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More on sun-climate relations

Filed under: — rasmus @ 9 March 2010

Four new papers discuss the relatiosnhip between solar activity and climate: one by Judith Lean (2010) in WIREs Climate Change, a GRL paper by Calogovic et al. (2010), Kulmala et al. (2010), and an on-line preprint by Feulner and Rahmstorf (2010). They all look at different aspects of how changes in solar activity may influence our climate.

The paper by Judith Lean (2010) has the character of a review article, summarizing past studies on the relationship between solar forcing and climate. The main message from her article is that the solar forcing probably plays a modest role for the global warming over the last 100 years (10% or less). It’s a nice overview, but I miss treatment of uncertainties.

Her analysis is based on the HadCRUT3 data, and I wonder if she would get similar results if she chose the GISTEMP or NCDC instead. The choice may in particular be relevant for the discussion of the temperatures after 1998.

Personally, I regard the data on solar activity before 1900 as quite uncertain too. The reason is that there are strange things happening to the solar cycle length in the shift from the 19th to the 20th century. Hence, any analysis based on the past centuries is uncertain because of suspect data quality in the early part of the record. Lean mentions that proxy-based records are uncertain, however.

Another source of uncertainty stems from the analysis itself – a regression analysis with chaotic data can easily yield misleading results. Gavin and I showed in a recent paper that multiple regression can produce strange results when applied to the global mean temperature and a number of forcings.

In other words, I think the reader may get the wrong impression from Lean (2010) that the link between solar activity and climate is better established than the data and methods suggest. Especially when she discusses forecasts for the near future (eg. for year 2014) – I fear that such a discussion can be misinterpreted and misused. However, that’s my view, and it does not necessarily mean that her paper is incorrect – quite the opposite, I think her main conclusions are sound (Her estimate of the solar contribution to the global warming over past century – 10% or less – is in good agreement with the figure Gavin and I got in our analysis).

The positive side is that the paper is probably clearer and more accessible without all these caveats. I also think she makes an interesting point when she discusses ‘fundamental puzzles’ associated with claims of strong solar role in terms of the past warming. She puts this into the context of climate sensitivity, arguing that it would imply that Earth’s climate be insensitive to well-measured increases in GHG concentrations and simultaneously excessively sensitive to poorly known solar brightness changes. Furthermore, Lean argues that it would also require that the Sun’s brightness increased more in the past century than at any time in the past millennium – a situation not readily supported by observations.

The paper of Calogovic et al. (2010) is a follow-up of a recent paper by Svensmark et al. (2009), looking into the claim that the cloud water content drops after a Forbush event. Their work involved estimating cosmic ray fluxes for the whole planet, and comparing it to local cloud information derived from satellites. They concluded that the Forbush events had no detectable effect on the clouds.

Moreover, they also argued that the analysis of Svensmark et al. (2009) gave unreliable results since it included a Forbush event on January 20, 2005 which was accompanied by a strong solar proton event. However, they did not explain explicitly why such proton events would disturb the measurements, but referred to another study by Laken et al. (2009) in Geophysical Research Letter. Laken et. al. only discusses the proton events briefly, and refers to a study by Fluckiger et al. (2005), who state that “The cosmic ray ground level enhancement (GLE) on January 20, 2005 is ranked among the largest in years, with neutron monitor count rates increased by factors of more than 50″.

But there is no reference to proton events in Fluckiger et al. (2005), so I’m not convinced that proton events will invalidate the analysis of Svensmark et al. (2009). Perhaps I’m missing something? Anyway, this is only a minor detail, and the rest of the analysis of Calogovic et al. (2010) seems more convincing. Their conclusion is supported by Kulmala et al. (2010): “galactic cosmic rays appear to play a minor role for atmospheric aerosol formation events, and so for the connected aerosol-climate effects as well”. Kulmala’s group in Finland boasts many world-renowned aerosol physicists.

The study by Kulmala et al. (2010) was based on near-ground measurements of aerosols, magnetic field, cosmic rays, sunlight intensity (solar radiation), and ionization over a 13-year long period (~1 solar cycle). They also used airborne Neutral cluster and Air Ion Spectrometer, LIDAR and Forward Scattering Spectrometer Probe measurements. They failed to detect any correlation between cosmic ray ionization intensity and atmospheric aerosol formation.

