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What we can learn from studying the last millennium (or so)

Filed under: — mike @ 15 May 2010 - (Español)

With all of the emphasis that is often placed on hemispheric or global mean temperature trends during the past millennium, and the context they provide for interpreting modern warming trends, one thing is often lost in the discussion: space matters as much as time. Indeed, it is likely that the regional patterns of past climate changes, rather than simple hemispheric or global mean temperature trends, will best inform our understanding of the dynamical mechanisms involved. Since much of the uncertainty in future projections relates to regional climate change impacts, it makes particular sense to focus on those changes in the past that involve regional changes and the underlying mechanisms behind them.

For instance, melting of the cryosphere (and consequent rises in sea level), subtle shifts in drought and rainfall patterns, and extreme events, are all regional effects that could be important threats to ecosystems and our environment. Such changes are often associated with phenomena like ENSO or the North Atlantic Oscillation. Yet there remain large uncertainties about how such mechanisms will respond to anthropogenic climate change.

There are a number of potential ways forward to improve our understanding. A first step is to look directly at the time-series of specific systems (like the ENSO index or the ocean temperatures in the North Atlantic) and try to extend them as far back as possible using proxy data. This gives more information on what the natural variations in these phenomena look like, and thus a better idea of how big a forced response would need to be before it could be reliably detected. Secondly, we can look to see if there is a relationship between various natural drivers of climate change (volcanic eruptions, solar variability or orbital forcing say) and any characteristics of these phenomena – amplitude, frequency or duration. Do volcanic eruptions appear to affect El Niño for instance?

For phenomena that need annual or decadal resolution data to be resolved, the last millennium or so is an obvious (and only) time period to be looking at for it is only for that period that there is sufficient paleo-data coverage of high enough temporal resolution. Other periods – such as the mid-Holocene 6000 years ago – are also useful, but the results are more long-term in nature (there is also a discussion of the value of different periods for reducing future projection uncertainty in this recent paper).

There are a number of different approaches to looking at reconstructions in recent centuries – some rely on high density regional networks (as seen in this recent paper by Guiot et al concerning European temperature trends for which they mostly used pollen data) and some rely on wider networks of more diverse proxies which aim to capture longer-range correlations to specific phenomena (such as the recent Mann et al (2009) paper).

When this is done, people usually find that while it was relatively cool in global mean temperatures from the 1400s to the 1800s known as the “Little Ice Age” and relatively mild in the 900s to 1300s interval ( sometimes termed the “Medieval Warm Period”). But the spatial reconstructions reveal, however, why such global terms can be quite misleading, and why alternative phrases such as the “Medieval Climate Anomaly” are being increasingly favored by the community. This latter terminology recognizes that while the interval displayed significant climate anomalies, they varied greatly, even in sign, from region to region. Many of the more profound climate anomalies, moreover, involve variables other than temperature, such as drought, rainfall, and atmospheric circulation. Though the medieval period is seen to be modestly warmer globally in comparison with the later centuries of the Little Ice Age (the peak global mean warmth is likely comparable to mid, but not late, 20th century warmth), some key regions appear to have in fact been colder, while other regions appear to have been warmer. Southern Greenland, for example, appears within uncertainties to have been as warm as today. However, much of the tropical Pacific was unusually cold, suggestive of the La Niña phase of the ENSO phenomenon (a similar conclusion was reached by Trouet et al (2009)). Thus even though some locations may have been as warm or warmer than today, the hemispheric mean appears not to have been.

Why does this matter? It matters because there are plenty of factors that can affect the overall mean temperature (solar variability, volcanoes, greenhouse gases, internal variability etc.) and so it is hard, given the uncertainties in the solar or volcanic reconstructions to precisely attribute the paleo changes in the global or hemispheric mean to these factors. But if we can look at more complex fingerprints of the changes, it might be possible to be more quantitative in those attributions since the spatial fingerprints of the different factors are easier to distinguish. Furthermore, if we can clearly tie the regional patterns to the different forcings, we might be able to use that information to inform regional projections under future conditions.

