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The Wall Street Journal vs. The Scientific Consensus

Filed under: — group @ 22 June 2005 - (Español)

We are disappointed that the Wall Street Journal (WSJ) has chosen to yet again distort the science behind human-caused climate change and global warming in their recent editorial “Kyoto By Degrees” (6/21/05) (subscription required).

Last week, the U.S. National Academy of Sciences and 10 other leading world bodies expressed the consensus view that “there is now strong evidence that significant global warming is occurring” and that “It is likely that most of the warming in recent decades can be attributed to human activities”. And just last week, USA Today editorialized that “not only is the science in, it is also overwhelming”.

It is puzzling then that the WSJ editors could claim that “the scientific case….looks weaker all the time”.

While we resist commenting on policy matters (e.g. the relative merits of the Kyoto Protocol or the various bills before the US Senate), we will staunchly defend the science against distortions and misrepresentations, be they intentional or not. In this spirit, we respond here to the scientifically inaccurate or incorrect assertions made in the editorial.

Since that Byrd-Hagel vote eight years ago, the case for linking fossil fuels to global warming has, if anything, become even more doubtful.

This statement stands in stark opposition to the actual findings of the world scientific community (e.g. the various National Academies, the Intergovernmental Panel on Climate Change (IPCC)), and the vast majority of actual peer-reviewed scientific studies.

The Earth currently does seem to be in a warming period, though how warm and for how long no one knows.

If we interpret to “know” as “is judged to be the case based on the available evidence”, the statement is patently false. As detailed in previous discussions at RealClimate (see here and here and here) it is the consensus of the scientific community, based on more than a dozen independent studies using both empirical data and theoretical models (including the most recent studies in Nature and Science), that average surface temperatures over the Northern Hemisphere during the past few decades appear to be unprecedented in a very long term context, probably over at least the past 2000 years.

In particular, no one knows whether this is unusual or merely something that happens periodically for natural reasons.

This is incorrect. The natural causes of past climate variations are increasingly well-understood, and they cannot explain the recent global warming. As discussed elsewhere on this site, modeling studies indicate that the modest cooling of hemispheric or global mean temperatures during the 15th-19th centuries (relative to the warmer temperatures of the 11th-14th centuries) appears to have been associated with a combination of lowered solar irradiance and a particularly intense period of explosive volcanic activity. When these same models are forced with only natural radiative forcing during the 20th century [see e.g. Crowley (2000)] they actually exhibit a modest cooling trend. In other words, the same natural forcings that appear responsible for the modest large-scale cooling of the “Little Ice Age” should have lead to a cooling trend during the 20th century (some warming during the early 20th century arises from a modest apparent increase in solar irradiance at that time, but the increase in volcanism during the late 20th century leads to a net negative 20th century trend in natural radiative forcing). In short, given natural forcing factors alone, we should have basically remained in the “Little Ice Age”. The only way to explain the upturn in temperatures during the 20th century, as shown by Crowley (2000) and many others, is indeed through the additional impact of anthropogenic (i.e., human) factors, on top of the natural factors.

Most global warming alarms are based on computer simulations that are largely speculative and depend on a multitude of debatable assumptions.

This is not correct. Concern about global warming is not based primarily on models, but rather on an understanding of the basic physics of the greenhouse effect and on observed data. We know from data that we have caused the CO2 concentration in the atmosphere to rise sharply during the past century: it is now much higher than any time during the past 650,000 years (which is as far back as reliable ice core data exist). And we know that this rise in CO2-concentration changes the radiation balance of the planet and leads to a warming of global surface temperature. This is scientifically undisputed and well-established physics, which has been known since in the year 1896 the Swedish Nobel prize winner Svante Arrhenius calculated the climatic effect of a rise in CO2.

Since there is a continued increase in emissions of (in particular) CO2, continued greenhouse warming is highly likely to continue. The models serve merely to quantify these basic facts more accurately, calculate the regional climate response, and compute effects (such as the expected increase in ocean heat content or sea level) which can be tested against observed data from the real world.

The editorial then returns to the issue of paleoclimate reconstructions and the so-called “Hockey Stick”, repeating literally each of RealClimate’s documented “Hockey Stick” myths:

Then there’s the famous “hockey stick” data from American geoscientist Michael Mann. Prior to publication of Mr. Mann’s data in 1998, all climate scientists accepted that the Earth had undergone large temperature variations within recorded human history.

The actual prevailing view of the paleoclimate research community that emerged during the early 1990s, when long-term proxy data became more widely available and it was possible to synthesize them into estimates of large-scale temperature changes in past centuries, was that the average temperature over the Northern Hemisphere varied by significantly less than 1 degree C in previous centuries (i.e., the variations in past centuries were small compared to the observed 20th century warming). This conclusion was common to numerous studies from the early and mid 1990s that preceeded Mann et al (1998). The Mann et al (1998) estimates of Northern Hemisphere average temperature change were, in fact, quite similar to those from these previous studies (e.g. Bradley and Jones, 1993; Overpeck et al, 1997), but simply extended the estimates a bit further back (from AD 1500 to AD 1400). In reality, the primary contribution of Mann et al (1998) was that it reconstructed the actual spatial patterns of past temperature variations, allowing insights into the complex patterns of cooling and warming in past centuries. In fact, regional temperatures changes (e.g. in Europe) appear to have been significantly larger, and quite different, from those for the Northern Hemisphere on the whole. Neglecting the significance of the large regional differences in past temperature changes is another classic pitfall in the arguments put forward by many climate change contrarians (see Myth #2 here).

The WSJ editorial continues,

This included a Medieval warm period when the Vikings farmed Greenland and a “little ice age” more recently when the Thames River often froze solid.

The sentence, first of all, perpetuates two well-known fallacies regarding the so-called “Medieval Warm Period” and “Little Ice Age”. See the RealClimate discussions of the Little Ice Age and Medieval Warm Period for explanations of why both the Viking colonization of Greenland and the freezing of the River Thames actually tells us relatively little about past climate change.

The actual large-scale climate changes during these intervals were complicated, and not easily summarized by simple labels and cherry-picked anecdotes. Climate changes in past centuries were significant in some parts of the world, but they were often opposite (e.g. warm vs. cold) in different regions at any given time, in sharp contrast with the global synchrony of 20th century warming.

The WSJ then continue with a statement that is problematic on several levels,

Seen in that perspective, the slight warming believed to have occurred in the past century could well be no more than a natural rebound, especially since most of that warming occurred before 1940.