Feulner and Rahmstorf address a speculation stated by Lean: the possibility of solar forcing countering anthropogenic global warming. Their paper examines the effect a solar grand minimum (low solar activity similar to that inferred for the Maunder Minimum) would have on the global mean temperature by 2100. By accounting for a corresponding reduction in forcing for the future in a climate model study, they conclude that the effect is negligible (less than 0.3K compared to 3.7 – 4.5K if the SRES A1b or A2 emission scenarios were assumed).

So what can we learn from these articles? What we see is how science often works – increases in knowledge by increments and independent studies re-affirming previous findings, namely that changes in the sun play a minor role in climate change on decadal to centennial scales. After all, 2009 was the second-warmest year on record, and by far the warmest in the southern hemisphere, despite the record solar minimum. The solar signal for the past 25 years is not just small but negative (i.e. cooling), but this has not noticeably slowed down global warming. But there are also many unknowns remaining, and the largest uncertainties concern clouds, cloud physics, and their impact on climate. In this sense, I find it ironic that some people still rely on the cosmic rays argument as their strongest argument against AGW – it does involve poorly known clouds physics!


192 Responses to “More on sun-climate relations”

  1. 51
    meteor says:

    JamesA

    The radiative TOA forcing determines the warming of what is under TOA.
    So, if you take a given climate sensitivity and a model of ocean, with the knowing of TOA forcings, you can easily reproduce the surface trend.
    Anybody can do it, I do it many times, and it works very well.
    To sophisticate a little you can introduce ENSO, if you want,and it is quasi-perfect.
    You need not “hellishly complicated GCMs” for that.

    For the solar forcing it seems that I speak in the desert and it is a problem that Rasmus never answers the questions.

    The 0.1K response of solar 11 years cycle is very often cited by Lean or Hansen, or others.
    And if I remember there is little lag, so the forcing must be greater than 0.175W/m2.
    Maybe there is another atmospheric process which explains it.
    But to warm the surface you must warm the ocean and you need heat.

  2. 52
    Hank Roberts says:

    > Meteor
    Sorry, my French isn’t adequate to understand your website and you’re not citing your sources here, so I can’t follow what you’re trying to say or tell if these are opinions or comments from research papers. Can you cite sources?

    I tried to find recent papers using terms from your posts and found these:

    http://www.cgd.ucar.edu/cas/Staff/Fasullo/refs/Trenberth2010etalGRL.pdf
    “The main changes in SSTs throughout the tropics are associated
    with El Niño Southern Oscillation (ENSO) events in which
    the dominant changes in energy into an atmospheric column
    come from ocean heat exchange through evaporation, latent
    heat release in precipitation, and redistribution of that heat
    through atmospheric winds. These changes can be an order
    of magnitude larger than the net TOA radiation changes,
    and their effects are teleconnected globally, and especially
    into the subtropics. Atmospheric model results are explored
    and found to be consistent with observations….”

    High frequency climate variability of the Norwegian Atlantic Current during the early Holocene period and a possible connection to the Gleissberg cycle
    http://hol.sagepub.com/cgi/content/abstract/20/2/245

    “… Constrained by the observed SSST changes and diatom assemblages, short-term SSST changes with a periodicity of 80—120 years are observed, and the length of this period might indicate a possible connection to the solar Gleissberg cycle…. the century-scale variability of 80—120 years cannot explain the large-scale variability during the early Holocene, but is of importance for understanding the underlying small-scale oscillations….”

    http://www.informaworld.com/smpp/content~content=a919320463&db=all
    Climate-model evaluation of the contribution of sea-surface temperature and carbon dioxide to the Middle Miocene Climate Optimum as a possible analogue of future climate change

    “The Middle Miocene Climate Optimum (MMCO), which occurred at about 15 Ma, is the most recent global warming episode. Given the fact that no dramatic tectonic movement had taken place, this historical warming episode mirrors the present warming event induced mostly by human activities. Proxy data indicate that the MMCO had a global mean surface temperature of ∼3-4°C higher than the present, equivalent to the warming predicted for the next century by the mid-range scenarios of the IPCC Fourth Report (AR4). With this comparable magnitude of warming, it is therefore of scientific interest to examine whether or not the present warming is similar to the MMCO warming. Since the MMCO boundary conditions such as paleogeography and paleobathymetry were not greatly different from today, contentious scientific issues on possible forcing mechanisms can be assessed…. [details of models run] …
    This may explain why the Arctic warms much more than the Antarctic in the MMCO and the decoupling of CO2 with temperature as determined by the proxy SST.”