Thus we can basically say that the warmer conditions of the Medieval era were tied to higher solar output and few volcanic eruptions and the cooler conditions of the Little Ice Age resulted from lower solar output and more frequent volcanic eruptions. But these drivers appear to have had an equally important, though more subtle, influence on regional temperature patterns through their impact on climate phenomena such as ENSO and the North Atlantic Oscillation. The modest increase in solar output during Medieval times appears to have favored the tendency for the positive phase of the NAO, associated with a more northerly jet stream over the North Atlantic. This brought relatively greater warmth in winter to the North Atlantic and Eurasia. A tendency toward the opposite negative NAO phase helps to explain the enhanced winter cooling over a large part of Eurasia during the later Little Ice Age period.

There is some model support for these patterns (see also instance Shindell et al, 2001) when the models include interactive ozone photochemistry to produce this dynamical response to solar forcing, but it is not captured in a simulation of the NCAR CSM coupled model which lacks those processes. Neither model simulation reproduces the apparent La Niña pattern seen in the Medieval temperature reconstructions:

Figure 1: Spatial pattern of mean temperature difference between the MCA and LIA periods (defined at the intervals AD 950-1250 CE and 1400-1700 CE respectively) compared with simulations of two different climate models forced with estimated differences in natural (volcanic and solar) radiative forcing between the two periods (Mann et al, 2009).

Other model simulations, however, using a climate model that exhibits a particular tropical Pacific mechanism, do reproduce such a response. In such models, the tropical Pacific counter-intuitively tends to the cold La Niña phase during periods of increased heating, such as provided by the increase in solar output and low volcanism of the Medieval era. If this response holds for the future, something that is still vigorously debated, it could imply a more La Niña-like response in the future. Most of the state-of-the-art climate models, e.g. those used in the IPCC Fourth Assessment, by contrast, suggest the opposite–a more El Niño-like future climate. The credibility of the models with regard to this phenomenon is not high, however, and lots more work is going to be needed (both on paleo-reconstructions and model improvements) before we can be confident in the future projections of changes in ENSO-like dynamics and mean state.

690 Responses to “What we can learn from studying the last millennium (or so)”

  1. 151
    Completely Fed Up says:

    “Lawrence, don’t forget methane oxidizes to CO2 ”

    Maybe a dumb question, but since CH4 -> CO2 leaves H4 out of the picture, and given that pH is all about Hydrogen in solution, are there competing processes acting against each other here? Or would you get more H2O from each CH4 than CO2 therefore exhaust accessible Oxygen making the production of CO2 from methane somewhat self-limiting.

  2. 152
    Stephen says:

    I’m interested in the assertion that:

    LIA = low solar + more eruptions, and
    MWP = higher solar + few eruptions

    (to quote, the article says; “Thus we can basically say that the warmer conditions of the Medieval era were tied to higher solar output and few volcanic eruptions and the cooler conditions of the Little Ice Age resulted from lower solar output and more frequent volcanic eruptions.”)

    I’m interested to know how robust this assertion is, and where I might read quantative data from those periods that support the assertion?

    Kind regards,

    Stephen

    [Response: There are up to date reconstructions (which remain somewhat uncertain in the details) available here. – gavin]

    [Response: There are thorough reviews of these issues in both the Third and Fourth Assessment Reports of the IPCC. Google these reports, you can find them online. You can also find some extensive discussion in this review paper by Jones and Mann. -mike]

  3. 153
    CM says:

    CFU, one question is whether there is an increasing frequency of warming-associated events consistent with the models. Another is whether they arise in the same way as in the models, which would tend to strengthen attribution. None of this can be argued from first principles.

    On the first question, the logic in your #129 is OK. But instead of speculating on how unusual the recent Southeast US drought might be, you could read the Seager et al. paper that was linked to at #93:

    The tree ring records show long periods of severe droughts that dwarf the turn-of-the-century drought in their persistence. (…) Curiously the early and mid 19th Century also appears as a long period of drier conditions after which the Southeast transitioned to a 20th Century that was noticeably wetter than the long term mean of the millennium.