Firstly, the overall warming of the globe of nearly 1 degree C since 1900 is hardly “slight”. That warming is about 1/5 of the total warming of the globe from the depths of the last Major Ice Age (about 20,000 years ago) to present.

Secondly, the argument that the climate should have naturally “rebounded” with warming during the 20th century defies the actual peer-reviewed scientific studies which, as discussed earlier, suggest that the climate should have actually cooled during the 20th century, not warmed, if natural factors were primarily at play. Anthropogenic greenhouse gases are required to explain the observed warming. Also, it is incorrect that most of the warming occurred before 1940; in contrast, the warming since 1970 is larger than that up to 1940.

The WSJ proceeds with the claim that key scientific findings that are common to numerous independent studies (specifically that late 20th century hemispheric warmth is anomalous in the context of past centuries) can somehow be pinned on one particular research group or even individual (see Hockey Stick Myth #1 here):

Enter Mr. Mann, who suggested that both the history books and other historical temperature data were wrong. His temperature graph for the past millennium was essentially flat until the 20th century, when a sharp upward spike occurs — i.e., it looks like a hockey stick. The graph was embraced by the global warming lobby as proof that we are in a crisis, and that radical solutions are called for.

This is patently incorrect.

The WSJ then echoes the final of the “Hockey Stick” myths discussed on RealClimate (see Myth #4 here), claiming that the “Hockey Stick” has now been discredited:

But then, in 2003, Canadian mathematician Stephen McIntyre and economist Ross McKitrick published a critique calling Mr. Mann’s work riddled with “collation errors, unjustifiable truncations or extrapolation of source data, obsolete data, geographical location errors, incorrect calculations of principal components, and other quality control defects.”

In fact, these claims have been demonstrated to be incorrect by an independent group of scientists at the National Center for Atmospheric Research (NCAR) . These authors have shown that the ‘alternative’ reconstruction promoted by McIntyre and McKitrick (which disagrees not only with the Mann et al reconstruction, but nearly a dozen independent reconstructions that agreee with the Mann et al reconstruction within statistical uncertainties) is the result of censoring of key data from the original Mann et al (1998) dataset. Unlike the original reconstruction of Mann et al (1998), the reconstruction that McIntyre and McKitrick produced using the censored data set fails standard statistical tests for validity, and, in the words of the NCAR group, is “shown to be without statistical and climatological merit”.

Correct for those errors, they showed, and the Medieval warm period returns.

This is just bizarre. The claimed reconstruction of McIntyre and McKitrick, in fact, indicates anomalous warmth during the 15th century. This period doesn’t fall even remotely within the interval commonly referred to as the “Medieval Warm Period” Instead, it actually falls within the heart of the “Little Ice Age” itself! The irony of contrarian supporters of the claims of McIntyre and McKitrick is that, if their reconstruction were valid (which it is not), it would actually argue for unusual warmth during the heart of the “Little Ice Age”.

Mr. Mann has never offered a serious rebuttal to the McIntyre-McKitrick critique.

This is not true. In fact, Dr. Mann has demonstrated the falsehood of the various McIntyre and McKitrick claims in excruciating detail on RealClimate (see here and here). More significantly, however, McIntyre and McKitrick’s claims have now been refuted by at least two independent teams of climate researchers (see here and here).

He has refused to fully explain his methodology.

Quite to the contrary, the methodology used was described in detail not just in the original 1998 publication, but in an expanded description provided last year on Nature’s supplementary website. The original description was adequate for other researchers with appropriate training to closely reproduce both the algorithm and the published results. In fact, the NCAR researchers referred to above have made their code for implementing the Mann et al (1998) method publically available here. In the process (scroll down to bottom of this page) , they demonstrate the impacts of the numerous fundamental errors made by McIntyre and McKitrick. With this publically available code and data, anyone can reproduce and check the reconstruction of Mann et al (1998).

Meanwhile, a review of about 200 different temperature studies was published in 2003 by Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics in the journal Climate Research. It likewise reaffirmed the longstanding consensus that there have been large temperature variations over the past millennium.

The irony here could not be more striking, for if the editors of the WSJ were familiar with the news reported by the WSJ, they surely should have been aware that the Soon and Baliunas study was discredited on the pages of the Wall Street Journal itself. Indeed, as described in that previous WSJ article, a team of leading climate researchers detailed the numerous fundamental flaws in the Soon and Baliunas paper in in the American Geophysical Union journal “Eos“. This matter has been discussed elsewhere at great length, including previously on RealClimate both here and here (see “Myth #2”).

computer models …suggest the upper atmosphere should have warmed substantially in recent decades. But data from weather balloons and satellites don’t match the projections.

There is indeed a discrepency between some analyses (but not others) of the satellite data in the lower troposphere and model predictions, yet the satellite data continue to undergo quality checking and re-processing and there are a few indications (such as Fu and Johansen, 2005) that problems still exist. The jury is still out on this issue (but they may be about to come back in to the room).

There’s also the matter of the alleged melting of the Antarctic ice cover, threatening a catastrophic sea level rise. In fact, recent data suggest the ice is thickening and temperatures are dropping in most of the continent.

Models actually predict that the interior of the ice sheets should gain mass because of the increased snowfall that goes along with warmer temperatures, and recent observations actually agree with those predictions. Some areas, such as the Antarctic peninsula and the West Antarctic ice sheet are losing mass, consistent with temperature trends there.

Finally, an increasing number of scientists are concluding that variations in solar radiation associated with sun spots — that’s right, the heat of the sun — play a major role in Earth’s climate.

Solar forcing of climate is indeed an important component, and in the pre-industrial period appears to explain a significant share of the century-scale variability (though there is large uncertainty in the magnitude of the effect). There is likely an increase in the early 20th Century as referred to above, however, since 1950 there is no evidence for increases in solar activity (most indices are flat) and so it is highly unlikely to be able to explain the bulk of the current warming trend.

The WSJ editors then try to reverse nearly two decades of scientific research by promoting a qualitative graph (which is not actually based on any real data) that was offered simply as a schematic by the IPCC back in 1990:

So what would be a fair representation of how most scientists view the climate of the past 1,000 years? We’d suggest the graph nearby, which we reprint exactly as it appeared in the first report of the U.N.’s Intergovernmental Panel on Climate Change (hardly a group of oil-funded hacks) in 1990. It shows that our own warming period is neither unique nor all that hot.

The WSJ may prefer to use 15 year-old guesses on which to base their opinion, but the scientific community has an understandable preference towards up-to-date and quantitified research.

