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Climate Science Update

  1. Nov 27, 2009 #1

    Xnn

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    Science marches on.

    The http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg1_report_the_physical_science_basis.htm" [Broken] for climate change was based on
    peer reviewed literature available in 2006. Since that time,
    there have been a number of newer studies that have contributed
    to a better understanding. These have been put together into a
    http://www.ccrc.unsw.edu.au/Copenhagen/Copenhagen_Diagnosis_LOW.pdf" [Broken] for the meeting in Copenhagen.

    In general, uncertainties resolved since 2006 point to a more
    rapidly changing and more sensitive climate than previously thought.
    There are several interesting sections in the report with lots of vivid
    color photos. However, overall it is a sombering report.
    CO2 emissions are accelerating while temperatures, sea level and
    water cycle increases are all expected to accelerate.
    It's very difficult to conceive the climate tracking anything but
    the upper end of the projections.

    Here are highlights from the new report:


    The full report is available here:

    http://www.copenhagendiagnosis.com/default.html

    Link directly to pdf file:

    http://www.ccrc.unsw.edu.au/Copenhagen/Copenhagen_Diagnosis_LOW.pdf
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Nov 27, 2009 #2

    vanesch

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    I have to say I hate this kind of semi-scientific-political publi-brochure. This kind of stuff is exactly what makes people wary of climate science. This looks like an advertisement !
    That doesn't mean that what's said in there is wrong, but I don't like the commercial way in which it is said.


    Just some things on the surface that shock me:
    From the first grey box, in fact the very first sentence of the report:
    There is also:
    Now how does that rime with figure 2, where we see an almost linear rise of CO2 in the atmosphere since 1980 ?

    It seems to me that especially alarming language is used here, as if one had to promote a certain product.
     
  4. Nov 27, 2009 #3
    It is kinda of a weird way of them to promote their findings though (in a brochure) but we have to think about who this is trying to sway... the common person. This isn't really meant for scientists to use it's meant to be a political tool (which I admit isn't the best thing but nearly all science has political aspects, climate change just has more due to its seeming importance to the world)
     
    Last edited: Nov 27, 2009
  5. Nov 27, 2009 #4

    sylas

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    My reaction is completely the reverse. The problem with this whole area is that there is a lot of public interest and a lot of confusion.

    If we were serious about simply following the scientific literature, then it would be pretty straight forward and you'd get conclusions pretty much like what is in this report.

    However, the scientific literature is written primarily for a different audience. And although the science should be pursued independent of any policy considerations; the reverse is not the case; policy needs to take into account the best available scientific information on matters of relevance.

    It follows that there is a need for scientists to communicate better, to a wider audience; not just the general public but governments and other policy makers. The IPCC reports are driven by this requirement.

    The interaction between science and politics and policy, in any ideal world, should be like the following:
    • The conclusions reached by science need to be obtained without any deference to policy implications of the conclusions. Science ideally seeks answers and confidence limits on those answers based exclusively on what the evidence and research actually can show.
    • The questions and issues addressed by scientists, however, might well be driven by secondary requirements of what is deemed important to know, for policy reasons.

    Precisely how we improve the communication of credible science is a good question; but anything you do along those lines should be in the way of providing accessible information.

    I think this only looks like an advertisement because there is such a gaping disconnect between what is happening in the world of science and what is being debated in the political world. There are a heap of open questions in climate science and all kinds of large uncertainties. But they are not the same as the major uncertainties debated more widely.

    The wider questions seem to be things like... is global warming real? is it caused by human activities?

    The answers to those two questions are actually very straightforward. It's yes, and yes.

    There are riders you can add, along the lines that everything in science is always in principle open to dispute and revision; but for an overview, the "yes" in both cases is about as strong as you can possibly get. The warming is measured. The importance of greenhouse effects is basic physics. And the association of that to human activities is unambiguous.

    These answers don't rule out all other factors; but the strong warming trend of the latter half of the twentieth century in particular is solidly linked to atmospheric composition and a stronger greenhouse effect.

    The relevant open scientific questions are about quantifying the warming trend, along with other effects, refining physical understanding to model it better (a never ending project of continual improvements) and sorting out things like the carbon cycle, the energy balance into the ocean, the feedbacks from cloud and weather and much else beside which bear upon the complex response of the climate system.