    On the second question, the logic in your #130 is wrong. It’s drought we’re talking about; of course rain comes into it. The Seager et al. paper, again, makes the following point: Models predominantly expect more precipitation, but even more evaporation, hence some net drying. This would be the man-made signature. Recent Southeast drought, however, appears to have been driven by a decrease in precipitation with no increase in evaporation. So it lacks the signature.

  4. 154
    Snapple says:

    Dr. Mann–

    Morano’s site claims the earth is heading for a cooling. Pravda is claiming an ice age is coming. http://english.pravda.ru/science/earth/106922-0/

    That Heartland conference is saying exactly what the government-controlled Russian media is saying. Pravda even quotes Inhofe in the citation below.

    Because the KGB and the oil and gas companies put their guys in the Kremlin, “conservative” U.S. Senator Inhofe, his former aid Marc Morano, and Attorney General Cuccinelli are in the same camp as the sensationalist Russian “girlie” tabloid Pravda [See ‘Climategate’ Exposes the Global Warming Hoax (11-30-09)], the Kremlin-controlled Russia Today T.V. channel, known as RT, which churns out English-language “Climategate” propaganda by the notorious conspiracist Alex Jones and other prominent deniers [See RT’s Youtube of Alex Jones on “Climategate: Hoax of all time a global Ponzi scheme”], and the conspiracist 9-11 Truther publication The Rock Creek Free Press, whose delusional editor Matt Sullivan promotes a variety of anti-government junk science conspiracies, such as the claim that “Climategate” is the “Science Scandal of the Century.”

    Links:

    http://legendofpineridge.blogspot.com/2010/05/leading-scientists-publish-open-letter.html

    This is a lot like the KGB propaganda campaign about crafty US scientists making AIDS to kill blacks.

    You climate scientists were defended by Dr. Sagdeev who blew that lie out of the water. You should tell people about what he did because what is happening to you is the same.

  5. 155
    Snapple says:

    I would not be surprised if RT (Russia Today) covers the Heartland conference.

  6. 156

    Naindj #104: how is ocean acidification being caused by climate change? to Glacier retreat is of course indicative of warming not AGW specifically but if it’s not AGW, what is the cause of warming? It is a counter to those who claim warming isn’t real, it’s instrument error.

  7. 157
    Completely Fed Up says:

    “146
    CM says:
    19 May 2010 at 4:21 AM

    CFU, one question is whether there is an increasing frequency of warming-associated events consistent with the models.”

    CM, no, the question is: when there is a drought, how does the temperature affect it.

    And the answer to that is that the hotter it is, the worse the drought.

    Stating anything different is so bad it’s not even wrong.

  8. 158
    Completely Fed Up says:

    ” Completely Fed Up says:
    Your comment is awaiting moderation.
    19 May 2010 at 2:30 AM

    “Peer reviewed literature follows problems, it does not lead on them.”

    Uh, the problem of AGW was written in a paper before people had seen it in measurements.

    I think you’re waving your arms around and screaming again…”

    Can I point to the posters own words on this:

    “137
    Aaron Lewis says:
    18 May 2010 at 7:13 PM

    Re 123 Hank,
    I use the Feynman method – I walk around screaming and waving my arms”

  9. 159

    Also of interest from ScienceDaily: kudzu, “the vine that ate the Southeast”–now found as far north as Pennsylvania and New York, with even an outlying patch near Leamington, Ontario, according to Wikipedia–has been shown to produce ground-level ozone at levels significant for human health.

    As such, its expansion is both a consequence of observed warming–since kudzu can’t survive hard freezes–and a contributor to warming, since O3 is a GHG. (Don’t know if it’s at all significant–anybody know the CO2e of O3? I poked around a bit to find it, but had no success so far.)

    http://www.sciencedaily.com/releases/2010/05/100517172302.htm

  10. 160
    Completely Fed Up says:

    CM here it is again:

    “116
    Rod B says:
    18 May 2010 at 9:43 AM

    CFU says,
    “…Can you say it would have been as bad if we weren’t warming?

    No.”

    I’ll say it would have been as bad. Prove me wrong.”

    “118
    Completely Fed Up says:
    18 May 2010 at 11:56 AM

    Easy:

    You get droughts when it’s hotter and AGW is causing warmer temperatures.”

