I was quoted by Andrew Revkin in the New York Times on Sunday in a piece about the 350.org 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, realclimate.org, 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 350.org 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 350.org 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 comments on this post.
  1. Icarus:

    Being misinterpreted, misquoted or misrepresented in the press is par for the course, isn’t it? When Andrew represents your view as being that “promoting 350… might be missing the point”, it *does* make it sound like you’re criticising the 350.org campaign, but that’s not what your quote is saying. That’s typical of journalism though – everything has to be hyped up, there has to be drama or conflict or disagreement injected into the story whether it exists in reality or not. Journalism is very rarely just about presenting the facts, and almost always about selling newspapers or gaining viewers or whatever, regardless of the facts.

    [Response: This is not the case here. Revkin was very clear about what we were talking about and wanted to make the point that I have clarified above. There are cases where you would have been correct with this diagnosis – but this is not one of those. – gavin]

  2. Jeff in Cincinnati, OH:

    Not having seen the original article, your excerpts here do sound like a criticism of 350.org. Thanks for the clarification! To be expected of you guys, you do great work!!

  3. Andy Revkin:

    I’d hoped to retain that great final line, but in the eternal space crunch, it got dropped.

    The vital question, I’m told repeatedly by specialists in the non-science arenas you list (economics, technological change, politics), is what policies have the best shot of producing a peak and decline that limits climate risks as delineated by the science.

    And most of those curves are quite similar no matter what end point is chosen, given the change required just to stablize at ANY concentration in a world heading toward 9 billion people seeking decent lives.

    A couple of useful additional perspectives that didn’t fit in print were offered by Rajendra Pachauri of the IPCC (who endorsed the 350 campaign):


    “We are dealing with a dynamic system. Hence, what would really be relevant is the trajectory of concentration levels and therefore emission trajectories. The 350 number has some appeal, because it would to some extent determine the peaking period and the rate of decline. Of course 350 by itself provides no solution. It would merely be the end point of a trajectory which theoretically can have infinite alternatives.”

    And Mike Hulme, the British climate maven who wrote “Why We Disagree About Climate Change”:


    “I never quite know what targets like 400, 350 or 280 mean…. If we mean stabilise back at 280 by 2200, say, then we can pump a lot of CO2 in the meantime, before some really good carbon scrubbing technologies in the 22nd century come along. Same argument actually for 280 by 2100 if you’re a technology optimist. So really if one wants to deal in long-term numbers then talk either about future C budgets (how many gigatons are you going to allow), or else set the peak concentration and by when. My guess is that for CO2 we will hit 500ppm sometime this century (harder to guess what CO2-equiv will be). On what to aim for – I wouldn’t play politics will long-term numbers: far too easy for them to be hijacked and used for all sorts of dubious reasons and causes. Much better is to focus on near-term goals (2015, 2020) and to break them down into manageable sectors (e.g. aviation, municipalities, aluminium sector, etc.). The rhetoric of global long-term targets raises the illusion that we can govern globally over the long-haul (the illusion of Copenhagen) – and we can’t.”

  4. bill mckibben:

    Many thanks to Gavin for his clarification, and for his work (and everyone else’s at RC) over the years. For whatever reason Andy chose to paint the 350 effort as unlikely in his story, but it was reported the day before we actually showed you could mobilize millions of people in 5200 events in 181 countries in what the press is calling ‘the mose widespread day of political action in the planet’s history,’ all around a scientific data point. I think tht should be heartening to all.

    The biggest point the number gets across, i think, is that climate change is not some future threat but a present crisis. If you have a moment, I recommend browsing through the photos we’ve got up at 350.org (a tiny subset of the 21,000 now in our flickr photostream) to get a sense of the people who are waking up to this reality.

    thanks to all who participated Saturday

  5. Andy Revkin:

    Just one last thought here, upon reading Bill’s comment.

    There were two things to report on (and my reporting continued through the actual day of action):

    1) The amazing coordinated globe-spanning mosaic of actions
    2) the basis for the focal point of that action.