    I don't understand your objection here, frankly. The context of this report is a world that is looking at managing carbon emissions as a matter of policy to mitigate against the risks associated with larger changes in the atmospheric greenhouse effect. The report is promoting the need for managing emissions and noting that they are continuing to increase at levels that are right along the high end of the range of projections considered in the most recent IPCC report.

    Figure 2 is completely consistent with the numbers given. The rate of increase IS increasing and you can see quite easily that the increase since 1980 is not linear. Just hold a ruler up against the graph if you want to check. Of course, the proper measure of linearity works from the numbers, not eyeballing a graph, and the numbers are as you have quoted from the report. What’s the problem?

    There are a number of other sources that are attempting to address the gap between what is published in the literature and what is accessible to policy matters or interested members of the public. Not all of them are thoroughly grounded in the scientific literature or well reviewed by directly relevant scientific researchers. This one is, however; and stands as a good summary of technical material, thoroughly grounded in scientific literature, produced by a large group of some of the most active scientists researching on the directly relevant science, and with a high level of oversight and review. I think it stands as a useful resource for helping follow this whole topic.

    Cheers -- sylas
     
  6. Nov 27, 2009 #5

    sylas

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    A better link

    By the way... the home page for this report
    gives easy access to the full report at two resolution levels, an online version, background on the authors, background on the reasons for the report, and so on; which may help understand some of the background to why and how it was written.
     
    Last edited: Nov 28, 2009
  7. Nov 27, 2009 #6

    Xnn

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    From the report:
    I agree that there is some alarming language in the report. However, the prospects
    of significant reductions in emissions are fairly low. As the report points out, emissions
    have only increased and I sense that the Climate Scientist that put the
    report together are very concerned and frustrated. It's apparent that there
    will be a significant climate shift over the next century.

    Anyhow, I also struggle with reconciling the 3 fold acceleration in emissions
    since 1990 while atmospheric CO2 concentrations have increased steadily
    with only the slightest hint of an acceleration.

    From the report:
    The report does reviews CO2 sinks, but jumps rather abruptly to vulnerabilities.
    What's obvious to me is that the sinks have increased almost as fast as emission
    have grown. That is rather odd. Sinks ought to be operating in proportion to
    atmospheric CO2 concentration, precipitation and winds.

    There are 3 major sinks: Plants & soils, the deep ocean and sediments (rocks).
    About 30% of CO2 emissions end up in plants and soils, 25% goes into the deep
    ocean and <1% ends up in sediments.

    The report makes the following statement concerning the deep oceans:

    So, I can only infer that plants and soils have been taking most all
    of the slack; in other words there is some good news that may
    have been overlooked.
     
  8. Nov 27, 2009 #7

    sylas

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    On the contrary. The rate of atmospheric CO2 increase has accelerated as emissions have accelerated. Remember to to look at the percentage change in the rate of increase; not merely the increase itself.

    The major CO2 observatory is the NOAA monitoring station at Mauna Luo. It provides ready access to most recent measurements and rates of change, both for the Mauna Luo site itself and a global estimate.

    The rate of increase varies from year to year; as short term variations that arise from any changes in the global carbon cycle. Over all there is a significant increasing trend in the rate of increase, and a 10 year moving average (for example) shows the rate increasing from around 1.5 ppm/yr to around 1.9 ppm/yr as described in the report. This is a more than a slight hint of acceleration. It is about 27%, though with limited precision.

    The data for emissions is cited to Le Quéré et al. (2009) which is listed as in press, though it has just now come out as advance online publication. See
    • Corinne Le Quéré et al (2009) Trends in the sources and sinks of carbon dioxide, Nature Geoscience, Published online: 17 November 2009 | doi:10.1038/ngeo689
      Preprint available http://www.civicgovernance.ca/files/uploads/Global_CO2_per_capita_report.pdf[/URL].[/list]
      This has been on my to-do list to write about, as it is particularly relevant to another recent thread on carbon cycles.

      This paper notes in the abstract that "fossil fuel emissions increased by 29% between 2000 and 2008", and the text notes an increase of 41% since 1990, as given in the report discussed in this thread. The supplementary information of the paper points us to [url=http://www.globalcarbonproject.org]globalcarbonproject[/url] for the emissions data; also tabulated [url=http://lgmacweb.env.uea.ac.uk/lequere/co2/carbon_budget.htm]here[/url].

