A new hockey stick

Since I’ve discussed hockey sticks before, I thought I would briefly mention a new paper by Wilson et al. called Last millenium northern hemisphere summer temperatures from tree rings: Part 1: the long-term context. The key message seems to be that the result is

relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time-scales from 918 to 2004

Good to see that we can now describe at least some hockey sticks as robust 🙂

The main figure is below and, bearing in mind that this is northern hemisphere summer, it doesn’t appear to really present anything that is particularly different to our current understanding; a warmer period during medieval times, a general cooling trend towards what is often called the little ice age, and then a general warming trend over the last century or so. In fact, to the untrained eye, it’s hard to see how this differs from what was presented in the Mann, Bradley & Hughes papers published more than 15 years ago. My understanding of the significance of this newer work, is that it increases the spatial and temporal resolution and allows one to probe details like variability and, potentially, climate sensitivity.

Credit: Wilson et al. (2016)

Credit: Wilson et al. (2016)


Maybe one of the interesting results of this new paper is that

1161-1170 is the 3rd warmest decade in the reconstruction followed by 1946-1955 (2nd) and 1994-2003 (1st – see Table 2). It should be noted that these three decades cannot be statistically distinguished when uncertainty estimates are taken into account.

It may be true that they’re not statistically distinguishable in this data, but I think we can distinguish decades in the 20th century using the instrumental temperature record. The three most recent decades have all been warmer than any previous decade in the instrumental temperature record, and – given this result – it seems that the last two decades were probably warmer than any other decade in the last 1000 years.

The result in the paper also still seems broadly consistent with what was presented in the recent IPCC documents which says (in Chapter 5)

the mean NH temperature of the last 30 or 50 years very likely exceeded any previous 30- or 50-year mean during the past 800years (Table 5.4)…….NH reconstructions covering part or all of the first millennium suggest that some earlier 50-year periods might have been as warm as the 1963–2012 mean instrumental temperature, but the higher temperature of the last 30 years appear to be at least likely the warmest 30-year period in all reconstructions (Table 5.4).

However, it does say that

the confidence in this finding is lower prior to 1200, because the evidence is less reliable and there are fewer independent lines of evidence.

It would, therefore, be interesting to know if this recent paper allows for stronger statements about the period prior to 1200.

That’s really all I have time to say, but if anyone has anything to add, feel free to do so through the comments. I think it looks like an interesting paper that hasn’t really changed our overall broad understanding, but may allow for more detailed analysis of variability on scales that earlier reconstructions were unable to consider. As you can probably imagine, those on Bishop Hill think there are issues, and apparently Steve McIntrye is going to be looking at it. I can hardly wait.

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136 Responses to A new hockey stick

  1. Maybe a small reminder. It is called Northern Hemisphere, but it is mainly the northern part of it because it uses tree rings from trees that need to be cold limited in their growth to be good proxies for temperature.

    N-TREND2015 includes 54 [Tree ring] records located between 40°N and 75°N

    The Northern Hemisphere shows more variability and will see more global warming than the global South, which has much more ocean, which dampens the warming.

    Also the northern parts of the Northern Hemisphere show more variability and will see more global warming due to polar amplification and the albedo feedback than the tropical parts.

    And smaller regions (than global) simply by virtue of being smaller show more variability.

  2. Victor,
    Thanks. I should have mentioned – as you’ve done – that it’s only records between 40N and 75N. You also make a good point about there probably being more variability and more global warming in the north than in the south.

  3. Vinny Burgoo says:

    And experiment:

  4. Vinny Burgoo says:

    And also this:

    (H/T anoilman.)

  5. RickA says:

    ATTP:

    You said:

    “The three most recent decades have all been warmer than any previous decade in the instrumental temperature record, and – given this result – it seems that the last two decades were probably warmer than any other decade in the last 1000 years.”

    The data does not support this.

    If you had instrumental temperature data from 1161-1170 (and it was third) you could say it – but “cannot be statistically distinguished” means you cannot draw your conclusion.

    What is even more interesting is that this paper also supports the argument that the recent warming is not unprecedented over the last 1000 years.

    If CO2 didn’t cause the warming in 1161-1170, what did?

    How do we know that whatever caused the warming from 1161-1170 isn’t a factor today?

    How do we know that 1/2 (or 75% or 25%) of the warming from 1950 to today isn’t non-human caused (natural)?

  6. Rick,

    The data does not support this.

    The current paper suggests that the warmest decade was 1994-2003. We can show from the instrumental temperature record that 2001-2010 is warmer than 1991-2000. It’s also the case that 2004-2013 is warmer than 1994-2003. So, that would seem to suggest that the two most recent decades are the two warmest in 1000 years.

    What is even more interesting is that this paper also supports the argument that the recent warming is not unprecedented over the last 1000 years.

    In what sense? Also, it’s not so much whether or not the last 100 years is necessarily unprecedented (although I think it probably is in terms of rate, if not unprecedented in terms of magnitude), it’s what the next 100 will be if we carry on emitting as we are.

    If CO2 didn’t cause the warming in 1161-1170, what did?

    It certainly wasn’t magic. As Victor points out, this is NH high latitudes only. It probably shows more variability than the globe as a whole and probably (because of there being more land than the South) shows more warming than the globe as a whole. It’s not only CO2. Solar, volcanoes and internal variability can also lead to periods of warming or cooling.

    How do we know that whatever caused the warming from 1161-1170 isn’t a factor today?