    On the first, there’s no question an epic effort was carried off with astonishing scope and skill.
    On the second, there remain large, substantive and vital questions. As I said in a comment response somewhere on my blog, a keystone question is 350 by when? As Pachauri and others explained, 350 ppm on its own is kind of like judging a car’s mileage by “miles” without the “per hour.”

    My story had to examine both the news and the context. We’ve been pilloried in the past for simply reporting what folks are saying without examining the evidence and argument. I’m not drawing ANY comparisons at all, but examples that come to mind are when a president pumps up the WMD threat, or when candidates rattle off jargon like “clean coal.”

  6. Mark A. York:

    Concur with Bill. We can’t let it get to 450. That’s the point of the movement. With no sense if immediacy there will be no incentive. People don’t respond to future problems.

  7. pete best:

    Re #3. There is no easy answer to limting AGW. You just turn off using 4.5 billion tonnes of oil per annum in any meaninfgul way without changes on every level. On energy sources, on our energy usage, on the technology that provides the means to use it, on your expections and aspirations in our lives (our culture) etc.

    There is no one single way to even limit emissions as the world wants more energy presently and its coming from fossil fuels for its infrastructure is vast and poewrful both dail, economically and politically.

  8. Deep Climate:

    Thanks for the clarification. I must admit it didn’t make much sense when I first read it, since the natural interpretation of “those promoting 350” would be as a reference Bill McKibben and 350.org. As I didn’t think you were actually criticizing them, and your quote would not have made sense in that context anyway, I was left to presume that your original point had been obscured.

    Probably, it would have made more sense for Revkin just to omit that phrase and referred to “those debating the 350 target”.

    #1 Icarus
    Of course, I strongly disagree. I’m sure Revkin was trying to paraphrase or summarize Gavin’s thoughts as accurately and succinctly as possible. You’d have to look at a transcript of the interview to know exactly how the misunderstanding or lack of clarity occurred. But surely there’s no reason to throw around accusations of deliberate distortion. There is no evidence of that whatsoever.

  9. sidd:

    May I draw attention to a paper


    which draw attention to the low hanging fruit of mitigation, specifically HFCs, black carbon, methane, and tropospheric ozone. In the Sturm und Drang around Copenhagen, we must not miss the chance to severely limit or eliminate these non CO2 contributors, especially since controls on these emissions is not so politically charged, therefore a good starting point for negotiation.

  10. Former Skeptic:


    Are you thinking of Paulina or are you thanking her? The former has, erm, interesting implications…

    Sorry to be a gramar/speeling Nazi :)

  11. Icarus:

    [Response: This is not the case here. Revkin was very clear about what we were talking about and wanted to make the point that I have clarified above. There are cases where you would have been correct with this diagnosis – but this is not one of those. – gavin]

    Then I apologise, of course – thanks for the correction.

  12. Former Skeptic:


    Whoops. Please forget about my previous post as I misread it totally. My bad!

  13. Gareth:

    First, let me thank Bill and his team: Oct 24 was a fantastic effort. For me, the key 350 message is not the number itself, but the point it makes: we’re already way past our target and need to take action that goes beyond any being considered at the moment. Most governments seem to be buying into 450ppm/2ºC without any clear appreciation that the 450 is CO2e(total), and the chances of staying under 2ºC only 50%. 350 nicely makes the point that 450 is dangerous. I asked my local MP on Saturday (my personal action – he put up with it for 20 minutes!), if he realised that his government’s targets if applied globally committed the world to damaging change? He didn’t, and while I doubt he’ll be arguing for 350 in his party’s caucus, at least he’s aware that 50% cuts by 2050 are no longer credible – for NZ or any other country.

  14. David B. Benson:

    I find “350” as far more memorable than my favority long term target, 300 ppm CO2e. The latter doesn’t exactly roll off the tongue.

    But first we need to stop going up.
    Then we need to start coming down.

