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Sorting out Settled Science from Remaining Uncertainties

Posted on 1 November 2011 by dana1981

Much ado is made about the phrase "the science is settled," but to what does the phrase refer?  There are certainly a number of climate issues for which the scientific evidence is so conclusive and robust, they can reasonably be called "settled."  For example, the fact that the increase in atmospheric CO2 levels is due to human emissions, the fact that the planet is warming (as confirmed once again by the BEST study), and the fact that the increase in CO2 is responsible for a substantial fraction of that warming.

settled science

New Scientist has published a useful resource on this subject, discussing climate knowns and unknowns.

Fake Skeptics vs. Real Science

Of course, the climate "skeptics" who want to delay and prevent action to address global warming love to argue that "the science is NOT solved."  And of course it will always be possible to make that argument, because there will always be aspects of the climate system which we don't fully understand, as is the case for every field of science.  For example, we know that there is a global energy imbalance, with more incoming than outgoing energy due to the increased greenhouse effect, which is the underlying cause behind global warming.  However, it's difficult to precisely determine that energy imbalance using either satellites or measurements on Earth.

Over the past decade, the warming of global surface temperatures has slowed down.  Studies have shown that climate model runs do predict that there will be periods on the order of a decade during which we expect to see this slowed rate of warming, even though the underlying man-made global warming signal remains  in place (i.e. Santer et al. 2011):

"Because of the pronounced effect of interannual noise on decadal trends, a multi-model ensemble of anthropogenically-forced simulations displays many 10-year periods with little warming."

If climate models were perfect, they could anticipate these short-term periods of little surface warming.  However, there are many different effects which can cause short-term temperature changes.  There are also important parts of the climate which we don't yet have good measurements for, such as the amount of heat in the deep oceans, and the amount of aerosols in the atmosphere.  Because climate scientists had a difficult time explaining the short-term slowing of the surface warming trend over the past decade, Kevin Trenberth infamously said (in a stolen email),

"The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't."

There have been a number of recent studies attempting to address this short-term slowed surface warming, which were nicely summarized in this article by Paul Voosen, which quotes a number of different climate scientists who are studying the issue.  Unfortunately, certain climate "skeptics" have grossly misrepresented these scientists, depicting them in a mocking caricature, and claiming that in trying to determine the cause of the slowed surface warming, they are just making "excuses."  Such is the state of the climate denial community, that they equate scientific research with making excuses.

Many Causes

But back to the science and the causes of the slowed surface warming.  As Susan Solomon put it,

"There is no silver bullet. In this case, it's four pieces or five pieces of silver buckshot."

Skeptical Science has discussed many of these contributors to the short-term slowed surface warming.  For example, some heat has been temporarily transferred to the deeper ocean layers, as Meehl et al. (2011) demonstrate (Figure 1).

Figure 1: Diagram illustrating "natural variability" with a long-term warming trend.

Additionally, increased human aerosol emissions (primarily from Chinese coal combustion), and more frequent La Niña events over the past decade have had a short-term cooling effect, as Kaufmann et al. (2011) found.  A decrease in stratospheric water vapor may have added another short-term cooling effect, as Solomon et al. (2010) concluded, and relatively small volcanic eruptions may be having a larger cooling effect than expected as well, as Vernier et al. (2011) suggest.  On top of all that, we just experienced an unusually long minimum in the 11-year solar cycle.

Despite Short-Term Uncertainty, Long-Term Warming Continues

In short, it appears that nearly every significant short-term effect on the global surface temperature was in the cooling direction over the past decade.  However, significant uncertainty remains regarding how large of a role each effect played in the short-term slowing of the increase in global surface temperature.

Kevin Trenberth believes the warming of the deep oceans was a major contributor.  James Hansen, on the other hand, believes that the increase in atmospheric aerosols can explain most of the offset, and that based on recent research, that the ocean doesn't mix heat into its deep layers as well as climate scientists thought.

If Hansen is right, there is a smaller global energy imbalance, which means less heat "in the pipeline" (less warming that we will experience after we stop increasing atmospheric CO2).  However, it also means that aerosols are offsetting more greenhouse gas warming than we previously thought, so as our air becomes cleaner, it will reveal more previously-hidden warming, as discussed in Hansen et al. (2011).