    Technically we cannot “know” anything with certainty. However, we do have evidence for the role of the Sun and the role of volcanoes. Their contribution is almost certainly much smaller than the anthropogenic contribution. The role problem (as I try to explain here) is how one can construct a physically plausible scenario in which more than 50% of the warming is non-anthropogenic. That it has warmed in the past is not a strong argument against a dominant anthropogenic influence in the recent warming.

  7. Vinny,
    All very amusing, but I’m missing the point.

  8. Vinny Burgoo says:

  9. Vinny Burgoo says:

    Alton Towers Traffic Police

  10. BBD says:

    Vinny

    If you’ve got nothing to say, then say it 🙂

  11. BBD says:

    Or stop tr0lling.

  12. Maybe Vinny’s only just worked out how to post images in blog comments 🙂

  13. Vinny Burgoo says:

  14. verytallguy says:

    “On the reception and detection of pseudo-profound bullshit”

    http://journal.sjdm.org/15/15923a/jdm15923a.pdf

    For Vinny

  15. Andrew Dodds says:

    RickA –

    Natural factors aside, there is some evidence that the expansion and contraction of agriculture is to blame for at least some of the pre-industrial variability.

    Basically, if war and plague kill enough people, land goes out of cultivation, forests regrow, CO2 is drawn down and temperatures drop very slightly. And between the Mongol devastation of the 1200s and the Black Death in the 1300s, there is certainly a correlation.

    Mind you, there is also a case that solar irradiance was slightly higher pre-1200 and volcanic activity a bit lower. Which could then explain the temperatures changes, and things like a slight shift in rainfall boosting the Mongol population, leading to migration and conquest..

    Hard stuff to sort out.

  16. lerpo says:

    Rick -just to play devil’s advocate:

    If CO2 didn’t cause the cooling in 1450-1500, what did?

    How do we know that whatever caused the cooling from 1450-1500 isn’t a factor today?

    How do we know that current anthropogenic warming isn’t dampened by 1/2 (or 75% or 25%) by;these natural factors? Based on this line of reasoning, it is hard to reject the possibility that anthropogenic contributions are as much as 150-200% of the observed warming.

    Lerpo

  17. lerpo,
    Indeed, if you want to invoke a potentially large non-anthropogenic contribution, you can’t rule out that it’s provided a cooling, rather than a warming influence.

  18. It should be kept in mind that the claimed anthropogenic net warming effect only got significant after ~1950.

  19. I don’t think that is the correct interpretation of the claim. The formal claim is simply that it is extremely likely that more than 50% of the warming since 1950 is anthropogenic. In fact, if you consider this Realclimate post the best estimate for the anthropogenice contribution since 1950 is a bit more than all of it. None of this, however, allows you to claim that the anthropogenic net warming effect only got significant after ~ 1950. In fact, if you consider the various forcings prior to 1950, it is quite likely that the anthropogenic contribution was still quite large prior to 1950, but that other factors (solar, variability, volcanoes) also played a reasonable role. A problem, though, is that we have less information prior to 1950, and so making strong claims is more difficult.

  20. ATTP, any anthropogenic contribution prior to ~1950 CANNOT be quite large. How can it be? This is not controversial.

  21. CANNOT be quite large.

    I meant a large contribution to what was happening at that time, not large in some absolute sense. Consider the GISS forcings. Now I haven’t looked at the precise numbers for a while, but anthropogenic forcings prior to 1950 make up maybe about 50% – or possibly more – of the change in external forcing, so a reasonable amount of the warming between 1900 and 1950, for example, could be anthropogenic. The point is that the since 1950 claim is based on being able to reject (with high confidence) that more than 50% of the warming was non-anthropogenic. It doesn’t allow one to really make any claims about the period prior to 1950.

  22. RickA says:

    lerpo:

    We don’t.

    That is my point.

  23. RickA,
    Except, as I tried to explain in the post I linked to earlier, trying to construct a physically plausible scenario in which a large fraction of our warming has been non-anthropogenic is very difficult. Hence, it is much more likely that most of our recent warming has been anthropogenic, than not. That’s essentially what the 95% attribution study is pointing out.

  24. RickA says:

    edimbukvarevic:

    Yes. So if it was statistically as warm in 1161-1170 as the two warmest decades, than humans didn’t cause it. Some natural forcing caused it.

    Some of these natural forcings could still be at play today.

    So I don’t believe we can say that humans have caused 110% of the warming from 1950 to the present.

    How can we know that?

  25. RickA says:

    ATTP said “trying to construct a physically plausible scenario in which a large fraction of our warming has been non-anthropogenic is very difficult.”

    What – we don’t think what happened in 1161-1170 is physically plausible.

    It happened – therefore it is physically plausible.

    It is because we don’t know how it happened that it is difficult to rule out the same natural forcings at work today.

  26. Yes. So if it was statistically as warm in 1161-1170 as the two warmest decades, than humans didn’t cause it. Some natural forcing caused it.

    Well, there are some who argue that there have been anthropogenic influences going back more than 1000 years, but – yes – the 1161-1170 warm period was probably natural, a combination of solar and volcanic, as vtg pointed out. Also, being only a decade, we can’t rule out internal variability.

    Some of these natural forcings could still be at play today.

    Of course, they don’t suddenly go away.

    So I don’t believe we can say that humans have caused 110% of the warming from 1950 to the present.

    Noone is saying that humans caused 110% of the warming. The point is that the best estimate is 110%. That you may not like it does not make this not true.

    How can we know that?

    We can’t know anything in this context. We can, however, do research and produce result that allow us to produce estimate for what we expect. Currently, the best estimate (median, I think) is that anthropogenic influences produced 110% of the warming since 1950. It could have been 50%, but that is very unlikely. Equally unlikely – but not impossible – is 170%.