      1990 was 6.14 Pg emissions; 2008 was 8.67. The uncertainties are around 6%. This is the 41% increase.

      There link from emissions to increasing atmospheric levels is surprising complex; but to a first approximation about 40% of emissions remain in the atmosphere.

      In any case, the increase in atmospheric CO[sub]2[/sub] is from about 1.5 ppm/yr to 1.9 ppm/yr: around 27%, but with a substantially larger uncertainty given the natural variations on top of the trend.

      This is not a discrepancy; we are measuring two different things, which are strongly related, but should not be expected to simply have the same value.

      Cheers -- sylas

      PS. Xnn, you'd be interested in Le Quéré et al (2009). It is looking at all those details of sources and sinks in the carbon cycle.
     
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  9. Nov 27, 2009 #8

    mheslep

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    I wonder where the balance of the CO2 emissions go - some to the oceans but surely not all?
     
  10. Nov 28, 2009 #9

    sylas

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    Some goes to terrestrial carbon sinks. It all has to go somewhere, and "land/ocean/atmosphere" is a simple classification of the many sinks involved.

    Within this broad classification there are all kinds of sinks and many unknowns. The ocean is a number of different regional oceans, which are not uniform, and involves exchanges over all depths, which are not clear. The land sinks are especially hard to figure out. Generally speaking the fraction of carbon that is taken up into the terrestrial sinks is estimated by seeing what is left over after the atmosphere and oceans are considered. There are attempts to further identify where the various terrestrial sinks can be found; but there's no complete accounting and no way to get a direct measurement of all the land sinks. Some wag once described this as the "missing sink", which now makes a good search term to get started finding relevant research.

    The "airborne fraction" is the best known; it is around 40% to 45%. That leaves 55% to 60% for other sinks. Page 12 of this report gives a quick summary. The paper by Le Quéré that I have cited is an important contribution and there is a lot more research on this if you want to keep hunting. From Le Quéré (2009):
    Combined evidence from atmosphere and ocean observations constrains the mean uptake rates of land and ocean CO2 sinks to 2.6±0.7 and 2.2±0.4 Pg C yr−1 for 1990–2000, respectively11,19–22.

    The emissions amount includes both direct industrial emissions (which is what has increased by 41% since 1990) and also emissions from land use change, especially deforestation. Put together As noted previously direct emissions in 2008 were 8.67 Pg. To this we add about 1.2 Pg from land use change (an estimate from Le Quéré 2009) for 2008, giving 9.9 Pg total in 2008.

    The atmospheric increase was 1.66 ppm in 2008, which you can simply multiply by 2.13 to get the atmospheric uptake of 3.54 Pg. This varies a lot from year to year, over recent years 1.9 ppm/yr is about the current rate; pretty close to 4 Pg.

    Further breaking it all down is an ongoing open question; sorting out how all carbon cycle will continue to work as it keeps being loaded with carbon is also a major open question and significant uncertainty. The "airborne fraction" is about 43%, and most research indicates this is increasing. This is described in the Copenhagen Diagnosis; and more detail is in Le Quéré (2009).
    On average, 43% of the total CO2 emissions each year between 1959 and 2008 remained in the atmosphere, but this fraction is subject to very large year-to-year variability (Fig. 2a). This ‘airborne fraction’ increased on average by 0.3±0.2% yr−1 between 1959 and 2008. There is a 90% probability that this increasing trend is significant taking into account the background variability (Methods). The trend and its significance are sensitive to estimates of LUC emissions, which have large uncertainties.​


    It seems likely that the trend of an increasing airborne fraction will continue.
     
    Last edited: Nov 28, 2009
  11. Nov 28, 2009 #10

    Xnn

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    Sylas;

    Thanks for the link to the Le Quéré paper. I see that she notes the problems
    of quantifying sinks and also explains how economic data is used to measure
    emissions along with a host of other estimates. So, there is considerable
    uncertainty with all of this.