137 Responses to “The Wall Street Journal vs. The Scientific Consensus”

  1. 51
    dave says:

    Re: 41 Gavin’s comment

    Unprecedented amounts of greenhouse gases (at least over the last few hundred thousand years) continue to accumulate in the atmosphere…

    Just to emphasize the point, from Atmospheric carbon dioxide concentrations over the past 60 million years by Pearson and Palmer (2000):

    Since the early Miocene (about 24Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.

    So, when we double to ~550 CO2 ppm, and we almost certainly will double under business as usual scenarios, our current knowledge says that these will be the highest levels in many millions of years. Maybe this doesn’t impress the close-minded, but it always amazes me….

  2. 52
    Lee A. Arnold says:

    Re #31 and others:

    It should be added that terrestrial wildlife ecosystems have been badly fragmented by human habitation, worldwide. This prevents many areas from reconstituting species lost in normal local extinctions (from an extreme winter, loss of food supply, etc.) because the normal immigration of plants and animals from other regions is stymied. Global warming will accelerate this fragmentation-extinction, as mobile species seeking to emigrate to another, more comfortable range are extinguished when they come up against, or try to make it through, the expanses of human habitat. A network of greenbelts interconnecting the largest wildlife areas will be necessary for some creatures.

    And it is absolutely necessary that all people everywhere stop the reduction of wildlife land area, and learn to engage in economic development by redevelopment and density concentration, instead of spreading out further. Despite decades of nonsense on the op-ed pages of the Wall Street Journal, nothing in economic theory says otherwise.

  3. 53
    Eli Rabett says:

    #49, Gerald, I am less than impressed by your logic. First of all, the sites I referred you to were full of reports on different aspects of climate. Read some of them and you will begin to figure out what is going on. You can even just dip in and look at the executive summaries OTOH, there are many textbooks, but, of course, they will not have much of the latest research. Still, they are good places to start. I like books on atmospheric chemistry (Wayne, chemistry of atmospheres, Brasseur, Orlando and Tyndall atmospheric chemistry and global change). Might be useful for our hosts to put out a reading list for us. It is summer, a great time for reading.

    The IPCC TAR is what is called an expert critical review. The US National Academy of Sciences was asked by the government for a quick review of the TAR. I pointed you to their report. They agreed that the TAR pretty much got it right. You and GB appear not to like the NAS and IPCC opinion but why do you expect others who might have a clue to ignore them?

    If you are shopping for something that meets your expectations wander over to sepp.

  4. 54
    Steve Bloom says:

    Re #49: Gerald, you say with repsect to the various national academies that “they are just quoting the IPCC Report, which is being questioned significantly now.” What do you mean by “now”? The IPCC is being questioned by nearly the same small, not especially well-qualified and (to a great extent) fossil fuel industry-funded crowd that was questioning it when the TAR first came out. If these “skeptics” are right, why haven’t they convinced anyone not already disposed toward their arguments? The fact is that both the consensus and those persuaded by it (which is where the USA Today editorial comes in; there is no chance they would have written anything of the sort in 2002) are continuing to grow.

    Please be aware that the posts (as distinct from the comments, many of which are from climate amateurs) to this site are from highly-qualified climate scientists, all of whom are thoroughly engaged in a study of global climate. (To check their qualifications, click on their names in the right-hand column of this page.) The posts variously cite and link to a surfeit of “thorough studies.” It sounds like you need to see that for yourself, so please have a look.

  5. 55

    The editorial can be found here.

    I am putting a link to your article over on European Tribune.

  6. 56
    Timothy says:

    About the movement of ecosystems:
    #52 makes very good points about the fragmentation of habitats and the geographically immobile way that conservation is currently made by way of National Parks and wildlife reserves.
    Also with reference ot #37. I’m sorry not to have a link for this, but I remember seeing something which stated that the rate of climate change now was so fast compared to previous glacial-interglacial changes that it could outpace the ability of the ecosystem to respond. I think they were specifically considering the northward movement expected of the Boreal forest regions in Russia and the worry from this study was that the precipitation and temperature changes would overtake the forests and ‘leave them behind’ so to speak such that they wouldn’t be able to keep up and would be lost. Clearly this would be something we could intervene in were we so inclined, but, nevertheless, it doesn’t look good.

  7. 57
    Magnus says:

    I have comented about this in Swedish here.

  8. 58
    Gerald Machnee says:

    RE #54 -The British Royal Society reference was not a study. They referred to various points in the IPCC Report. I do not intend to question the qualifications of the various scientists – each has his specialty. I will note that the Canadian government has not been able to provide me with any study in Canada confirming man-caused warming. They have just quoted IPCC. I am more concerned with pollution of the air, land, and water and the food we eat than the temperature variation which may be a cycle. I agree with industry cleaning up the emissions in the air and surface. In the mid-1970’s many scientists were worried about the coming deep freeze. I will also note that Dr. Landsea left IPCC because his presentation on hurricane activity was being “misquoted” for lack of a better word.

  9. 59
    Florifulgurator says:

    Re 47:
    > It will die, along with millions of people
    Millions was last century. This century will quite probably see billions of deaths. Be fruitful and multiply…

  10. 60
    caerbannog says:

    Sorry about political (as opposed to scientific) angle here, but it looks like that WSJ editorial has inspired a bit of a GOP-based inquisition:

    Check out (Rep. Joe Barton’s web-site) see what sort of trouble that WSJ editorial has stirred up for the scientific community. There are some rather disturbing “letters of inquisition” (PDF documents) addressed to IPCC Chairman Rajendra Pachauri, NSF director Arden Bement, and Dr’s Mann, Bradley, and Hughes.

    Perhaps it would be a good idea (if it hasn’t been done already) to get RealClimate’s rebuttal here into the hands of the “good guys” in Congress ASAP…

  11. 61
    Jeff says:

    You state that there is a “consensus” view and cite the Joint Science Academic’s statement as evidence. How then do you exmplain the 17,000+ scientists and related professionals who signed the Oregon Petition thereby going on record as believing “there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gasses is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.

    How also do you reconcile your statement with the recent survey by Dennis Bray of Germany’s GKSS National Research Centre conducted among his colleagues, which found that any ‘consensus’ on the causes and effects of Global Warming is “not that strong.”