This means that although climate scientists still can't perfectly explain the temporarily-slowed warming of surface temperatures, they know that regardless of the explanation, there is much more global warming left in store.  We know this because of the settled science discussed above.  We are increasing the amount of CO2 in the atmosphere, and through the greenhouse effect, that increased CO2 will continue to warm the planet.

The short-term effects can only temporarily dampen (or amplify) that long-term man-made global warming trend.  For example, aerosols only remain in the atmosphere for a year or two before they're washed out, so the aerosol cooling effect can only continue to offset greenhouse gas warming if we continue to pump more and more aerosols into the atmosphere.  However, because they have adverse impacts on human and environmental health (i.e. see the air in China, literally), most countries are trying to reduce their aerosol emissions (including China).  El Niño and La Niña are cycles which cancel each other out over the long-term.  And while we can't predict how solar activity would change, a solar minimum as big as the largest in the past several centuries would only offset 7 years' worth of man-made warming (Figure 2).



Figure 2: Global mean temperature anomalies 1900 to 2100 relative to the period 1961 to 1990 for the business as usual scenario. The red line represents temperature change for current solar levels, the blue line represents temperature change at Maunder Minimum levels. Observed temperatures from NASA GISS until 2010 are also shown (black line) (Feulner 2010).

The Climate Casino

We can think of the climate like a casino.  Any given gamble is unpredictable, and you may very well take money from the casino in a given bet or after a given day's worth of gambling.  But the odds are stacked in the casino's favor, so it is certain to make money on average from all the bets that are placed.  The longer the timeframe and the more bets that are placed, the more certain the casino can be that it will make money from the gamblers.

Likewise, over short timeframes, global temperature changes can be difficult to predict.  However, over the long-run, the underlying man-made global warming trend will dominate as all of those short-term effects average out.  Right now the gamblers are on a lucky streak, but it simply cannot last indefinitely.  The casino will aways win out in the end, as will the long-term man-made global warming signal.

And in keeping with the casino analogy, by continuing to pump more and more greenhouse gases into the atmosphere, we are all taking a very big gamble with the future of the global climate, and thus with the future of the human race.

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Comments

Comments 1 to 37:

  1. I have a couple of questions, both of which are OT but I don't know where else to ask them.
    1 I receive SKS e-mails linking to articles on climate change and wonder why so very many of them (probably 80%)are of a skeptical or denialist nature - is this a conscious attempt to provide 'balance', or because there are just so many denialist articles online?
    2 ACC will affect the entire globe but there seem to be very few articles on SKS that deal with the effects that can be expected in the tropics - almost all non-global articles seem to deal with the US or Australia. Is this because there a few articles/papers concerned with Africa, tropical Asia etc.?
    Sorry for the OT questions but I don't know where else to ask them.
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    Response:

    [DB] Thanks for the questions!

    1.  The latter (there are just so many denialist articles online).  But I note that the volume of neutral or pro-ACC scientific papers dwarf those anti-ACC articles appearing in the scientific literature.

    2A.  There are indeed relatively few articles dealing specifically with the tropics on SkS relative to those dealing with other regions, such as the poles.  The biggest reason for that is the ACC effects initially are being realized in the polar regions due to polar amplification effects.  It is those amplification effects that are causing regional warming (initially mostly in the Arctic) which are causing changes which will be felt globally.  Hence the focus on those areas.

    2B.  Many non-global articles that focus on the US or Australia do so to counter the sheer volume of denier articles coming from, and based on, those areas.

    HTH.

  2. Love the analogy of the gambler in a casino! With exponential growth in greenhouse gases under a business-or-usual scenario, the fake skeptics are like gamblers betting double or nothing in a futile attempt to recover their losses.
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  3. @cliffeking #1:

    Are you sure that the emails you are receiving linking to skeptical/denialist articles are from this Skeptical Science website?
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  4. @Dana:

    Please add a footnote defining the "Maunder Minimum."
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  5. Hi Dana et al,

    Over the last decade it seems that, according to the PIOMAS data, something in the region of 6,000 cubic kilometres of Arctic sea ice has turned to water. This is much faster than the 30 year trend.