    Her charts show both land and ocean sinks trending more negative,
    although in 2008 there was a small up tick in ocean sinks due to La Niña
    and the southern annular mode:
    Anyhow, it's curious that the sinks are trending towards more negative values
    and I wonder if maybe perhaps the GDP method of estimating emissions is biased
    as the residual chart (figure 2 e) appears to generally be accumulating.
     
    Last edited: Nov 28, 2009
  12. Nov 28, 2009 #11
    Sylas posted:
    Nice try; but such speculation is political in nature not scientific...38,000 scientists (who signed correspondence to the UN) and others who wrote the US congress strongly disagree about man made causes of climate change.

    Even in Australia, home of the uopdated report referenced by Silas, government there remains in turmoil over man made global warming and carbon reduction plans. The Australian senate appears likely to reject such legislation for plans passed by their house.

    The legitimate answers to those two questions is ACTUALLY dependent on valid data, valid scientific theory, and models that work...NOT what East Anglica "scientists" concocked/invented/created fraudulently for the IPCC.

    The earth IS likely warming, just like it has thousands of times in the past...but the earth has emerged from numerous ice ages, some when the earth was virtually covered in mile thick ice...and it will most likely cool as well in the future, also repeating past changes long before man was here.

    One recent recent study shows that infrared radiation from a cabon thick(er) atmosphere actually increases, not decreases, as climate models would have you believe. So there is much left to learn before we declare "victory" in our understanding of climate...besides, whose to say that a warmer climate would not be a big net plus??? The Vikings, who tried to settle Greenland when it was previously warm enough to be productive for farming, would likely have argued HOORAY for some warming....
     
    Last edited: Nov 28, 2009
  13. Nov 28, 2009 #12

    sylas

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    That's "she", for what it is worth. http://lgmacweb.env.uea.ac.uk/lequere/ is Professor of Environmental Sciences at the University of East Anglia. Her home page has some good further links.

    Yes, it is interesting; the residuals are large, which is a good indication of how much still is unknown about the carbon cycle.

    I don't think GDP is used to estimate emissions. The connection between GDP and emissions is an observation given the data on each one, and the paper speaks of a need to decouple this observed relationship. Emissions are estimated from energy statistics, according to the associated http://lgmacweb.env.uea.ac.uk/lequere/co2/carbon_budget.htm webste, same link as I gave previously for the tabulation of data used in this paper.

    All the charts in figure 2 have error bars indicated. The largest uncertainties are associated with carbon sinks on the land; both the indirect emissions (figure 2a) from land use changes and the highly uncertain terrestrial sinks (figure 2c).

    The residual is basically a count of how much carbon is missing after they add up the emissions and the estimates for sinks. The comment in the paper itself is:
    Our estimates of sources and sinks of CO2 were based on largely independent data and methods. Thus, when all the sources and sinks were summed every year they did not necessarily add to zero, because of the errors in the various methods. The sum of all CO2 sources and sinks, which we call the ‘residual’, spanned a range of ±2.1 Pg C yr−1 (Fig. 2e). This residual was not explained by the atmospheric CO2 growth rate, the CO2 emissions from fossil fuel combustion or the ocean uptake, because the uncertainties in these components were much smaller than the variability of the residual. Errors in LUC flux may explain a small part of the residual, for instance during the late 1990s, when fires in Indonesia were partly caused by land clearance taking advantage of the drought conditions17. Our fire-based LUC anomalies for 1997 were 0.7 Pg C greater than normal and account for one-half of the residual for that year. Overall, the residual was most probably caused by the regional responses of terrestrial vegetation to climate variability, indicating that land models overestimated the response of vegetation to the relatively cool/wet La Niña-like climatic conditions of the mid 1970s and underestimated the response to the volcanic eruption of Mount Pinatubo, in the Philippines, in the early 1990s. This later underestimation has been explained elsewhere as resulting from a missing response in the models to the aerosol-induced increase in the diffuse-light component of surface irradiance, and the subsequent enhancement of light penetration into vegetation canopies29.

    From the tabulations, you can use a spread sheet to verify that in fact, the residuals are on average slightly positive with a small trend to being more positive; but of course they are all over the place in general. (Mean 0.273, sd 0.957) (Caution: the tabulation uses slightly different sign conventions to the diagram.) If the paper is correct in supposing that the greatest part of this is due to inaccuracies in estimating how vegetation is taking up CO2, it would mean that some years over estimate and other years underestimate the amount of carbon taken into this sink.