    [Response: Easy. The ‘Oregon Petitition’ is years old and even when it was current the number of confirmed names on the list who could be said to be actual climate scientists was tiny. The Bray survey had a number of flaws – first and foremost the question being asked was ambiguous and it wasn’t clear whether recent climate change was being discussed, secondly, the methodology was flawed in that the access to the survey was posted on a number of mesage boards which allowed many people (not just climate scientists) to vote early (and potentially, often). The IPCC was specifically tasked with providing a consensus report – it had thousands of authors (all of whom are in the field), thousands of reviewers (ditto) and exhaustive drafts and revisions until most people were happy. Go to any relevant meeting (AGU, EGU etc.) and you will find at most one or two posters or presentations (out of hundreds to thousands in relevant fields) that question the ‘consensus’. It is just not controversial anymore among scientists. -gavin]

  12. 62
    caerbannog says:

    How then do you exmplain the 17,000+ scientists and related professionals who signed the Oregon Petition thereby going on record as believing “there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gasses is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.”

    Have you actually seen the OISM petition? You can check it out right here:

    Now take a close look at the names on that petition. Are those MD’s, DDS’s, and DVM’s (veterinarians!) that you see? Why yes, they are!

    Now ask yourself, “what the heck would a dentist or veterinarian know about climatology?”. I mean, if you needed root-canal work, would you trust a climatologist to take on the job? Do you think that a climatologist would be qualified to lop off Fido’s gonads?

  13. 63
    Doug says:

    Above, RealClimate states:

    “In short, given natural forcing factors alone, we should have basically remained in the “Little Ice Age”. The only way to explain the upturn in temperatures during the 20th century, as shown by Crowley (2000) and many others, is indeed through the additional impact of anthropogenic (i.e., human) factors, on top of the natural factors”

    This seems like a good argument, yet it’s the first I’ve heard of it. Can it be found elsewhere on this site stated so concisely?

  14. 64
    Jeff says:

    I am unconvinced by your rebuttal to the Oregon Petition, although your responses are noted and have already been considered. The timeframe is not large enough so as to be significant, and the criteria of being an “actual climatologist scientists” is questionable when you consider that James L. McCarthy is considered to be an authority on global warming, yet his bio gives no indication he is a climate scientist.

  15. 65
    grundt says:

    Jeff, James McCarthy has a Ph.D. from Scripps Institution of Oceanography.
    Oceanographers study climatology. If not, they would not be oceanographers.
    And the link you provide shows indeed he has authority to talk about global warming. You have read about what is his research dealing with..
    at least what we can see from the link you kindly give us:

    ” His research interests have focused on the regulation of plankton productivity in the sea. He has worked extensively on the upper ocean nitrogen cycle in many areas of the world’s oceans, and in the past decade has directed these efforts primarily towards regions that are strongly forced by physical processes, such as annual mixing processes, monsoonal cycles and the ENSO system; processes likely to be altered temporally or spatially by global climate change. Over the past two decades he has become increasingly involved in the planning and implementation of interdisciplinary research efforts. In the mid 1980s he was the founding editor for the American Geophysical Union’s Global Biogeochemical Cycles…….”

    Well, and all the bibliography the links provides shows he knows about Global Warming. Thanks, Jeff! A good link!

  16. 66
    Joel Shore says:

    Re #61 and 65: Another fact about the Oregon Petition is the deceptive way in which it was circulated. Basically, a mass mailing was sent out to various science departments with a “paper” that was full of deception and half-truths but was formatted to look like a paper appearing in the Proceedings of the National Academy of Sciences. It was accompanied by a letter from Frederick Seitz, who is an elderly physicist and was a former President of NAS some 30 years ago but is now frankly an extreme anti-environmentalist.

    The deception was so extreme that NAS took the unusual step of issuing a statement noting that the paper being circulated had not appeared in the Proceedings of the NAS, the mailing was in no way associated with NAS, and furthermore that the paper’s conclusions were not in line with studies by the Academy.

    Basically, this petition was run like an old Soviet-style election: The recipients were bombarded with propaganda and then asked to vote but only the YES votes were recorded.

    And, despite what you claim, the time difference between when this all happened and now is significant because back in 1997-1998, scientists outside of climate science were unlikely to know what the general opinion of the peer-reviewed scientific community was and thus more likely to be deceived by such a stunt. Now, there has been enough coverage of the NAS studies and so forth that hopefully that situation is changing.

  17. 67
    Steve Bloom says:

    Re #63: There may not be another such statement, but it sounds like what you’re looking for is the analysis to back it up. Start with the site FAQs and then read through the “hockey stick”-related posts. It may be that you need to look at the Crowley study, which may or may not be available on-line (although the abstract will be, and maybe that’s enough). There’s the IPCC TAR itself, which certainly includes a discussion on this point but may well not be all that concise. You might also try some of the links at

    Re #64: You quote the petition (written at a time when the science on various potential catastrophic climate events was much less advanced than now) as saying “there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gasses is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.” As one of those alarmists, I’m not sure I could disagree with that statement even given the current science. This is because the concern for the future is in part a matter of catastrophic risks that necessarily have some uncertainty associated with them (for the straightforward reason that we haven’t been around to observe the various risked events actually happen), and in part a matter of cumulative harmful changes that are bad enough in themselves even if they never rise to the level of catastrophe.

    To list just two examples of potential catastrophic (in my opinion) change, we know that with a sufficient rise in temperature the Arctic Ocean clathrate deposits will release and the Greenland ice sheet will melt. The problem is that nobody knows exactly what increased temperature sustained over what period of time will commit us to those events. What is known is that we are risking both of them now (to different degrees). But even given that, are the consequences of either of these events necessarily catastrophic? That would be in the eye of the beholder.

    Analogizing to insurance, people who own houses are well-advised to buy fire insurance even though they believe it is highly unlikely that a catastrophe (i.e., a fire that burns their house down) will occur during the time they own a given house. Should they be advised to drop their insurance unless there is “convincing evidence” that their house “will” burn down? We can talk adaptation to some degree, but our basic insurance against the risks of climate is to reduce the level of GHGs.

    Looking at the petition language again, I see another problem in that it postulates combined conditions of catastrophic heating *and* global climate disruption. I’m not sure what that means. Is there some condition where we could have catastrophic heating *without* such disruption? Hard to imagine. On the flip side, could we have substantial climate disruption without catastrophic heating? That’s a lot easier to imagine. As well, what is meant by the addition of “forseeable” to “future”? It seems to me that it’s meant to imply “near” without saying so directly.

    Finally, let’s not forget that there is a major non-climate risk (ocean acidifcation) associated with CO2 increases. So you see that the problems with the Oregon petition aren’t just that it’s old.

