in the first pass.) Offhand I don’t know the details of how cloud albedo is distributed over wavelength, but based on liquid water absorption coefficients, I’d expect the albedo to drop off going away from blue towards either UV or red and solar-IR. Thus, the reflection by clouds may have less ability to enhance upper-level solar heating of ozone (UV) or CO2 (near-IR) than otherwise. But generally, clouds will reduce the SW forcings at the surface, but perhaps increase the forcings at TOM and 200 mb by giving gases more room to reduce the albedo of the planet.

  6. 306
    Patrick 027 says:

    Clouds would reduce the stratospheric cooling that could occur by reducing the upward LW flux at the tropopause; thus, clouds should make the TOM and 200 mb forcings more similar.

    correction – they reduce the upward LW flux at the tropopause, and reduce the room for other agents to do the same. But there are other issues – for example, given an approximate description of the CO2 absorption band, I think clouds shouldn’t change the instantaneous LW forcing on the stratosphere forcing from a doubling of CO2.

  7. 307
    Brian Dodge says:

    I wonder if part of the answer to the faint young sun paradox is a lack of oxygen in the atmosphere led to increased levels of CH3 radicals from the reaction CH4 + OH -> CH3 + H2O, and slowed the removal of Abiogenic CH4 from the early atmosphere.
    Another part of the answer might also be that the climate sensitivity is higher than 3 degrees per doubling of CO2, and/or departs from a logarithmic response at higher concentrations.

  8. 308
    Patrick 027 says:

    Re 307 Brian Dodge – CO2 expains part of it; what I’ve read is that there are times, or at least one time, when the geologic record indicates that there was insufficient CO2, but that may correspond with a time when CH4 was higher. Yes, CH4 could have been much more, especially in the Archaen eon – something on the order of 1000 ppm, I think (see Catling et al, ”
    Biogenic Methane, Hydrogen Escape, and the Irreversible Oxidation of Early Earth” http://www.sciencemag.org/cgi/content/abstract/293/5531/839 ;
    This looks promising:
    “Palaeoclimates: the first two billion years” Kasting and Ono
    http://www.geosc.psu.edu/~jfk4/PersonalPage/Pdf/Phi_Trans_B%20(Kasting&Ono)_06.pdf )

  9. 309
    Patrick 027 says:

    “something on the order of 1000 ppm” – or 100 ppm, but much higher than now, anyway. Remember though that when there is so much CH4, the forcing per additional mole of CH4 is reduced a lot; actually, CO2 is more powerful than CH4 when in equal amounts (consequences for possibility of initiating a snowball by release of oxygen – would occur more readily if there is enough but not too much CH4).

  10. 310
    HenryP says:

    Here is a simple question for your panel. I measured the evaporation rate of my 50m2 swimming pool and I was amazed to find that 2500 litres evaporated in one week (no discharge, clear blue skies all week, 31-34 C max. in the day,temp. of pool 25-26C.)
    Compare this to the tank of patrol (gas) I use in one month. (40 litres)
    What worries me is that to survive, humans are creating many shallow
    dams and waters that are easily prone for such high evaporation. (higher temp= >> higher vapor pressure)
    e.g. for irrigation, for consumption, for hydro power (electricity-
    China!), for recreation and for land creation.
    Add to this all the water vapor from burning fuels (including jet &
    rocket fuel, the countless water cooling plants in every factory (including those for nuclear energy),the boiling, cooking, bathing etc. etc.
    Now if I look at the fact that H2O accounts for most of the greenhouse
    effect, why would you think that the odd 100 ppm’s of CO2 that were added to the atmosphere since 1960 are much more relevant than all that extra water vapor being added to the atmosphere due to human activities?
    Even if it (the water vapor) ultimately does condense, the heat (40.7
    kJ per mole = 18 g) has to go somewhere, my guess is ca. 50% to earth and 50% to space.

    What do you think?

  11. 311
    Edward Greisch says:

    Would that “Land Hurricane” that just went by the US midwest qualify as a result of GW? Hurricanes are supposed to be ocean beasts.