  27. BBD says:

    RickA

    Some of these natural forcings could still be at play today.

    So why can’t we detect them?

    Where’s the energy coming from?

    So if it was statistically as warm in 1161-1170 as the two warmest decades

    Just an aside, but since Wilson16 provides a reconstruction of *summer* NH mid- high-latitude temperatures, I don’t think we can make direct comparisons with modern global, annual, average temperatures as you are trying to do here.

  28. Rick,

    What – we don’t think what happened in 1161-1170 is physically plausible.

    It happened – therefore it is physically plausible.

    That isn’t what I said. Read it again. (Hint: given the forcings for the period from 1950 onwards, it is very difficult to construct a physically plausible scenario). If the 1161-1170 period had stronger solar forcing and reduced volcanic activity, then that could explain that warming. Also, it is much more difficult to explain an extended period of warming, than a single decade.

    It is because we don’t know how it happened that it is difficult to rule out the same natural forcings at work today.

    Nonsense. That we don’t understand what happened 1000 years ago, does not suddenly nullify our understanding of what is happening now.

  29. RickA says:

    ATTP:

    The formal claim is:

    More than half of the observed increase in global mean surface temperature (GMST) from 1951 to 2010 is very likely due to the observed anthropogenic increase in greenhouse gas (GHG) concentrations.

    To me this means that before 1951 we cannot make this claim.

    Maybe for pre-1951 you could argue it is “likely” instead of VERY LIKELY – but this is a statistical claim and if they could have pushed the year back and made the same claim, they would have. They couldn’t statistically.

    I think they were intentionally vague pre-1951 because our data just isn’t that great and CO2 emissions were to small.

    Just one persons opinion.

  30. To me this means that before 1951 we cannot make this claim.

    Even stronger. Based on the claim that you quoted about the warming after 1950, we can make no claim about the period prior to 1950.

    I think they were intentionally vague pre-1951 because our data just isn’t that great and CO2 emissions were to small.

    Indeed, I think the data is not good enough to make any strong claims. However, the change in forcing due to anthropogenic emissions was not small relative to the other changes in forcings since 1750. Hence suggesting that there was no (or a negligible) anthropogenic contribution prior to 1950 (or that it started in 1950) is simply wrong.

  31. “so a reasonable amount of the warming between 1900 and 1950, for example, could be anthropogenic.”

    Could be? Not according to the consensus hypothesis. There is no (significant) divergence between the models driven with just natural forcings and observations before roughly the mid-20th century.

  32. Could be? Not according to the consensus hypothesis.

    Rubbish. The consensus hypothesis is not that it was not significant prior to 1950.

    There is no (significant) divergence between the models driven with just natural forcings and observations before roughly the mid-20th century.

    Look at your own figure. We clearly warmed between 1900 and 1950. The models with anthropogenic influences clearly match the observations better than those without. Of course the amount of warming was such that we can’t rule out a much bigger natural contribution prior to 1950 than after, but the claim that it was not significant prior to 1950 is simply not a claim that you can make.

  33. RickA says:

    BBD:

    The 20th century was the most active sun we have seen in quite some time. Maybe like ATTP’s theory for 1161-1170, the sun provided the energy, and there is some delay in the system which causes the atmosphere to heat up 20 or 30 years later, from the solar energy input provided by the active sun of the 20th century.

    For all we know, forcings are playing out today which were received and stored centuries ago.

    Isn’t that what el nino does over a shorter period of 2 to 7 years?

    I am not saying this is what happened – just that it is possible and hard to rule out.

  34. Maybe like ATTP’s theory for 1161-1170, the sun provided the energy, and there is some delay in the system which causes the atmosphere to heat up 20 or 30 years later, from the solar energy input provided by the active sun of the 20th century.

    If you’re going to start promoting pseudo-science, this discussion is going to be very short.

    For all we know, forcings are playing out today which were received and stored centuries ago.

    No, that doesn’t really make any sense.

    Isn’t that what el nino does over a shorter period of 2 to 7 years?

    ENSO events are certainly cyclical and some are periods of warming, and others are periods of cooling. The problem with trying to argue for something similar over much longer timescales is that we know the energy balance and energy content of the system. There is not really a physically plausible mechanism in which we can store energy that can then be released over a period of ~ 100 years while still retaining a positive planetary energy imbalance. It doesn’t really make physical sense.

    I am not saying this is what happened – just that it is possible and hard to rule out.

    No, I think it’s pretty easy to rule out.

  35. lerpo says:

    Rick – suggesting that our impact on global temperatures could be quite a bit larger than scientists believe is likely does not further the cause of inaction.

  36. RickA says:

    ATTP said “Even stronger. Based on the claim that you quoted about the warming after 1950, we can make no claim about the period prior to 1950.”

    Well the formal claim is >50% from 1951 -2010.

    So maybe it could be <=50% before?

    So just to pick a number – 49% from 1900 – 1950?

    Is that inconsistent with the formal claim?

  37. “The models with anthropogenic influences clearly match the observations better than those without.”

    At most ~0.1 degree better in places, so you prove my point. Or even better compare the trends from 1860 to 1950.

  38. RickA says:

    Lerpo says “Rick – suggesting that our impact on global temperatures could be quite a bit larger than scientists believe is likely does not further the cause of inaction.”

    So what.

    I just think the uncertainty is larger than we realize, because we know so little about the climate (and learn more everyday).