  18. 68
    David Wojick says:

    Regarding “It is puzzling then that the WSJ editors could claim that “the scientific case….looks weaker all the time”,” I think I know what they are referring to. Research into natural variability has mushroomed, so the theory of anthro-GHG warming has a lot of new competition. In fact I notice that you seem to claim to be able to explain everything from the MWP-LIA cycle to the solar-climate link. I imagine a lot of experts in those things would disagree. My read on the science is that the uncertainties have increased with the research. Science is like that.

  19. 69
    Dano says:

    You’re right, Jeff – the MD stands for Meteorological Doctor, and the DDS is Doctor of Dendrochronological Science – all able to speak to the science. You’ve been duped. Here is a good breakdown of the story, easily Googleable, plus 1.

    Your alarm bells, however, should sound when you see no affiliations in the OISM – where the heck are these people from?!? Where are their credentials? Every scientific petition you see has affiliation. Every one. Look at the NAS, for example.

    The OISM petition also came under fire for being deceptively packaged: The petition was accompanied by an article purporting to debunk global warming that was formatted to look as though it had been published in the journal of the respected National Academy of Sciences. The resemblance was so close that the NAS issued a public statement that the OISM petition “does not reflect the conclusions of expert reports of the Academy.”



  20. 70
    Dan Allan says:

    We are reaching a pretty disturbing point in our society where not only do the right and left disagree about the conclusions of scientific facts, they disagree about the facts themselves.

    The right has developed its own information sources – Fox news, WSJ editorial page, Heritage Foundation, American Enterprise Institute – to name just a very few – and these sources all quote each other, and none of them seem to care where their “facts” came from in the first place. All of the cross-quoting still creates an imprimatur of legitimacy.

    Followers of these information outlets no longer need to test their “facts” against any broader information source.

    Further, as soon as a piece of rightwing pseudo-science has been generated, mainstream news outlets feel obligated to present “both sides” even though one side has no credibility whatever. The public in general concludes that there is likely to be some truth on both sides, just because there are two sides that disagree.

    We were all supposed to believe that Terry Schiavo was capable of rehabilitation. That Intelligent Design (i.e., Yahweh) directs evolution. That, although temperatures are rising, and carbon-dioxide in the atmosphere is rising rapidly, and increased CO2 is sure, according to the known laws of physics, to raise global temperature, by some miracle, the CO2 increase is not the cause of our rising temperatures. Some other, non-human factor (Yahweh again?) is at work.

  21. 71
    Steve Bloom says:

    Re #66: “I imagine a lot of experts in those things would disagree.” Based on the published peer-reviewed studies in the field, that would indeed have to involve your imagination. Also contrary to your impression, increased knowledge about natural variability has confirmed the consensus view. There is little to cite to the contrary, and to my knowledge what little there is has been debunked. You say that the “theory of anthro-GHG warming has a lot of new competition.” Please post published, peer-reviewed examples to back up your claim.

  22. 72
    SteveF says:

    r.e. #56,

    “Also with reference ot #37. I’m sorry not to have a link for this, but I remember seeing something which stated that the rate of climate change now was so fast compared to previous glacial-interglacial changes that it could outpace the ability of the ecosystem to respond. I think they were specifically considering the northward movement expected of the Boreal forest regions in Russia and the worry from this study was that the precipitation and temperature changes would overtake the forests and ‘leave them behind’ so to speak such that they wouldn’t be able to keep up and would be lost. Clearly this would be something we could intervene in were we so inclined, but, nevertheless, it doesn’t look good.”

    The climate change I referred to, the Younger Dryas, occurred more rapidly and was of greater magnitude than those predicted for global warming. The ecosystem response was pretty rapid to this, including the response of certain tree species. Some aquatic organisms responded in a couple of decade and the vegetation only in a few decades more in the above study I referred to.

    This is not to say that, for example, the boreal forest would keep up with climate change. The situation at the Younger Dryas boundary is not exactly analagous. However, the results of multiproxy studies such as Gerzensee and Krakenes were surprising and indicated that certain ecosystems are sensitive and can respond quickly. You could look at this in two ways – species could migrate to survive or, many of our local eosystems will be lost as climate gets warmer.

    [Response: Make sure to not confuse changes in global mean temperature with regional changes; the latter can be much larger and faster, as they can be caused by changes in heat transport by ocean or atmosphere. Global mean warming at the end of the last ice age amounted to 4-7 ºC and took about 5,000 years i.e., an average rate of about 0.1 ºC per century. Current and future warming looks very rapid compared to that.
    Regionally, especially in north Atlantic high-latitude areas, larger and especially much faster climate changes have occurred (such as the Younger Dryas cold event), most likely due to rapid ocean circulation changes.
    Concerning the response of ecosystems, two further factors must be considered. First, humans are now using much of the Earth’s surface; natural ecosystems are fragmented in many places, species live in small pockets of remnant natural ecosystem surrounded by agricultural lands etc., and cannot simply move. Second, for the past several million years (a time scale relevant for evolution), climate has oscillated between predominantly colder conditions (ice ages) and shorter intervals with conditions roughly like the present (interglacials). Species are adapted to this. Many survive the warm times high in the mountains, on islands of cold in a sea of warmth, so to speak. Now we’re moving into much warmer climate, unlike anything seen for several million years. The cold-adapted species will have nowhere to go – they move upwards along the mountains (as a recent article in Science put it) “until they reach the top and go to heaven”. -stefan]

  23. 73
    Doug Clover says:

    Dear Realclimate

    This may be inappropriate place to do this, but I would like to pass on my support to Dr Mann at this time. I have read that the Chair of the House Energy and Commerce Committee has started what I can only call a witch hunt over the original 1998 study.

    As an non-technical policy advisor working in the area of climate change I highly value the science and science communiciation work done by Dr Mann and all the other Realclimate contributors.

    Keep up the great work and don’t let the bastards grind you under.

    Doug Clover
    New Zealand

  24. 74

    Hello folks!

    This site is simply fantastic.

    I would also like to offer my support to Dr. Mann. If there is anything, anything at all that we can do to help, please ask.


    Dan (Staff Scientist, IODP).

  25. 75
    grundt says:

    RC, You are making History.
    I am very impressed!
    The solid supportive community you have is growing. Congratulations!

  26. 76
    Joseph O'Sullivan says:

    An additional note on anthropogenic climate change’s (ACC) effect on ecosystems, there were a couple of more links to studies I should have included. They both discuss widespread signs of ACC on ecosystems that have already occurred they are widely cited in scientific literature. Both are in Nature but they are on non-subscription sites.