  3. 53
  4. 54
    Texas Reader says:

    Would someone please give us non-techies a few sentences on the conclusions of these articles? Like, do the papers all conclude that solar radiation is insufficient to account for the global warming we are seeing? Thanks.

  5. 55
    Septic Matthew says:

    49, David B. Benson: instead use the known physics

    Those predictions will be good enough if the known physics is known with good enough accuracy and if the unknown physics is unimportant enough. If I had to bet on one single prediction I would bet on the prediction of the Beenstock and Reingewertz model, but with knowledge as it is I prefer to hedge my bets.

  6. 56
    JamesA says:

    meteor,

    I hope you’ll forgive me for being sceptical, but claims of finding problems with big models based on work with small models are cheap to make and don’t exactly have a particularly good hit rate in the grand scheme of things. From what you describe, it sounds like you’ve just kept feeding a 0D model with arbitrary parameters until the lines look like they match up, which doesn’t inspire much confidence.

  7. 57
    Hank Roberts says:

    the “izle” spambot copied from 44 Bob Tisdale and posted a crap link in 65.
    Avoid. Watch out for this bot, it’s changed its name recently.

  8. 58
    David B. Benson says:

    Texas Reader (54) — It is primarily CO2 which is driving the warming experienced over the last 130 years. See the comment linked below for instance.

    Septic Matthew (55) — The known physics accounts for almost everything; see Rasmus’s essay beginning this thread for example. The paper you mention includes none of the physics known since Arrhenius first worked in out in 1896 CE; his approximate formula is still in use; for example see IPCC AR4.

    Now I’m willing to make a short range prediction (+-0.25 K) based just on the Arrhenius formula (almost everythng) and AMO (sight adjustment for other factors):
    http://www.realclimate.org/index.php/archives/2010/02/whatevergate/comment-page-23/#comment-164509
    I don’;t go further than the 2010s because I’m not prepared to make up various forcing scenarios nor guess where AMO might go. But in any case, some climatologists are so willing. Also if you have questions about my simple conceptual model, do ask.

  9. 59
    R. Gates says:

    Philip Machanick #53 response:

    “Look at this the other way around: is it not surprising that in the deepest solar minimum for nearly 100 years, we are still at or near record maxima?”

    I guess “surprising” to whom? Depends on what side of the fence you stand on in the AGW issue. I think the AGW skeptics will be really scrambling to explain away the record warmth in the years ahead, but now of course they can just claim the data is flawed or corrupted.

    Thanks for your response–very to the point. I agree of course the longer term trend is the only important issue here. Not being a trained scientist, I was just wondering how much the solar cycle factored into the Met forecast. With cycle 24 starting to get active and the solar minimum behind us, and with the El Nino still hanging around, it seems reasonable to predict the likelyhood of record global warmth in 2010…and if not, then certainly in the next few, before the next solar minimum rolls around. The trend is clear.

    And in regards to your statement above

  10. 60
    Pete Dunkelberg says:

    Texas reader, you’re right, any known change in solar radiation is insufficient to account for the global warming we are seeing. Go back to the last paragraph of the top post. But also note that ultraviolet solar output is not known within close bounds.

    In general we get more energy from the sun when there are more sunspots. These increase and decrease in an eleven (give or take a year) cycle. The most recent solar sunspot minimum lasted longer than usual so these have been cool years on the sun. The newly started solar cycle is not expected to reach a strong maximum. See
    http://solarscience.msfc.nasa.gov/
    http://solarscience.msfc.nasa.gov/SunspotCycle.shtml
    and also space weather http://spaceweather.com/
    which says that today there are zero sunspots.

    I think that the decline of the sunspot numbers since 2002 or so could have countered about 6 or 7 years worth of CO2 emissions at current rates. If the sun stops cooling and warms a bit as predicted I expect a scorcher El Niño around 2014, 15 or 16. Then very few people will still say there is no problem. El Niño and La Niña just redistribute energy. An El Niño year is not global warming, but the heat available for redistribution will be impressive I expect.

  11. 61
    paul says:

    your quote

    “I find it ironic that some people still rely on the cosmic rays argument as their strongest argument against AGW – it does involve poorly known clouds physics!”

    Are you kidding . What do you know about poorly known clouds physics ?

    nothing or something explain

  12. 62
    Gilles says:

    “Over this time period, the planet has actually cooled considerably: with mean global temperature more than 8°C higher at the end of the time of the dinosaurs. This, despite the increased solar output.