    If it can be as warm 1000 years ago as today – whether caused by some natural forcing or not – well than we have to realize that just because we have the correlation of CO2 emissions (which are undeniable) with modern warming doesn’t necessarily mean it might not just be a giant coincidence. Because it got as warm without CO2 emissions 1000 years ago.

    At least that is my take on it.

    We should be more humble about our certainty.

  39. BBD says:

    RickA

    The 20th century was the most active sun we have seen in quite some time. Maybe like ATTP’s theory for 1161-1170, the sun provided the energy, and there is some delay in the system which causes the atmosphere to heat up 20 or 30 years later, from the solar energy input provided by the active sun of the 20th century.

    For all we know, forcings are playing out today which were received and stored centuries ago.

    As ATTP says, pseudoscience.

    Where could the solar energy go? The sea? Where in the sea? Why isn’t the sea cooling down as the energy comes back out and heats the atmosphere? All major ocean basins are warming up, not cooling down etc.

    Just desperate nonsense.

  40. RickA says:

    ATTP said:

    “There is not really a physically plausible mechanism in which we can store energy that can then be released over a period of ~ 100 years while still retaining a positive planetary energy imbalance. It doesn’t really make physical sense.”

    Well, isn’t that what humans are doing by burning hydrocarbons.

    We are taking energy from the sun which has been stored for millions of years and burning it to today (releasing it).

    Coal deposits have never burned naturally before?

    Doesn’t it take energy to melt ice (I hope I don’t have that backwards)? Are not ice sheets formed during ice ages storing energy which is release later when the ice sheets melt?

    You see my point.

    I think there are many natural mechanisms in which energy is stored for long periods of time and then released.

  41. MarkB says:

    RickA
    Well the formal claim is >50% from 1951 -2010. . .

    The claim from 1951 rests on two things. The central estimate is a bit over 100% and the error in that estimate is such that the probability tail is insignificant below 50%.

    The understanding from prior to 1951 is that the central estimate is about 50% but the distribution is not as well constrained as for the later period because the likely anthropogenic contribution is smaller than post 1951 and because of greater uncertainty in other forcings. Hence a reasonable statement might be that “it is likely that more than 0% of the warming 1900-1951 is anthropogenic with a central estimate of 50%”. I’m not sure that I’ve ever seen it put that way, but the gist is that there is a pre-1950 anthropogenic component that is probably not negligible.

  42. RickA says:

    BBD said “Why isn’t the sea cooling down as the energy comes back out and heats the atmosphere?”

    It is.

    Or are you proposing that el nino doesn’t cool the ocean?

    Maybe it is just hard to measure.

  43. lerpo says:

    Rick,

    It is possible that the problem is not as well constrained as scientists believe, but I think that view is rather alarmist.

  44. BBD says:

    RickA

    Or are you proposing that el nino doesn’t cool the ocean?

    Ah, so you think that ENSO is driving global warming. Bzzzzt! You’ve just violated conservation of energy. As I said, desperate nonsense.

  45. MartinM says:

    You only have to look at the reconstruction to see the difference between the warmth of 1161-1170 and today. The former is a brief spike during a period in which nothing very interesting is happening. The latter is a sustained rise. They’re not directly comparable.

  46. BBD says:

    It’s magic, lerpo. You just have to believe.

  47. John Mashey says:

    See PAGES2K, which has much better global coverage.

    See Bill Ruddiman’s Earth Transformed(2013), his 2013 AGU Tyndall Lecture, or the recent paper Late Holocene Climate: Natural or Anthropogenic?, by W. F. Ruddiman1*, D. Q. Fuller2, J. E. Kutzbach3, P. C. Tzedakis4, J. O. Kaplan5, E. C. Ellis6, S.
    5 J. Vavrus3, C. N. Roberts7, R. Fyfe7, F. He3, 8, C. Lemmen9, J. Woodbridge7.

    45-75N is ~13% of the Earth’s surface, and the land surface there is less

    Human effects started ~7,000 years ago and serious paleo researchers understand the Holocene rather better than commenters on blogs…

  48. John Mashey, it is not my understanding – it’s the “official” IPCC consensus understanding. The total anthropogenic forcing prior to roughly the mid-20th century is very small. The divergence between the models with anthropogenic influences and without is at most ~0.1 K by ~1950.

    The Rudimann’s hypothesis is not generally accepted, not even close. Now if you want my understanding, I think it’s laughable.

  49. > Now if you want my understanding […]

    It might not be a good idea to ask that question, Edim:

    I looked into HIV/AIDS controversy 10 years ago. The more I read about it, the more sceptical I became. I am still a HIV/AIDS sceptic, but haven’t looked into it lately.

    http://judithcurry.com/2011/07/12/historic-variations-in-sea-levels-part-1-from-the-holocene-to-romans/#comment-85952

    Thank you for your concerns.

  50. Jim Eager says:

    Rick A is just doing what he always does: grasping at straws with complete disregard for the physics, and then waving his hands when someone calls him on it.

  51. RickA says:

    BBD:

    How does heat move from the ocean to the atmosphere without cooling the ocean?

    You do know that el nino moves heat around, right?

  52. Stephen Spencer says:

    I am not an expert on Climate Science but ATTP and some of the commenters here are experts.
    Here is my question: If temperatures in the medieval era were similar to current ones as some people claim, what implications does that have for climate sensitivity? My impression is that a warm medieval era would imply a high climate sensitivity. Are there any studies on this question?

  53. pbjamm says:

    What Jim Eager said.

    This is absurd. The Uncertainty Monster rears it ugly head yet again. To reach the conclusion that current warming could be the result of the same factors that caused warming 900 years ago you have to ignore the last 100 years of science.