    A globally coherent fingerprint of climate change impacts across natural systems
    Fingerprints of global warming on wild animals and plants

    It is important to note as Lee Arnold and Timothy have earlier that ACC will act together with other anthropogenic effects like fragmentation to compound the impact on ecosystems. Steve Bloom thanks for pointing to google scholar it is very useful.

  27. 77
    H.D. Larsson says:

    Would anyone care to comment on any of the statements made in the following essay? I am very puzzled to find one of three Vice Chairs of the IPCC is the author.

    “Climate Change: Not a Global Threat”
    by Yury Izrael, Director, Global Climate and Ecology Institute, Russian Academy of Sciences and IPCC Vice President

    The essay includes this line-

    “There is no proven link between human activity and global warming.”

  28. 78

    Global Warming
    An interesting rebuttal to a WSJ editorial on climate change….

  29. 79
    Lynn Vincentnathan says:

    Here is what I sent NRDC & Environmental Defense (of which I’m a member). Included is the beginning rough draft of a letter I plan to send to the House Committee on Energy and Commerce & a copy to my own rep:
    It has come to my attention that a climate scientist, Dr. Michael Mann (of the hockey stick fame), is being harassed by the House Committee on Energy and Commerce. He has done nothing wrong, but some unsigned editorial(s) in the Wall Street Journal (6/21/05 & 6/14/05?) have accused him of scientific wrong-doings, prompting the House Committee on Energy and Commerce to request that he and several others answer various obnoxious questions, almost like an inquisition. See the letters at

    You can also go to for information. Their entry on “Wall Street Journal v. Scientific Consensus” has some information that may help (or you can contact them & Dr. Mann, who is a contributor to the site).

    I feel the environmental community needs to be informed about this inquisition, and we need to write letters to the Committee on Energy & Commerce, and to our reps. I would hope that you might inform our members about this. The science and issues are fairly complex–I, for one, trust the scientists and journals like Science, Nature, and Scientific American–but now it seems we all need to learn more, so as to refute the contrarians in government & industry, who are becoming more vicious the more evidence there is of climate change.

    I haven’t written my own letter yet, but the gist would be something like this:

    “I am quite dismayed that you are harassing the well respected climate scientist, Dr. Michael Mann, by requesting information from him that is a matter of public record, and/or available to anyone who wishes to have it. Furthermore, I am greatly astonished that you are getting your scientific information from the Wall Street Journal, and from a few select global warming contrarians. I had imagined that at least someone in our government on someone’s staff had enough scientific knowledge and had been keeping up on the climate change literature to know that your request of Dr. Mann was unnecessary and amounts to harassment. It is further unnecessary, because even without Dr. Mann’s studies, many other scientific studies from a variety of perspectives have conclusively proven anthropogenic climate change. His studies are not linchpin evidence of climate change, but only give further support for it.

    Might I remind you that your duty is to serve the American people and your constituents. Global warming is a very serious problem that is having adverse consequences even now, and threatens to greatly harm Americans in the future. Scientists require high levels of certainty to claim there is a problem; they need to avoid false positives to protect their reputation, so that people will continue to believe them in the future. Your goal should be to avoid false negatives (claiming global warming is not happening when in fact it is happening), so as to protect Americans and the world. It is unconscionable to take a more conservative, do-nothing stance, requiring higher levels of certainty than scientists, when such a grave potential (and current) problem faces us.

    Furthermore, since I am sure you must know America can significantly reduce its CO2 emissions by half, through energy/resource efficiency/conservation and alternative energy, in cost-effective ways that help the economy, there is absolutely no reason at all not to pursue vigorously solutions to global warming (that would also solve many other problems & reduce harm/costs in other areas). I, for one, reduced my energy consumption since 1990 by one-third cost-effectively without lowering our living standard, and even raising it in areas, and now we are on 100% wind-generated electricity, lowering our CO2 even further and saving $1 a month over conventional fossil energy. For cost-effective energy/resource reduction at the national level, please refer to works by Amory Lovins and Rocky Mountain Institute.

    I would hope that you focus more on Main Street USA, and how global warming will negatively affect it, than on Wall Street and its very narrow foci and inability to comprehend that the environment is fundamental, the economy contingent. Without adequate sustenance provided by the environment people cannot survive.”

    I still have to work on this….

    Hope you will alert our members.
    If anyone has suggestions for improvements in the letter to the House Committee, let me know. I plan to send the letter sometime next week. I already sent this as an email to NRDC & ED, and hope they will do something about it.

  30. 80
    grundt says:

    thanks, H.D. Larsson
    I am astonished.. What does RC group think happened to Y. Izrael? Is there something strange behind this?

  31. 81
    grundt says:

    I see, Izrael already did not have a definite position a couple of years ago:

    As Dr. Yury Izrael, chair of the organizing committee for the conference, sums it up: “The most important issue is whether ratifying the Kyoto Protocol would improve the climate, stabilize it or make it worse. This is not very clear.”

  32. 82
    Michael Jankowski says:


    Even 2 yrs ago, Izrael had basically the same stance.

  33. 83
    Steven T. Corneliussen says:

    Some RealClimate participants may want to have a look at the following commentary rebutting the WSJ editorial. It was posted this morning by The American Prospect:
    By Chris Mooney
    The Wall Street Journal’s take on global warming
    gets more desperate all the time.
    The commentary links to the RealClimate posting that’s being discussed here. Chris Mooney is identified at the end of the rebuttal as the author of “The Republican War on Science,” to be published in September by Basic Books.

  34. 84

    Wall Street Journal: Lying liars on global warming
    Finally (via Atrios), this act of intimidation against a scientist by a Congressman is simply stunning, and shows why all reasonable people oppose the Bush regime and the Republicans.

  35. 85
    Joseph O'Sullivan says:

    Representative Barton, a conservative politician with close ties to oil and gas industries and a demonstrated hostility to environmental regulation, is launching an investigation of climate science. This is again about the regulatory implications of accurate science. With the recent passage of the resolution in the senate that accepts anthropogenic climate change, the climate change regulation opponents are getting worried. This is in no small part accounts for the timing and content of the WSJ editorial. IMO Dr Mann and Realclimate are being targeted for publicly standing up for accurate science.

    There is something that we can do to stop Barton’s attempts to suppress accurate climate science and to support science and the scientists. We should contact our representatives in congress by e-mail, fax, printed letter or even by calling on the phone. These things definitely influence our congressmen. See these sites for contact information:

    What should we tell them? Focus on one issue. Legislators receive a lot of mail, so keep it short and to the point. Tell them you are unhappy about this. Let them know that congress’ attempts to suppress accurate science and harassment of the scientists who work to find accurate science is not acceptable especially when such actions are motivated by some members of congress dislike for regulation. Let them know your vote could depend on or be influenced by their decision on this matter. Of course tell them about what the accurate science is and why these questions do not need to be asked again.