    The energy invested in this phase change is huge: 333Joules per gram of ice melted. The same amount of energy would raise the temperature of one gram of water by 80°C.

    So quite a lot of "missing" heat may have gone onto the melting in the Arctic.

    If the Arctic sea ice were to disappear completely, as it looks very likely to do by 2016 +/- 3 years, one would then expect the global temperature to rocket.
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  6. meagain @6
    600 cu km of ice loss per year would require some 0.2 zJ to melt. That is small compared to rises in annual Ocean Heat Content which are twenty times bigger (at least). So on a global scale the Arctic sea ice melt is not so big. But for the Arctic, the impact has got to be large.
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  7. I fear a return of solar activity, as the deniers will then say it is the sun now, it was the sun, and it will always be the sun.

    A little bit of luck could turn this either way (ie a heat wave/El Nino in the US before the next election would put global warming back on the agenda; a strong solar showing could feed the deniers for years).
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  8. @ John Hartz#4
    Seeing as I signed up to receive e-mails from this very site and have not signed up to any of the far-too many denier sites, I think that, yes, the e-mail links are from SKS. Anyway, HTH has provided an explanation for this above.
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  9. You learn something everyday. I didnt know you could receive email from SkS. I found it now. Thanks/
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  10. @cliffeking #1 and #8:

    In your first post you state, "I receive SKS e-mails linking to articles on climate change and wonder why so very many of them (probably 80%)are of a skeptical or denialist nature..."

    To the best of my knowledge, the only broadcast emails from Skeptical Science are the daily notices about new articles (including the Weekly Digest) that have been posted on SkS. Your claim that 80% of this material is "skeptical" or "denialist" does not make sense to me.
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  11. SkS also sends out daily emails of links to outside climate stories/studies/etc. These are links which have been added via the SkS Firefox plug-in by those who have it installed and use it. Those people generally keep an eye out for new (or repeated) "skeptic" myths to add to the database. Thus most of the links in the email are from "skeptics".
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  12. @dana1981 #11:

    Thanks for the clarification. I now presume that Cliffeking #1 was referring to emails generated by the SkS Firefox plug-in.
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  13. To learn more about the SkS Firefox plug-in system, click on the "Software" button embedded in the SkS toolbar.
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  14. @actually thoughtful writes: "I fear a return of solar activity, as the deniers will then say it is the sun now, it was the sun, and it will always be the sun."

    Well in many ways they're right -- best first to agree with them that the energy for the warming comes from the sun -- always has, always will -- and therefore the rate of warming will vary according to the sun's output. Then when they're nodding in agreement go on to say that the real issue is that we're increasing the thickness of the duvet on the bed; so as the central heating provided by the sun turns up, under the covers we start to overheat.

    In other words the concentration of CO2 in the atmosphere is purely passive -- just like a duvet on the bed -- but as it thickens, the heat it traps raises the temperature to uncomfortable levels.

    This explanation usually works.
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  15. Only one of the three examples for settled science (presented in the first paragraph of the article) is valid fact. The other two examples are conclusions, not facts.

    It IS a fact that the Earth’s surface has warmed.

    To claim as fact that "...the increase in atmospheric CO2 levels is due to human emissions..." assumes that the 90% (give or take) of Earth's CO2 which resides in the oceans isn't also a significant contributing source of atmospheric CO2.

    To claim as fact that "...the increase in CO2 is responsible for a substantial fraction of that warming" assumes that the feedback role of water vapor and clouds is factual as well. This isn't the case at all. It’s assumed that water vapor and clouds must amplify the raw CO2 warming to produce the harmful warming attributed to manmade CO2. Without this assumption, there’s no case against manmade CO2.

    Explaining the slowed surface warming is especially problematic. If natural forces are powerful enough to cool and offset warming attributed to manmade CO2, might they also be powerful enough to cause the warming attributed to man to seem greater than it really is?

    Who really believes that the science is settled? This is a political question. Too many scientists have yet to embrace AGW to consider the science to be settled.
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    Response:

    [DB] "Too many scientists have yet to embrace AGW to consider the science to be settled."

    As in more than 2-3?  You must cite specifics with links to sources to back up your assertions.

