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The IPCC Fourth Assessment SPM

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We’ve had a policy of (mostly) not commenting on the various drafts, misquotes and mistaken readings of the Fourth Assessment report (“AR4” to those in the acronym loop) of the IPCC. Now that the summary for policy makers (or “SPM”) has actually been published though, we can discuss the substance of the report without having to worry that the details will change. This post will only be our first cut at talking about the whole report. We plan on going chapter by chapter, hopefully explaining the key issues and the remaining key uncertainties over the next few months. This report will be referenced repeatedly over the next few years, and so we can take the time to do a reasonable job explaining what’s in it and why.

First of all, given the science that has been done since the Third Assessment Report (“TAR”) of 2001 – much of which has been discussed here – no one should be surprised that AR4 comes to a stronger conclusion. In particular, the report concludes that human influences on climate are ‘very likely’ (> 90% chance) already detectable in observational record; increased from ‘likely’ (> 66% chance) in the TAR. Key results here include the simulations for the 20th Century by the latest state-of-the-art climate models which demonstrate that recent trends cannot be explained without including human-related increases in greenhouse gases, and consistent evidence for ocean heating, sea ice melting, glacier melting and ecosystem shifts. This makes the projections of larger continued changes ‘in the pipeline’ (particularly under “business as usual” scenarios) essentially indisputable.

Given all of the hoopla since the TAR, many of us were curious to see what the new report would have to say about paleoclimate reconstructions of the past 1000 years. Contrarians will no doubt be disappointed here. The conclusions have been significantly strengthened relative to what was in the TAR, something that of course should have been expected given the numerous additional studies that have since been done that all point in the same direction. The conclusion that large-scale recent warmth likely exceeds the range seen in past centuries has been extended from the past 1000 years in the TAR, to the past 1300 years in the current report, and the confidence in this conclusion has been upped from “likely” in the TAR to “very likely” in the current report for the past half millennium. This is just one of the many independent lines of evidence now pointing towards a clear anthropogenic influence on climate, but given all of the others, the paleoclimate reconstructions are now even less the central pillar of evidence for the human influence on climate than they have been incorrectly portrayed to be.

The uncertainties in the science mainly involve the precise nature of the changes to be expected, particularly with respect to sea level rise, El Niño changes and regional hydrological change – drought frequency and snow pack melt, mid-latitude storms, and of course, hurricanes. It can be fun parsing the discussions on these topics (and we expect there will be substantial press comment on them), but that shouldn’t distract from the main and far more solid conclusions above.

The process of finalising the SPM (which is well described here and here) is something that can seem a little odd. Government representatives from all participating nations take the draft summary (as written by the lead authors of the individual chapters) and discuss whether the text truly reflects the underlying science in the main report. The key here is to note that what the lead authors originally came up with is not necessarily the clearest or least ambiguous language, and so the governments (for whom the report is being written) are perfectly entitled to insist that the language be modified so that the conclusions are correctly understood by them and the scientists. It is also key to note that the scientists have to be happy that the final language that is agreed conforms with the underlying science in the technical chapters. The advantage of this process is that everyone involved is absolutely clear what is meant by each sentence. Recall after the National Academies report on surface temperature reconstructions there was much discussion about the definition of ‘plausible’. That kind of thing shouldn’t happen with AR4.

The SPM process also serves a very useful political purpose. Specifically, it allows the governments involved to feel as though they ‘own’ part of the report. This makes it very difficult to later turn around and dismiss it on the basis that it was all written by someone else. This gives the governments a vested interest in making this report as good as it can be (given the uncertainties). There are in fact plenty of safeguards (not least the scientists present) to ensure that the report is not slanted in any one preferred direction. However, the downside is that it can mistakenly appear as if the whole summary is simply up for negotiation. That would be a false conclusion – the negotiations, such as they are, are in fact heavily constrained by the underlying science.

Finally, a few people have asked why the SPM is being released now while the main report is not due to be published for a couple of months. There are a number of reasons – firstly, the Paris meeting has been such a public affair that holding back the SPM until the main report is ready is probably pointless. For the main report itself, it had not yet been proof-read, and there has not yet been enough time to include observational data up until the end of 2006. One final point is that improvements in the clarity of the language from the SPM should be propagated back to the individual chapters in order to remove any superficial ambiguity. The science content will not change.

Had it been up to us, we’d have tried to get everything together so that they could be released at the same time, but maybe that would have been impossible. We note that Arctic Climate Impact Assessment in 2004 also had a similar procedure – which lead to some confusion initially since statements in the summary were not referenced.

How good have previous IPCC reports been at projecting the future? Actually, over the last 16 years (since the first report in 1990), they’ve been remarkably good for CO2 changes, temperature changes but actually underpredicted sea level changes.

When it comes to specific discussions, the two that are going to be mostly in the news are the projections of sea level rise and hurricanes. These issues contain a number of “known unknowns” – things that we know we don’t know. For sea level rise the unknown is how large an effect dynamic shifts in the ice sheets will be. These dynamic changes have already been observed, but are outside the range of what the ice sheet models can deal with (see this previous discussion). That means that their contribution to sea level rise is rather uncertain, but with the uncertainty all on the side of making things worse (see this recent paper for an assessment (Rahmstorf , Science 2007)). The language in the SPM acknowledges that stating

“Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude.”

Note that some media have been comparing apples with pears here: they claimed IPCC has reduced its upper sea level limit from 88 to 59 cm, but the former number from the TAR did include this ice dynamics uncertainty, while the latter from the AR4 does not, precisely because this issue is now considered more uncertain and possibly more serious than before.

On the hurricane/tropical strorm issue, the language is quite nuanced, as one might expect from a consensus document. The link between SST and tropical storm intensity is clearly acknowledged, but so is the gap between model projections and analyses of cyclone observations. “The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period.”

We will address some of these issues and how well we think they did in specific posts over the next few weeks. There’s a lot of stuff here, and even we need time to digest it!

364 Responses to “The IPCC Fourth Assessment SPM”

  1. 151
    John Stubbles says:

    For some reason, my comment #107 was truncated.I wanted to say that according to the DoE-EIA 2006 Annual Report, even by 2030, the collective contribution of wind, solar, geothermal and biomass to U.S. kWh will be less than 5% (250 billion vs >5000 billion kWh annually).Coal will still be king unless we have draconian legislation to curb CO2 and destroy our economy. Of course,curtailed oil imports would be an even bigger problem, since we really don’t have a substitute for oil. In 1900, they must have been worried about the supply of horses. Where will we be in a hundred years?