    There is already a drought. AGW would make it worse than if there was no AGW because AGW means warmer global climate.

    Making it warmer makes a drought worse.

  11. 161
    Completely Fed Up says:

    “104
    Naindj says:
    18 May 2010 at 5:40 AM

    I believe you are talking about indicators of “climate change”, not indicators of “AGW”.”

    AGW IS climate change. Therefore any indicator of AGW is an indicator of climate change, because AGW is climate change.

    Your complaint is rather like complaining that investigations into mortality rates is not an indication of mortality rates but indicators of how many people are dying.

  12. 162

    Link to the Lerdau paper on kudzu and ozone:

    http://www.sciencedaily.com/releases/2010/05/100517172302.htm

    The unusual physiological combination of moderate to high emissions of isoprene and a high N-fixation capacity able to double soil NO fluxes in Georgia makes kudzu a unique source of the key precursors to tropospheric ozone in the United States; it may be as close to a “polluting plant” as one can find. In addition, kudzu’s vine growth form and its ability to fix nitrogen—a combination of traits common among tropical plants but largely absent from vines commonly found in the United States—are likely to allow it to increase its rate of spread and to expand northward as atmospheric CO2 concentrations and winter temperatures increase in coming decades. Vines in general have shown larger and more sustained growth responses to increased CO2 than trees have (30), and the growth responses of N-fixers such as soybean have shown little acclimation to elevated CO2 (31). Currently, winter temperatures seem to define the northern boundary of kudzu’s distribution, possibly as a result of freezing induced embolisms (32). As it is released from these limits on its growth and spreads, kudzu invasion is expected to extend northward by hundreds of kilometers (33); an observed trebling in the number of populations on Long Island, NY, and the recent discoveries that kudzu is established as far north as Maine and Ontario may represent early evidence of that expansion (33, 34).

    Still curious about the net GH effect of this biogenic ozone. Still don’t have a CO2e, and in any case the picture is a bit complicated: O3 is a GHG, but also contributes to breakdown of methane due to reactions which produce free radicals. So the net effect of ozone presumably will be dependent upon CH4 concentrations locally. Also, the effect–whatever it is–is going to be strongly seasonal, with ozone production occurring primarily during the warmer parts of the year.

  13. 163

    Dang, that was the link to the press release, not the PDF of the paper. Sorry. Trying again:

    http://www.pnas.org/content/early/2010/05/12/0912279107.full.pdf+html

    . . . there we go.

  14. 164
    Completely Fed Up says:

    Guys, on the website, specificclick is running dog slow. Sitemeter often does too.

    It’s counterproductive: http://ask.slashdot.org/article.pl?sid=07/08/17/1617259

  15. 165
    Naindj says:

    Philip Machanick,

    I just wanted to clarify, because this is a usual confusion, and also because I may have missed something, so please correct me if you think I’m wrong. (that would not be the first time!)
    All these events or measurements show that there is a recent warming, clearly. And you are right saying that it is “a counter to those who claim warming isn’t real, it’s instrument error”. But without any further explanation or theory, this is it. To link all this to human activities (the “A” in AGW) you need far more and this is why there are all these debates (Hockey Stick and MWP, cliamte sensitivity and feedbacks, etc…)
    Acidification is a separate issue. As far as I could understand this has very little to do with AGW (neither climate change, you are right). Both are supposed to have the same origin: excessive atmospheric CO2 content, due to human emissions.

  16. 166
    Naindj says:

    Completely Fed Up, 161:

    No my complaint is rather like complaining that investigations into mortality rates is not an indication of suicidal rates.

  17. 167
    Frank Giger says:

    “149.I guess Frank is OK with drugs in sports, because you can’t point to someone winning having performance enhancing drugs and say that the drugs did that.”

    1. No, I’m not okay with it.

    2. You hit on a perfect analogy. Let’s say a biathon athelete is using steroids to improve his time. It will certainly improve his skiing, but not his shooting, as steroids don’t improve the fine motor skills required. To say that performance enhancing drugs effected his ability to hit a bull’s eye on any given squeeze of the trigger is tenuous and influenced on the periphery.

    The same is true here. The drought in question, as demonstrated by peer-reviewed scientific research wasn’t caused by global warming.