    Over this timespan, the atmospheric concentration of CO2 has ranged from between 1,000 and 2,000 ppm ”

    So this gives 8°C for about 8 times the preindustrial concentration, so 3 doublings, and a sensitivity of 2.6 °C/doubling , right ? with climate inertia, is it right that with such a value, we won’t be over 2°C if the CO2 concentration stays below 560 ppm ?

  13. 63
    john says:

    the gatesphere seems to believe that AGW theory is falsified say if a certain glacier does not recede, etc, so is it true to say that AGW theory starts and ends in itself with the physics and the prediction of temperature rise associated with doubling of co2,
    that everything else, eg , more storms , glacier loss etc are theories that
    are based on but not part of the actual AGW scientific theory ,
    i know that this is a simple interpretation but does seem to cause lots of confusion

  14. 64
    Completely Fed Up says:

    re 63: And? So are you going to say 2C is not significant?

  15. 65
    Completely Fed Up says:

    “55
    Septic Matthew says:
    9 March 2010 at 5:54 PM

    49, David B. Benson: instead use the known physics

    Those predictions will be good enough if the known physics is known with good enough accuracy and if the unknown physics is unimportant enough.”

    So prove that those conditions do not hold, SM.

    Prove it likely that the unknown physics is not unimportant enough.

  16. 66

    David A. Benson,

    I just sent a paper to J. Climate identifying the AMO as the second strongest influence on the temperature record after greenhouse gases. I used Granger causality tests and Cochrane-Orcutt iteration to show that it wasn’t a spurious regression. I doubt the AMO itself can be a direct cause of global temperatures, but I speculate that for some reason, it closely reflects how much energy is being transferred between air and ocean globally.

  17. 67
    votenotokyoto says:

    The time lag for solar activity is between 6-12 years (The oceans of the Earth are a huge heat sink). Solar cycle 23 peaked from 1999-2003. The sea warmth of the current El Nino is probably related to this peak. The sun has been quite quiet since with cycle 23 considered long and cycle 24 slow to get going. I note that there have been no sunspots for the last few days. We will see the cold from this dip in solar activity in 6-12 years. Unfortunately instead of the scorcher El Nino predicted by Pete Dunkelberg (61) in 2014-16 we may instead experience cooler conditions. I have read some predictions of a repeat of the Dalton minimum during the 2010′s. I hope they’re wrong.

  18. 68
    Ray Ladbury says:

    Gee, voteno, it would appear that the climate response doesn’t know about your 6-12 year delay, as it has followed the solar cycle pretty closely with a much shorter delay going back as far as we have data.

    Yes there’s a big heat reservoir. There’s also an atmosphere that responds on a timescale of a year.

  19. 69
    Bob says:

    Question: Is it possible and maybe even likely that climate will become more instantly/immediately sensitive to solar forcings than is usual (for a climate in relative equilibrium), because simultaneous forcings are additive while the ocean’s (temporal) capacity as a heat sink is limited (with respect to how much in how short a time)?

    That is, if CO2+feedbacks are adding/trapping X energy per decade, which is already a rate above that which the oceans can absorb and “hide,” will the time lag for solar activity vs. observed temperature impacts shorten, and so will the apparent correlation between solar forcings and observed temperatures increase?

    To put it another way, is a climate under stress temporarily more sensitive to minor and short term variations in radiative forcings, particularly positive ones?

  20. 70
    Frank Giger says:

    “Would someone please give us non-techies a few sentences on the conclusions of these articles? Like, do the papers all conclude that solar radiation is insufficient to account for the global warming we are seeing? Thanks.”

    From what I gather, solar variance is a nudging factor in the climate. It has influence on the Big Blue Ball, but usually not the final say.

    When it becomes really important is when one reaches the upper bounds of climate change limits (both sides – cooling and heating).

    The movie analogy (a greatly exaggerated one for effect here) is the car balanced on the edge of the cliff, the protagonist bug-eyed as he realizes any change will cause it to fall over the edge. Solar variance is the squirrel/dog/bird on the trunk.

    If a second bird lands, the car tilts towards safety. If the first flys off, it plummets.

    Human nature is to blame the bird for the car falling over the cliff; we do this all the time with nudging effects. If the monthly budget is blown, we blame the tire we had to replace versus the other expenses, even though it represented the smallest percentage of the bills.