  2. 152
    Pat Neuman says:

    The ref in my newsvine link also includes this statement:

    “The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we are likely to emit the same amount over the next three centuries,”.

    Thus, thousands of years, or 10,000 years, is viewed by Prof. James Zachos as an abrupt shift in Earth’s climate…

    fast enough to result in widespread marine species extinctions.

    Related articles can be found at my Newsvine site:


    My agreement with 2 in # 134 was based on the text below:

    “Careful measurements have confirmed that CO2 is increasing in the atmosphere and that human activities are the primary cause. CO2 measurements have been taken directly from the atmosphere over the past few decades. CO2 trends for earlier times have been derived from measurements of CO2 trapped in air bubbles in glacial or polar ice. The 36% increase (in 2006) in atmospheric CO2 observed since pre-industrial times cannot be explained by natural causes. CO2 concentrations have varied naturally throughout Earth’s history. However, CO2 concentrations are now higher than any seen in at least the past 650,000 years”.

  3. 153
    Justin Schoof says:

    Re: 131: SRES refers to the IPCC’s Special Report on Emissions Scenarios. It can be found with the other IPCC publications on In the most basic terms, one of the largest uncertainties associated with climate model projections is the role of human activities. The future concentration of atmospheric greenhouse gases will depend on numerous socio-economic factors. Each of the SRES scenarios assume different global characteristics with respect to population, economies, etc and hence represent different pathways for the time series of atmospheric greenhouse gas concentrations. I hope this also answers your second question – none of the SRES scenarios consider decreases in greenhouse gas emissions consistent with Kyoto or other agreements that would otherwise limit emissions.

  4. 154
    Scott L. Montgomery says:

    To Susan, #134. Yes, Bodman and staff are very definitely political appointees, like much of the executive branch as a whole. A cleanly swept White House and cabinet wouldn�t be enough, however, as there are the legislative and judicial branches of the great democratic tree to prune or tune also. The reality is that the executive is largely inactive, in narcotic denial.

    Things, however, are happening in the other two branches. Recall that there are now four very different bills before Congress on various schemes to limit greenhouse gases, plus the current case before the Supreme Court, Commonwealth of Massachusetts vs. EPA, regarding the possible designation of carbon dioxide as a gas that should fall under regulatory statutes associated with the Clean Air Act. I am certainly wondering if the SPM will have any effect on the latter, as the case won�t be finally decided most likely for a few months.

    The bills before Congress right now have a great deal to do with personalities and related politics, not just the issue alone. There are stormy times in progress on the House floor, as the women from California, meaning Pelosi, Feinstein, and Boxer, make their presences forceful. Pelosi has convened a special committee on the climate change issue and therefore grabbed turf away from Dingell�s Energy and Commerce Committee. Dingell is a very powerful, smart, savvy career democrat from Michigan, the auto state, and has acted partly as a roadblock to major, effective climate change legislation.

    In any case, the four bills can be briefly described as follows:

    Jeff Bingaman: cap and trade, economy wide, but upstream only, requiring a whopping 7% reduction from current levels by 2050, i.e. a Bud Lite carbon bill.

    Diane Feinstein: cap and trade for electric utilities, requiring a 45 percent reduction in ghg emissions from current levels by 2050, i.e. a compromise bill with molars but no incisors, so to speak

    Bernie Sanders and Barbara Boxer: range of measures aimed at increased energy efficiency, low carbon trading program, and market based programs, calling for an 85 percent reduction in ghg emissions by 2050. Represents the other end of the spectrum from Bingaman. A full set of teeth in this one.

    McCain and Lieberman: the yet again bill, calling for 70% reduction by 2050 through a combination of cap and trade and regulation of power plants, refineries, and other major energy users. This bill has been proposed before, of course, mainly as a gesture of good faith and intentions, since its chances of passage in a Republican controlled Congress were essentially nil.

    Most observers feel certain that something will be done this year, that one of these bills will get passed, in modified form, and probably not Bingaman�s, as that would simply be a euphemism for inaction and would bring down no small calumny on our beloved representatives.

    But you see that a cap and trade system is by far the most likely mitigation action that�s going to be taken. Obviously, I can�t guarantee this, but it seems extremely likely now that Congress has been retaken by the dems.

  5. 155
    Hank Roberts says:

    Timing is all, Asa.
    “So theyâ��re gone, so what?
    “As a foundation of the food chain, a loss of pteropods will affect all other life. …The attached picture tells the story: Where it is blue, there is not enough aragonite for the small animals, the pteropods, to live and grow shells. They will vanish. This picture is the middle, or median, estimate of ten models that were calculated. These ten models ranged from minimum additional levels of industrial carbon dioxide into the ocean; based on the most minor of climate change, to the highest climate change estimates.

    “… These chemical effects are well known and measurable and it is basic science. …

    “Researchers have run experiments where they have watched pteropod shells dissolve when the seawater becomes acidic at the levels of carbon dioxide that will be reached in fifty years. The problem with global warming is that itâ��s a growth game. The earlier we make cuts to greenhouse gases the less reduction we have to make.”

  6. 156
    Mitch Golden says:

    Wrote this earlier but it seems to have been lost: Re #117 (and another lost post)

    I believe that what they’re saying (look at footnote 2) is that the 280 ppm CO2 that was there in pre-industrial times doesn’t count as a “forcing”. If you go from 360 to 379 ppm, the anthropogenic part has gone from 80 to 99, which is somewhat more than 20%.

    I’m not sure that the radiative forcing is proportional to the CO2 density, but that’s how I read it.