    Now either you accept the peer-reviewed science on the matter or you don’t.

    At the risk of sounding snarky, I’ll stick with the scientists on this matter.

    You are free to deny their finding, of course.

  18. 168
    Ani says:

    Hello. It seems to me that by using your studies we may be able to come up with regional differences during certain time periods. By using this we may be able to determine what the predominate longwave pattern or jetstream pattern was during these time periods. This then would help us today helping with regional differences and warming. IMHO.

  19. 169
    Jeff Id says:

    Per #5, I wonder if you can provide a copy or URL for the pseudoproxies you used? Of course it’s difficult to recreate these on my own.

    [Response: see the supplementary online information (e.g. here) for Mann et al (2007) for an extensive array of pseudoproxy networks of varying size and spatial distribution and varying signal-to-noise ratios and noise attributes. -mike]

  20. 170
    Hank Roberts says:

    Naindj
    CO2 explains both unusual fast warming and unusual fast ocean pH change.
    Nothing else known is sufficient to explain either change.
    To believe that some unknown hidden cause is credible requires a second unknown hidden cause that would subtract the known effect of CO2.

    http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-es.html
    Warming is radiation physics.

    http://scholar.google.com/scholar?q=ocean+ph+change
    Ocean pH change is simple chemistry.

    http://scholar.google.com/scholar?hl=en&q=rise+of+slime+“Jeremy+Jackson”
    Biological changes are already far advanced, huge losses documented.

  21. 171
    Ike Solem says:

    Global cooling cycle? What global cooling cycle?

    April 2010 the hottest April on record: WMO

    Geneva (AFP) May 18, 2010
    April 2010 was the hottest April ever recorded, with an average temperature of 14.5 degrees celsius (58.1 degrees Fahrenheit), the UN weather agency said Tuesday.

    Citing data from the US National Oceanic and Atmospheric Administration, the World Meteorological Organisation said that the average temperature on both land and ocean this April reached 0.76 degrees Celsius above that of the 20th century average of 13.7 degree Celsius.

    I wonder what the Heartland Conference attendees make of that…

  22. 172
    Hank Roberts says:

    > Re 123 Hank [Please, kids, cite some kind of source….]

    > CFU
    > I use the Feynman method – I walk around screaming and waving my arms

    Feynman: real person, with a real publication record, a trusted source whose work can be looked up by anyone. Like the Contributors here, Feynman could say things and be trusted, because they could be verified.

    You? Please, cite some kind of source. Assertions of belief without citation — even when I likely could find support for them if I did the homework — aren’t credible to new readers without lots of background.

  23. 173
    Completely Fed Up says:

    “1. No, I’m not okay with it.”

    But why? You can’t prove that those drugs improved his performance then, since they could have been ineffective.

    “The drought in question, as demonstrated by peer-reviewed scientific research wasn’t caused by global warming.”

    We aren’t talking about it being CAUSED BY AGW.

    Did you not read? It’s been down here about a half dozen times.

    Here it is again:

    Has the drought event THAT HAS TAKEN PLACE been made WORSE by AGW.

    Yes.

    How?

    Because warmer weather makes a drought WORSE.

    There’s no paper showing this for the same reason there is no paper showing that turning on my electric kettle caused the water to boil.

  24. 174
    Completely Fed Up says:

    Namjd, AGW is climate change. If there’s no climate change, there’s no AGW. Therefore to prove AGW you have to prove climate change.

    Therefore evidence for AGW is evidence of climate change.

  25. 175
    Completely Fed Up says:

    ““149.I guess Frank is OK with drugs in sports, because you can’t point to someone winning having performance enhancing drugs and say that the drugs did that.”

    1. No, I’m not okay with it.”

    Really? Can I point you to your earlier statement:

    “Pointing to specific weather events and declaring they would be worse or more severe if climate change wasn’t happening is just flat wrong”

    Now, lets try a little substitution:

    Pointing to specific track events and declaring that they would have changed if drugs hadn’t been taken is just flat wrong.

    AGW (climate change) creates warmer weather. Performance enhancing drugs enhance your performance at track events.

