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Filed under: — gavin @ 27 October 2009

I was quoted by Andrew Revkin in the New York Times on Sunday in a piece about the International Day of Climate Action (involving events in 181 countries). The relevant bit is:

Gavin A. Schmidt, a climate scientist who works with Dr. Hansen and manages a popular blog on climate science,, said those promoting 350 or debating the number might be missing the point.
“The situation is analogous to people trying to embark on a cross-country road trip to California but they’ve started off heading to Maine instead,” Dr. Schmidt said. “But instead of working out ways to turn around, they have decided to argue about where they are going to park when they get to L.A.”
“If you ask a scientist how much more CO2 do you think we should add to the atmosphere, the answer is going to be none.”

I’ve been told that some readers may have misinterpreted the quote as a criticism of the campaign itself. This was not the intent and in fact my metaphor wouldn’t have made sense in that context at all. Instead, it was a criticism of people who are expending effort arguing about whether 350 is precisely the right number for a long term target, or whether it should be somewhat higher or lower. Since we aren’t currently headed anywhere near 350 ppmv (in fact we are at 388 ppmv CO2 and increasing by about 2 ppmv/yr), we need to urgently think of ways the situation can turn around. Tapping into the creativity and enthusiasm shown by the campaigners will certainly be part of that process.

We discussed some of the thinking behind this ‘Target CO2‘ when Jim Hansen and colleagues’ paper first came out, where I think we made it clear that picking a specific CO2 target to avoid ‘dangerous’ climate change is an inexact science at best. The comments by Robert Brulle and Ray Pierrehumbert at DotEarth and James Hrynyshyn also highlight some of that complexity. And I think the suggestions by ‘Paulina‘ for how a tweaked article might have been clearer are very apropos.

However, as the final line in my NYT quote should make clear, personally I think the scientific case not increasing CO2 any further is very strong. Since the planet has not caught up with current levels of concentrations emissions (and thus will continue to change), picking an ultimate target that is less than today’s level is therefore wise. Of course, how we get there is much trickier than knowing where it is we should be going, but having a map of the destination is useful. As we discussed in the ‘trillionth ton‘ posting a couple of months back, how we get there also makes a difference.

In my original email to Andy Revkin, I had actually appended a line:

If you ask a scientist how much more CO2 do you think we should add to the atmosphere, the answer is going to be none.

All the rest is economics.

(and technology, and sociology, and psychology and politics etc.) but the point is that working out how we get there from here is the real challenge and the more people who are aware and involved in developing those solutions the better.

214 Responses to “350”

  1. 51
    Karen Street says:

    Jeffrey (32), I use IPCC to tell me which economists they trust. International Energy Agency Analysis analysis is at the top. I understand that some scientists consider economists too optimistic because Science magazine interviewed 3 scientists when the Working Group 3 Summary for Policy Makers was released, and all 3 made that comment. Generally, when Science magazine prints a result like 3/3, there may be a pattern. Since WG2 predicts a decline in hydro in many locations between now and 2030, and WG3 predicts an increase in hydro in the developing world, with no comments on the developed world, I can see their point.

    Chris (38), you cite a source that differs from the analysis of IPCC and the sources IPCC depends on. Would you be willing to look at cost estimates in Working Group 3, or International Energy Agency?

    David (33), you’re kidding? Nuclear power and CCS are opposed by quite a few people who were at the local 350 protest. I’ve also heard “me, change my behavior?” from a large number of people, though I don’t know that any went to the local 350 event.

  2. 52
    tharanga says:

    Phil, 46:

    If a group is going to pick a number and define a public movement around it as a rallying cry, then you wouldn’t expect people to ask why you picked that number, and whether it was achievable on any realistic time frame?

    If you don’t want people to miss the forest for the trees, then don’t adopt a strange-looking tree as your public rallying cry.

  3. 53
    Jim Galasyn says:

    Re the “CO2 is good for crops” argument:

    Crops face toxic timebomb in warmer world

    SINGAPORE (Reuters) – Staples such as cassava on which millions of people depend become more toxic and produce much smaller yields in a world with higher carbon dioxide levels and more drought, Australian scientists say.