    SOme of the coming down actions can offset going up actions until the latter stop. An example is planting lots of forests. Lots.

  15. manonthemoon:

    “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’m a scientist and my answer is “it doesn’t matter”. CO2 is good for plants and CO2 is driven by temperature change, not vice versa.

    [Response: I should have clarified that I meant ‘scientists that know what they are talking about’. – gavin]

  16. Chip Knappenberger:

    “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.”

    You are kidding me, right? Or does “a” refer to a specific “scientist”?

    Perhaps I am missing the context here.

    There are plenty of agronomists, and probably even some climatologists, among other scientific disciplines, who think that adding CO2 to the atmosphere is not a bad thing.


    [Response: They would be the extremely short-sighted agronomists. As we have discussed on many occasions. – gavin]

  17. Steve:

    I thought the whole point of the 350.org thing was to challenge people to understand that we’re currently driving in the wrong direction, and somehow or other we have to get back to an atmospheric concentration that is lower than today’s. For the last few years, there was a lot of talk about 450 being feasible. Bill McKibben set out deliberately to challenge this thinking as too feeble. So, the metaphor of driving in the wrong direction is exactly what 350 is all about.

    Plus, you have to admit that the question “what is an appropriate level of atmospheric CO2?” is a much more productive question for getting non-climatologists to think about than the simplistic yes/no questions of “is climate change happening?”, “is CO2 the wrong villain?” and “is geoengineering a good idea?” that get bandied about in the media. (Hat tip to Michael Tobis for pointing this out in a talk yesterday).

    I think this is one of the communication issues that climatologists have been slow to understand. “Is 350 the right number?” is a lousy research question for a climate scientist. But it’s a very productive way to frame the discussion for the non-science audience.

  18. Mark:

    “Re #3. There is no easy answer to limting AGW. You just turn off using 4.5 billion tonnes of oil per annum in any meaninfgul way without changes on every level.”

    Reduce 7% a year.

    That’s all.

    Just 7% current production, each year.

  19. Susan Anderson:

    Thanks to Andy Revkin and Bill McKibben for the clarifications above, as well as the article. I could wish the NYTimes would allow Andy to have included the vital sentence. As news emerges every day of consequences far and wide, I’m beginning to notice that people on the street are more aware of climate change than pundits. Time for them to get out of their lairs and notice that most people can see things are changing, not for the better.

    it is amazing that the organized and well funded denial effort continues to have traction. Labels instead of facts, lies instead of reflection, parsing every little word for something to exploit, making the story about personalities, changing the subject, providing expertise that is anything but, it goes on and on.

    350.org is a brave effort and I hope we will all continue to support it.

  20. David B. Benson:

    manonthemoon (15) — For a scientist, you are remarkably un- and mis-informed. Start with the “Start Here” link at the top of the page.

  21. Lennart van der Linde:

    Thanks, Gavin, for this extended clarification! Returning to 350 this century will probably require a WW-II style mobilization, as Lester Brown has been arguing for some time now. So it’s good to know that Obama is now starting to use the WW-II mobilization metaphor as well:

    And also good to know that some economists at least think 350 seems quite feasible:

    I don’t think that’s the whole story, since Kevin Anderson has been arguing for a ‘planned recession’ and Herman Daly for a steady-state economy. And besides CO2 there seem to be other planetary boundaries as well, according to Hansen, Schellnhuber, Crutzen and others:

    The real political debates haven’t even begun yet.

  22. Eyal Morag:

    In the original paper The number is 450 ± 100 so 350 is about the upper limit of the safe zone.
    But in the Paper it clear that it isn’t the finale number and only a reference for start. It give us a clear message that we are already in the dangerous zone. I think we can agree on that.