  7. 157
    Ike Solem says:

    RE#149, Asa here’s a quote from the 2007 IPCC report:
    “Annual fossil carbon dioxide emissions increased from an average of 6.4 [6.0 to 6.8] 5 GtC per year in the 1990s, to 7.2 [6.9 to 7.5] per year in 2000-2005” (1 GtC = one billion tons of carbon atoms)

    Now, the estimated total fossil fuel resources left to burn (as of 2000) from
    Conventional oil – 263 (GtC)
    Shale oil, etc. – 525
    Natural gas – 422
    Coal bed gas, etc – 450
    Coal – 3370

    The atmospheric carbon dioxide content (as carbon) was 580 GtC (280 ppm) in 2000 was 750 GtC (380ppm)

    How many gigatonnes of carbon per year stay in the atmosphere? Around half, so if current total CO2 emissions (as carbon) are at 7.2 GtC (only looking at fossil fuels), then around 3.6 Gt of carbon stay in the atmosphere each year – and it’s worth wondering what processes account for the uptake of the other half. See the Woods Hole discussion of the missing carbon sink. What you don’t know can hurt you… meaning that it’s possible that more CO2 could start lingering.

    If we burn all the fossil fuel, that means adding 5000 GtC to the atmosphere, (if half stays up, that’s 2500 Gt) and warmer oceans and stressed forests will probably absorb less CO2, resulting in a minimum CO2 content of around 1500 ppm (and probably quite a bit higher, due to sink limitations.. and the oceans may degas methane and CO2 if they warm up a lot … odd that no mention of ocean / permafrost methane & carbon stores is made, other then that the permafrost is thawing…). There’s also no reason to assume that all that CO2 wouldn’t stay in the atmosphere for millennia, either – meaning no ‘global cooling effect’ after the fuel is gone. This is a bit beyond the worst-case scenario in the IPCC report.

    Fossil fuel industry spokespeople will tell you that people absolutely need oil, and we’ll just keep burning it till it’s all gone – but the fact is that recent economics indicate that renewables become economically preferable as oil approaches $100 a barrel, and another fact is that you can replace all fossil fuel demand with a mixture of renewables (solar, wind and biofuels), temporary nuclear and tight energy conservation – but only if we figure out how to stop the endless growth of energy demand in the US, China, India, and the rest of the world. It turns out that the only barriers to a global renewable energy economy lie in an entrenched growth-driven economic and political system that is very resistant to drastic and disruptive changes – which are coming anyway, due to global warming. Thus, the task is daunting but not hopeless – but a large fraction of global fossil fuels must remain in the ground, unburnt.

  8. 158
    Charles Muller says:

    #130 (Raypierre comment)

    “Given that it takes about 1000 years for the first 80% of the carbon dioxide to disappear into the ocean, and 10,000 to 100,000 years for the rest to go away”

    I’m amazed by these orders of magnitude. Half-life of a CO2 is often estimated at 100-150 yrs in textbooks, and I don’t know how we presently calculate the long-term rate of capture by the different sinks (in the particular case of a rapid growth like modern process, ie out of a natural equilibrium of emission/sequestration).

    Do you have some references from recent carbon cycle models on that point? Thanks.

  9. 159
    Roger Smith says:

    RE 146, if I understand you right you are saying that it might be possible there there were some periods where CO2 naturally rose to levels similar today and then fell back again without leaving a record in the ice cores.
    That sounds to me like “the truth is out there.” I think the IPCC report can be stated to be based on the evidence we have today, not based on what could be true but where we have no evidence. Feel free to try to disprove it by drilling ice cores.
    Of course, either way we know that recent CO2 levels are from human activity and not some unknown process that spikes CO2, so it seems largely irrelevant.

  10. 160
    Asa says:

    Ike Solem (#157) thanks for the great answer. Very interesting info.

    I guess I would like to see an economic model of what would happen with no emissions measures, ie. measuring the costs and benefits of fossil fuels continuing to burn until there are none left or they become uneconomical, like in your US$100 a barrel scenario.

    I would then like to see a model of the economically most efficient scenario. The difference between the two would give us — in economics terms at least — a policy guidance.

    I think once fossil fuels become spent or uneconomical you will see a very swift transition. Completely retooling global infrastructure may seem expensive and daunting now, but when the economics come into line I think it will happen very rapidly and cheaply. Vast global infrastructures can spring up and/or disappear within a decade or two (eg. the Internet).

  11. 161
    Eric (skeptic) says:

    Re 158: My original comment was concerning the CO2 measurements in the atmosphere. My second link in #138 shows the impulse response of the CO2 in the atmosphere calculated from the flows between the reservoirs in the diagram (well agreed-upon). That worked out to about 33% left in the atmosphere after a century. The disintegration of CO2 into other carbon forms (i.e. more permanent storage) was was Raypierre was referring to (the Archer paper). That time is about an order of magnitude longer (i.e. 17-33% left after 1000 years).

  12. 162
    Eric (skeptic) says:

    Re 159: Roger, I do not dispute the evidence we have today, I just pointed out that it is not proof that spikes did not exist since it has poor resolution (centuries at best at the time scales mentioned (650,000 years). My ice cores unfortunately would not be any better. But I am very hopeful that fossilized proxies will be discovered with annual resolution (and I believe they are). As is the nature of proxies they will show a lot more measurement variation and it will a difficult and perhaps controversial problem to map their readings to CO2 measurements.

  13. 163
    Martin Chavez says:

    Who are you and what makes you qualified to be so certain?

    First, I want to express my overwhelming appreciation for this forum because it is environment that fosters the embracement of complexity, whereas the vast majority of recent IPCC coverage, on both sides of the debate, demonstrates a paucity of scientific detail. What I find most heartening is that most contributors who support the conclusions of the report, rarely resorts to ad hominem level rebuttal, but rather back their claims with thoughtful prose.

    Nevertheless, from this layman’s point of view, the deep sense of conviction intoned by the prose of those who are inclined to affirm the IPCC conclusions and are vastly more educated and experienced in the field than myself does not justify the supercedure of the instinct of many to seek a greater truth to the causation of the current global warming trend. If the mission of RC is to elucidate the public on the true nature of climate issues facing this planet, its efficiency would be greatly enhanced by the posters providing a brief CV or making it a separate field in posting process; to be published directly below the name and timestamp. Some may respond to this by recommending I follow the hyperlink of each individual poster, but before you do, remember the simple goal is efficiency.

    [Response: Click on the ‘people’ button above (or here)]

    In reality, my greater goal is context. Although I earlier applauded the thoughtfulness of most contributors as they key accolade for the quality content purveyed by the form, there are further efforts made to add context to close the credibility gap for us irksome fence-sitters on the matter. The answer, albeit in my lesser mind, is metadata. Publish the metadata of the individuals along with the content, specifically the scientific background. Without it, those skeptical inquirers among us are left to assume that most contributors are climate scientists preaching to the choir; which leads to the deepest part of my agenda.