  12. 312

    HenryP, let me answer your question @ #310 with another: given that more than 70% of the planet’s surface is ocean, and that terrestrial plants supply vast amounts of water vapor to the atmosphere via transpiration, why would you assume that the human water vapor contributions you mention are in fact large enough to make any difference whatsoever?

    Notice that the only quantitative analysis you have done was relative to your swimming pool. . .

  13. 313

    HenryP 310: why would you think that the odd 100 ppm’s of CO2 that were added to the atmosphere since 1960 are much more relevant than all that extra water vapor being added to the atmosphere due to human activities?

    BPL: Because a pulse of water vapor stays in the atmosphere nine days, but a pulse of CO2 stays in the atmosphere 200 years.

  14. 314

    313 Barton Paul Levinson and 303 David B. Benson,

    Models can be enormously sophisticated, but they are like clanging brass if they have not correctly taken into account the natural processes. Thus, our BPL has come to think that there is no way for CO2 to be taken out of the atmosphere. Forests work; clams, coral, and barnacles work. And oceans take up heat in a way that is only vaguely understood.

    There is of course, a flow in and a flow out. And of course the models take this into account. And it appears there has been a significant deficit running for some time. That has to be fixed. Let’s get to it.

    I am a little puzzled by what happened in the 1800s as the heavily forested North America was converted into farmland. It would seem that should have dumped a vast load of CO2 into the atmosphere. Is that explained in the record?

  15. 315
    HenryP says:

    Henry@KevinMcKinney (abt 310)
    Don’t change the question. The question was, given that most of the greenhouse effect is caused by water vapor & clouds, : why would you think that the odd 100 ppm’s of CO2 that were added to the atmosphere since 1960 are much more relevant than all that extra water vapor being added to the atmosphere due to human activities?
    if you consider that 70% of earth is water, than you are not far away from the truth: more warming (of water) brings more vapor, which bring more clouds which brings more cooling (due to deflection of sunlight).So….?

    [Response: You may not be aware but this is one of the most often rebunked confusions. Try reading this older post on “Water vapour: feedback or forcing?“. The bottom line is that our emissions of water vapour (via irrigation, combustion, river management) are sometimes noticeable in local climate, but don’t affect global climate much at all (because the amount of water vapour adjusts very quickly because of the large amount of condensation and evaporation). CO2 increases on the other hand persist much longer and provide persistent forcing globally. If you are getting these ideas from a particular source, you might want to reassess its credibility. – gavin]

  16. 316
    HenryP says:

    Henry@Patrick 027
    Thanks, but the truth is: there really is no one that can tell me exactly, from actual tests + measurements, what the net effect is of the warming and cooling caused by CO2. If you want those answers than you land up with incomprehensible mathematics and then I ask: but what about the overlaps in the 14-15 um band of O2 and water vapor? Although the absorption of O2 in the 14-15 um is fairly weak, O2 is 21% whereas CO2 is only 0,04% in the air. Water also absorps at 14-15. So how is this all separated? Well, in that case, then there is just so much more incomprehensible mathematics. And of course, nobody has made any errors. But the truth is: there are no measurements, not one actual physical test. I think Newton would turn in his grave if he heard all those wild warming theories caused by the CO2.
    I say more carbon dioxide is good. I base this on my simple observation that without CO2 there would not be any food.

    [Response: Brilliant logic. Let’s apply it to some other circumstances: Since water is necessary for life, more water is good and so no-one can drown. Hmmm… what about vitamins are necessary for life, and so more are good, and no-one ever has a problem from vitamin overdoses…. Oh. Must be something wrong there, I wonder what? Clue: ‘incomprehensible mathematics’ might only be incomprehensible to you. (PS. comments that just parrot long debunked inanities are not interesting. Please try another tack). – gavin]

  17. 317
    Didactylos says:

    HenryP: to put it another way, we simply cannot add water vapour to the atmosphere. If we try, it just rains out. Even in the short term, we cannot increase the amount of water in the atmosphere.

    The actual amount of water vapour is governed by temperature.