  54. Feel free to think you know it better than the IPCC, but first please read what the current estimates for the forcings for the different periods before and after 1950 were in Chapter 8 or WG1 AR5: Anthropogenic and Natural Radiative Forcings.

    Knowing these things and the spatial patterns of the warming means that we can still say that the current warming is man-made even if there would have been a previous period where the warming was just as strong.

  55. lerpo says:

    BBD is right. Oceans are accumulating energy:

    Ocean heat content: http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/
    Sea surface temperatures: http://davidappell.blogspot.com/2016/01/sea-surface-temperatures-blow-away.html

  56. JCH says:

    On the issue of whether or not El Nino cools the oceans, on net, in the presence of anthropogenic CO2 in the atmosphere, during most El Nino episodes the oceans continue warming. The big exception on this graph is 1997-98 El Nino:

  57. Rick,

    So maybe it could be <=50% before?

    So just to pick a number – 49% from 1900 – 1950?

    Is that inconsistent with the formal claim?

    Why is this complicated? The formal claim refers only to the period after 1950. Therefore there is no claim about the period before 1950 that is consistent, or inconsistent, with the formal claim.

    Edim,

    it is not my understanding – it’s the “official” IPCC consensus understanding.

    It’s your rather mangled interpretation of it.

    The total anthropogenic forcing prior to roughly the mid-20th century is very small. The divergence between the models with anthropogenic influences and without is at most ~0.1 K by ~1950.

    That does not change that prior to 1950, the change in anthropogenic forcing was still large compared to the total change in external forcings (relative to 1750). Your use of the “significant” and “small” appear to be based on the numbers being small, rather than on the relative influence being small, which is what is actually relevant.

  58. RickA,

    It is.

    Or are you proposing that el nino doesn’t cool the ocean?

    Maybe it is just hard to measure.

    BBD’s point is that we have been warming while ocean heat content has continued to rise (and ice sheets have been losing mass,…) This is not possible if the energy driving the warming is coming from inside the system. It’s only possible if the system is out of energy balance and is gaining more energy than it is losing. What could be causing that, especially considering that this post is based on a paper that further confirms that we’re probably warmer now than we’ve been for 1000 years? In fact, I’ll tell you the answers; it’s because we’ve been releasing greenhouse gases – mainly CO2 – into the atmosphere.

  59. Stephen,

    If temperatures in the medieval era were similar to current ones as some people claim, what implications does that have for climate sensitivity? My impression is that a warm medieval era would imply a high climate sensitivity. Are there any studies on this question?

    Yes, that is essentially the case. The more variability we see in the past, the more likely it becomes that our climate is quite sensitive to radiative perturbations. So, those who argue that a warm medieval period somehow counts against the basic AGW theory are both wrong in the sense that it clearly does not, and that it might actually be evidence in support of a reasonably high climate sensitivity. That’s kind of why I was suggesting that these higher resolution reconstruction could be interesting from the perspective of potentially helping to constrain climate sensitivity.

  60. Marco says:

    It may help people understand where RickA is coming from when you read this:

    http://scienceblogs.com/gregladen/2015/12/22/mark-steyn-the-dc-appeals-court-and-congress/#comment-629557
    “Dr. Mann’s science papers are advocacy. It is my opinion that he has an axe to grind. It is my opinion that he takes the data and massages it until it is “spun” to best show what he is trying to show. Namely that the warming has been “unprecedented” in the last 400 years (MBH98) or the last 1000 years (MBH99) or the last 2000 years (MBH2008).

    It is the argument that the warming is unprecedented which is advocacy. It is important to Dr. Mann that the warming be “unprecedented” because that is his proof that the culprit is human emitted CO2.

    If the warming we are experiencing is no more than the MWP (which was not caused by CO2) than his cries for action are not as persuasive.

    If the warming is no more than the Roman warm period – ditto.”

  61. It is important to Dr. Mann that the warming be “unprecedented” because that is his proof that the culprit is human emitted CO2.

    Well, that’s bit silly. The evidence that the warming is human emitted CO2 is based on many lines of evidence, including basic radiative physics and – as Victor points out – details of the recently observed warming. Of course, some of the evidence is also based on paleo work, such as Milankovitch cycles. That it might have been as warm in the past is not somehow evidence against CO2 being a radiatively active gas.

    Somehow I was thinking about last night is that the change in external forcing since 1950 is around 1.7Wm-2. Something we all apparently agree on is the influence of CO2 (about 1.2oC per doubling). So, unless the TCR to ECS ratio is very small, CO2 alone could explain more than 50% of the observed warming since 1950. So, if you want more than 50% to be non-anthropogenic, you somehow need natural influences to cancel some of the potential CO2 warming, while also providing more than 50% of the observed warming. I don’t think that makes any sense, especially given that the physical processes that would do this would be essentially the same as those that feedback on CO2. How can they operate whan the underlying warming is natural, but not when it’s anthropogenic. Again, it seems logically inconsistent.

  62. BBD says:

    ATTP says:

    That it might have been as warm in the past is not somehow evidence against CO2 being a radiatively active gas.

    While not the case with the MCA, which appears to have been forced by other factors, past warmth is very strong evidence that CO2 is an efficacious climate forcing. Obvious examples include the Cenozoic hyperthermals but there’s the question of why it was so hot ~50Ma at the peak of the Eocene hothouse – and why it is so cold in the Pleistocene. This is succinctly addressed in Hansen & Sato (2012) (emphasis added):

    CO2 is the principal forcing that caused the slow Cenozoic climate trends. The total amount of CO2 in surface carbon reservoirs (atmosphere, ocean, soil, biosphere) changes over millions of years due to imbalance of the volcanic source and weathering sink, and changes of the amount of carbon buried in organic matter.