    Normally, of course, a bird on the trunk of a car is meaningless to the overall weight of a vehicle, and nobody cares.

    Again, this is a greatly exaggerated analogy about nudging effects.

  21. 71
    Ray Ladbury says:

    Bob, the model Tamino treats here is instructive wrt your question.

    Basically, you can think of the oceans as an integrator that tends to smooth things out with a timescale of 30 years. They’ll continue to do that–for warming or cooling.

  22. 72
    Gilles says:

    “CFU And? So are you going to say 2C is not significant?”

    if it’s addressed to my 62 (not 63) post, I would say that I think it is very unlikely that we can avoid them if the CO2 sensitivity is this one. So, whether significant or not, the best is to prepare adaption. Personally I don’t think that adaption to 2 degrees is that hard. I think a lot of people have done worse in the past, simply by moving in other countries (actually France has experienced a one degree warming in 10 years in the 80′s http://www.univers-nature.com/images/actu/rechauffement-global-terre.jpg , but I can’t say people really worry about it – i mean KNOW about it : the difference between North and South of this 1000 km wide country is already 4 or 5 °C :)).

    BTW it’s rather bizarre that you seem to assume that mankind would easily adapt to a strong decrease of fossil fuel consumption, but would be unable to adapt to a variation of 2°C. I can’t see any know fact supporting this idea – actually those I am aware of rather show the opposite.

  23. 73
    Bob says:

    Ray, yes, that’s I guess exactly my point… if you think of the ocean as a smoother, or better yet, a shock absorber… if you’re already pounding it beyond its limits, can you expect it to continue to behave the same way, or have you overwhelmed it so that it doesn’t work as well as it normally would? Or is it so massive that it isn’t being and couldn’t be overwhelmed, and will continue to be an effective 30-year-smoother?

    Also: Please clarify your reference to “the model Tamino treats here.” I don’t see anything such in the text of the RC post, or the comments trail. Did you mean to include a link?

  24. 74
    Nick Gotts says:

    BTW it’s rather bizarre that you seem to assume that mankind would easily adapt to a strong decrease of fossil fuel consumption, but would be unable to adapt to a variation of 2°C. I can’t see any know fact supporting this idea – actually those I am aware of rather show the opposite. – Gilles

    I suggest you read the reports of AR4 WGII (impacts) and WGIII (mitigation), which deal with precisely these questions. France, of course, is a rich country: it is thus well-placed to adapt to climate change. Africa, most of south and south-east Asia, and much of Latin America, are much less so – and of course changes in where and when rain falls and the number of extreme weather events are more important than simple changes in mean temperatures. Nonetheless, it is not being asserted that adaptation to this amount of change is impossible, only that it will be very costly and hit the poor hardest – something those urging inaction and weeping crocodile tears over the effects of reducing fossil fuel use on the poor always ignore. The era of cheap fossil fuel is in any case coming to an end – there is plenty of coal and tar sands and shales, but the possibility of poor countries developing industrially on the cheap oil the rich countries have been able to use does not exist.

    Your calculations @62 are in any case faulty: you ignore the fact that the sun has indeed brightened considerably over the last 60 million years; without that, the fall in temperature would have been considerably greater. You also ignore the large uncertainties in measuring both temperatures and CO2 concentrations that far back in time.

  25. 75
    Septic Matthew says:

    65, Completely Fed Up: So prove that those conditions do not hold, SM.

    You can not prove that what you don’t know does not matter. Usually the burden of proof in science is on those who claim to know. The engineers who designed the Golden Gate Bridge and Tacoma Narrows Bridge knew a lot about building bridges but not a lot about wind. In one case that ignorance (compared to what is known now) of wind did not matter, and in the other case it did matter. It could not be proved beforehand which was which.

    Analogously, physicists’ claim that there was no energy source sufficient to power continental drift turned out to be false, though Wegener was never able to prove that it was false. It just turned out that way.

    The test (“proof” in one sense["the proof of the pudding is in the taste", "proving ground"], but not in the mathematical sense) will be in the predictions covering the next 30 years.

  26. 76
    Pete Dunkelberg says:

    Giles, with the warming so far, more than one meter higher sea level is predicted by 2100 or sooner, and time and tide don’t stop in 2100. Where do you propose to put Miami? How much weaker and impoverished from the expense of pulling back from our coasts do you favor, since you seem to advocate doing nothing special about global warming?