  4. 54
    SteveF says:

    On the CO2 – crop yield front, elevated CO2 has been observed to increase yield in some cases. However, the picture can be complex. Here is a prime example:

    Spring wheat (Triticum aestivum L. cv. TRISO) was grown for three consecutive seasons in a free-air carbon dioxide (CO2) enrichment (FACE) field experiment in order to examine the effects on crop yield and grain quality. CO2 enrichment promoted aboveground biomass (+11.8%) and grain yield (+10.4%).

    however, from the same paper:

    However, adverse effects were predominantly observed on wholegrain quality characteristics. Although the thousand-grain weight remained unchanged, size distribution was significantly shifted towards smaller grains, which may directly relate to lower market value. Total grain protein concentration decreased significantly by 7.4% under elevated CO2, and protein and amino acid composition were altered.

    Hogy, P. et al. (2009) Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment. Plant Biology, 11, 60-69.

    An extremely worrying new study looked at cassava tubers, a staple food product in many poorer regions of the globe, and reported that yield decreased and concentrations of toxic cyanogenic glucosides in the leaves increased with higher CO2:

    We found that total plant biomass and tuber yield (number and mass) decreased linearly with increasing C-a. In the worst-case scenario, tuber mass was reduced by an order of magnitude in plants grown at 710 ppm compared with 360 ppm CO2. Photosynthetic parameters were consistent with the whole plant biomass data. It is proposed that since cassava stomata are highly sensitive to other environmental variables, the decrease in assimilation observed here might, in part, be a direct effect of CO2 on stomata. Total N (used here as a proxy for protein content) and cyanogenic glycoside concentrations of the tubers were not significantly different in the plants grown at elevated CO2. By contrast, the concentration of cyanogenic glycosides in the edible leaves nearly doubled in the highest C-a. If leaves continue to be used as a protein supplement, they will need to be more thoroughly processed in the future. With increasing population density, declining soil fertility, expansion into marginal farmland, together with the predicted increase in extreme climatic events, reliance on robust crops such as cassava will increase. The responses to CO2 shown here point to the possibility that there could be severe food shortages in the coming decades unless CO2 emissions are dramatically reduced, or alternative cultivars or crops are developed.

    Gleadow, R.M. et al. (2009) Growth and nutritive value of cassava (Manihot esculenta Cranz.) are reduced when grown in elevated CO2. Plant Biology, 11, 76-82.

  5. 55
    Chris Dudley says:

    Karen (#50),

    Indeed yes, I think Storm van Leeuwen and Smith (2005) have got a good handle on directly associated emissions should there be a build up of nuclear power. However, the opportunity cost aspect was not fully addressed. We should definitely wait for a carbon free energy supply before considering any more nuclear power.

  6. 56
    SecularAnimist says:

    Karen Street wrote: “Nuclear power and CCS are opposed by quite a few people who were at the local 350 protest.”

    I did not attend any 350 protest event, although I support the campaign. I oppose nuclear power and CCS because they are neither necessary nor effective means to reducing CO2 emissions, so there is no need to deal with the very real and very serious problems and harms that they would bring. Indeed, squandering resources on nuclear power and “clean coal” takes resources away from actual effective solutions — i.e. rapid deployment of efficiency and renewable energy technologies, organic agriculture, reforestation, mass transit, etc. — and thus exacerbates the problem rather than helping to resolve it.

    Unfortunately, given the massive, entrenched economic and political power of the coal and nuclear industries, it is probably inevitable that lots of resources will be wasted on both, enriching a few corporations while doing nothing to reduce GHG emissions, particularly in the time frame within which major reductions are urgently needed.

  7. 57

    Gavin (re: #47),

    What you say about the factors driving ever-increasing crop yields is very true and largely explains why crop yields have been ever-increasing while the climate has been changing. The impact of atmospheric CO2 enrichment is hard to quantify as it takes many roles—from direct fertilization and mitigation of other environmental stressors (water, heat, air pollution, etc.), to climate alterations. The effect of the first two on crop production is certainly positive, the effect of climate alterations is perhaps more debatable (extended growing seasons vs. high temperature limitations, precipitation delivery, etc.).

    But, I think that you would encounter little argument, that if you were just to assess the overall vegetative health of the earth, more atmospheric CO2 would be better.

    But obviously, there are other things to consider in this issue besides just the general response of plants (and of the things that eat them).


  8. 58
    Harmen says:


    “As I said in a comment response somewhere on my blog, a keystone question is 350 by when?”

    I was present at the event in Amsterdam..
    The most common chant was “350 Now!”

    But since we all know that is not possible..
    350 asap?

  9. 59
    Mark says:

    “But, I think that you would encounter little argument, that if you were just to assess the overall vegetative health of the earth, more atmospheric CO2 would be better.”

    Not for corn.

    Do you eat dandilions and thistles or corn and wheat?