    […]

    The fact that CO2 is the dominant cause of long-term Cenozoic climate trends is obvious [from] Earth’s energy budget. Redistribution of energy in the climate system via changes of atmosphere or ocean dynamics cannot cause such huge climate change. Instead a substantial global climate forcing is required. The climate forcing must be due to a change of energy coming into the planet or changes within the atmosphere or on the surface that alter the planet’s energy budget.

    Solar luminosity is increasing on long time scales, as our sun is at an early stage of solar evolution, “burning” hydrogen, forming helium by nuclear fusion, slowly getting brighter. The sun’s brightness increased steadily through the Cenozoic, by about 0.4 percent according to solar physics models (Sackmann et al., 1993). Because Earth absorbs about 240 W/m2 of solar energy, the 0.4 percent increase is a forcing of about 1 W/m2. This small linear increase of forcing, by itself, would have caused a modest global warming through the Cenozoic Era.

    Continent locations affect Earth’s energy balance, as ocean and continent albedos differ. However, most continents were near their present latitudes by the early Cenozoic (Blakey, 2008; Fig. S9 of Hansen et al., 2008). Cloud and atmosphere shielding limit the effect of surface albedo change (Hansen et al., 2005), so this surface climate forcing did not exceed about 1 W/m2.

    In contrast, atmospheric CO2 during the Cenozoic changed from about 1000 ppm in the early Cenozoic (Beerling and Royer, 2011) to as small as 170 ppm during recent ice ages (Luthi et al., 2008). The resulting climate forcing, which can be computed accurately for this CO2 range using formulae in Table 1 of Hansen et al. (2000), exceeds 10 W/m2. CO2 was clearly the dominant climate forcing in the Cenozoic.

    RickA will note the emphasis on physical mechanisms, including quantified forcing estimates. If you apply the same physical approach to millennial climate, the emergence of a substantial blade to the hockey stick in response to a substantial increase in CO2 forcing is inevitable.

  63. If you apply the same physical approach to millennial climate, the emergence of a substantial blade to the hockey stick in response to a substantial increase in CO2 forcing is inevitable.

    David Appell made that same point a little while ago. It would be extremely surprising were our millenial temperature history not roughly hockey-stick-like.

  64. RickA

    So if it was statistically as warm in 1161-1170 as the two warmest decades, than humans didn’t cause it. Some natural forcing caused it.

    Some of these natural forcings could still be at play today.

    So I don’t believe we can say that humans have caused 110% of the warming from 1950 to the present.

    “So if much of Europe’s population died of the Black Death during medieval times, then humans didn’t cause it. Some natural event caused it.

    Some of these natural events could still have been at play in the 1940s.

    So I don’t believe we can say that WW2 killed much of Europe’s population during the 1940s, it could have just been some kind of bug going around.”

  65. paulski0 says:

    RickA,

    If CO2 didn’t cause the warming in 1161-1170, what did?

    I think there are a few relevant issues. One is that NH Extratropical Summer temperatures are expected to show millennial cooling due to Earth-orientation insolation changes. Absent anthropogenic influence current temperatures should be somewhere in the region of 0.3degC cooler since 1000CE. For that reason temperatures at the beginning of the record are more likely to be warmer than those towards the end, absent anthropogenic factors.

    Figure 2b and c show the reconstruction a bit clearer. The 1161-1170 decade is really a blip, with temperatures immediately either side about 0.5C cooler. There appears to be greater decadal variability in the reconstruction for the period before 1500CE. This may be “real” or an artefact of lower data availability. Either way, greater variability makes apparent warmer and colder decades more likely, which needs to be taken into account when making probabilistic comparisons.

  66. RickA says:

    Good analogy Frank. Disease did kill millions during WWII in Europe. Humans killed millions also. So it would be foolish to say humans killed 110% of the people who died.

  67. RickA, not as foolish as it would be to say that WW2 was therefore nothing to worry about, nor indeed that it wasn’t responsible for pretty much all excess deaths at the time (including those from disease). In any case the point is more like that it is really not that odd to say that people full of bullet holes were mostly likely shot and didn’t die of the flu. We know that GHGs have increased and we see not only the warming but the signature of GHG warming, so we have found the weapon and the bullet wounds, as well as the body.

    Also, as I understand it and as mentioned by others, evidence for an MWP would be evidence for higher climate sensitivity not lower.

    Neither do I understand the idea that the warming (so far) has to be ‘unprecedented’ to be of concern. If an asteroid was about to hit the earth would it be comforting if somebody pointed out that it had happened before?

    (Plus the rate of climate change is also a concern – after all history also shows us what can happen when the climate changes quickly: http://edition.cnn.com/2013/11/19/opinion/frum-global-cooling-impact/ )

  68. Willard says:

    > it would be foolish to say humans killed 110% of the people who died. […]

    How can you be so sure, RickA?

    You forget about zombies:

    Percentages like 110% makes sense in a multi-causal analysis.

    If you or Judy got moithered by it, no big deal.

    Here’s NG:

    If natural cycles are regular and repeatable, the net temperature change over one complete natural cycle will be approximately zero. The warming during part of the cycle is cancelled by cooling during the other part of the cycle. What’s left is the long-term rise caused by man.