    “planet being nearly ice-free until CO2 fell to 450 ± 100 ppm; barring prompt policy changes,
    that critical level will be passed, in the opposite direction, within decades. If humanity wishes to
    preserve a planet similar to that on which civilization developed and to which life on Earth is
    adapted, paleoclimate evidence and ongoing climate change suggest that CO will need to be reduced from its current 385 ppm to at most 350 ppm ”

    ” We suggest an initial objective of reducing atmospheric CO2 to 350 ppm, with the target to
    be adjusted as scientific understanding and empirical evidence of climate effects accumulate.
    Although a case already could be made that the eventual target probably needs to be lower, the
    350 ppm target is sufficient to qualitatively change the discussion and drive fundamental changes
    in energy policy. Limited opportunities for reduction of non-CO2 human-caused forcings are
    important to pursue but do not alter the initial 350 ppm CO2 target. ”

    Target Atmospheric CO2: Where Should Humanity Aim?
    James Hansen et al.

  23. David B. Benson:

    “Currently the level of CO2 and CO2 equivalents in the atmosphere is 463 parts per million.” from

    [Response: We’ve discussed the CO2, CO2-eq_kyoto and CO2_eq_including_aerosols issue before. It isn’t particularly relevant here since the CO2 and CO2_eq_including_aerosols are actually quite close. CO2-eq_kyoto is not what the climate responds to. – gavin]

  24. Chip Knappenberger:


    I would venture that there is a difference between:

    “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 ask a scientist that knows what they are talking about (according to me, Gavin) how much more CO2 do you think we should add to the atmosphere, the answer is going to be none.”

    Thanks for the clarification! ;^)


    [Response: That’s fine. Though you’ll find that the intersection of the class of people who do actually know what they are talking about and the class of people who I think know what they are talking about is quite large. – gavin]

  25. Pierre Allemand:

    I am convinced that if you were from Siberia, answer should not be “none”. Nor if you where a citizen of China or India.
    So, “none” is the answer of people (confortably) living in Europe or in the USA.
    Taking in account the actual number of people and their way of life I am not at all sure that “none” is actually the “right” answer nor the most frequent.

    [Response: Permafrost melt in Siberia is a serious issue that is affecting a lot of their infrastructure, billions of people in India and China depend heavily on glacier-fed water that is already being affected by warming and which might lead to summer drying up of rivers like the Ganges if the situation continues. I doubt very much that many residents in those watersheds would think that the CO2 should be increased at that cost. Note that this is not a policy proposal, just an aspiration. – gavin]

  26. Hank Roberts:

    I get email (examples of work already being done)

    A “How to develop a forest stewardship plan” class will be offered by the Northwest Natural Resources Group on December 12th, 2009. The fee is $45. For more info visit http://www.nnrg.org/news-events/events/12-12-how-to-write-a-forest-management-plan/

    Next Generation Conservation: the Government’s Role in Emerging Ecosystem Service Markets October 23, 2009 The Duke Environmental Law and Policy Forum (DELPF) announces its 2009 SYMPOSIUM together with the USDA Office of Ecosystem Services and Markets. The symposium will bring leading experts together to discuss the role of the Federal government in shaping and developing markets for ecosystem services. Admittance is free and open to the public. For more information visit http://www.law.duke.edu/journals/delpf/symposium or email tomer.hasson@duke.edu **

    The symposium will be accessible via webcast: http://www.law.duke.edu/webcast/

  27. Chip Knappenberger:

    Re: 24,

    “…the intersection of the class of people who do actually know what they are talking about and the class of people who I think know what they are talking about…”

    I am not quite sure how to assess the former, but clearly the latter is readily assessable!

    I hesitate to guess how close I may be to that intersection…


  28. Karen Street:

    350 ppm may be a commendable goal, but according to my reading, a PNAS report, Irreversible climate change due to carbon dioxide emissions, deemed it unlikely (http://www.pnas.org/content/early/2009/01/28/0812721106.full.pdf+html).

    It is my sense that a general agreement that health care today is a problem hasn’t helped us to the solution. What is needed is a shift towards understanding the economists. I agree with Gavin, “All the rest is economics.” I’m struck by the number of people in the public who trust IPCC for the science, but get their policy information from sources other than IPCC. I can see the scientific concern that economists are too optimistic (about hydro in 2030, bioenergy in 2030) but not the concern among many in the public that IPCC is not optimistic enough.