    Fully opening the kimono of my inquest, I mostly eager to understand the true makeup of the superlative consensus of ‘scientists’ affirming anthropologic global warming touted by most mainstream media outlets. Such a generalization of the vaunted title may serve to mollify the mass’ appetite for oversimplification, however any true scientist, I postulate, would never eschew far greater distinctions. The intellectual barrier I would need to overcome in order to accept the IPCC affirmations is derived from this simple logic:

    The sun is approximately 333,000 times the mass of Planet Earth.

    The sun is the major factor in the daily 25 F degrees or so temperature fluctuation in my region (Albuquerque, New Mexico to be exact).

    The sun is an entity in flux, never in a constant state.

    How is it that on the scope and scale of factors that the sun, an entity in flux, presents to our planet on a cyclical basis, not a major consideration in this discussion?

    The only answer I can assume is that most of the world’s physicists are not participating in the aforementioned consensus. Forgive my glibness, but I am in close proximity to some of the greatest minds in the physical sciences, where this world there are physicists and the rest are mere mortals. My suspicion about the lack of their participation is not relegated to the lack of consideration of solar effects on global warming, but extends to the even deeper realms of quantum mechanics. Would Albert Einstein support the recent conclusions of the IPCC?

    My intent is not ridicule the validity of scientific achievements of those who dedicated their lives to environmental science by appealing to perceived higher authority, but to ensure scientists of ALL backgrounds have seat at the table of those arbitrating the conclusions. That is not clear, and perhaps someone will be kind enough to point out a URL with a concise list of SPM contributors and their scientific background. I’d love to eat crow about all this and settle the issue in my mind quickly, but as I previously mentioned I am an irksome fence-sitter.

    Some of you may be inclined to dismiss my writings as the rantings of an uneducated rube, for, in the interest of full disclosure; I am only salesman by trade. Nevertheless, I have natural knack for the soft science of psychology having convinced some of the smartest to spend millions to affect billions; and if you believe that no human emotion entered into the most recent IPCC conclusions, thus an artifact of pure science…I have a bridge to sell you.

    So tell me, who are you and what makes you qualified to be so certain?

    Marty Chavez – Albuquerque, NM – Business Development Professional – BS in Health Sciences

  14. 164
    John L. McCormick says:

    Martin, do you pose the same questions to your primary care physician when the diagnosis is not to your liking? If you are like most of us, you get a second, maybe a third opinion. You try to get a consensus to satisfy your concern or fear that your doctor was correct.

    That is basically how the IPCC began and now operates. Lots of opinions from people who do the researach, gather the data, synthesize what they observed/learned and throw it out to the world community of scientists to accept or reject.

    Does that begin to answer your questions?

  15. 165
    Ben Hocking says:

    My understanding that the IPCC predicts that Indonesia will lose 2,000 islands by 2030. Is this true? If so, what are the factors this prediction based on? Surely sea level rise alone cannot account for that!

  16. 166
    Hank Roberts says:

    What’s the source of your understanding, Ben?

    I’ve seen it, but never seen it attributed to any IPCC source. Do you have a source?
    I found it here, for example, a second or third hand story:

  17. 167
    Hank Roberts says:

    Someone here presciently observed that you don’t need the water to rise so much the city’s inundated — all you need is the water high enough that the sewers don’t drain downhill.
    Even heavy rain on overlogged Indonesia, with cities on low lying land, accomplished that:

    340,000 Flee Deadly Floods In Indonesian Capital Jakarta 5 Feb 2007 05:31 GMT
    … 340,000 Flee Deadly Floods In Indonesian Capital Jakarta Water bursts from the banks … “and the toilets cannot flush,” Brahmanta said. Environment Minister Rachmat Witoelar has blamed the floods … had not paid enough attention to the ecological impact of their construction projects.

  18. 168
    Ed G. says:

    Re #138, Eric
    I am not a climate scientist, but I looked at the equation in your 2nd link, and one of the time constants used (the “tau’s”) for about a 31.6% fraction of the CO2 pulse is only 2.57 years, so that fraction of the CO2 is gone in about half a decade.
    My guess is that this time constant can be understood to refer to processes that are already assumed to be at equilibrium in the longer term models. Whan I see numbers presented for CO2 emissions, humans are actually emitting about 6-7 GtC/yr, but the net increase in the atmosphere is only about half that amount due to CO2 fluxes from the atmosphere to the oceans and land. (See, for example, the Technical Summary of the IPCC 2001 Working Group I report.) Measurements of CO2 increase in the atmosphere are different than a CO2 pulse because effects with short term time constants are already in approximate equilibrium.

  19. 169
    Peter Namtvedt says:

    I am waiting with bated breath for the description of what’s really new. By that I mean, not reasonings about interpretation but rather, what facts are now in hand that were not available for use in the third assessment of 2001.

    All of the news has been about what seems to be a “willing oneself up” by scientists and policy-wonks to a greater estimate of the probability of human activity being most responsible for the warming trend. Arctic ice loss seems to be the one item that is new, and actually little has happened there since 2001.

    We still do not have evidence that the earth’s mean temperature is higher than it was in CE 900; only that the rise in that temperature in the last 50 years is without precedent.

  20. 170

    [[We still do not have evidence that the earth’s mean temperature is higher than it was in CE 900]]

    I believe some recent historical reconstructions have pushed back past 1000 years to 1300 years. Gavin, Ray? Does anybody have a cite?

  21. 171
    Ben Hocking says:

    Hank, I probably just conflated it in my head because the news came out at about the same time as the AR4.

  22. 172
    Ron Taylor says:

    Re Eric 162

    Let me see if I understand your logic. You make an assertion with no evidence that it is true. Then you state that since it cannot be proved to be false, we must assume that it may be true. Hmmm… Have I got that right?

  23. 173
    llewelly says:

    Barton Paul Levenson said:

    [[We still do not have evidence that the earth’s mean temperature is higher than it was in CE 900]]
    I believe some recent historical reconstructions have pushed back past 1000 years to 1300 years. Gavin, Ray? Does anybody have a cite?