    Also e-mail the letter to your local paper and to politically active groups like the Union of Concerned Scientists. Lynn Vincentnathan the NRDC is a good choice; they have been active on the issue of undue political influence on science. Climate change contrarians like to cast the major environmental groups in the U.S as radical but in reality they are quite moderate and are also sophisticated political operators. Their political success has made them a target of the contrarians. Yes, contacting a politically active group is inherently politically partisan, but on the issue of political pressure we do need the help of politically active groups.

    I do find climate science to be a challenging topic and as challenging it can be, it is much easier when the politics are removed from it. Getting back to the science, thanks Stefan for bringing up the magnitude of the warming and it’s effect on ecosystems. When I consider anthropogenic climate change’s effect on ecosystems I compare anthropogenic climate change’s effects to the climate changes during the recent glacial/interglacial periods, but I forget that current warming is beyond that and can have serious and unforeseen effects on ecosystems. I learned something new from Realclimate.

  36. 86
    Hugh says:

    Well, what can I say?

    Having read the letters (thanks for the link, Lynn) I would suggest that the Committee on Energy and Commerce are just about to find themselves in a corner from which there is but one escape…and the best bit is that they will only be able to blame themselves when they realise what they’ve done.

    By calling for comprehensive statements from Mike et al I would suggest that they will actually have to listen to what they are being told. If this committee have been content to rely on peer-reviewed (sic) publications like ‘E&E’ and the WSJ for their ‘facts’ up until now, it’s about time they discovered what PEER-review actually means.

    I trust I am not being too optimistic…I am after all from a country whose Government at least attempts to confront the ACC issue with a substantial amount of rhetoric (if questionably little else).

    My thoughts and support are with you chaps from across the pond.

  37. 87
    Tom Fiddaman says:

    Re: #77 & #80

    I don’t have any personal knowledge about Y. Izrael, but that essay is full of misinformation and non-sequiturs. It doesn’t even do much to support its own headline. Maybe he was a political appointee to the IPCC?


    – Early on he says “There is no proven link between human activity and global warming”, but later agrees that “Global temperatures will likely rise by 1.4-5.8 degrees during the next 100 years.” Why would that be then?

    – He says “Many specialists estimate the peak atmospheric carbon dioxide concentration at 400 PPM.” We should be so lucky as to have such effective emissions controls. We’ll probably pass 400ppm at full speed.

    – Next he says “Our calculations show that carbon-dioxide concentrations would increase by just 800 PPM if all known and produced fuel were incinerated in the space of a few hours.” Off the top of my head, that corresponds with fossil resources of something like 1500 gigatons carbon, which is a ridiculously low estimate. China’s ultimate coal resource alone is estimated at about 5000 gigatons (raw coal, not carbon, admittedly including very deep seams).

    – Immediately after, he writes “In other words, we must comprehend what will happen while the carbon-dioxide levels will grow from the current 378 PPM to 800 PPM, that will hypothetically occur when all the fuel on earth is burned.” That implies a resource only half as big. Which is it?

    – I’m sure the citizens of Bangladesh will be relieved to know that relocating a third of their country will be quite cheap.

    He did get one thing right: “Unfortunately, some political decisions disregard the opinion of science.”

  38. 88
    Steve Bloom says:

    At a minimum this appears to not be a very good translation, as there is a fair amount of self-contradictory language. But, taking the article on its face:

    He indeed says “There is no proven link between human activity and global warming.” But after some discussion, he then concludes “Therefore I believe that the link between man’s activities and rising temperatures has not been proved completely. Natural factors and the impact of man seem to be interlinked.” The contradiction is obvious.

    Pointing out a couple of other problems, he says “The European Union has established by fiat that a two-degree rise in global temperatures would be quite dangerous. However, this data is not scientifically sound.” Well, for one thing it’s not data. As any careful reader of this site will know, it’s not possible to make hard and fast predictions of exact effects that will be associated with a given increase in temperature. Rather, risk assessment is involved. Later on, he dismisses concerns about sea level rise (which I believe was a big part of the basis for the EU’s two degree figure) by saying a) it won’t happen soon enough for us to worry about and b) rebuilding ports and relocating low-lying populations will be cheaper that Kyoto compliance. The first point is a value judgement that we can disagree with or not; my personal view is that we ought to be worried about whether a temperature rise now will commit us to, e.g., Greenland melting even if we’re confident the major sea level rise won’t happen for hundreds of years. The second point, I think, is just plain wrong (taken on its own terms, that is, since compliance with Kyoto alone won’t do much to halt the sea level rise).

    He also makes the curious claim that “Many specialists estimate the peak atmospheric carbon dioxide concentration at 400 PPM.” I don’t recall hearing this from even one specialist. We’re at 378 now, are increasing at roughly 2 ppm annually and there’s nothing in emissions trends for the next decade would cause a significant reduction in the rate of increase. The impression I have is that the most wildly optimisitic hopes are for a leveling out at 450 ppm, and that even that level assumes strong governmental action we don’t appear likely to get soon enough.

    There’s lots more, but I’ll stop there other than to make the general comment that this article may have a somewhat political basis given the unusual circumstances under which Russia signed on to Kyoto. I would be curious to know if the RC authors can shed any light on this guy.

  39. 89
    Magnus says:

    There also is rumours that Italy and Russia are paining to leave the Kyoto protocol… is that right?

  40. 90
    David Wojick says:

    Re#71, you say “increased knowledge about natural variability has confirmed the consensus view.” I disagree completely. I think our increased knowledge has confirmed two things. First, natural variability is much larger and more prevalent than was suspected just 10 years ago. Second, we do not understand it. My evidence is the great deal of work and speculation that is going on. It fills the peer reviewed journals.

    There are a host of natural mechanisms and phenomena under intensive study, any one of which can in principle explain the recent surface warming record. Indirect solar forcing, for example, or abrupt events, even just emergence from the LIA. We don’t know that they do, but we also don’t know that they don’t, singly or in combination, that’s why we are studying them. The uncertainty has increased dramatically. Or do you think this research is all a waste of time?

  41. 91
    David Donovan says:

    Re 82.

    Please review the post on this site of 3 May 2005
    entitled “Planetary energy imbalance?”