    A positive residual means either over estimated emission or (much more likely) underestimated sinks. Hence: "missing sink".

    Cheers -- sylas
     
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  14. Nov 28, 2009 #13

    Mark44

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    The home of the Hadley CRU, which has come under a serious cloud in the last week or two.
     
  15. Nov 28, 2009 #14

    Mark44

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  16. Nov 28, 2009 #15

    sylas

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    That's a classic ad hominem; and worse, an indirect smear. It's highly inappropriate.

    She's not in the CRU. She's not in any of the emails, except in one case that was an enormous cc to hundreds of scientists all over the world. There's nothing linking her to anything in the whole CRU emails brouhaha. It isn't Hadley CRU, by the way. The Hadley Centre is part of the UK Met Office, a different thing entirely. It's a common confusion. And finally, although there are issues showing up in the hacked emails affair concerning how some CRU personnel responded to the excessive flood of FOI requests they were receiving, there is nothing there whatever to indicate anything wrong with the science.

    None of the other co-authors to the paper are in the CRU either. Indeed, Le Quere is the only one of the 31 authors from the Uni of East Anglia. The others come from all over the world, and their contributions and affiliations are in the paper.

    If you think there's a science issue, then that might be something for this forum, in a different thread I would suggest. Matters of policy and politics, such as how to deal with FOI or adequate openness with data and so on belong in the Politics and World Affairs forum.

    I do understand that people are concerned, and want to have questions answered in relation to the hacked files. I have chosen to be firm to underline that this is actually very serious. Accusations of fraud, or malfeasance, or scientific misconduct, are serious matters. It's not okay just to slip in an insinuations like this in a public forum without some credible basis. Being at the same university doesn't count. Heck; even the emails don't count for much; though that's a different subject for the other forum since it isn't actually about the quality of the science itself. The thread to use at present is [thread=355595]this one[/thread] that is mainly about the hacked files affair.

    Also, thanks for picking up my Freudian slip. I've fixed it!

    Cheers -- Sylas.

    PS. How many Freudian psychologists does it take to change a light bulb?

    Answer: Two. One to fit the new bulb, and another to hold my p... THE LADDER. I mean the ladder. :blushing:
     
    Last edited: Nov 28, 2009
  17. Nov 28, 2009 #16

    Xnn

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    Naty1 & Mark44;

    There is clearly a heated political debate concerning what to do about
    global warming and that is all well and good. However, the science is
    robust enough that attempts to suggest that CO2 emissions are not
    at the root of it fall short of being credible.
     
  18. Nov 28, 2009 #17

    sylas

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    It is not speculation. It is not political. It is basic science independent of any political or policy concerns, based on measurement and elementary physics, and not in any credible scientific dispute. It is a starting point for looking at all the many more interesting open questions in climate science that are now a focus of active research and investigation. It is also a good starting point for the goal of basic science education, which is what I see as the main role of physicsforums.

    These two points don't resolve the big political questions surrounding climate; but they do form a kind of basic solid ground that can be used no matter what your political or policy preferences.

    Measuring global warming

    The measurement of temperature increase can be seen in multiple independent research efforts, and they all give the same result to within measurement accuracies; a strong overall warming trend over the twentieth century, becoming particularly strong since about 1975, generally stronger over the land than the ocean. There is no published research indicating this is incorrect or giving any substantially different result. It really ought to be an elementary starting point for the scientific discussions of how the warming trend is measured, what values can be given to it, what causes it, how it is distributed regionally, and so on.

    References:

    The cause of warming

    The measured warming trend is substantial, and has a cause. There have been many factors that are involved in the changes of global temperature over Earth's long history. The change in this specific instance is primarily from an enhanced atmospheric greenhouse effect; and that is being driven by human activities.

    There are still many open questions about quantifying the temperature response of Earth to the changing energy balance. It is a solid discovery, however, that human activities have made a substantial change to the Earth's atmosphere, and this has substantially increased the atmospheric greenhouse effect. The factors the drive changing temperatures are called forcings; and all the research that actually quantifies these gives the same result; anthropogenic greenhouse effect is the dominant factor over the twentieth century and especially in the latter half, where we have the best measurements and the strongest warming.