    From the AR4 SPM:

    Paleoclimate information supports the interpretation that the warmth of the last half century is
    unusual in at least the previous 1300 years. The last time the polar regions were significantly warmer
    than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to
    4 to 6 metres of sea level rise. {6.4, 6.6}


    Average Northern Hemisphere temperatures during the second half of the 20th century were very likely
    higher than during any other 50-year period in the last 500 years and likely the highest in at least the past
    1300 years. Some recent studies indicate greater variability in Northern Hemisphere temperatures than
    suggested in the TAR, particularly finding that cooler periods existed in the 12 to 14th, 17th, and 19th
    centuries. Warmer periods prior to the 20th century are within the uncertainty range given in the TAR. {6.6}

    Both from page 8 .

    Unfortunately thaat’s just a summary. Beyond that I only know of RC’s many articles on the hockey stick and related papers.

  24. 174
    llewelly says:

    I tried to post this last night, but it disappeared.
    Ben Hocking said:

    However, as I understand it (I have not read any of the AR4 myself), the IPCC itself is saying that Indonesia should expect to lose 2,000 islands.

    I would like to know where you read that, Ben. The AR4 SPM says nothing specific about island loss (beyond what is implied by 18cm – 59cm + ice flow SLR), and the rest of the AR4 isn’t due out for a couple of months. Some TAR statements about islands can be found here and here . I cannot find in the TAR a specific number of islands expected to be lost.

    Since few if any places have 0 elevation change, I can’t understand how any individual island loss can be solely or discretely attributed to global warming (similar to how no individual hurricane or tornado can be attributed solely or discretely to global warming) . What is needed is not the ability to blame global warming (beyond recognizing the role of AGW-induced sea level rise), but the ability to make a projection of each island’s habitability for a given scenario of future emissions, erosion control, land reclamation, etc.

  25. 175
    Steve Reynolds says:

    Re 156:

    >Re #117 (and another lost post)[tamino]
    >I believe that what they’re saying (look at footnote 2) is that the 280 ppm CO2 that was there in pre-industrial times doesn’t count as a “forcing”.

    You are right; I should have looked at the footnote.

    But now that calls into question the rest of the SPM statement:
    “The carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years. {2.3, 6.4}”

    I calculate (roughly, based on figure 2.4 of the draft IPCC WG1 Fourth Assessment Report) that the increase in radiative forcing from 1970 to 1980 was from 0.84 to 1.06 W/m^2, which is 26%. So the SPM statement appears to be incorrect that the largest % change was 1995 to 2005. Any comment from RC staff?

    Of course this is due to % change in forcing from 1750 being a likely poor way of characterization. 1865 to 1875 appears to show a 34% change using this method!

  26. 176
    Ed G. says:

    Land typically becomes uninhabitable long before sea level rise inundates it. All it takes is a significant rise in occasional flooding due to storm surges or destruction of fresh water sources due to salt water leakage. Lots of areas have a significant percentage of the inhabitable area only a meter or two above the highest high tides (especially islands). If storms are also tending to get stronger the situation only gets worse.

  27. 177
    Martin Chavez says:

    Re: #164

    Mr. McCormick,

    I thank you for your prompt response and effort to begin to explain the IPCC mechanism. In my profession, there is a cliche about high level executives, that basically serves as an equalizer, it goes something like “he puts his pants one leg at time, just like any other man” (apologies for this male centric metaphor). I approach any Medical Doctor, Nuclear Physicist, or Politician the same way – there is no self-respect in sycophantism. Nonetheless, the direct answer to your question is that I would only obtain a second, third, etc.. opinion based upon graveness of the diagnosis.

    Which segues nicely with my main point, and one, with all due respect, you neglected to even begin directly answering. If I had liver cancer, I would not only consult an oncologist but also an endocrinologist, an interest, and cancer victims as well; plus many many more sources. And you can very well be assured that I would be fully aware of credentials and full experience of each; which is all I am asking here.

    The grave diagnosis for Planet forwarded by the IPCC, deserves the full attention of the greatest minds of all scientific backgrounds. I am indeed confident that the “scientists” (The ” ” are emphasizing the generality of the term and NOT any kind of derision) that affirm the claims are well qualified to do so, and have done so with conscientious diligence. I would further assert that their credentials are well documented. However, they do not seem to be well aggregated enough to promote efficient scrutiny; which I am heretofore unaware of such a source.

    I currently maintain that the superlative “consensus” promoted by media, non-scientist activists and politicians, is nothing more than extreme rhetorical hyperbole, meant as a well-intentioned (hopefully not a path to Hades) call to action to the at large public. Again that is summed up by the simple sun logic presented in my previous post (#163) and the basic question where are the physicists? I don’t think I am going to get the answer from Charlie Gibson anytime soon.

    Furthermore, if the vast majority of contributors are climate scientists, and little input comes from outside that community, I am gravely concerned about the bias that kind consensus breeds. I want to be clear, I believe the planet is warming and alternatives to hydrocarbon based energy sources should be pursued with extreme vigor, mostly for political and economic stability reasons, and definitely for sheer integrity. My goal is to understand the perspective of individuals that make of the body the consensus on AGW. If it is indeed lacking for prominent physicists, statisticians, economists, et. al. outside the discipline of environmental sciences, then the conclusions, I submit, are far from closed to debate.

    To me it is a fools errand to assume all of the causation for any GW forcing is solely on a global scale with out considering those perpetrated by factors on a solar, galactic, universal or even sub-atomic scale. My overall request is that everyone layout relevant their biases with there content, it what Teddy Roosevelt called the arena of ideas, and furthermore the AGW debate must not be closed before credible evidence from outside CS community is submitted for consideration.

    I’ll leave you with on inescapable fact, not only does every man put his pants on one leg at a time, he also has possesses an emotional ego that leaves a fingerprint on everything he does. That doesn’t mean he is wrong to do so, but admitting it only enhances his credibility.

    Marty Chavez – Albuquerque, NM – Business Development Professional – BS in Health Sciences

  28. 178
    James says:

    Re #163: You say “The sun is the major factor in the daily 25 F degrees or so temperature fluctuation in my region”, but a little thought should show you that that’s not in fact the case.

    Your problem here is one of perspective: Do you remember an old song (maybe ’70s?) about how a “fool on a hill sees the sun going down, and the eyes in his head see the world spinning ’round”? It’s not any change in the sun that causes your temperature fluctuations, it’s the turning of the world that makes day & night, just as its axial tilt makes the seasons and other orbital variations the ice ages – and all this would still be happening if the sun were absolutely constant & invarying.