  16. daisym - "Only one of the three examples for settled science (presented in the first paragraph of the article) is valid fact. The other two examples are conclusions, not facts."

    Sadly, daisym, all three statements are settled facts. I strongly suggest you follow the links embedded in those three statements in the OP, and look at the copious evidence that supports them.

    Unless you can point out some references (preferably peer-reviewed) that indicate CO2 rise is not due to our emissions? Or that CO2 does not increase the greenhouse effect, or that the 4% water vapor rise over the last 30-35 years is not acting as a feedback? Otherwise, you are simply making unsupportable denialist claims.
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  17. daisym : "Too many scientists have yet to embrace AGW to consider the science to be settled."


    Very subjective statement there : care to back it up with a number for that "too many" assertion ?
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  18. 15, daisym,

    The ocean cannot be contributing to the buildup of CO2 in the atmosphere because it is, in fact, itself absorbing a large amount of the anthropogenic emissions (i.e the amount of CO2 in the ocean is measurably increasing, not decreasing).

    Visit here and here for more information (to start).

    As far as your claims of assumptions... they are false. You are yourself making a great number of (false) assumptions about the science without understanding it, but I can't direct you to just one or two links to settle that matter, because the gap is too large.

    You need to study more, and assume less. You will find that the answers to most or all of your own assumptions and misconceptions can be found on this site if you take the time to look, read and understand.

    The question of who believes that the science is "settled" (itself a strawman argument) not a political question, and is not in doubt. That some would like to make it seem to be a political question is true. That a very, very small but vocal number (like Spencer and Curry) can fool people such as yourself is true.

    But if you were a skeptical person, you would learn more, understand more, and see through the illusions they present.
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  19. Daisy, I suggest you click the links in the article, which show that these examples are indeed facts/settled science. Your claims to the contrary are simply wrong, and based on a misunderstanding or lack of understanding of the scientific evidence discussed therein.
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  20. If natural forces are powerful enough to cool and offset warming attributed to manmade CO2, might they also be powerful enough to cause the warming attributed to man to seem greater than it really is?
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  21. Thanks for your feedback.

    Please see:

    http://en.wikipedia.org/wiki/List_of_scientists_opposing_the_mainstream_scientific_assessment_of_global_warming

    This link will provide names of scientists who disagree that the science is settled. There's no point to include the Oregon Petition or Sen. Inhofe's list of 700. Others have already managed to discredit ALL 30,000 names on the Oregon Petition, and Inhofe's 700, as well. Make sure any such list includes the names of Professors William Happer, Harold Lewis, Ivar Giaever, Fred Singer, Roy Spencer, Patrick Michaels, Bjorn Lomborg, Ian Plimer, John Christy, and Roger Pielke, Sr.

    Also see:

    www.esrl.noaa.gov/gmd/icdc7/proceedings/abstracts/gruberFF335Oral.pdf (Oceanic Sources and Sinks for Atmospheric CO2 -- Gruber et al). Apparently, outgassing of CO2 is occurring in some areas, with uptake occurring in other areas. Do the oceans outgas only manmade CO2?

    I find it curious that no one commented on a question I raised: If natural forces are powerful enough to cool and offset warming attributed to manmade CO2, why aren’t they also powerful enough to cause the warming attributed to manmade CO2 to seem greater than it really is? It’s the $64,000 question.
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    Response:

    [DB] Quite frankly, everything you've written is known to be incorrect (it's a style called Gish Gallop). You could find it all out for yourself, if you wanted to, simply by using the Search function in the upper left of every page here.  Ranging from the Oregon Petition, Inhofe's list, just about all of the individuals you name, to CO2 oceaninc fluxes, natural vs manmade warmings, attribution forcings (to name but a few stream-of-conscious denialist memes), all have been looked into here at Skeptical Science.

    I, for one, find it curious that some continually aver things to be "natural" in origin without having taken the time to actually get a handle on the science for themselves.  And this especially applies to those who have been commenting here for as long (over a year and-a-half) as you have.  That's the $64,000 question.

    No one says understanding a multi-disciplinary field like climate science would be easy.  It's not, if you want to get a good grip on the details.  But the details are all readily available, for those interested in learning.