  10. 60
    Hank Roberts says:

    > 47, 57
    Well, yeah, if you were trying to help people learn about the _consequences_ instead of selectively pointing to the selling-point “advantages” you’d look at, for example

  11. 61
    David B. Benson says:

    Karen Street (51) — I wasn’t kidding, I just wanted to know what those at your event were against.

    SecularAnimist (55) — CCS technolgies, when ready, can be employed with a variety of fuels. For example, oxy-fuel natgas turbines ought to be ready within 15 years. As for “clean coal”, if some capture technology actually works, then it will also work for a wood or biochar fired burner. These last are actually carbon negative. Irrespective of that, be quite sure that nations with abundant coal resources will continue to burn coal; South Africa, India, Indonesia, Australia and China come to mind. Be better if they use CCS, what?

    As for the debate about nuclear I’ll just point to
    which emphasizes the postive aspects of nuclear and attempts to refute the negative missives. Irrespective of that, it seems that China has on order or under construction another 16 Westinghouse AP1000 units; probably better than more non-CCS coal burners, methinks.

    As for diverting attention from all those other things, I certainly hope not. (Forgive me for now shouting.) ALL of the above are required; this is a planetary emergency and nothing can be left undone.

  12. 62
    Jeffrey Davis says:

    We’ve been above the pre-Industrial Revolution rate of CO2 now for 150-200 years or so. Are plants significantly bigger or more robust than they were in the 18th century? Even if they were, where could we plant stuff that isn’t currently already planted with stuff?

  13. 63
    Wildlifer says:

    Chip (re57),

    You should probably add another qualifier – or reduced CO2 fertilization due to limited soil nitrogen.

  14. 64
    Jim Bouldin says:

    lulo says:
    “…Every plant scientist in the world knows that CO2 has been impoverished for the past 20 million years or more”

    Impoverished eh? You don’t say. And contrary to your assertion, there is plenty of ‘debate’ on how CO2 affects plants, given that there are millions of plant species growing in every conceivable environment on the planet.

    And Chip there’s much more to CO2 effects on plants then their effects on managed crops, as will become apparent when any accelerated terrestrial carbon gain to date starts to asymptote out under the influence of other limiting factors, and show up as an accleration of CO2 in the atmosphere and oceans instead. Sinks can saturate you know.

  15. 65
    Mark says:

    Ae, what lulo means is “There used to be more CO2 so therefore we need more CO2!”.

    Which is a bit of a turnaround from “CO2 is a miniscule amount! It CANNOT have any effect!”.

  16. 66

    Mark (re: 59),

    Maybe you would find this book interesting:

    The Essential Nettle, Dandelion, Chickweed & Thistle Cookbook


  17. 67
    SecularAnimist says:

    I don’t intend to launch into another futile argument with proponents of nuclear power. I was responding to Karen Street’s comment which I understood to be suggesting that it is inconsistent to support the goal of the 350 campaign (i.e. rapid reductions in GHG emissions) while opposing nuclear power and “clean coal”.

    In my view it is not inconsistent, since nuclear power and CCS are neither necessary nor effective for rapidly reducing emissions, and indeed the “opportunity costs” of unnecessarily investing resources in nuclear and CCS when those resources would be far more effectively invested elsewhere hinder our efforts to rapidly reduce GHG emissions rather than helping.

    You may argue that I am mistaken about nuclear and “clean coal”, but given that I do believe they are unnecessary and unhelpful, it is not inconsistent of me to support the 350 campaign while opposing nuclear and “clean coal”.

  18. 68
    Susan Anderson says:

    I love it when Gavin gets going. Nice language, fun to read.

    On the subject of plants and CO2, consider poison ivy and the like, which love it. Thistles might be OK, but …

    A little off topic, I got a bee in my bonnet a while ago about algae, but as I begin to get more up to speed, am finding out how dangerous it is. There was an interesting radio “Science Friday” on new speculation that algae killed the dinosaurs. This is a point well worth considering. The “dead zone” off the mouth of the Mississippi was cited. Now that Exxon has taken over the project, we have serious Pandora’s box potential here.

  19. 69
    tharanga says:

    Can somebody post a link to a good site that gives current data and historical trends for CO2e (equivalent), as opposed to just CO2? I suppose I could calculate it myself, but I haven’t the time for that.

    58: “But since we all know that is not possible..
    350 asap?”

    sounds a bit silly, doesn’t it?

    If one has to reduce this to a slogan, there has to be a better one.