    Land use changes may, it is true, change rates of evaporation and precipitation at a regional scale. But evaporation just isn’t something that worries people – compared to the vast extents of the oceans, a swimming pool or lake here and there is completely negligible. But that extra 100 ppmv of CO2 is in every cubic metre of the atmosphere. From ground level, to the top of the atmosphere, many kilometres above us.

    “the heat (40.7 kJ per mole = 18 g) has to go somewhere”
    Energy has to come from somewhere. And it is true, processes releasing water vapour into the atmosphere do often involve waste heat. But by any measure, the waste heat is negligible compared to the main energy input into the earth system – the sun.

    Now, back to the subject of humidity. Relative humidity may not be changing, but absolute humidity is changing. It is increasing. This is because humidity is governed by temperature, and the fact that absolute humidity is increasing is in independent proof that the global temperature is increasing. And yes, that extra water vapour does alter the greenhouse effect. This is (I think) the most important feedback process that amplifies the effect of the increased CO2.

  18. 318
    ghost says:

    I’m sorry I missed the comment lock on Jim’s fine post about bark beetles, and I want to thank him for it. It truly is a sad tale, but one that must be told. I look forward to the next installment. Thanks, Jim.

  19. 319
    Anonymous Coward says:

    [de-duplicating] Let’s look at Jim Bullis’ latest quantitatively. I’m not any kind of specia-list so my numbers and conversions might be way off, I might be making a serious mistake and so on… so please correct me!
    I estimate about +13 ppm for the 19th century (eyeballing Law Dome). Assuming a 50% airborne fraction, this gets us about 55GtC of emissions needed to explain the change. But some of the 19th century increase in atmospheric CO2 is probably a temperature feedback. So let’s assume 45 GtC of emissions. This number is probably way off but hopefully it’s in the ballpark.
    Fossil fuel burning is estimated at 12 GtC for the 19th century (CDIAC referencing economic historians). So that leaves 33 GtC of emissions to be explained.
    I don’t know where to find actual data about this but I’ll put my high estimate of aera deforested in the United States and Canada during the 19th century at 2.5 millions of square kilometers. Assuming an average of 140 tC emmitted per hectare, that would imply 35 GtC of emissions.
    So I’m not seeing any discrepancy so far. No doubt that was dumb luck and that proper estimates would be much further apart than my 33 and 35 GtC, if only because my deforestation estimate is implausibly high. There was also lots of deforestation outside North America. And I’m probably missing something big. But, at first approximation, nothing extraordinary seems to be begging for an explanation.
    Could you please provide quantitative ballpark estimates yourself next time, Jim Bullis? This way people will at least be able to point out where you have erred in overstimating the importance of forests. I’m sure you’d rather not bother considering how much you post but RC is supposed to be a halfway serious venue.

  20. 320

    JB 314: our BPL has come to think that there is no way for CO2 to be taken out of the atmosphere.

    BPL: How does that follow from anything I said? I’m familiar with the short-term carbon cycle, thank you very much.

  21. 321
    SecularAnimist says:

    gavin wrote: “… comments that just parrot long debunked inanities are not interesting”

    Not to mention depressing.

    I mean, global warming itself is mighty depressing.

    But the proclivity of so many people to seize upon and regurgitate “long debunked” idiotic drivel, often with haughty, sneering arrogance and condescension that seems to exceed even their ignorance and gullibility, is also pretty depressing.

  22. 322
    Hank Roberts says:

    > JB 314
    Yes–in the 1800s, land conversion, coal use, and CO2 increased.
    http://scholar.google.com/scholar?hl=en&q=co2+1800s+coal+forest+timeline
    see e.g. Ruddiman, How did humans first alter global climate? (2005)

  23. 323

    #315–Ah, so now you’re admitting that human H2O emissions aren’t significant!

  24. 324

    313 and 320 BPL

    You ask regarding my 314, “How does that follow?” —

    But you said, ” – – a pulse of CO2 stays in the atmosphere 200 years.”

    Are you meaning that the marginal impact will carry forward?