  42. 92
    DrMaggie says:

    On the topic of (plant) ecosystem responses to climate change, Louis Pitelka et al. have written an interesting article on “Plant migration and climate change” for American Scientist (vol. 85 (1997) pp. 463-473) that can be accessed (albeit without figures) on a non-subscription site.

    I found the discussions in the paper on the timescales of dispersal vs establishment especially enlightening – even though individual seeds of a given species are able to germinate far away from its parent plant, that does not guarantee a successful colonization of new territory even if the environmental characteristics of the new site in principle would be well suited for that species. Thus the ability of e.g. a tree species to “migrate” (i.e. change its typical distribution zone) in response to climate change may well be smaller than one might think. The successful movement of entire complex ecosystems – built up from a wide range of plants and animals – could be well-nigh impossible, even if the change is slow.

  43. 93
    Steve Bloom says:

    Re #82: At risk of repeating myself: A link to published, peer-reviewed studies in support of your argument would be nice. (When I say in support of your argument, I mean studies that have analyzed one of the factors you mention, have concluded that the analysis creates additional uncertainty with respect to the consensus view, and have indications of some breadth of support in the field. This latter condition is to cut out some of the more speculative stuff like the “celestial climate driver” discussed in a May 15 RC post.) Before you say I should do the same, first have a look at all of the posts on this site relating to this subject (and which generally are pretty thoroughly footnoted and linked to the relevant studies.) Be sure to include the one on global dimming (May 19).

  44. 94

    Return of the Inquisition
    More kudos to RealClimate. In case you missed it, their response to this recent editorial in the Wall Street Journal, once again, makes it clear that the arguments raised by climate contrarians have nothing to do with real science, and…

  45. 95
    Extagen says:

    I can not for the life of me understand why everyone in the scientific and political world is concerned whether global warming is due to natural events or human beings. The climate is warming! We need to start working on doing what ever we can to slow the process down regardless of it’s cause!

  46. 96
    Michael Jankowski says:

    Re#91 and 93,

    I am simply pointing-out that Dr. Izrael had a similar stance to years ago, which conflicts with the “what happened to him” post of #80. I’m not quite sure how your responses relate to this. Was there another post #82 which was later deleted and replaced with mine?

  47. 97
    Steve Bloom says:

    Re #96: I’m not sure what happened, but the comment numbers do appear to have changed. What was #82 is now #90, and going farther back my #71 was in response to a #66 that is now #68. I wonder if there’s some problem with the software when there are too many posts in the queue at once?

    [Response:Sorry about that. If there is a back-up for approvals the numbering can get confused. -gavin]

  48. 98
    Tomislav Rus says:

    Here’s a link to what Yury Izrael (Director, Global Climate and Ecology Institute, Russian Academy of Sciences and IPCC Vice President) has to say about climate change:

    “Climate change: not a global threat”

    Tomislav Rus

  49. 99

    Bravo for Real Climate, much needed in responding to ignorance like this WSJ article which seem to thrive on apathy and a low sense of esteem for the scientific community. A newspaper such as the Wall Street Journal and many other outlets seem to utterly fail in simply reporting facts. Being from the High Arctic for the last 20 years, right at the front line of AGW, and having personally witnessed rapid changes in our climate, I gladly like to state that some medias are suprisingly good, by reporting just facts, something WSJ might like to do one day, such as increase in twilight brightness due to thermal inversions, the incomprehension by aboriginal elders on what is going on with a massive change in dominant winds everywhere in the Arctic and in some cases with all this open water. But I find WSJ 6/21 editorial completely off base, totally out of sync with our times, in particular with respect to 2005 being yet another very warm year (if not the warmest), amongst a whole lot of recent historical highs all within the last 20 years. Last May WSJ journalists obviously failed to report 30 degree C weather over most of Arctic Quebec with its numerous lakes still frozen, I wonder if they would have written this editorial if they only knew?

  50. 100
    David Wojick says:

    Re #93, responding to my old #82, now #90 (last I looked). You say “A link to published, peer-reviewed studies in support of your argument would be nice. (When I say in support of your argument, I mean studies that have analyzed one of the factors you mention, have concluded that the analysis creates additional uncertainty with respect to the consensus view, and have indications of some breadth of support in the field.”

    I am not referring to studies that have concluded that the analysis creates additional uncertainty for the anthro GHG theory. In point of fact some studies of natural variability do mention inter alia that the theory of anthro warming might have to be rethought, but most do not. Scientific studies almost never explicitly contradict one another, even when that is the intention of the authors, which is not the case here. (I think this is where Oreskes went wrong. She apparently looked for abstracts explicitly contradicting the anthro theory, and found none.)

    The judgement that a study creates additional uncertainty for the anthro theory is mine, not the authors. The logic is simple. If a study provides new evidence, or a new mechanism, for natural variability, that is consistent with what we observe, then that supports the theory that the present warming is natural, not caused by human emissions. Such results are quite numerous.

    Right now the global climate research budget is about $4 billion per year, world-wide. Peer reviewed publications run maybe 10,000 pages per year. A lot of that research is in natural variability, and the results are impressive. The biggest growth area is indirect solar forcing of climate, but other contenders are coming on strong. So it is not a matter of citing this or that study, it is a matter of the direction of climate research taken as a whole.

    Let me draw an analogy. The arguments for the anthro theory are like showing that a suspect in a crime had motive and opportunity. This is a necessary condition for conviction, but it is not sufficient if there are other suspects who also had motive and opportunity. As I read the science there are now several kinds of natural variability under investigation, each of which is capable in principle of explaining the warming in the surface record. Each has its problems, but so does the anthro theory. The jury is still out, because the science is still vibrant.

    [Response: Which kind of natural variability could explain the 20th Century warming?
    Solar variability? Shows no trend since 1940 – see this post.
    Orbital changes? They caused the ice ages, but recent orbital changes are very weak and could not explain warming.
    Volcanoes? Can only explain temporary cooling episodes.
    Internal variability modes of the ocean-atmosphere system? Can cause regional changes that locally mask the global warming trend, but can only cause small fluctuations in the global mean temperature, certainly not a global warming trend of 0.7 ºC over 100 years.
    Concerning the suspect CO2: The gun has been fired, the CO2 is in the air – that’s a measured fact. That increased CO2 leads to warming is not just a “suspicion”, it is a fact of physics that has been known for over 100 years. The amount of warming expected from the CO2 happens to be just right to explain the observed warming.
    For more details on how natural and anthropogenic factors work together in the 20th Century, see the recent paper by Hansen et al. 2005 in Science, presented in this post. See also the further discussion of this under the subheading “A strange temperature graph” here. -stefan]