    [Response: Try AGGI from NOAA. – gavin]

  20. 70
    Eyal Morag says:

    “If you ask a scientist how much more CO2 do you think we should add to the atmosphere,” To answer a scientist as human need to combine his values with his science. Since all scientist are humans it natural. Saying more CO2 will have these consequences… is the answer to what are the consequences of adding more CO2 to the atmosphere. Almost all scientist that don’t like billions of refugees and dead people till the and of the century will say NONE.

    The other are puzzle of the human nature how and intelligent person don’t see that if no rain nothing will grow But I think I have a hint

    “On the deck of the Estonia ferry, which sank in the Baltic Sea in 1994, one man smoked a cigarette. Others sat in groups, doing nothing, as the water surged onto the ship.
    The most common response in most disasters is not panic, but rather the opposite.
    Our first instinct is to normalize the situation – to come up with wildly creative and reassuring explanations for why smoke might be creeping across the ceiling or why oxygen masks might have dropped from the airplane ceiling.”

    Fighting for survival
    By Amanda Ripley
    Author of The Unthinkable: Who Survives When Disaster Strikes – and Why

  21. 71

    Chip Knappenberger, quoting some agronomist:

    “The rising level of atmospheric CO2 is a universally free premium, gaining in magnitude with time, on which we all can reckon for the foreseeable future. Direct effects of increasing CO2 on food production and the output of rangelands and forests may be more important than the effects on climate.”

    I regressed world cereal production 1961-2002 on CO2, fertilizer consumption, and temperature anomaly. With fertilizer taken into account, partial-F tests show that neither of the other two variables matter.

    So, in effect, there is NOT a “CO2 fertilization effect.” Not where it counts.

  22. 72
    Lulo says:

    If at any point, I have given the impression that I think that CO_2 cannot have any effect because it is present only in ppm, then I wish to point out that I do *not* hold this opinion. I actually *do* agree that CO2 has a positive effect on the Earth’s radiative balance. I simply, for a variety of reasons not worth rehashing here, remain skeptical of the magnitude of change predicted. I am also confident that not all of the expected environmental effects of CO2 are deleterious. I am, therefore, technically only a climate change ‘skeptic’ in terms of its details.
    As a matter of fact, as a private citizen, I am always happy to support green technology and the idea of carbon taxes, such has just been instituted in some European countries. I do not drive a car – ever, and I can very easily afford to. Efficient care of our finite resources is always a good plan. However, I also happen to believe that the focus on climate change is the worst thing that has happened to the environmental movement since it began in earnest in the late 1960’s. The obsessive focus on a theme that has been understood in its basic theory since Tyndall and Arrhenius discovered it in the 19th Century has driven the world’s attention away from the truly devastating environmental problems of our time: land degradation and deforestation, soil erosion, destruction of the ocean floor, water pollution, toxic contamination, persistent organic pollutants, invasive species – the list goes on, all multiplied in their respective footprints by population growth. Today, on the other hand, everyone seems to think that if their only footprint is a carbon footprint. If they control that, they are somehow environmental activists.
    So, if I question the emphasis on climate change as a private citizen, it is assumed that I am no longer on the left wing, which seems to have effectively obtained the patent on environmental righteousness. If I use reason and peer-reviewed fact to question the details of climate change as a scientist, I am viewed as an outsider – a wacko, oil-backed thug… as an atheist and a non-smoker, I have even had people relate climate change skepticism to creationists and the smokers lobby! What utter balderdash!
    By far the worst, however, is that, when I don’t include the tangential climate change mumbo-jumbo in my papers and funding applications, reviewers always make comments like… ‘the methods are sound and the analysis appropriate, but the authors could more effectively relate the implications of their study within the context of climate change… yada yada yada.’ But I don’t study climate change! Why the heck would I put it in my papers. If there are implications in the context of climate change, are they not apparent? So, I am forced to stick crap like this into papers, even though I don’t study climate change, because that is the order of the day. On paper, I am the biggest proponent of climate change going, and this is what really ticks me off.
    Pretty soon, Nature is coming out with yet another climate change journal (yawn)… including policy, impacts and science. Why so keen to place policy and impacts go into scientific journals? Are we scientists or lobbyists? I am beginning to wonder.
    (end rant)

  23. 73
    Lulo says:

    Secular Animist: If you want to slow the rise of CO2 and you think you can do this without nuclear, you are living in a dream world. Besides, why do you want this dream? To be simplistic, nuclear power requires nothing more than a little uranium mining and careful disposal and we get massive quantities of energy. What would you prefer? Tar sands wiping out an area the size of Lake Erie from the face of the Earth? Conventional oil with tens of thousands of oil-laden ships? Oh, that’s right, you think you can convince people to use so much less energy that we will be able to rely on alternative fuel? Believe me, I am a proponent of wind, solar, geothermal and tidal energy, as well as use reduction… but where do you suppose the lower and middle classes are going to suddenly come up with the funds to purchase geothermal and solar energy for their homes, apartments and trailers? They have other things to worry about. If you want to limit CO2 emissions in the short or medium term, you are left with little choice but nuclear all the way. Nuclear energy is the solution.