  25. 325
    Ray Ladbury says:

    Henry P., given that your name links to a megachurch (my wife calls them Christmart), are you even real? Good Lord, man, you are utterly ignorant of how the climate works, cannot construct a logical argument and seem to be unable to learn. Pray, why the hell should we waste our time with you.

    Fact: The greenhouse effect accounts for about 33 Kelvins of Earth’s temperature.

    Fact: CO2 is responsible for about 25% of that amount.

    Fact: CO2 is increasing.

    Fact: It is warming.

    Fact: CO2 sensitivity is more than 2 degrees per doubling with 90% confidence

    So, while YOU may want to bet the future of humanity on a 20:1 longshot, the actual scientists among us have a problem with that.

  26. 326
  27. 327
    Rick Brown says:

    > pulse of CO2
    > marginal impact

    Archer, David, and Victor Brovkin. 2008. The millennial atmospheric lifetime of anthropogenic CO2. Climatic Change 90, no. 3 (6): 283-297.

    However, despite all these differences, the models agree that the substantial fraction of projected CO2 emissions will stay in the atmosphere for millennia, and a part of fossil fuel CO2 will remain in atmosphere for many thousands of years.

    Archer, David, and Victor Brovkin. 2008. The millennial atmospheric lifetime of anthropogenic CO2. Climatic Change 90, no. 3 (6): 283-297. doi:10.1007/s10584-008-9413-1.

    Nowhere in these model results or in the published literature is there any reason to conclude that the effects of CO2 release will be substantially confined to just a few centuries. In contrast, generally accepted modern understanding of the global carbon cycle indicates that climate effects of CO2 releases to the atmosphere will persist for tens, if not hundreds, of thousands of years into the future.

    Solomon, S., G. K Plattner, R. Knutti, and P. Friedlingstein. 2009. Irreversible climate change due to carbon dioxide emissions. Proceedings of the National Academy of Sciences 106, no. 6: 1704.

    This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop.

  28. 328
    Rick Brown says:

    correction:

    Nowhere in these model results or in the published literature is there any reason to conclude that the effects of CO2 release will be substantially confined to just a few centuries. In contrast, generally accepted modern understanding of the global carbon cycle indicates that climate effects of CO2 releases to the atmosphere will persist for tens, if not hundreds, of thousands of years into the future.

    is from:

    Archer, D., M. Eby, V. Brovkin, A. Ridgwell, L. Cao, U. Mikolajewicz, K. Caldeira, et al. 2009. Atmospheric lifetime of fossil fuel carbon dioxide. Annual Review of Earth and Planetary Sciences 37: 117–134.

  29. 329
    Dan H. says:

    Edward,
    We can neither confirm nor deny that the land hurricane is the result of GW. Although uncommon, these storms can occur this time of year, and in Michigan are commonly referred to as the “Gales of November,” for the havoc they can wreck on shipping and boating.

  30. 330
    Patrick 027 says:

    Re ‘Land Hurricane’ – first, it deserves mentioning that the pressure drop equivalent to something you might expect from a cat 5 hurricane (right?) doesn’t produce the same wind speeds in an extratropical cyclone – even over water – for two reasons:

    1. stronger coriolis effect – you need less wind speed to have the coriolis force balance the pressure gradient force (although there’s also the centrifugal force to consider)

    2. the pressure anomaly is spread over a larger area; reduced pressure gradient

    Anyway, I’m wondering how the latent heating compares to other such storms – that is something that you’d expect to increase in global warming, at least in general.

    Also, was this a case of upstream development – drawing energy off the earlier storm that hit the Pacific Northwest?

  31. 331
    Patrick 027 says:

    … no, that would be downstream development.

  32. 332
    Patrick 027 says:

    Re 316 HenryP

    Thanks, but the truth is: there really is no one that can tell me exactly, from actual tests + measurements, what the net effect is of the warming and cooling caused by CO2. Exactly? No, of course not. Approximately? Yes!