    The people I knew who went to the local 350 event are all over the place on solutions: we can be all renewables by Thursday, we need a strong nuclear component, we can get there from here by lowering our own footprint. Perhaps the various groups putting on events will encourage a discussion of IPCC WG3?

  29. Jim Cross:

    Gavin: “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.”

    You can’t be speaking as a scientist when you say this. A scientist might say more CO2 will have these consequences and there could be scientific debate over the consequences, but when you make a value judgment about none, you are outside of science and into politics and ethics.

    [Response: Yup. – gavin]

  30. David B. Benson:

    Karen Street (28) — This is such a difficult goal that the answer is “all of the above”.

    Jim Hansen says burn no coal without CCS. Yup.
    Some advocate renewables. Yup.
    Others talk up nuclear powered electricity generation. Yup.
    Still others promote air capture via photosynthesis. Yup.
    A few advocate air capture via other chemistry. Yup.
    Many advocate energy efficiency. Oh my, yes!

  31. Karen Street:

    David (28) All of the above is indeed needed, with the need for CCS R&D appearing in recent uber reports in 2nd coming font. However, of the people I know who went to the local 350 event, many oppose some of the larger solutions in “all of the above”.

    Now how do we morph support 350 to support for all of the above?

  32. Jeffrey Davis:

    re: 28
    “What is needed is a shift towards understanding the economists.”

    Economists? One of their school (freshwater) doesn’t even read the other (saltwater). These are the people who are going to evaluate the expense of something that hasn’t been defined yet?

  33. David B. Benson:

    Karen Street (31) — What is being opposed? I certainly would like to know.

    There are those who oppose mountaintop removal coal mining. I do too. But even the US has ample supplies of coal mined other ways and many other countries also burn lots of coal and are most unlikely to stop.

  34. L. David Cooke:

    Dear Dr. Schmidt or fellow RC team member,

    Just a few quick questions. If as has been discussed in the past, that the natural carbon cycle appears to have an annual difference between emission and uptake; Is this difference not the motivation behind groups like the “350” as opposed to a warning of exceeding a set target level with error bars?

    Also based on your learned opinion; is the current energy demand and demand through the next 50 years achievable with little negative impact on the current society and economic base?

    The reason for the first question is this would suggest that there would be a belief that if “All Things Remained the Same”, if we were to return the population or mineral/fossil energy demand to pre-1950 levels and use today’s aerosol and possible CO2 entrapment/abatement technology the current conditions could be reverse-able.

    The reason behind the second question is that this becomes one of the leading oppositions to the Carbon and Energy Security Bill currently in Congress. It would seem that if we could more accurately outline the direction and the results of actions taken we could demonstrate the value in taking action quickly.

    Dave Cooke

  35. Dan Robinson:

    It took the recession to cause a drop in our rate of emissions. Will H1N1 be needed to do the same for ppm? How soon then will we see temperature start to drop, and stabilize? It would be nice to see some of this done intentionally. In any case, people will probably just claim then that there was no real problem and go back to their pleasures.

  36. Chris Dudley:


    Thanks for the clarification. I’ve appreciated your statements in the past that turning emissions growth around is the first step that is needed but I’m glad that you can voice some support for a goal beyond that now. Not everyone is going to be on board before Copenhagen, if that is the right phrase. Yet, Copenhagen needs the greater urgency that having 350 in the air can provide. Having your more explicit support together with David Archer’s is very welcome.

  37. George Ortega:

    350 is one way to look at our situation. Another is using recommended CO2 reductions. In 2007, the IPCC, under the assumption that 450 was the operative number, warned of catastrophic consequences if we do not reduce CO2 emissions by 80 percent of the 1990 level by 2050. A ballpark guess would be that 80 percent of the 1990 level would translate to over 90 percent of current 2010 level. But, if we are talking about 350 rather than 450, another ballpark guess would be that we actually need to reduce CO2 by what — 100 percent, 110 percent, 120 percent of the 2010 level?