    [Response: As I’ve said before – not every thread has to devolve into a discussion of nuclear energy. No more please. – gavin]

  24. 74
    Lulo says:

    Benson: Clean coal? You still have to put energy into its mining… if you’re into lopped off mountain tops and massive transportation issues, that’s your call. Why not just go nuclear? Oh, yeah… coal is cheap and there is tons of it in the good ol’ USA. I guess you bought their lobby line.

  25. 75
    Jim Bouldin says:

    re 62:

    It’s not nearly as much a matter of bigger, as a matter of faster, via increased efficiency. And at any rate, bigger is a much harder thing to ascertain than faster.

  26. 76
    Jim Bouldin says:

    Algae killed the dinosaurs? Gary Larson’s a liar.

  27. 77
    David B. Benson says:

    Lulo (74) — Love coal? Leave it in the ground!

    However much that might happen in the USA, it certainly will not in those other countries which have plentiful supplies. As for the US, burning coal produces many harmful emissions; I’d rather we didn’t but if wishes were horses beggars would ride.

    I advocate a shotgun approach, try some of everything even halfway sensible to see what works better than other methods.

  28. 78
    Ray Ladbury says:

    Lulo, Just curious. Do you manage to maintain your perfect state of self delusion without drugs or do you require pharacological assisance?

    First, you would be challenged to find any well accepted, peer-reviewed research that supports your sanguine attitude. Aside from a few lightweight denialist screeds, all the literature points toward climate change being a serious theat to human civilization.

    Second, wrt plant growth, if you understood anything about ecology or agriculture, you would know that what happens in some laboratory trial under perfect growth conditions is irrelevant. What matters is what happens to yield of crops in the field–especially in a world with population approaching 9 billion.

    Third, no serious person is advocating that we ignore other critical environmental issues. That is a straw man. What matters is building a sustainable economy.

    To that end, it is also a mistake to prejudge winners in the future energy infrastructure–be they nukes or renewables.

    So, please, get serious and learn some real climate science.

  29. 79
    RichardC says:

    Increased CO2 makes the production of carbohydrates easy, and protein difficult. As you alluded to with the cookbook, weeds grow best, while protein-rich plants produce no extra protein. For human consumption, that’s a bad thing. For sugar cane ethanol, it’s probably a good thing.

    On 350 — I think 350 is the number which has gathered the most common citizens’ hearts. It sounds good, it’s reasonable, and it isn’t quick to accomplish. Gavin points out that the actual number is not so relevant as turning the car around. I say that anyone who opposes using the number 350 as a first guess for a safe level of CO2 is wasting time arguing. Accept the number as a reasonable first guess. Whatever the safe amount really is, it isn’t a set number, anyway. If we go up quickly, then it will put more inertia towards further heating, and then the number could be 325. It depends on where tipping points lurk.

  30. 80
    Jim Galasyn says:

    Yes, clean coal: EPA Report Details Coal Ash Threat.

  31. 81
    Chris S. says:

    I’d like to see Chip Knappenberger’s response to SteveF’s post (#54). He responded to post #59 so he can’t have missed it…can he?

  32. 82
    CM says:

    Lulo (#72) said:

    The obsessive focus on [climate change] has driven the world’s attention away from … land degradation and deforestation, soil erosion, destruction of the ocean floor, water pollution, toxic contamination, persistent organic pollutants, invasive species

    Do you have evidence to show that there has been less attention paid to these issues, or are you just reasoning from (a) the fact that there has been more attention to climate change, and (b) the assumption that there is only so much attention to go around (the zero-sum fallacy)?

    Deforestation has if anything received renewed policy attention as a climate change issue. Witness Brazil’s recent 80% play, etc. There are risks here as well as opportunities, but with REDD on center stage of climate negotiations you can hardly say climate change has put deforestation in the shade.