    Why does the IPCC conclude that the long-term rise is caused by man? The primary logic is simple, really. Of all the things driving long-term changes in the climate system, the biggest by far over the past 60 years is greenhouse gases. Second on the list is particle pollution, or aerosols, which partly counteract the greenhouse gases. Over the past 60 years, natural forcings (sun, volcanoes) have also had a cooling effect. So arguments over the relative importance of different kinds of forcing don’t really matter for explaining the past 60 years of temperature rise: the only large one on the positive side of the ledger is greenhouse gases.

    http://climatechangenationalforum.org/your-logic-escapes-me-by-john-nielsen-gammon/

    Auditing zombified arguments never ends.

    Your rope-a-dope will soon end, RickA.

    Justified disingenuousness has limits.

    Even if sometimes it goes up to 11.

    Here, let’s add this sentence.

    And another one.

    Thank you.

  69. RickA,

    Disease did kill millions during WWII in Europe. Humans killed millions also. So it would be foolish to say humans killed 110% of the people who died.

    Wow, you really are trying your damndest not to get what is essentially an utterly trivial point. Some things can lead to cooling, others to warming. The best evidence at the moment is that, since 1950, natural influences have had a net cooling effect that has offset some of the anthropogenic warming. If you can’t even recognise that this is even possible, we really should just stop right now.

  70. Mal Adapted says:

    RickA, as quoted by Marco:

    Dr. Mann’s science papers are advocacy. It is my opinion that he has an axe to grind. It is my opinion that he takes the data and massages it until it is “spun” to best show what he is trying to show.

    RickA’s comment on Greg Laden’s blog demonstrates the efficacy of the Serengeti Strategy. That’s the name Mike Mann gave to the campaign by professional AGW-deniers to cast him as the mastermind of the evil climate science conspiracy. By crediting him with superhuman powers of persuasion, they’ve made Mann out to be the Antichrist, and the hockey stick the mark of the beast!

    Jim Eager has the right of it:

    Rick A is just doing what he always does: grasping at straws with complete disregard for the physics, and then waving his hands when someone calls him on it.

    For the reality-based, it’s easier just to accept the science. Occam’s Razor, you know.

  71. OPatrick says:

    So it would be foolish to say humans killed 110% of the people who died.

    But it would seem quite reasonable to say that WW2 was responsible for 110% of the reduction in population at that time, if, say, medical improvements had led to lower natural death rates.

  72. Tadaaa says:

    I have had a quick look at the greg laden link

    And one observation I have regards a reply made to some denier point regarding “proof”

    Imo this is a classic denier trap

    As far as I am aware (someone correct me if I have got this wrong) the concept of “proof” has no real meaning in science, it is really a legal (or mathematical) term.

    Robust scientific theories, like AGW rest on many many mutually corroborating lines of evidence, no single one “proves” it (and no single one disproves it).

    Debate with any 911 twoofer or creationist for more than 3 seconds and you will be asked for “proof”

    Proof that evolution is true (they actually want to see a cat give birth to a tiger) or proof that explosives were not involved in the (gravity led) collapse of WTC .

    But both those are impossible – certainly to the standards of CT’rs, Creationist and AGW deniers require – ergo they win!

    They simply don’t understand that “theories” in the scientific sense, rest on an overwhelming body of evidence – the problem is, if they believed in the value of evidence in the first place they would not be CT’rs Creationist and AGW deniers.

  73. As Michael Mann (and maybe others) said: “proof is for alcohol and mathematics”. Science is typically about rejecting hypothesis, not proving them.

  74. anoilman says:

    In reading this paper I noticed that the 2sigma error margins were much tighter than before (MBH 98). This is as expected, and good to know.

    I’m not up to date on all my data on the MWP… was that global or just northern hemisphere? Also, what were the causes?

    I think Vinny was trying to say that he thinks Steve McIntyre was going to have a hard time with this data set;

  75. JCH says:

    That’s a great dog picture.

    For some reason the skeptics keep affirming that the MWP happened throughout the world, but at different times. They are strangely adverse to doing a global average on a date.

  76. anoilman says:

    Tadaa, Anders, I always thought the world dealt in margins of error. Its pretty hard to get an exact number or proof on anything.

    Heck, your PC doesn’t run on ones and zeros. It runs on Gaussian distributions of high and low voltages, and your computer only works when those two distributions don’t overlap. 🙂 Its simpler to understand it as binary 1’s and 0’s. (At high temperatures the distributions begin to overlap.)

    Tadaa, I’d be interested in seeing how this hockey stick with error margins overlaps MBH 98’s hockey stick;

  77. anoilman says:

    JCH: Graph?

  78. JCH says:

    By far the most detailed is still:

  79. anoilman says:

    JCH: 🙂 That’s almost as good as Mr Bean’s Whistler!

    Perhaps this is a better source on the MWP;
    https://www.skepticalscience.com/medieval-warm-period-intermediate.htm

  80. “It’s magic, lerpo. You just have to believe.

    technically it’s unicorns

    Let’s put a sciency sounding name to it. LTP

  81. “I think Vinny was trying to say that he thinks Steve McIntyre was going to have a hard time with this data set;

    Not really.

    he will start where you always start. Data selection

    Many thousands of tree-ring site chronologies are archived
    within the International Tree-Ring Data Bank but the majority are
    either relatively short (<200-years in length), have not been
    updated to the recent post-2000 period and/or do not reflect
    summer temperatures (St. George, 2014; St George and Ault, 2014).
    For N-TREND, rather than statistically screening all extant TR
    chronologies for a significant local temperature signal, we utilise
    mostly published TR temperature reconstructions (or chronologies
    used in published reconstructions) that start prior to 1750. This
    strategy explicitly incorporates the expert judgement the original
    authors used to derive the most robust reconstruction possible
    from the available data at that particular location.