    References:

    It would be easy to go on; but my aim is not to simply overwhelm with references. The point is that the answers to these two rather basic questions that I am giving are not politics, but really are science. Furthermore the confidence given in these answers is very high.

    There are other questions, such as estimates of sensitivity, or details of the carbon cycle, or all kinds of other things, where the literature will be expressed quite cautiously and with acknowledgment of large uncertainties.

    The two questions I have proposed, however, are not really in that category. They are legitimately discoveries; and a backdrop to all the truly open questions. Everything in science is in principle open to question and revision; you never get absolute certainty in anything. But IMO there's really not any credible prospect of getting these questions answered with any meaningful additional confidence -- only with more precision.

    I appreciate that there are many people who are skeptical of the answers I have given to these two questions. The question is -- is there any actual scientific basis for withholding basic assent to these answers? If so, then given the guidelines for the forum, you should provide some peer reviewed reference, or credible equivalent, and we can look at the scientific case on its own merits. I don't think there is any such literature except possibly a handful of isolated and minimal impact papers of dubious worth on their own immediate merits; but I truly am interested and open to suggestions if you disagree. Just make sure that they do address the questions at issue; and not some other less strongly constrained matter.

    Other matters

    In your post, you raise a number of further peripheral matters that I think would be better taken up elsewhere, if at all. I am quoting extracts; linked back to the original as usual.
    The petition you allude to is notorious; and further discussion on that belongs in the politics forum. The implosion of our liberal party over climate issues would be very relevant in the politics forum. There is no indication whatever of invalid data or theory in the CRU hack affair, but discussion of that belongs in the politics forum. Your comment that the Earth likely IS warming appears to be agreement with my first point; if you can just recognize that this is actually a measurement. Changes in the past and in the future, for all kinds of reasons, are not in dispute. This says nothing about the specifics of what in particular is driving the change in the present. Your recent study requires a citation. It may well be a paper I have recently blogged about, along with three others in my PF blog as https://www.physicsforums.com/blog.php?b=1493 [Broken]. If so, it has been discussed here before; but I'm very familiar with it and happy to consider it again in the main forums. The question of whether changes in climate are "good" or "bad" is another irrelevancy to the scientific question raised here; let's not have politics or policy distort consideration of scientific answers to the two questions.

    Cheers -- sylas
     
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  19. Nov 28, 2009 #18

    Mark44

    Staff: Mentor

    There is also a scientific debate about whether the earth is warming at all, with some climate scientists predicting a major cooling period in the next 20 years in their peer-reviewed paper (Zhen-Shan, L. and S. Xian. 2007. Multi-scale analysis of global temperature changes and trend of a drop in temperature in the next 20 years. Meteorology and Atmospheric Physics, 95, 115–121.)

    For science that is supposedly "robust" there are certainly lots of scientifically trained people who aren't buying it. The Global Warming Petition Project (http://www.petitionproject.org) has had over 30,000 signers, of which over 9,000 hold PhDs. The following is one of the two paragraphs that make up this petition.
    “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.
    Moreover, there is substantial scientific evidence that increases in atmospheric carbon
    dioxide produce many beneficial effects upon the natural plant and animal environments
    of the Earth.” ​
    Information about the signers includes their professions, broken down as follows (I have rounded the numbers)
    atmospheric, environmental, or Earth sciences - 3800
    mathematics or computer science - 900
    physics and aerospace sciences - 5800
    chemistry - 4800
    biology and agriculture - 3000
    medicine - 3000
    engineering and general science - 10,000

    The academic credentials of the signers are broken down by degrees attained, with ~9000 PhDs, ~7000 MS, ~2600 MD or DVM, and ~12,700 BS or equivalent.

    Granted, science is not and should not be a democratic process, so the numbers for and against a particular theory are for the most part irrelevant. My point is that for science that is "settled" there sure are a lot of people who don't think so.
     
  20. Nov 29, 2009 #19

    sylas

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    Excellent... a valid reference. I am genuinely interested in this and appreciate the link; I have found the paper and had a look at it.