  27. 77
    Pekka Kostamo says:

    #72 Gilles: “BTW it’s rather bizarre that you seem to assume that mankind would easily adapt to a strong decrease of fossil fuel consumption, but would be unable to adapt to a variation of 2°C. I can’t see any know fact supporting this idea – actually those I am aware of rather show the opposite.”

    That is not the point at all. No action means adaptation to some 5°C of warming, or probably more as some imperfectly known thresholds will be passed. And much more if a longer time horizon is considered.

  28. 78
    Completely Fed Up says:

    “75
    Septic Matthew says:
    10 March 2010 at 11:48 AM

    65, Completely Fed Up: So prove that those conditions do not hold, SM.

    You can not prove that what you don’t know does not matter.”

    Yes you can.

    A box contains 1kilo of stuff after I’ve poured in 100 9.8g cubes.

    I don’t know what else is in the box, nor what it is made of, but I DO know that whatever else is in there doesn’t take up much weight, if any.

  29. 79
    Completely Fed Up says:

    “72
    Gilles says:
    10 March 2010 at 11:12 AM

    “CFU And? So are you going to say 2C is not significant?”

    So, whether significant or not, the best is to prepare adaption.”

    What about stopping something that will take us another 2C?

    What if mitigation means we have 80 years to “adapt” and BAU means 30 years?

    Mitigation is itself an adaption: you adapt to the ghg nature of fossil fuels by NOT BURNING THEM.

  30. 80

    Gilles, 72–

    Your metal model of adaptation as analagous to a personal move is faulty, I’m afraid.

    In the case of a move, the availability of ecological services does not change: though you may be (for example) in Algeria rather than France, the local ecosystems in both places still operate as they have, and large-scale factors (say, the primary productivity of the Mediterranean, as another random example) remain unchanged as well.

    With global warming, every place becomes “a stranger to itself”–every ecology must adapt, and in many cases it is reasonably foreseeable that some adaptations may be difficult or impossible.

    As to the relative difficulty of adapting to temperature change or the disuse of fossil fuels, I’d ask you to consider that, although the economy depends on a functioning ecology, the reverse is not true. I’d even say that the reason that we do not do a good job of valuing environmental “externalities” is precisely that economies have (with rare and local exceptions) always existed in the presence of functioning ecosystems. (And some of the exceptions, like Easter Island, should give us pause.) Thus, the ecological services are “assumed” (as you seem to do prospectively in the case of AGW)–or perhaps “taken for granted” would be a better term.

  31. 81
    Ray Ladbury says:

    Bob, Sorry the model is here:

    http://tamino.wordpress.com/2009/08/17/not-computer-models/

    I guess my question would be, how do you take a thermal reservoir beyond its limits unless:
    1)you get a phase change (ain’t gonna happen)
    2)you somehow break down the circulation–e.g. by shutting down the thermohaline conveyor. (probably unlikely)

    I’d expect future behavior to be at least comparable.

  32. 82
    dhogaza says:

    Analogously, physicists’ claim that there was no energy source sufficient to power continental drift turned out to be false, though Wegener was never able to prove that it was false. It just turned out that way.

    SM appears to be one of those that doesn’t realize that Wegener’s proposed mechanism *was* physically impossible, and that plate tectonics is an entirely different mechanism?

  33. 83
    HarryDinPT says:

    I can’t wait to see the results from the CLOUD at CERN experiment.

    What are you going to say when the physics of the GCR/cloud is established?

  34. 84
    Didactylos says:

    Septic Matthew:

    Your argument has a flaw. It is not time-specific. We already have 30 years (and more) of strong evidence, with nothing to contradict it.

    What is to stop you from demanding, in 30 years time, that you need 30 more years (or a hundred), and that the 60+ years of rising temperatures could be just a coincidence?

    You throw around words like “proof of the pudding” and “those who claim to know” – yet you are silent when it comes to terms such as “Occam’s Razor” and “hedging bets”. You are also silent when it comes to quantifying unknowns. Yes, there are things we don’t know. But we can put bounds on these things that we don’t fully understand yet, and plan accordingly.

    Scientists already have estimates for the high and low forcings from cloud effects. The gap is very large, but even if we take the best case, it doesn’t help us. Therefore, nothing much will change when scientists add to our understanding and pin down the exact numbers more precisely.

    We can’t afford to wait around for the unknown unknowns. We have to do what we can with what we know, and what we know we don’t know.