    If you want those answers than you land up with incomprehensible mathematics

    Don’t confuse number crunching with complicated logic. The math is quite simple. It’s just that there is a tremendous amount of data that the formulas must be applied to, with numerical integration, to actually get an accurate answer. But qualitatively, it’s mostly quite intuitive. Imagine walking through a fog – what can you see? Now make the fog thicker. Now imagine that you’re seeing at wavelengths where the fog is not scattering so much as it is emitting incandescently and absorbing radiation, and there’s a temperature gradient so that it emits more or less from different places; make the fog thinner or thicker (make it thicker and three things happen: greater emission in a given volume, greater absorption in a given volume of whatever radiation is available, and the distances that photons travel between emission and absorption is shortenned) – what do you see? What you see is what you get (aside from the distinction between flux/area and intensity).

    Look up these two terms: Schwarchild’s equation (PS the one about radiation – I’m not sure offhand but some stuff about black holes may go by the same name) and ’emission weighting function’.

    and then I ask: but what about the overlaps in the 14-15 um band of O2 and water vapor? Although the absorption of O2 in the 14-15 um is fairly weak, O2 is 21% whereas CO2 is only 0,04% in the air. Water also absorps at 14-15. So how is this all separated? Well, in that case, then there is just so much more incomprehensible mathematics.

    The total amount of O2 in the atmosphere is nearly transparent to LW radiation; this takes into account the 21 % figure.

    Water vapor is concentrated in the lower atmosphere; much CO2 effectively sits on top of water vapor and has room to affect the LW fluxes at the tropopause and at TOA even at many wavelengths where water vapor blocks almost all radiation from the surface; water vapor is essentially transparent in the stratosphere over a range of wavelengths containing the CO2 band.

    You don’t need to seperate it out unless that’s what you want to know. To seperate, just do the calculations with various things added or removed; the overlaps between different greenhouse agents mean that the last greenhouse agent added generally could make a bigger difference on it’s own if it was the first agent added, etc. This doesn’t really concern the effects of doubling CO2, in that the calculation of the forcing of doubling CO2 is done with everything else present if the purpose is to find what it is for the Earth as it is (you can approximate this by using some representative atmospheric column, but in principle the accurate answer for global average forcing is found by calculated the forcing for all places and times in the climatic state and then finding the global average).

    But the truth is: there are no measurements, not one actual physical test.

    False – optical properties (of at least gases) can be measured in the laboratory, and the calculated effects on radiation through or from the atmosphere can be confirmed by measurements of radiant fluxes. It is even possible to see the reduction in OLR caused by CO2 increases using a satellite.

  33. 333
    Patrick 027 says:

    Re 316 HenryP – some very mature physics backs this all up.

  34. 334

    327 Rick Brown,

    Thanks for the references, but somehow there is something that seems wrong here.

    Simplifying, if all CO2 emissions stop today, and trees continue to grow, the organic compounds that are wood will be produced by taking up the present day supply of CO2 according to the rate at which trees grow in mass. Surely, if forests were to cover the earth to the extent that their mass matches the mass of fossil fuels that was burned over the last 200 years, that would have to soak up the CO2 that came from these fossil fuels.

    That would take a long time, but way short of forever. Do the models assume that no permanent standing forests would be possible?

    Or is this all dependent on something else happening, whereby more sources of CO2 develop, such as with permafrost or such, and the additional CO2 mixes with and reduces the rate that the original CO2 gets taken in by trees? If this is what we are talking about, the whole thing depends on timing of solutions, but the statement about how long CO2 lasts is a conditional statement, not an absolute one.

  35. 335
    Ray Ladbury says:

    Edward@311 and Dan H.@329, Please! The so-called land hurricane is weather. Period. It is an extreme event and so by definition, we do not know what the probability distribution for such events looks like from past data. Look for TRENDS over TIME. There is plenty of evidence that the climate is changing. Getting 3 hundred year floods in a decade provides more evidence than a single extreme event.

  36. 336

    BPL: “How does that follow?” –

    JB: But you said, ” – – a pulse of CO2 stays in the atmosphere 200 years.”
    Are you meaning that the marginal impact will carry forward?