    There’s a simple answer to the question of why solar variations aren’t included in climate models (though in fact they may be in some): there have been satellites in orbit for the last 40 years or more, making careful measurements of the sun’s output. From those we know to a fraction of a watt per square meter (IIRC) just how big the variation is, and it’s not anywhere near large enough to cause significant temperature changes. There are several articles on the subject here, if you want details.

    (As to your question about my scientific qualifications: I started with a degree in math & physics, but have mostly (barring occasional forays into commercial software) worked in computer modeling, in fields ranging from electric power systems to weather & mesoscale climate to my current interest in neurobiology.)

  29. 179
    Hank Roberts says:

    > causation for any GW forcing is solely on a global scale with
    > out considering those perpetrated by factors on a solar, galactic,
    > universal or even sub-atomic scale.

    You’re wrong about that. This has been considered, because we can observe several other planets — which ought to reflect any solar, galactic, or universal forcings. Start here:

  30. 180
    Ark says:

    Mitch (#156), thanks, that explains it for me!
    Now one remaining question (hope I didn’t miss another footnote) regarding expected warming by 2030 (2nd bullet on page 10 of 21):

    “Warming by 2030 is very likely to be at least twice as large as the corresponding model-estimated natural variability during the 20th century .”

    Can somebody explain me what a warming of twice a variability means?

    Thanks in advance!

  31. 181
    Peter says:

    In the popular press, there have been a number of apocalyptic descriptions of what is implied by various temperature rises. These may or may not be accurate predictions.
    What I have not seen is any sober predictions and analysis of what variability we can expect, and what implication this has for agriculture. If there is anything that is worse for agriculture than change, it is more weather.

  32. 182
    tamino says:

    Re: #163, #177, #178

    Regarding physicists: it is patently false to claim that “the physicists” have been left out of the scientific research on climate. Climate scientists are physicists — the ones who specialize in earth’s climate. Including particle physicists or cosmologists or those from a host of other subdisciplines, who generally have little expertise in the details of earth’s systems, would be of little help. Those who wish to learn the ins and outs of climate science, and contribute to research, are not in any way excluded.

    Regarding the sun: its variations are indeed far too small to account for the temperature increase in the modern global warming era. But they are not negligible, and are included in all realistic climate models. Without accounting for solar variations, the models fail to match the early-20th-century warming very well; with them, the models match the entire 20th century with stunning accuracy.

    Regarding credentials: those of the moderators are trivially easy to discover, and you’ll find they are among the world’s leaders on the subject of climate science. Most comments come from non-scientists, but there are a fair number of working scientists (myself included) who comment here regularly. I have a fairly long list of publications in peer-reviewed scientific journals — but not in climate science, so parading my credentials would be of little use. And before I venture to add to the scientific research on climate, I’d be sure to learn all I could from actual climate scientists who have, for the most part, devoted entire lifetimes to its study.

  33. 183
    Martin Chavez says:

    Re: #178


    Thank you for the thoughtful and engaging response. Your Fab Four metaphor is duly appreciated. While my perspective may not fit the more accepted explanation, I remain confident we agree on the fact that it is solar irradiance that is mostly responsible for the energy that warms the ambient temperature throughout the day and its absence is the culprit for the majority of cooling at night. To me that seems empirically evident in the variations between temperatures in the shade and direct sunlight and the major reason that significant remnants of December snow, despite above freezing daylight temperatures, that persist in my north facing driveway while those of my neighbors across the street are bone dry vs. radial momentum of the Earths orbit being the prime energy source for such phenomena.

    Regardless, your main point is that solar energy fluctuations are not significant enough to be considered in most climate models. I will read up on it as you suggest, however I hope that those assertions are made by those most qualified to make them. That is not to say, the valid perspectives of others outside of solar scientists should not be considered, by all means they should. I am sure you see my point.

    Now its time to shut up and read. By the way, very cool of you to provide your background.

    Marty Chavez – Albuquerque, NM – Business Development Professional – BS in Health Sciences

  34. 184
    llewelly says:

    But now that calls into question the rest of the SPM statement:
    “The carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years. {2.3, 6.4}”
    I calculate (roughly, based on figure 2.4 of the draft IPCC WG1 Fourth Assessment Report) that the increase in radiative forcing from 1970 to 1980 was from 0.84 to 1.06 W/m^2, which is 26%. So the SPM statement appears to be incorrect that the largest % change was 1995 to 2005.

    Percent of what?
    Let’s try the AR4 SPM statement again, with a bit of editing to show what the ‘20%’ figure is a percent of:

    The combined radiative forcing due to increases in carbon dioxide, methane, and nitrous oxide is +2.30
    [+2.07 to +2.53] W m-2, and its rate of increase during the industrial era is very likely to have been
    unprecedented in more than 10,000 years (see Figures SPM-1 and SPM-2). The carbon dioxide radiative
    forcing increased by 20% [of the 1750 to 2005 change in radiative forcing] from 1995 to 2005, the largest change for any decade in at least the last 200
    years. {2.3, 6.4}

    Bold text is my inference from context.
    Now let’s try your statement again, with a bit of editing to show what your ‘26%’ figure is a percent of:

    I calculate (roughly, based on figure 2.4 of the draft IPCC WG1 Fourth Assessment Report) that the increase in radiative forcing from 1970 to 1980 was from 0.84 to 1.06 W/m^2, which is 26% [of the 1750 to 1980 change].

    Bold text is my inference from context.

    If my inferences are correct, you are comparing apples to pears.
    This is a general problem with percent – one must always read carefully to determine ‘percent of what‘ .

  35. 185
    Ben Hocking says:

    llewelly: It appears that I’ve managed to conflate the prediction that Indonesia will lose 2,000 islands with the IPCC. I suspect that the source where I originally got that information might have been partly responsible for that, but perhaps I did it all on my own. Again, thanks on your link last night (which appears to have been lost to the database gods), which did manage to answer many of my questions.

  36. 186
    Steve Sadlov says:

    RE: #130 – Please describe the experimental procedure(s) used to characterize the rate of oceanic CO2 fixing.