    Warmer weather makes drought more severe. Enhanced performance makes your time in a track event quicker.

    Droughts are made more severe if you increase temperatures. Your winning time is reduced if your performance is better.

    Therefore saying that AGW (climate change) made a drought worse is flat out wrong. Therefore saying that performance enhancing drugs decreased the winning time is flat out wrong.

    How do you manage to call one flat out wrong but not the other?

    You must be disagreeing with one of the intermediate steps leading to the conclusion.

    Which one?

  26. 176
    Completely Fed Up says:

    “To link all this to human activities (the “A” in AGW) you need far more ”

    We have CO2 from human sources. (anthropogenic)

    We have cooling stratosphere. (climate change)

    We have quicker warming at high latitudes. (climate change)

    We have quicker warming at night. (climate change)

    So complaining that evidence is merely evidence of climate change is falsely accusing: it HAS to be evidence of climate change.

    So what then is causing the climate change?

  27. 177
  28. 178
    Completely Fed Up says:

    “> CFU
    > I use the Feynman method – I walk around screaming and waving my arms

    Feynman: real person, with a real publication record”

    I know.

    Also, did you notice who said what there? CFU didn’t say that.

    Please check your sources.

    “You? Please, cite some kind of source.”

    Yup, here it is:

    http://www.realclimate.org/index.php/archives/2010/05/what-we-can-learn-from-studying-the-last-millennium-or-so/comment-page-3/#comment-174950

    Quote:

    “137
    Aaron Lewis says:
    18 May 2010 at 7:13 PM

    Re 123 Hank,
    I use the Feynman method – I walk around screaming and waving my arms until I have THE correct answer.”

    My cite for the quote.

    Please cite your source for me saying what you seem to be quoting me as saying.

  29. 179
    John E. Pearson says:

    171: Ike Solem wonders what the Heartland Conference attendees make of that…

    April 2010 was the hottest April ever recorded, with an average temperature of 14.5 degrees celsius (58.1 degrees Fahrenheit), the UN weather agency said Tuesday.

    Uhhhh …. Crappy thermometers? No. Gimme a sec, I’ve got it. THe UN. Aren’t they part of the IPCC?

  30. 180
    Rod B says:

    Ray, No, I have no problem with trends as long as they are statistically significant from a climate perspective. The Iceland volcano, e.g., isn’t; Katrina, e.g., is a long way from statistically significant; as is one minor specie migrating a bit north, e.g.

  31. 181
    Doug Bostrom says:

    NAS releases three reports on climate change today, one of them including this gem:

    Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.

    STRONG EVIDENCE ON CLIMATE CHANGE UNDERSCORES NEED
    FOR ACTIONS TO REDUCE EMISSIONS AND BEGIN ADAPTING TO IMPACTS

    Notice that NAS has activated its caps-lock key, which coming from this conservative and rhetorically parsimonious organization is quite an event in itself…

  32. 182
    Doug Bostrom says:

    John E. Pearson says: 19 May 2010 at 12:54 PM

    Uhhhh …. Crappy thermometers? No. Gimme a sec, I’ve got it. THe UN. Aren’t they part of the IPCC?

    No, it’s because Al Gore is fat. Blog science tells us so.

  33. 183
    Frank Giger says:

    “Has the drought event THAT HAS TAKEN PLACE been made WORSE by AGW.

    Yes.”

    Wrong. NO. No, it wasn’t. Read the research. It wasn’t impacted either way by climate change. It was in the normal variance of historical climate and had NONE of the earmarks of Global Warming.

    Not every weather event – even ones that make a very statistically noisy 18 month long one – is tied to Global Warming.

    You’re such a zealot that you can’t budge from your beliefs when the science is clearly proving you wrong.

    Who’s the denalist here? Look in the mirror.

  34. 184
    Hank Roberts says:

    Yup, I should’ve said
    > CFU
    >> Adam Lewis
    Same point because I’m saying this generally: waving arms is credible for people we can trust but verify by looking at their publications.

    Assertions of belief without sources won’t help readers who can’t know who to trust and can’t verify.

    http://scholar.google.com/scholar?q=how+to+know+who+to+trust%3F

    It’s not my site and I’m not a moderator; what they allow is what we get. Try to be effective, people. Being right isn’t enough. You need to be convincing.