    In any case climate change will exacerbate many other environmental problems. Species extinction globally, for one thing (not on your list). Regarding soil erosion and water pollution (prominent on your list), consider a sample paragraph on North America from IPCC AR4 WG2, section 14.4.1:

    Climate change is likely to make it more difficult to achieve
    existing water quality goals (high confidence)… Restoration of beneficial uses (e.g., to address habitat loss, eutrophication, beach closures) under the Great Lakes Water Quality agreement will likely be vulnerable to declines in water levels, warmer water temperatures, and more intense precipitation… Based on simulations, phosphorus remediation targets for the Bay of Quinte (Lake Ontario) and surrounding watershed could be compromised as 3 to 4°C warmer water temperatures contribute to 77 to 98% increases in summer phosphorus concentrations in the bay… and as changes in precipitation, streamflow and erosion lead to increases in average phosphorus concentrations in streams of 25 to 35%… Decreases in snow cover and more winter rain on bare soil are likely to lengthen the erosion season and enhance erosion, increasing the potential for water quality impacts in agricultural areas…

  33. 83
    Mark says:

    “However much that might happen in the USA, it certainly will not in those other countries which have plentiful supplies. ”

    The US has extensive coal and oil reserves.
    Which made their alarmist query on Iran “They have oil? Why do they need nuclear?” rather ironic.

  34. 84
    Mark says:

    “Maybe you would find this book interesting:”

    I know that thistles and dandilion CAN be eaten.

    But when wheat and corn are plentiful, how much dandilion and thistle is eaten?

    Heck, the tripes and sweetbreads (the dangly bits) of animals are eminently edible. As are pigs trotters and brawn (the head). The tongue of many animals were commonly eaten.

    In most cases because there was nothing better to eat.

    So you’re requesting that we go back to a serf-level diet as the poorest members of middle age society ate?

    Funny, I seem to remember you were against going back to the stone age.

  35. 85
    Mark says:

    “simply, for a variety of reasons not worth rehashing here, remain skeptical of the magnitude of change predicted.”


    The reasons are not being rehashed because they have been shown to be insufficient and you wish to just be able to repeat “I have my reasons” when they are not your reasons since they do not explain your skepticism.

    What leads you to think that with all the feedbacks (positive and negative) that CO2 doubling would cause significantly less than 3C change?

    Why do you think it impossible?

    Have you done the maths?

    Gilbert Plass did them in 1956. You should be able to get the answer yourself in no time with the power you’re typing on available.

    If you’re skeptical, TEST. That’s what a skeptical scientist does. They don’t go “I’m skeptical” and then leave it there.

  36. 86
    Gail says:

    Lulo, you might be interested in this approach:

    Personally, I think to focus on just CO2 or just “pollution” is a distinction without a difference. Maybe more CO2 makes plants grow faster – I am not convinced it makes them healthier or more nutritious. But certainly, the emissions from fossil and biofuels that produce ozone and peroxyacetyl nitrates are toxic to all forms of vegetative life – as well as humans, creating cancer, emphysema and asthma. We need to stop burning oil, coal and biomass as a source of our energy or we will simply destroy our food supply.

  37. 87
    Chris S says:

    In addition to my comment @81, I’d also like to draw Chip’s (and others) attention to the Journal of Experimental Botany’s special issue on “Crop Science for a Changing Climate”.

    I’d recommend reading Leakey et al. “Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE” which is accessible here: in full (or at least the lesson summaries). The summary for lesson 6 I reproduce in full:

    “Controlled laboratory and field chambers have provided an immense database on plant responses to rising [CO2] and, more importantly, insight into potential mechanisms of response. FACE on the other hand, which allows treatment of plants under field conditions at a realistic scale, has provided an important reality check. It has both shown where hypotheses developed in controlled environments do or do not apply, as well as insights into the mechanisms that may cause the difference.

    Overwhelmingly, this has shown that data from laboratory and chamber experiments systematically overestimate the yields of the major food crops, yet may underestimate the biomass production of trees.

    Improved projection of these hugely important parameterization data for predictive models will require many more FACE experiments, since the large-scale FACE experiments have been conducted at best at just one or two locations in a given ecosystem type.”

  38. 88
    afeman says:

    ‘I’m not sure what “hegemonic hypothesis” really means, but it sounds so good, I’ll use it in my next lecture.’

    Ask Alan Sokal down at NYU for help, he’s pretty good at that stuff. :-)

  39. 89
    Rene says:

    “NASA climate scientist Gavin Schmidt predicts 2010 may break a record, so a cooling trend ‘will be never talked about again’”.

    Was this report correct?