  37. 187
    Steve Reynolds says:

    Re 184:
    >The carbon dioxide radiative forcing increased by 20% [of the 1750 to 2005 change in radiative forcing] from 1995 to 2005…

    llewelly, I think that you are calculating the same way Lord Monckton did to get 17% rather than 20%. I believe they are using: % of the 1750 to 1995 change in radiative forcing from 1995 to 2005.

  38. 188
    Hank Roberts says:

    >rate of oceanic CO2 fixing

    Here ya go, Steve, these abstracts will get you started on the methods:

  39. 189

    [[There’s a simple answer to the question of why solar variations aren’t included in climate models (though in fact they may be in some): there have been satellites in orbit for the last 40 years or more, making careful measurements of the sun’s output. From those we know to a fraction of a watt per square meter (IIRC) just how big the variation is, and it’s not anywhere near large enough to cause significant temperature changes. ]]

    While I agree with the thrust of your comments, I want to point out that most climate models do take Solar variation into consideration, especially if they’re doing multi-year simulations. The Solar intensity variation over the 11-year cycle isn’t huge, but it’s big enough to be noticeable.

  40. 190

    [[Warming by 2030 is very likely to be at least twice as large as the corresponding model-estimated natural variability during the 20th century .”

    Can somebody explain me what a warming of twice a variability means?]]

    What they’re saying is that the warming will be large enough that we can rule out natural variability as the cause. In fact, I think that’s already happened.

  41. 191
    lars says:

    re #189
    don’t forget the 100,000 years cycle……..

    “*Sun’s fickle heart may leave us cold”
    There’s a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years – exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star’s core.

    [Response:“utterly implausible” (last paragraph). – gavin]

  42. 192
    BarbieDoll Moment says:

    90.) “One other small point, we do not have anywhere near enough fossil fuels reserves to achieve the higher and hence more alarmist scenarios unless we invoke large scale positive feedback loops for large releases of CO2 from natural sources such as the siberian permafrost, or rain forests etc “…

    149) “Is it fair to say that all of the fossil fuel reserves will be burnt eventually, and that it’s merely a question of how slowly or quickly we burn them?”…

    Perhaps conventional is the keyword here. Additionally, fossil fuel emissions are not the only source of greenhouse gas emissions that we have to contend with;
    albeit one can find ambigious or diverging viewpoints on what could or could not be the outcomes (positive versus negative) in relation to emission sources.

    {As I posted this on the 3rd, I’ll assume that mine was one of the “lost” postings.}

    “Peak Oil, Exxon Mobil” Money Week (9-28-06)

    …”In later comments, Mr. Nolan explained the Exxon â??viewâ?? that â??the world has abundant energy resources.â?? He stated, â??According to the U.S. Geological Survey (USGS), the Earth currently has more than 3 trillion barrels of conventional recoverable resources and so far weâ??ve produced 1 trillion of that. Conservative estimates of heavy oil and shale oil push the total recoverable resource to over 4 trillion barrels.â??”…

    Energy Information Administration / International Energy Outlook 2006
    Chapter 3 World Oil Markets


    International Petroleum (Oil) Reserves and Resources

    World Proved Reserves of Oil and Natural Gas, Most Recent Estimates
    Table Posted: January 9, 2007

    Under footnote 2)
    …”BP notes that “the figure for Canadian oil reserves includes an official estimate of Canadian oil sands ‘under active development’.”…

    footnote 3)
    …”Oil & Gas Journal’s oil reserve estimate for Canada includes
    5.2 billion barrels of conventional crude oil and condensate reserves and 174.0 billion barrels of oil sands reserves.”…

    footnote 4)
    …”World Oil states that its
    Canadian oil reserves estimate “Includes reserves that are recoverable with current technology and under present economic conditions. Includes
    7.58 billion bbl [barrels] of oil sands and bitumen.” “…

    “About Oil Shale”
    United States Department of the Interior, Bureau of Land Management (BLM)/Argonne Labs
    ..”Present U.S. demand for petroleum products is about 20 million barrels per day. If oil shale could be used to meet a quarter of that demand, the estimated 800 billion barrels of recoverable oil from the Green River Formation would last for more than 400 years1.”…..


    Expedition to the Deep Slope
    NOAA Ocean Explorer, (Jun 2006)
    “The â??Expedition to the Deep Slopeâ?? expedition is the first systematic exploration of hydrocarbon seep communities deeper than 1000m in the Gulf of Mexico.”…

    Stable carbon isotope records of carbonates tracing fossil seep activity off Indonesia
    Geochemistry Geophysics Geosystems 7 (11), 11009 (2006)
    “”Stable isotope records of carbonates from up to 20 m long sediment cores from the forearc basin of the Sunda arc display significant 13C depletion, deviating from expected normal marine levels by 5 to 40â?° (Peedee belemnite (PDB)). This depletion is interpreted to be caused by methane seepage and associated authigenic carbonate precipitation in sediments near the seafloor. “…

    Contribution of anthropogenic and natural sources to atmospheric methane variability.
    P Bousquet et al. Nature. 443 (7110), 439-43 (28 Sep 2006)
    …”Since 1999, however, they indicate that anthropogenic emissions of methane have risen again. The effect of this increase on the growth rate of atmospheric methane has been masked by a coincident decrease in wetland emissions, but atmospheric methane levels may increase in the near future if wetland emissions return to their mean 1990s levels.”


    [edited — sorry, we can’t allow excessively long posts, otherwise everyone else’s comments get lost. please feel free to link to some site elsewhere where you can provide more extensive information]

  43. 193
    Steve Sadlov says:

    RE: #188 – Close but no cigar.

  44. 194
    Bob says:

    Re #163, #183, etc. Other physicists keep climate physics from straying too far:

    There is also a reason involving sociology of science. Among the most important regular scientific meetings for Climate Science is the Fall meeting of the American Geophysical Union. The society includes sections focused on Space Physics and Planetary Sciences. The December 2006 meeting had 32 sessions organized around Solar and Heliospheric Physics ( Given how mind-numbing it can be to listen carefully to several days of rapid-fire presentations in your own subdiscipline, taking in a few interesting talks in another field is one way to clear your head. (That’s at least in my experience.) If climate modeling methods required overly dubious assumptions about solar variability and behavior, at least once a year leading experts in heliophysics need only walk to another room down the hall to start to set things straight–the “embarrassing question from the back of the hall” being a common way to begin such a corrective process. [tongue partly in cheek] In addition, there are places where Cosmologists regularly attend invited scientific lectures by Climate Scientists, and vice versa. (The Goddard Space Flight Center being one of those places.)