  35. 85
    Completely Fed Up says:

    SM: “The test (“proof” in one sense["the proof of the pudding is in the taste", "proving ground"], but not in the mathematical sense) will be in the predictions covering the next 30 years.”

    They’ve already shown that proof in the past 40 years:

    http://www.realclimate.org/index.php/archives/2009/12/updates-to-model-data-comparisons/

    What’s to say you won’t repeat the same thing in another 30 years?

  36. 86
    Frank Giger says:

    Um, Miami stays where it is. One does not move cities.

    The people, OTOH, will relocate. We can handle it – there is plenty of land. Similarly, one can’t say it would be all negative economic impact.

    Similarly, it isn’t like one day everyone is going to wake up underwater.

  37. 87
    Hank Roberts says:

    > predictions covering the next 30 years

    Why would you want to specify 30 years?

    Let’s call it, oh, 34 years. Surely that’s convenient for you.

    http://pubs.giss.nasa.gov/cgi-bin/abstract.cgi?id=wa07100z

    Wang et al. 1976

    Wang, W.-C., Y.L. Yung, A.A. Lacis, T. Mo, and J.E. Hansen, 1976: Greenhouse effects due to man-made perturbation of trace gases. Science, 194, 685-690, doi:10.1126/science.194.4266.685.

    Anthropogenic gases may alter our climate by plugging an atmospheric window for escaping thermal radiation.
    Download PDF

    Of course, by demanding endless refinement of the predictions, you can continue to move the goalposts at a steady distance into the future.

    Your unspoken assumption there is that the future will be the same as the present, with no regrets.

    Pretty strong assumption, given the facts observed to date.

  38. 88
    David B. Benson says:

    Barton Paul Levenson (67) — Good! After looking through the NOAA AMO web site, I speculate that AMO is, in part, an index of MOC rate. If so, it is a reasonable index for internal variability at decadal scales.

    Septic Matthew (75) — We already have sufficient data and theoretical understanding to understand that it is CO2 and almost nothing else. Another 30 years, given a 130 year instrumental record and given a great amplitude of paleoclimate studies, won’t make any difference.

  39. 89
    Witgren says:

    “Frank Giger says:
    10 March 2010 at 2:55 PM
    Um, Miami stays where it is. One does not move cities.

    The people, OTOH, will relocate. We can handle it – there is plenty of land. Similarly, one can’t say it would be all negative economic impact.

    Similarly, it isn’t like one day everyone is going to wake up underwater.”

    Let’s pose a hypothetical. Let’s suppose you own a nice house and a business in Miami.

    One day, it becomes irrefutable to all but the most dense and fanatical of denialists that Miami will be going underwater and will be threatened enough by storm surges and high tides to make the city nigh uninhabitable in a few years.

    Most of your personal funds are tied up in your business and home. How much do you think they are now worth to anyone? And so you must sell for pennies on the dollar and relocate.

    Now multiply that out by a few million people (just for Florida alone, not including all the others along the coastal US that may be in the same position, or globally for that matter). See the problem yet?

  40. 90

    CO2 in atmosphere, measured at Mauna Loa this February, makes big jump to 389.9 ppm, +2.5 ppm year-on-year: http://bit.ly/MaLoMon

  41. 91
    Doug Bostrom says:

    Frank Giger says: 10 March 2010 at 2:55 PM

    A slow and painful death of Miami is what we’ll see, like New Orleans but with variations. Both places are particularly vulnerable thanks to sitting in the statistical bulls-eye for hurricane paths and accompanying storm surges. Both will see recurring catastrophic damage gradually becoming unaffordable to repair, with various sections of each city abandoned to nature as we discover we can’t shovel fast or cheaply enough to maintain the border between artifacts and entropy.

    Other places will face different arrangements of the same challenge and features. Here’s a nice article on Rhode Island and dawning recognition, from NOAA:

    http://www.climatewatch.noaa.gov/2009/articles/rhode-islands-rising-tide

  42. 92
    Septic Matthew says:

    85, Completely Fed Up: What’s to say you won’t repeat the same thing in another 30 years?

    It depends on what happens between now and then. Tsonis’ model predicts 20 more years of relatively little warming like we have had in the last 10 years, whereas Latif’s model predicts only 5. The polynomial cointegrated model of Beenstock and Reingeweertz makes only “conditional” predictions, based on the changes in the CO2 and solar activity, but we will be able to see how its predictions pan out (with and especially without parameter updates.) Those predictions may not be discernibly different from the straight line with autocorrelated error, but most likely at least one will be a discernibly worse fit to the data.