    BPL: Read my lips. A single molecule of CO2 may only stay in the air 5-10 years, but there are molecules coming in as well as going out. Raise the CO2 level and it will still be significantly higher 200 years later. In fact, for about a sixth of it there’s a long tail out to 100,000 years.

    The water cycle lasts about 9 days.

    CO2 matters, H2O does not, except as an amplifier.

  37. 337
    Anonymous Coward says:

    Jim Bullis,
    Forests can not realitically soak up all the carbon from the fossil fuels that were burned, especially considering that more keeps getting burned. Take a look at the numbers for yourself.
    But forests don’t need to soak it all up to bring atmospheric CO2 levels way down because a substantial fraction of the carbon emitted by fossil fuels and industrial deforestation has effectively been sequestrated in the oceans and will stay there for a long time. Because there are several flows and reservoirs, you really have to look at this quantitatively to figure out what the net effect of a scenario would be. Guesstimates are only trivial when a flow totally dwarfs the others such as current emissions from fossil fuels.
    I suspect that, assuming no large carbon releases from warming, a drop in fossil emissions to zero followed by massive reforestation would draw down most of the excess of atmospheric CO2 over the pre-industrial baseline in a matter of decades as CO2 continues to flow into the oceans as well as the forests but that CO2 levels would then remain elevated for millenia in spite of continued growth of the forests because the net flow between the oceans and the atmosphere would reverse. But it of course depends on how much CO2 the new forests would draw (and how quickly). Do you have any numbers you care to propose to illustrate your scenario?
    Of course the statements about the airborne fraction of CO2 emissions over time are conditional but please stop pretending that reforestation on the scale needed to offset the burning of fossil fuels is in any way realistic without hypothetical developments in genetic engineering, geoengineering or some other magitech. If you think your “solutions” hold water, post your numbers!

  38. 338
    Hank Roberts says:

    Jim Bullis, read Archer.
    Or look at all the available sources.
    http://www.google.com/search?q=co2+atmospheric+residence+lifetime
    http://scholar.google.com/scholar?q=co2+atmospheric+residence+lifetime

    If you want to help people understand this, read for yourself and come back and post your understanding.

    Posting incredulity and FAQs just encourages those who won’t read for themselves.

  39. 339
  40. 340
    Rick Brown says:

    Jim Bullis @ 334

    Relying on my memory is a dubious proposition but that’s all I have time for right now. Estimates of the sink potential of earth’s forests are comparable (same order of magnitude at least) to what would need to be removed from the atmosphere to go from current levels to 350 ppm. I don’t think such estimates account for degradation of forest sink capacity due to continuing climate change (an example of which Jim Bouldin described in his Seeing Red post), so only an unrealistically optimistic scenario would provide for forests even drawing down the current excess, leaving no room for forests to “offset” continuing fossil fuel emissions.

  41. 341
    Hank Roberts says:

    And this, from the Archer et al. piece, explains why so many people are so confused about how long CO2 lasts — the policymaker summary screwed up the explanation of this in the 1990 IPCC Report.

    —- excerpt follows—-

    “The 1990 Intergovernmental Panel on Climate Change (IPCC) report … carefully explained in the technical Chapter 1 … that, on human timescales, CO2 really has no sinks, it just equilibrates….
    … the equilibration timescale is no indication of how long the climate impacts of CO2 release will last. But this distinction was confused in the “Policymaker Summary,” in which the timescale is referred to as an atmospheric lifetime, which is incorrect, and it is used as a rationale to limit the time horizon for calculating global warming potentials of greenhouse gases to 100 years, which is not logical either….
    … “the door to misinterpretation had been left open. Others have and continue to walk through it.”

    Subsequent IPCC reports in 1995 and 2001 compounded the mistake …. The result has been an erroneous conclusion, throughout much of the popular treatment of the issue of climate change, that global warming will be a century-timescale phenomenon. Simple thermodynamics of CO2 dissolved in seawater plus paleo-evidence, in particular the PETM event 55 Mya tell us otherwise.
    —— end excerpt —-

  42. 342

    If anyone is interested, new satirical thoughts on the almost, but not quite, falsified Younger Dryas impact hypothesis.