    [Response: Kind of. I said that 2010 might break a record (given that it will start off with a reasonable sized El Nino), and that if it did, we’d stop hearing about the cooling from 1998 nonsense. But of course, as soon as 2012 rolled around, we’d start hearing about how it’s been cooling since 2010…. – gavin]

  40. 90

    Re: #s 54, 81, 87, and everyone else,

    Sure there are studies that show along with every other plant, weeds grow better as well.

    For descriptions of an overwhelming number of papers that show positive vegetative response to elevated CO2 concentrations,
    here’s what the authors of Chapter 5 (Food, Fibre, and Forest Products) of the IPCC AR4 WGII conclude:

    Experimental research on crop response to elevated CO2 confirms Third Assessment Report (TAR) findings (medium to high confidence). New Free-Air Carbon Dioxide Enrichment (FACE) results suggest lower responses for forests (medium confidence). Crop models include CO2 estimates close to the upper range of new research (high confidence), while forest models may overestimate CO2 effects (medium confidence).
    Recent results from meta-analyses of FACE studies of CO2 fertilisation confirm conclusions from the TAR that crop yields at CO2 levels of 550 ppm increase by an average of 15%. Crop model estimates of CO2 fertilisation are in the range of FACE results []. For forests, FACE experiments suggest an average growth increase of 23%for younger tree stands, but little stem-growth enhancement for mature trees. The models often assume higher growth stimulation than FACE, up to 35% [, 5.4.5].


  41. 91
    Lulo says:

    CM: Species loss was my primary reason for including deforestation, land degradation and ocean floor destruction. I hope you are right that I have made a zero-sum error and these issues are getting the attention they deserve. Would climate changes exacerbate what is already the world’s sixth great mass extinction? I believe so. I also believe even larger gains could be made by re-establishing and protecting natural ecosystems directly. This would also enhance resilience in the face of change. Most plants can exhibit remarkable acclimation to new environmental stress, but there would be winners and losers at a much faster pace than the slow process of speciation.

    Gail: I agree with your comments.

    Mark: I have discussed the equations on RC before (last winter). I do not have qualms with the mathematics, but some of the assumptions that precede them (eg. proportion of CO2:Tair relationship caused by CO2 over 30%), and some of the parameterization choices (tendency for choices to be made that result in high- end radiative forcing impacts). I conceded back then and today as well, that I am not a climate scientist (though I have encoded SVATs, it had nothing to do with these equations). You disagreed with me, provided some interesting food for thought, but didn’t convince me to change my mind. The only issue I wanted addressed here was Lindzen’s satellite data being in disagreement with model values for the cloud feedbacks related to SSTs. Gavin has provided me more reason to be skeptical of his claim, but I respectfully submit that he hasn’t refuted it.

  42. 92
    Hank Roberts says:

    Anyone know how to find a copy of this? Might be what Chip Knappenberger is referring to?

    [CITATION] Obstacles to Environmental Education: a hegemonic hypothesis
    M Maher – Unpublished paper presented at biennial conference 1982
    Cited by: Towards a map of commitment: A socially critical approach to geographical education, J Fien – … Research in Geographical and Environmental Education, 1999 – Routledge

    Another perhaps likely possibility in context: the term “Hegemonic Hypothesis” also shows up in this, paywalled:

    An indifference thesis: Constitutional law and politics in an era of “conservative domination” of the judiciary
    Author(s): Ira L. Strauber
    Book Series: Studies in Law, Politics and Society
    Year 2008, Volume:44, Page: 35 – 71, ISSN:1059-4337

  43. 93
    Mark Cunnington says:

    Dramatically reducing carbon emissions would be very easy. If we really wanted to we could be there within 20 years, almost completely off fossil fuels except for specialized applications like aviation and other industries that have specific technical requirements for burning fuels in furnaces (steel production, for example.)

    Of course the problem is the same old problem that our economies have been struggling with for decades — an antiquated patent system that is just begging for abuse by established industries to use it as a tool to stifle new technical developments for the purpose of maintaining the status quo. The most famous and significant example being of course Chevron’s withholding of the electric car battery.

    Here is how we could get off fossil fuels:

    – convert to electric cars: they are better, cheaper, and produce no emissions. This will be happening rapidly over the next decade anyways once the batteries are free to flourish unencumbered through the market. In 10 years I predict 98% of the market for new cars will be electric.

    – put solar panels on your roof: depending on where you live and a few other factors, this would provide more energy than you use over the year. This is currently not cost quite competitive however, but soon will be since hey are developing rapidly. The government could really help this along with incentives.

    – get rid of your natural gas furnace and put in a heat pump which uses electricity. This is a bit more expensive than a gas furnace but the benefit is that you produce no carbon emissions. The extra electricity required could be balanced by the solar panels on your roof.