  22. John Hartz@10
    If you had carefully read my initial comment and the moderator's response, and taken note of Scaddenp's post @9, you would have realised that yes, SKS, does send out e-mails linking to online and peer-reviewed articles, that I was not mistaken in thinking the mail I get was from SKS, and you would not have needed Dana1981 to 'clarify' things for you. It's a bit irritating to be told I'm wrong when the commenter writes from a position of ignorance.
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  23. daisym, I noticed your question when I got online (5:12 pm my time) and was going to respond. Then I noticed that you berated us for not answering the question just 11 minutes after you posed it. And then again, 31 minutes later in a near identical cut and paste of your second post.

    Clearly you are not interested in answers, just in spamming this thread. As you are not interested in learning, I find that I have no time for you.
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  24. daisym "It makes no sense to think that natural variation only cools."

    So it's just as well that no-one's ever said it, isn't it.

    What do you think all those graphics comparing TSI, temperature and GHGs are for? They're used to show that it's not the sun this time.

    It's been the sun plenty of times before and it will be again. But not for the last 40 years.
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  25. daisym @ 21 - Your list is full of the usual suspects. This is old hat for SkS, but not apparently to you. Most of the questions can be answered by clicking on the 'arguments' button at the top of the page.

    In as far as CO2 outgassing from the ocean. This is well known, but what matters is the total or net exchange. Far more CO2 goes into the ocean than leaves it. This process is causing ocean acidification. Click on the OA is not OK button at the top left hand corner of the page, to learn about this.

    As far as global warming is concerned, considering natural factors only, the Earth should be gradually cooling due to orbital factors.

    If you're interested in learning we can help, but if this is simply dogmatic repetition, there are other blogs for that.
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  26. @daisym

    You are simply regurgitating old climate myths that we've heard a thousand times before. Everyone here is very familiar with the 'Oregon Petition', for instance, which was published in the last century -- which, at the very least, means that it's long past its sell-by date.

    I implore you to open your mind to the scientific evidence which is provided on this site, starting by clicking on the 'Most Used Climate Myths', top left. You'll find all the answers you seek, there. Choose one and read it first before posting your question below it. If you dive in and start showing that you've not looked at the science first, you just make yourself look foolish.
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  27. 20, daisym,
    If natural forces are powerful enough to cool and offset warming attributed to manmade CO2, might they also be powerful enough to cause the warming attributed to man to seem greater than it really is?
    Just for the record I'll answer this.

    No.

    Scientists have estimated, entirely separate from the observational record, the effects and degree of anthropogenic CO2. The observational record now supports those estimates, both qualitatively and quantitatively.

    Given this, why would you go looking for another, unknown and inexplicable cause or amplifier?

    It seems to me rather like someone who finds a note saying Mr. X is planning to shoot Mr. Y, watches Mr. X shoot Mr. Y., recovers the gun and the bullet and matches all of the forensic and ballistic evidence of Mr. Y's murder to Mr. X -- and then declares that we can't rule out other suspects, or even death by natural causes.

    Your next argument, no doubt, will be to declare that we do not have such evidence or supporting knowledge of the predicted effects of CO2. Before you make that argument, you need to read, absorb and understand all of the science on this site.

    Your problem right now, I believe, is that you are speaking and thinking from a position of extreme ignorance, reflected no doubt by ideas planted there by others (WUWT, Nova, etc.) who do not want you to understand and simply want you to be angry about what they tell you that you should believe.
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  28. I'd like to point out something new and unusual about daisym's attack. He doesn't say CO2 isn't the culprit. He instead implies that the effects of CO2 are minor and that natural causes, while not the cause of recent warming, are an amplifier, as if without them the effects of CO2 wouldn't be that bad at all and wouldn't be worth the effort to address.

    Is this the beginning a new tactic in denial?

    Accept the science to a large degree, but declare it exaggerated and minor compared the the vast, unknowable, unpredictable, unconquerable natural forces that we cannot hope to understand, control or in any way compete against.

    Of course, in a way he's right. Except there's a specific name for those natural forces. They're called "feedbacks," in this case "positive feedbacks." The only problem is that we do understand them, and yes, they do explain why the effects of CO2 are amplified.
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  29. daisym - I suspect (it's certainly true in my case) that the reason nobody discussed your "natural forces" question is that it was just part of a longer post littered with other errors.