    So even if the IPCC does omit recruiting experts working on the unification of General Relativity and Quantum Mechanics, the approaches used in Climate Science do have to stand up to some level of scrutiny across disciplines.

    [Response: Well – maybe my previous (brief) life working on General Relativity is of some use after all? -stefan]

  45. 195
    llewelly says:

    llewelly, I think that you are calculating the same way Lord Monckton did to get 17% rather than 20%. I believe they are using: % of the 1750 to 1995 change in radiative forcing from 1995 to 2005.

    If so I apologize. Unfortunately there is no way I can be sure – the AR4 SPM does not say what the change in forcing from 1750 to 1995 was, and my interpretation of their 20% figure was only an inference – the AR4 does not specifically say what the 20% is of.

  46. 196
    Steve Reynolds says:

    Re 194:
    >Unfortunately there is no way I can be sure – the AR4 SPM does not say what the change in forcing from 1750 to 1995 was…

    Please see figure 2.4 in IPCC Working Group I Contribution to the Fourth Assessment Report of the IPCC
    Second-Order Draft:

  47. 197

    REPOST DUE TO DATABASE CORRUPTION: I am definitely surprised that AR4 has come to a stronger conclusion than the TAR. Yes, there has been much work since the TAR and the models are much better, but that is the problem. We also now know much more about how flawed the models are. AR4 has ignored the draft reviewers and their own diagnostic subprojects, such as Roesch that showed ALL of the models had positive surface albedo biases (against solar) that are much larger than the global energy imbalance thought to contribute to the warming. They should have no confidence in model projections and climate sensitivity after that.

    There are no model independent assessments of climate sensitivity that have the same coupling to the climate as the well mixed GHGs. The inability to explain 20th century warming without the GHGs should come as no surprise when the models are throwing away 2.7 to 3.8 W/m^2 of solar forcing, when the annual imbalance is only 0.5 to 0.8 W/m^2 of warming, both figures globally and annually averaged.

    The anti-solar bias figures are obtained by applying the net solar flux from

    of 198 W/m^2, to the globally and annually averaged positive surface albedo biases found reported by Roesch.

    So much for “peer review”. It appears that AR4 came to their conclusions before they started, and were unwilling to rebuke the overly “confident” TAR.

    Roesch A. (2006), Evaluation of surface albedo and snow cover in AR4 coupled climate models, J. Geophys. Res., 111,D15111, doi:10.1029/2005JD006473.

  48. 198
    Martin Chavez says:

    Re: #163, 164, 178, 182, 183 & 189

    Another skeptic bites the dust…

    To all who took the time and requisite patience to open my eyes to a new understanding of AGW, I thank you. Here’s a few boilerplate reference URL’s for the next spade of lay entrants in to your realm that present the what about solar energy variation? question:

    …and there are the physicists, where they were the whole time. I especially appreciated the writings of Spencer Weart, who took a historical approach to the science. It goes to show you that is about how you tell the story to some people.

    So the consensus is justified, and there is a huge challenge ahead. As a businessman, I know that the greater the challenge, the greater the opportunity, which markets truly respond best to overtime, much more than the short term effects of fear. The point is that if AGW is truly the next disruptive change for humanity, then those who develop the commercial solution will be the economic winners. It is not hard to imagine the great fundamental shift in wealth a fossil fuel alternatives become the dominant global energy source. Don’t count out the Oil giants as partners in this future. There ifrastructure goes way beyond fossil fuel exploration & petrochemical processing…think distributin and marketing. Although it was inevitable that politics was the natural vehicle to bring the issue to prominence, I would not place much faith in its remedies to such a complex issue, otherwise we would have conquered disease, famine, and have sustained world peace long ago.

    Nevertheless, I wish the skeptics well, and my hope is that they will not be crucified by the mob. I urge you to allow them into arena of ideas for perpetuity. They will only sharpen your skills to forge better arguments and perhaps we’ll all breath a sigh of relief if they turn out to be right. Furthermore, insisting on holding the monopoly on the orthodoxy has its own set of nasty consequences.

    Lastly, I want to apologize to anyone offended about my assertion around physicists holding special place in the pantheon of science, and implying that climate scientist’s credibility may be less significant. It’s ironic that I got what I wanted through a little agitation through oversimplification, when I claim to eschew such tactics. If its any consolation, I am most embarrassed about this last point.

    Thanks again for sending me on my way, better educated and more humble. I look forward to the innovation that will meet this most grave challenge.

    All the best!

    Marty Chavez – Albuquerque, NM – Business Development Professional – BS in Health Sciences

  49. 199
    Hank Roberts says:

    > It is not hard to imagine the great fundamental shift in wealth
    > as fossil fuel alternatives become the dominant global energy source.

    Practically and parochially speaking, it’s the only way the United States can hope to redeem the debt now held by the Chinese government. If we can create the tools to make it through the next century, they’ll want to buy them.

    And they have all those US Treasury Bonds, so we know they can pay, if we can create the technology faster than they can.

    See today’s Wall Street Journal, for a discussion of how the “Chinese plus US” economy can be considered as one large economy, Eastern and Western branches but with most of the “ChiMerican” trade internal to that set.

    “Out of great need comes great ingenuity.” I forget who said that.

  50. 200
    Dave Cohen says:

    Re #89

    While it is the expert judgement of many glaciologists that dynamical melting will accelerate very rapidly, there aren’t the needed models or terrain surveys in place as yet to be able to do more than make educated guesses.

    Sorry, Steve but this does miss my point. As far as I can see, data for flows from the ice sheets are not considered after 2003. Sometimes the best data you have is what you are looking at right now. I acknowledge that the trend is short, but why wasn’t the “expert judgement” of the people who know what they are talking about included in the summary?

    Perhaps it really doesn’t matter. The world will add a cost to carbon emissions or not, right? The sea level problem is major, in my view — “downplayed” in the report — but perhaps that won’t matter, it will be overwhelmed by every other unfortunate consequence. Still, if you wait six years for a “definitive” statement, and then parts of it suck, disappointment follows.