    In the meantime, don’t forget that I support investment in alternative energy supplies and CC&S. Thirty years of continuous investment in those technologies will make a great difference. If the Brazil model with sugar ethanol is any guide, biofuels including cellulosic ethanol will be cheaper than gasoline, unless petroleum consumption drops and OPEC collapses. I expect that by then the US will be CO2 negative (there is a debate about whether it is already, and there is the complication that the US imports goods that produced CO2 in their manufacture.)

    88, David B. Benson: Another 30 years, given a 130 year instrumental record and given a great amplitude of paleoclimate studies, won’t make any difference.

    That is a testable prediction, and we’ll see how well it does.

  43. 93
    Septic Matthew says:

    This is off topic but it might interest you: the Caltech-Harvey Mudd math contest for high school students.

    http://chmmc.caltech.edu/problems.html

    no physics, just math. answers not posted yet.

  44. 94
    Ray Ladbury says:

    Frank Giger says, “The people, OTOH, will relocate. We can handle it – there is plenty of land. Similarly, one can’t say it would be all negative economic impact.”

    Spoken like a man who hasn’t thought things through. You do realize that we’ll have about 1.5 times as many people on the planet by then…that much of the population growth will occur precisely in coastal and low-lying areas…that aquifers will be polluted with salt water…that the land inundated will be among the most productive and valuable on the planet. And the thing is, if the warming happens, WE cannot handle it. We are foisting it off on our progeny.

  45. 95
    MartinJB says:

    The mind boggles. For those who don’t want the cost and government intrusion of a program to reduce GHGs, imagine the cost and government involvement of relocating or sea-proofing multiple cities along the coast of the US. Seriously, I bet orders of magnitude more on both accounts.

    And we’re talking about just one of the impacts of global warming! And then there are all the other countries. Bangladesh, anyone?

    The idea of dismissing action on global warming because of the cost is just ludicrous.

    –Martin

  46. 96
    quokka says:

    Frank Giger says, “The people, OTOH, will relocate. We can handle it – there is plenty of land. Similarly, one can’t say it would be all negative economic impact.”

    In addition to what Ray Ladbury says, have you thought about the political consequences of moving tens or hundreds of millions of people across national boundaries? Look at the political hysteria and xenophobia generated today by the resettlement of a relative handful of refugees. Multiply that by a couple of orders of magnitude and it looks ugly in the extreme.

  47. 97
    Thomas says:

    The other point is that we will get getting off fossil fuels within a geologic instant in any case. The only thing that matters is whether it bacuse we run out of them or because we voluntarily got off then sooner. The difference in time span of BAU for both of these potential scenarios is only two of three decades at the most. But the difference in how much continuing adaptation will be needed by those seven generations (or seventy) from now will be very substantial.

    Besides the easiest and earliest steps to take, which mainly involve energy efficiency more than pay for themselves.

  48. 98
    Hank Roberts says:

    > March 9 … zero sunspots

    March 10, two new sunspots, at the moment: 1054 and 1055
    http://www.solarcycle24.com/pictures/spots.jpg

  49. 99
    Philippe Chantreau says:

    HarryDinPT said this in comment#83:
    I can’t wait to see the results from the CLOUD at CERN experiment.
    What are you going to say when the physics of the GCR/cloud is established?

    Too bad you can’t wait, because you’re probably going to have to. It’s been over 3 years since the 2006 experimental run and the paper was published only in 2009. As of now, if CERN hasn’t put this thing on the back burner they have their priorities seriously screwed up.
    About that 2006 run, it seems that the experimental design wasn’t quite up to par.
    Eli has looked into the paper, the referee’s interactive comment is quite interesting:
    http://rabett.blogspot.com/2009/10/punching-bag-unnoticed-in-recent-pile_28.html

    Even if some physical mechanism was uncovered, its significance in the real world remains to be shown. The lack of correlation turning up in other-than-Svensmark works suggests it is likely not significant.

  50. 100
    Hank Roberts says:

    > sunspots
    Did nobody bother to re-refute the ‘votenotokyo’ poster’s claims about sunspot cycles controlling El Nino?
    Well, http://tamino.wordpress.com/2008/04/05/stalking-the-elusive-solar-cycletemperature-connection/


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