    Click on my name link if you dare, thanks.

  43. 343
    John E. Pearson says:

    HenryP said: \the truth is: there really is no one that can tell me exactly, from actual tests + measurements, what the net effect is of the warming and cooling caused by CO2.\

    Before July 16 1945 there really wasn’t a soul on the planet who could tell you exactly from actual tests + measurements what would happen if one rapidly compressed a sphere of plutonium. All there was was a bunch of mathematics that you would have found incomprehensible. Only after July 16 1945 at 5:30 AM (MWT) was it known. At 5:29AM MWT no one had the foggiest idea what would happen. The US govt. spent a billion 1940’s dollars or thereabouts to perform the experiment. Wow. Don’t you think they were lucky?

  44. 344
    Edward Greisch says:

    See:
    http://www.conservation-economy.org/2010/10/engaging-with-climate-change-psychoanalytic-perspectives/
    I still don’t believe in Freud, but this could be interesting anyway.

  45. 345

    Rick Brown, Hank Roberts, Barton Paul Levenson, Anon. Coward, and others

    I can’t take time to respond appropriately, but I have read and appreciate your responses. Thanks.

    In general, I don’t see much that addresses the big ‘what if?’ that I started with that was in reaction to the EPA discussions of ‘CCS’ for new coal fired power plants. Trying to keep the focus on ‘new’ and ‘standing’ forests rather than getting into the past, present, and future of existing forests, I had hoped to greatly simplify the discussion. However, I realize that there is much to be learned from all the work by others. But still, there seems to be no insurmountable obstacle to creating new forests to solve an expanding problem. It might be useful for trimming back CO2 from our existing power generation practices.

    If it comes to nothing more, I at least, can see better than ever, the need for more attention to keeping our existing forests in good health.

    But I still see potential in new forests, yes, with somewhat rearranged water distribution.

  46. 346
    Didactylos says:

    Please will someone correct me if I am wrong… but my present understanding is that forests (rainforest, at least) is surprisingly carbon-neutral. The carbon sources and sinks within the forest neatly balance on a small scale, and the idea of rainforests as the “lungs” of the planets has been largely discredited.

    I probably read about this here, so if someone could remind me where and what I got wrong, that would be great.

  47. 347
    Hank Roberts says:

    JB: http://www.newstatesman.com/environment/2009/10/carbon-emissions-sahara-plan (and quite a few other places, you can find the discussions)
    You might pursue the idea someplace that people are discussing it; it’s been in print for over a year now.

  48. 348
    Edward Greisch says:

    Raymond T. Pierrehumbert, why aren’t you the Green Party candidate for Obama’s senate seat?

  49. 349
    Hank Roberts says:

    didactylos, “lungs” may be confusing.
    Look at primary productivity (use of sunlight for photosynthesis).

    These might help:
    http://www.enviroliteracy.org/article.php/1154.html
    http://www.agu.org/pubs/crossref/2010/2009JD012913.shtml
    http://www.springerlink.com/content/5ya2xh872g25fglt/

  50. 350
    Hank Roberts says:

    Interesting comparison —

    http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2009.02071.x/full

    Negative feedback in the cold: ice retreat produces new carbon sinks in Antarctica 15 SEP 2009

    “we show that the loss of ice shelves and retreat of coastal glaciers around the Antarctic Peninsula in the last 50 years …. New annual productivity, as opposed to standing stock, amounts to 3.5 × 10[e]6 tonnes yr−1 of carbon, of which 6.9 × 10[e]5 tonnes yr−1 deposits to the seabed. By comparison the total aboveground biomasses of lowland American tropical rainforest is 160–435 tonnes ha−1. Around 50% of this is carbon. On this basis the carbon held in new biomass described here is roughly equivalent to 6000–17000 ha of tropical rainforest. As ice loss increases in polar regions this feedback will become stronger …”