    The method used is a kind of curve fitting process called "Empirical Mode Decomposition". This is similar to fourier analysis, but it is performed in the time domain. I had not heard of it before, but it certainly looks very interesting indeed. There seems to be significant interest in this technique, and I am going to look at it more carefully and consider using it myself as possible analysis method.

    A good reference to explain the method (and more readable) is:
    Wu et al (2007) is a mathematical paper rather than a climate paper; but this publication uses the global temperature anomaly as an illustrative example, which makes it particularly relevant. Professor Huang is the major developer of the method, which is also the basis for the Hilbert-Huang transform.

    In the process of looking at this I am now drafting a post that may be better in a thread of its own; but I want to post this much now to acknowledge a useful reference with thanks. This method, and both the papers, actually obtain pretty much the same underlying trend as the references I have given. Using this technique, it appears as a residual function after removing the "stationary" (quasi-periodic) intrinsic mode functions, which represent cyclic variations in the signal. The trend is not linear; but it gives the same total amount of warming as other methods I have cited above -- as we should expect, since this is still precisely the same physical measurements involved. That is, this is not new data. This is clear in both the references cited. Furthermore Lin and Sun (2007) explicitly identifies CO2 as the major factor in the trend; ironically it therefore is also answering "yes" to the two questions I have proposed.

    The point at issue is the added variance on top of the central trend from a multi-decadal cycle revealed in the analysis; and for which no physical cause is known -- as the reference itself makes clear. This variance is exceptionally large in the Sun and Lin paper, and hence leads them to propose the possibility of an extended but temporary fall in global temperatures in coming decades. The fall is explicitly temporary, as the multi-decadal variance, by definition, has no trend. There are reasons to be dubious of extending the analysis as a projection in this way; but I'll leave that to a subsequent post.

    The Sun and Lin paper has not had much impact at all. The other paper gives a smaller magnitude for the multi-decadal cyclic component and no expectation of a fall in temperatures. Neither one, I suggest, can really be used to give a safe projection; but I'll take that up later.

    I don't dispute your final sentence; nor do I find it all that unusual. I know of several such cases like this, where science is disputed by a lot of people, including many who have some science training, despite the points at issue being considered settled by almost all the scientists actively working on it. However, why that occurs and to what extent is off topic for this thread, and indeed for this whole Earth forum.

    If there are actual scientific arguments to raise, that can be done here; and as you note the numbers don't matter. As Einstein once famously remarked, in response to a pamphlet entitled 100 Authors Against Einstein: "If I were wrong, one would be enough."

    Cheers -- sylas
     
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  21. Nov 29, 2009 #20

    vanesch

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    Scientific communication, especially towards the public, should have some soberness to it. Note that it's not only in climate science that a certain way of communicating in an advertisement-style works on my nerves ; I already had that feeling in my own original field of particle physics, when crazy claims of "exploring the big bang" and so on were made in order to advertise for the LHC for instance.

    I think in the long term, science wins by having some soberness to it - although immediate funding maybe not.

    Indeed. That's my point. This report isn't at all like this, and it is what is disturbing me.

    The accessibility is not to be confused with trading emotion and rhetoric for complication.

    No, it looks like an advertisement because the same communication techniques are used as in advertisements: implicit associations (look at all the - beautiful, that's true - irrelevant, but emotionally loaded pictures that are scattered around the report (of dried-out trees in a desert and so on) ; look at all the emotionally engaging qualifiers used throughout the text. This report is not just trying to convey information, it is trying to convey a desire for action. Like a commercial is trying to convey a desire to buy or something and uses similar techniques.

    You can see this by the imbalance between the statements. For instance, the *greening* of the Sahel and part of the Sahara is mentioned only very briefly (although scattered with "drying out" pictures). Even though it is said that this is probably an important effect, nowhere this is found in any conclusion. The fact that temperate regions might receive MORE precipitation is also not to rhyme with the general spirit of a barren, hot, dried-out world they want to sell. All this is pretty much "advertisement language". This is not "popular science" simplification.

    When you look at a pseudo-scientific ad for a new SUV, you might see similar things: some scientific data about emissions, rpm/couple, braking,... with scattered pictures of strong men on an adventurous trip in wild nature and pretty girls full of admiration, trying to convey the desire to buy such a car, by association with certain emotions. It's no different here.
     
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