  35. 185
    Brian Dodge says:

    re ozone in the troposphere and methane in the water column
    “According to new calculations, methane’s effect on warming the world’s climate may be double what is currently thought. The new interpretations reveal methane emissions may account for a whopping third of the climate warming from well-mixed greenhouse gases between the 1750s and today. The IPCC report states that methane increases in our atmosphere account for only about one sixth of the total effect of well-mixed greenhouse gases on warming.

    Part of the reason the new calculations give a larger effect is that they include the effect methane has on air pollution. A major component of air pollution is near-surface-level or tropospheric ozone, which is not directly emitted, but is instead formed chemically from methane other hydrocarbons, carbon monoxide and nitrogen oxides. The IPCC report includes the effects of tropospheric ozone increases on climate, but it is not attributed to particular sources. By categorizing the climate effects according to emissions, Shindell and colleagues found the total effects of methane emissions are substantially larger. In other words, the true source of some of the warming that is normally attributed to smog is really due to methane that leads to increased smog.”
    http://www.nasa.gov/vision/earth/lookingatearth/methane.html

    “Small numbers of instantaneous rate measurements are difficult to interpret in a dynamic, advecting coastal environment, but combined with the concentration and stable isotope measurements, they do offer insights into the importance of methanotrophy[1] as a control on methane release. Fractional oxidation rates ranged from 0.2 to 0.4% of amb- ient methane per day in the deep water (depths >370 m), where methane concentration was high (20–300 nM), to near-undetectable rates in the upper portion of the water column (depths <370 m), where methane concentration was low (3–10 nM). Methane turnover time averaged 1.5 yr in the deep water but was on the order of decades in the upper portion of the water column."
    http://dx.doi.org/10.1016/S0016-7037(01)00625-1

    [1]methanotrophy – microbial methane oxidation – isn't necessarily dependent on oxygen. see http://www.amethox.com/ "Anaerobic methane oxidation is an enigmatic process that was first discovered in 1974." and http://www.nature.com/nature/journal/v464/n7288/full/nature08883.html "This apparently anaerobic, denitrifying bacterium encoded, transcribed and expressed the well-established aerobic pathway for methane oxidation, whereas it lacked known genes for dinitrogen production. Subsequent isotopic labelling indicated that ‘M. oxyfera’ bypassed the denitrification intermediate nitrous oxide by the conversion of two nitric oxide molecules to dinitrogen and oxygen, which was used to oxidize methane."

    I messed up the limks at my post at 87
    "the trend is up" should point to http://www.woodfortrees.org/plot/hadcrut3vgl/from:1999/plot/hadcrut3vgl/from:1999/trend/plot/uah/from:1999/trend
    and the snow cover anomaly plot is http://www.imagenerd.com/show.php?_img=sno_cover_anomaly-gZZqa.jpg

  36. 186
    Septic Matthew says:

    176, CFU: So what then is causing the climate change?

    Except possibly for people already committed to one belief or another, that is a most interesting question.

    Is it related to the (yet to be confirmed) discovery that the rate of sea level increase has declined over the last 100 years? And if so, then how?

  37. 187
    Completely Fed Up says:

    “Katrina, e.g., is a long way from statistically significant; ”

    Katrina and 50 other hurricanes however could be.

    PS you haven’t countered your post #116’s rebuttal in post #118. Since you’re the one who answered the query, you at least should know what the query was (since you answered it).

  38. 188
    Hank Roberts says:

    http://www.newscientist.com/special/living-in-denial

    ” The first thing to note is that denial finds its most fertile ground in areas where the science must be taken on trust…. global warming … must be taken on trust, usually on the word of scientists”

    http://www.newscientist.com/article/mg20627606.100-living-in-denial-why-sensible-people-reject-the-truth.html

  39. 189
    Completely Fed Up says:

    “and I doubt that oxygen concentration is very high below the surface, since it must be regenerated by photosynthesis”

    Extremeophiles. Anaerobic options. Outgassing. Diffusion from higher layers. And overturning (of which the El Nino/La Nina systems are merely one example, the North Atlantic Conveyor another, and one that runs up the west coast of Canada, etc).