    It seems that the percentage of CO2 reduction required presents a clearer picture of the challenge we face than the ppm estimate.

  38. Chris Dudley:

    Karen (#31),

    You ask how support for 350 ppm can be translated into support for nuclear power. It really can’t be because nuclear power has such a large carbon opportunity cost that it can’t be a part of a solution. All of the above might work for 650 ppm, but we need the best of the above for 350 ppm.

  39. Chris Shaw:

    Re. the idea that science is seperate from economics, sociology etc doesn’t stand up to scrutiny. For example, many scholars have catalogued the intimate relationship between the eulogising of scientific knowledge claims and the capitalist profit motive. Studies in the sociology of science have shown that science isn’t conducted by non-social beings in a non-socialized context. And how true is this of climate science, the most politicized of all sciences (witness debates around IPCC press releases and assesments). The division you propose is false.

  40. Mark:

    “You can’t be speaking as a scientist when you say this. ”

    Jim Cross, don’t interpret a statement you don’t like with not being one a scientist would make.

    It may not be possible to not put CO2 into the system but we should certainly put none in if at all possible and work toward putting none in now.

    Why would a scientist not hold that?

    An economist may (it may be more costly to avoid). An engineer may (it may make some solutions to engineering problems impossible). But why a scientist?

  41. Lennart:

    The Club of Rome now also supports Target 350, although without time frame:

    They also state that current economic growth-mania is unsustainable.

  42. Philip Machanick:

    To those alleged scientists (#16) who claim more CO2 is good for plants, point us to your publications. I’ve searched for literature on this subject and yes, plants generally grow faster with more CO2. But the rate of improvement varies greatly, and there can be downsides, like more CO2 without increasing nitrogen = lower nutritional value. When you start factoring in deleterious effects of climate change as well, there’s no serious case. Rice for example drops in yield dramatically as temperature increases, and much of the world’s rice is grown near its upper temperature limit. Here’s something you could read for a start:

    Fulu Taoa et al. Global warming, rice production, and water use in China: Developing a probabilistic assessment, Agricultural and Forest Meteorology Vol. 148, Issue 1, 7 January 2008, pp 94-110

  43. Gail:

    Thank you, Gavin!

  44. Jim Galasyn:

    It’s as if Mordor came to The Shire to emit carbon:

    Tablas de Daimiel wetland: then and now

  45. Chip Knappenberger:

    Philip (re: #42),

    Re: 42,

    For starters, check out the book Food, Climate, and Carbon Dioxide by Sylvan Wittwer–a crop scientist who conducted some of the early work on crop production and atmospheric CO2 enrichment.

    Here is an excerpt from the final paragraph in the book:

    “Now after more than a century, and with the confirmation of thousands of scientific reports, CO2 gives the most remarkable response of all nutrients in plant bulk, is usually in short supply, and is nearly always limiting for photosynthesis…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.”


    [Response: Perfect example of someone who might be a great plant guy but who has absolutely no clue about the larger context. And frankly, I surprised that you are going down the ‘CO2 – they call it pollution: We call it life’ self-parody hole. – gavin]

  46. Phil Mitchell:

    I have become disillusioned with Andy Revkin’s reporting on climate change. The need to turn a report on 350 Day into a debate between so-called experts about the validity of the number 350 is part of the same junk journalism that we have seen all along on climate change. He is missing the forest for the trees. The point is not that 350 is exactly the right number. The point (as Gavin said) is that we are going in exactly the wrong direction. I would add that, the way Gavin was quoted, it definitely sounded to me like he was criticizing participants in 350.org equally with their “opponents”. Lame reporting.