    – continue with expanding wind energy generation for the grid.

    Technically, we are already there, we need no new developments. Economically, the transition will not hurt the economy overall, rather it will help it by opening up new opportunities. It is POLITICALLY that is the stumbling block, because established vested interests really don’t want us to move away from fossil fuels because then they won’t be making money anymore. Unfortunately, they are in large part the ones in control.

  44. 94
    dhogaza says:

    CM: Species loss was my primary reason for including deforestation, land degradation and ocean floor destruction. I hope you are right that I have made a zero-sum error and these issues are getting the attention they deserve. Would climate changes exacerbate what is already the world’s sixth great mass extinction? I believe so. I also believe even larger gains could be made by re-establishing and protecting natural ecosystems directly

    Climate change is already starting to undo decades of conservation in north american coniferous forests. Huge swaths within protected wilderness areas, national parks, etc dying from insect infestations tied to warming, increased catastrophic fire risk due to warming (and past suppression, sure), etc etc.

    Ever hear of The Nature Conservancy? A few years back they started research with the goal of trying to figure out just how severely coming warming is going to trash their privately-purchased conservation tracts.

    Suggesting that we can directly protect natural ecosystems while ignoring warming is stunningly ignorant.

  45. 95
    Sam Gralla says:

    “If you ask a scientist how much more CO2 do you think we should add to the atmosphere, the answer is going to be none.”

    If you make preposterous claims like this you will undermine both the authority of science (by invoking it in a statement that is false) and the public respect for scientists (by telling them that we would all say such an obviously stupid thing). So, please don’t. Rather, say something true like “many scientists would insist that we should emit no more carbon, because the dangers they see far outweigh economic benefits of emission.”

    [Response: That’s exactly what I said. Phrase it any way you like. – gavin]

  46. 96
    Mark says:

    “I do not have qualms with the mathematics, but some of the assumptions that precede them (eg. proportion of CO2:Tair relationship caused by CO2 over 30%)”

    So how about the need for at least 1.5C per doubling or the PETM needs an infinite amount of CO2 to occur?

    “and some of the parameterization choices (tendency for choices to be made that result in high- end radiative forcing impacts).”

    So you would not believe over 4.5, but why do you believe this is proof that under 2 is real?

    Did you do the mathematics? Gilbert Plass didnt make any assumptions.

    Why then do you not believe the higher than IPCC figure he gets? Is it just that you like assumptions like “It’s lower than 1C per doubling because we don’t have to stop burning CO2 then”?

    [Response: Actually, the Plass calculations are full of assumptions… but more on this at a later date. – gavin]

  47. 97
    Mark says:

    “Sure there are studies that show along with every other plant, weeds grow better as well.”

    Well you missed that out, didn’t you.

    Weeds are already a pest and getting harder to control. Making them more powerful yet is not going to help feed us, is it.

  48. 98
    Gail says:

    Mike Cunningham, that is an excellent summary of the situation. There aren’t any obscene profits in renewable solar and wind energy so it is going to take public demand to make the transition. That is why I think the “other” greenhouse gases are so important to investigate. CO2 and climate change may seem real and urgent to a relatively small proportion of the population, but to most folks so far they are far off problems that don’t matter to their daily lives.

    Explain to them that ozone and emissions from ethanol are responsible for terminal illnesses and that epidemic of asthma that is keeping kids out of school, and maybe they’ll figure out how dangerous burning fossil and biofuels is to them personally.

    And start the conversation about how those same volatile organic compounds are lethal to vegetation – like the trees that give us shade, lumber, nuts and fruits, and shelter to so many other species. Not to mention annual crops, all of which are already showing the telltale symptoms of ozone damage.

    It’s enough to concentrate the mind.

  49. 99
    Geno Canto del Halcon says:

    I might have used a metaphor that reaching the 350 ppmv goal is more like deciding you want to drive from New York to Hawai’i by car. Until we recognize just how completely unrealistic we are being about our goals, we are more likely to drown than to get where we want to go. We have technology we refuse to use, while pursuing technology that will become a maintenance nightmare in a few decades, to generate power. “None” is not an achievable goal so long as we try to drive our car to Hawai’i, instead of using air or water craft.

  50. 100

    What I really like about this site is how denialist trolls result in real good information being posted as follow-ups, e.g., some of the stuff about plant responses to CO_2 (confirming my own reading on the subject, but good to hear from others who’ve checked into it in more detail). Keep it up (not the trolls, the good stuff).