  40. 190
    Completely Fed Up says:

    JEP (#179), nah, just Heat Island Effect (just wait till Watts writes his paper…). Oh, and show the RAW data!!!

    I.e. Business As Usual.

  41. 191

    BPL @ 121:

    My linear regression is enough to show that the idea that the PDO causes it all and CO2 is insignificant is wrong. I really don’t have to get more sophisticated than that.

    Right, but the fact that you got 76% for CO2 means that you need to say what the rest is. Because otherwise “the rest” is going to be asserted to be whatever is causing the current changes, and that’s all that care about.

    Like American companies and their fixation on quarterly results, long-term profitability be damned.

  42. 192
    David B. Benson says:

    FurryCatHerder (191) — Here is a way of explaining the rest of the variance as internal variability:
    http://www.realclimate.org/index.php/archives/2010/03/unforced-variations-3/comment-page-12/#comment-168530

  43. 193
    Ambler says:

    #171, 179 — recent hot times might be tough to blame on UHI or the UN. The satellite-based RSS and UAH series both show this April as 2nd-warmest April in their records — and March 2010 the 1st-warmest March.

  44. 194
    Completely Fed Up says:

    186 Septic Matthew :Except possibly for people already committed to one belief or another, that is a most interesting question.

    You mean except for yourself, yes?

    You already seem to be convinced that there’s no problem with anthropogenic sources of greenhouse gases.

    “Is it related to the (yet to be confirmed) discovery that the rate of sea level increase has declined over the last 100 years?”

    No, because you can’t relate something to an effect that hasn’t yet been discovered.

    It also has no bearing on what’s causing the majority of the warming: sea levels are rising. Ice is melting.

    [edit]

  45. 195
    Completely Fed Up says:

    Fred: “Wrong. NO. No, it wasn’t.Read the research. ”

    So where is the research you’re citing, Frederick?

    “It wasn’t impacted either way by climate change.”

    So warming has nothing to do with droughts???

    Really?

    “It was in the normal variance of historical climate and had NONE of the earmarks of Global Warming.”

    What are the earmarks of Global Warming?

    Warming, isn’t it?

    Are you saying that global warming CANNOT and NEVER affect droughts?

    Really?

    How does evaporation work on your world, Frank? Does it go up when it cools?

  46. 196
    Rod B says:

    CFU says, “…Katrina and 50 other hurricanes however could be statistically significant…”

    Or not.

  47. 197
    Frank Giger says:

    @ Mr. McKinney and the kudzu:

    This is pretty big, as anyone who has dealt with the stuff knows. There are only two decent ways to control kuzu – cattle grazing and machete, and only one way to kill it, a pickaxe to find and destroy the crown root.

    I say “decent” because the volume of herbicides required to kill kudzu makes one wonder if the cure isn’t as bad as the ill due to runoff into the water table.

    A particularly nasty second order effect of warming that I do not wish on our Yankee friends.

  48. 198
    Completely Fed Up says:

    No, it *IS* “could be”.

    With 50 events it is DEFINITELY possible to draw statistically valid conclusions from the dataset. Depending on rarity, three is enough. If you have three one-in-a-century storms in three years, the chance of this being a statistical clustering is about 1-in-10,000. This is pretty solid statistically).

  49. 199
    Completely Fed Up says:

    Look, moderator, why do you continue to let through people giving irrelevant statements but splash loads of edits on me?

    CM, Frank and Rod have ALL said “the drought was not caused by global warming” in a argument thread about whether a drought was worsened by global warming. NOT CAUSED.

    Apparently being irrelevant isn’t too much of a problem there…

    [lets just do our best to keep this civil, ok? that will work out in everyone’s favor. -moderator]

    [you are the last one with any right to complain about edit policies here–you’ve been extended an enormous amount of latitude given your attitude. start your own blog if you don’t like it here–moderator 2]

  50. 200
    Completely Fed Up says:

    So, Septic, what do YOU say is causing the warming? You seem to have missed that out, leaving it to just insinuation and half-statements.