    I would suggest you use the "Search" box for "natural". Alternatively, you might want to start with It's a natural cycle or It's internal variability.

    You've been making some serious Gish Gallop posts here - you're certainly not actually discussing the science. Until you do, I for one will not take your posts seriously - Sorry.
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  30. @Sphaerica

    For some month's now I've had an on-line 'discussion' with a person in denial (favourite site: WUWT) who maintains exactly that. He appears to accept all the main arguments -- effect of CO2; rising atmospheric concentration; Arctic ice melting; temperatures rising (slowly); etc -- but he just won't accept that the outcome could be bad. He particularly objects to any suggestion that it could be 'catastrophic', or that we should spend any more than a token amount of money to halt emissions. It makes it much more difficult to persuade people that we need to act when they take that stance.

    I suspect that in a few years time the argument will move completely in the direction of risk management.
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  31. Sphaerica, I think this is similar to something Roy Spencer has been floating for a while. Essentially, Spencer has argued;

    1: Yes, CO2 forcing exists.
    2: However, net feedbacks are negative or only slightly positive and therefor warming from human CO2 emissions will be mild.
    3: The reason we have already seen atmospheric warming in excess of what these negative/slightly positive feedbacks would generate is due to short term natural fluctuations overlaying the signal.

    Basically, the apparent pronounced anthropogenic warming since the 1970s is 'actually' very mild anthropogenic warming accompanied by a temporary spike from non-anthropogenic sources. A variation on the classic 'it is natural cycle XYZ'... just with acknowledgment that some CO2 warming exists, but the claim that it is minor compared to internal variability.


    There are, of course, a host of problems (e.g. past sensitivity, measured positive feedbacks, major natural factors were cooling during the warming phase, no return to the 'baseline' cool temps, et cetera) with this position, but I think that is the underlying idea. The 'benefit' of this argument is that it 'accepts' incontrovertible results, but then assumes that the 'correct' values in all the uncertainty ranges (or perhaps a bit outside the range of uncertainty) all line up to produce the 'best case' result... rather like Spencer's original satellite temperature series (prior to corrections).
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  32. daisym, with regard to the consensus, you should read the information at one (or, even better, all) of the following links, and comment further on this matter on one of those :

    There is no Consensus

    Less than half of published scientists endorse Global Warming

    500 Scientists refute the Consensus

    Naomi Oreskes study

    The Science isn't settled

    Over 31,000 Scientists signed the OISM Petition Project

    You should utilise the opportunity to explain why you believe that the tiny minority of scientists not involved in Climate science (especially those who are dead and emeritus, or who may be doctors or economists, etc.) you have pointed towards, should be given more notice than all those Climate scientists currently working in the field - of whom 97% agree with the consensus.
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  33. 21, daisym,

    I thought I should address your misunderstanding of the abstract in Oceanic Sources and Sinks for Atmospheric CO2 (Gruber et al), as evidenced by your question:
    Do the oceans outgas only manmade CO2?
    From the abstract:
    ...we can constrain the oceanic uptake of anthropogenic CO2 to within an unprecedented narrow range of 2.20±0.25 Pg C yr-1 for a nominal year of 1995. The inversely estimated pre-industrial air-sea fluxes reveal the expected pattern with CO2 outgassing in the tropics and CO2 uptake at mid to high latitudes. The subpolar regions of the Southern Hemisphere defy this trend, exhibiting strong outgassing of natural CO2. This outgassing nearly cancels the large uptake of anthropogenic CO2 in this region, leading to a near zero net contemporary flux.
    First, note that they have constrained the anthropogenic CO2 uptake to a specific value. "Uptake" means that overall the oceans have absorbed, not released, CO2. Please note the unit of measure. Pg means "peta grams". "Peta" is the prefix for one quadrillion. Pg refers to 1015 grams of carbon.

    The paper notes that generally the tropics outgas while the other areas are net sinks. This is expected, and frightening. Warmer waters hold less CO2. This means that the oceans at the equator, where temperatures are warmest, are not able to absorb more CO2 and are instead releasing it as they warm. Yes! That is yet another sign that the planet is warming.