  47. Lulo:

    As a lukewarmer who understands the positive effect of CO2 on leaf photosynthetic productivity, water-use efficiency and nitrogen-use efficiency among plants, but was concerned about its effect on climate, I am tempted to join the dark side after taking a look at the ERBE and CERES data in Richard Lindzen’s pdf presentation, posted on your nemesis Watts Up. Is there a good reason why all models predict a positive feedback and the data show negative feedback? There had better be, or I’m going to fall off the fence onto the side of CO2 as a plant food with only a small climate effect. Jeer away (as I cower in fear, peeking through the holes between my fingers)!


    P.S. Don’t bother with all the dissuasive political nonsense… just jump right to SLIDE 45 and SLIDE 46. I await your reasoned dismissal of his clear demonstration of negative feedback.

    [Response: We’ve gone over this before – there is plenty of evidence that total feedback can’t be negative. Thus it becomes an interesting issue to investigate why Lindzen comes up with the result he does. Perhaps you’d care to try and replicate it? How in fact did he pick his time periods that he uses? What difference does the inclusion or not of the Pinatubo forcing have? Why didn’t he use the coupled models as opposed to the atmosphere-only models? Does this analysis actually correlate to the sensitivity in the models themselves? The curious thing is that Lindzen was convinced the sensitivity was around 0.5 deg C years ago (see Morgan and Keith, 1995) before this analysis was even possible and based on no evidence that has stood the test of time, and now (surprise!) his analysis finds exactly the same number. I think a little scepticism is in order and I’m sure that there are some explorations of the robustness of this result in the works. – gavin]

  48. Chip Knappenberger:


    Should I bother to provide more examples of crop scientists who think CO2 is could be a net benefit, or will they all fall, by default I guess, outside your intersection of scientists-who-know-what-they-are-talking-about and those that you think know what they are talking about?


    [Response: Do what you want, it’s your time you are wasting. CO2 concentration is a completely minor factor in determining crop yield compared to better management, fertiliser use, more appropriate crops, mechanisation, water resources etc. It is a tiny issue in assessing cost and benefits of climate change regionally and yet if you want to parade a suite of people who can’t see beyond their nose, feel free. It will demonstrate more about your political approach than anything concerning a proper assessment of the issues. In fact, it would show directly that you weren’t concerned with the latter. Go ahead, make my day. – gavin]

  49. Lulo:

    Gavin: Why is that a ‘self-parody hole?’ The benefit of CO2 to plant growth has been known (and utilized) for decades or longer. The same is true of its effect on climate. The only difference is that there is no debate on the former. Every plant scientist in the world knows that CO2 has been impoverished for the past 20 million years or more. I concede and worry about the radiative forcing effect of CO2, and that human civilization developed in low CO2, but really, how is focusing solely on its benefit to plant life any more self-deprecating than devoting one’s career to focusing only on data that supports the hegemonic hypothesis of climate modelling scientists.

    [Response: Because no-one is worried about CO2 because of the effect it has on plants (which for all the quotes coming from Chip et al is much more complicated than the talking point suggests particularly when you think about what kind of plants benefit most and the other limiting nutirents). It’s like someone coming along to a lecture on how to prevent drownings by insisting that everyone needs water to drink. It’s simply not relevant and is put up as a political distraction. I’m not sure what “hegemonic hypothesis” really means, but it sounds so good, I’ll use it in my next lecture. – gavin]

  50. Daniel C. Goodwin:

    Punting back and forth of the 350 number above brings to mind a related numerical balance illustrated by Senator Boxer’s recent comment on the senate climate bill (http://www.huffingtonpost.com/sen-barbara-boxer/telling-the-whole-story-o_b_333290.html):

    “According to CBO’s estimate, if we act now to address global warming and invest in clean energy, the economy 40 years from now may be about 249 percent bigger, instead of 250 percent bigger. And we’ll still get to 250 percent – in May instead of January 2050.”

    The mathematics of eternal growth, as alluded to here, are evidently incompatible with life on Earth. This statement sounds delusional to me. We a being told that a somewhat limited form of delusional thinking is the best we can hope for from our system.