    Cooler waters further from the equator are more than compensating, however, by absorbing both anthropogenic CO2 and the CO2 being released in the tropics.

    For now. That's the frightening part. It is well known that warmer waters hold less CO2, and so it is well known that as the planet warms the oceans will be less and less capable of absorbing anthropogenic CO2. The day will arrive, in fact, when the oceans begin spitting it out and adding it to the atmosphere, even after we've halted our own emissions.

    [The paper does note an unexpected behavior in the southern subpolar regions which has a net zero impact in this region -- unexpected outgassing combined with uptake.]

    Do you understand now why your reference does not support your position, and in fact perfectly contradicts it? Do you also understand that the system is far more complex than a hand wave can cover, and that scientists in fact have a very, very good handle on both how things should work and how things are working?
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  34. daisym, aside from echoing the previous suggestions that you use our site's search tool to find the answers to your questions, I would also like to point you to some text in the post above which you seem to have missed:
    "The short-term effects can only temporarily dampen (or amplify) that long-term man-made global warming trend."
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  35. CBD#31: "the claim that it is minor compared to internal variability."

    It would be interesting to see the evidence for this cart-before-horse argument, if any exists.

    Here, on the other hand, is a demonstration that there is an ongoing warming trend with short-term variability written on top of that trend.


    - source

    The red is BEST with a 12 month mean; green is the linear trend. Then use the detrend operator to remove that, yielding the blue curve. That can be described as short period, with a constrained amplitude and oscillation around 0; if this was an electronic signal, it sure looks like noise short-term internal variability to me.

    Of course, tamino did this with greater sophistication last year.

    Has anyone in deniersville produced a graph like this showing that internal variability swamps the trend or are we supposed to just take their word for it?
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  36. I'm not sure why daisym @21 puts Prof William Happer at the top of the list of must-have scientists who disagree with AGW.
    There is a quality aspect to such lists (indeed they can be easily subject to discrediting) so why kick-off with Happer.
    Happer is a man I have a serious misgivings about. He is the man who, while discussing the Truth About Greenhouse Gases in a GWPF Policy Document (so not a place for ill-considered comments) describes the PETM, a time of mass extictions & stresses on species that resulted in, for instance, bats evolving: desctibed all this as "life thrived abundantly.
    He also asserts that "our ancestors" survived the Younger Dyras Event "just fine". Perhaps the same argument about ancestors would also work for the Black Death or World War 2.
    I would suggest that when listing scientists as evidence of legitimate scepticism, Happer is a name that would be best not seen at all, certainly never at the very top of the checklist.
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  37. A significant additional factor to the ones you mention which is almost as large as the effect of declining solar irradiance is described by Hansen in his Earth’s Energy Imbalance and Implications paper.

    Hansen calls this the Pinatubo “rebound”.

    His discussion is in section 12-4, i.e. page 26.

    Volcanoes cause a negative planetary energy imbalance during the 1-2 years that the aerosols are present in the stratosphere, followed by a rebound to a positive energy imbalance. This rebound is most clearly defined after the Pinatubo eruption, being noticeable for more than a decade, because of the absence of other volcanoes in that period

    I hacked a portion of his Figure 18(f) chart from page 27, and added a red arrow over the decade he’s talking about. This is a second negative impact on the planetary energy imbalance that can be attributed to the eruption of Pinatubo, in addition to the initial -2 W/m2 spike that goes away after a few years.

    Pinatubo’s “rebound” effect


    The blue line shows the eruption immediately imposing a bit more than -2 W/m2 forcing on the planetary system which rapidly heads back towards zero as the PInatubo aerosols settle out of the stratosphere. But because -2 W/m2 even over that short period is enough to cause the global ocean to cool slightly, after the Pinatubo aerosols are gone the Earth is left radiating less heat than it otherwise would be radiating to space for a period afterward. This amounts to a slight positive forcing, that as it declines toward zero reduces the planetary energy imbalance. Hansen calls this the “rebound”. He doesn’t supply a number for the peak. My estimate from his chart is that the peak was about 0.16 W/m2.

    Compare that 0.16 W/m2 to the number Hansen puts on the effect of the cyclical declining solar irradiance during almost the same period , i.e. about 0.14 W/m2. This factor is almost as large.
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