    The lines of argument that flow from this are pretty clear.

  82. BBD says:

    Steven

    The lines of argument that flow from this are pretty clear.

    Are you suggesting that McI might argue that collectively the dendroclimatologists don’t know nuffing? IIRC he did once call the field ‘dendrophrenology’ or some such.

  83. Brandon Gates says:

    Rick A: If CO2 didn’t cause the warming in 1161-1170, what did?

    ATTP: It certainly wasn’t magic.

    The question is akin to confronting a geologist with 10 years of earthquake events, and upon failing to obtain a satisfactory explanation for the exact timing and magnitude of each and every one of them, declaring the theory of plate tectonics dead.

  84. Pingback: O's digest a richiesta e non - Ocasapiens - Blog - Repubblica.it

  85. anoilman says:

    Steve, I looked looked through 6 months of posts by Steve McIntyre complaining that he couldn’t order Briffa to exclusively use bad tree data. (That was when he was one of the reviewers for one of his papers.) Its hardly a credible approach to data.

    In any case, Briffa released a paper with all the tree rings in it, specifically the ones the hockey stick warriors were pontificating about, and still the stick emerged.

  86. BBD says:

    You always get a hockey stick, because the climate system responds to net forcing change, and by far the most significant forcing change in the last several thousand years is this.

    How could one *not* get a hockey stick?

  87. Kevin O'Neill says:

    “How could one *not* get a hockey stick?”

    Yes, that’s pretty much the point – anything that attempts to measure temperatures over this period that does *NOT* result in a hockey stick is pretty much an outlier and immediately suspect just because there’s so much other evidence that *DOES* result in hockey sticks. It would be a good subject for a ‘Pattern Recognition in Physics’ article.

  88. “Are you suggesting that McI might argue that collectively the dendroclimatologists don’t know nuffing? IIRC he did once call the field ‘dendrophrenology’ or some such”

    No. I said the line of argument is clear

  89. “How could one *not* get a hockey stick?”

    you will always get a HS. that’s never been the chief dispute.

  90. guthrie says:

    Which chief dispute though? The denialist one? Obviously there are many different denialists with different disputes, so which one do you mean?

  91. Andrew dodds says:

    SM –

    Well, he’d have to demonstrate a better data selection. Just whining about it in the classic McIntyre ‘they must be up to something because The Team’ manner doesn’t cut it.

  92. Steven,

    you will always get a HS. that’s never been the chief dispute.

    I think you’re slightly rewriting history here. There are clearly many who dispute the hockey stick as a reasonable represention of millenial temperatures.

  93. BBD says:

    Steven

    No. I said the line of argument is clear

    Clearly not to me. So resolve my confusion by being more specific. If Andrew is correct and the issue in mind is data selection, then surely this implies that those dendro chaps don’t know nuffing?

    Or is there a darker implication?

    Set me right, please. I’m floundering here.

  94. BBD says:

    that’s never been the chief dispute.

    What was the chief dispute?

  95. Michael W. says:

    Jeez, ATTP, BBD, and some of the rest of you, you’ve got the patience of saints. How long has RickA been bouncing around various climate science sites with his act? Repeating the same PRATTs (Points Refuted a Thousand Times); making unsourced claims and accusations; asking what he thinks are gotcha questions (that two minutes of searching could find solid scientific answers for) and ignoring the answers he’s given; assuming that if he can’t understand X, that means no one does… etc. I mean, “If CO2 didn’t cause the warming in 1161-1170, what did?”… seriously? It’s difficult to credit him with a sincere desire to engage or learn.

    Another of the all-too-common examples of the anti-intellectualism that seems to be so deeply embedded in anglophone cultures (I don’t think it’s coincidence that climate change denial and creationism are so much more prevalent in North America, the UK and Australia than in other developed nations). RickA seems to really believe that he not only can fairly easily master this stuff, well enough to show up smarty-pants professional scientists, but that he already has.

  96. John Mashey says:

    MedievalDeception 2015: Inhofe Drags Senate Back To Dark Ages,
    JCH probably knows this, did *not* claim that image was from IPCC(1990) … but for everybody else, it wasn’t. (See URL above).
    It is same as:
    2001.xx.xx Waiting for Greenhouse John Daly, Western Fuels Association “science advisor.”

    2005.03.16. The Significance of the Hockey Stick Steve McIntyre, note 1995 and Deming story

    2005.05.11 Presentation for George Marshall Institute and Competitive Enterprise Institute Steve McIntyre and Ross McKitrick. (Ignore 2012 dates when Dan Vergano uploaded.)
    On p.10 they repeat the falsehood of Daly’s that this graph was from IPCC 1995, needed to amek the story (especially with Deming) be slightly less nonsensical. (
    Joe Barton’s staffer seems to have given this to Ed Wegman and Yasmin Said in Sept 2005, and they must have digitized that, as indeed Wegman said, Strange Scholarship in the WR, p.50
    “DR. WEGMAN. No, I don’t have it. I take no responsibility for what IPCC did in 1990. There is no way I could do that. Their data is not available to me. In fact, the reason it was digitized was that I had to go back and construct it from their picture. That doesn’t mean no data exist. And in fact, as far as I know, it was based on European and Asian temperature profiles that were available in the 1990s.” (It was Central England.)

    See pp.89-95 about key files that magically disappeared, including Yasmin Said’s ill-fated presentation, p.8 has that image, not well scanned, but certainly not the image from IPCC 1990. (The 1995 falsehood was discovered sometime after May 2005, because the WSJ claimed it was 1990 image, not 1995.

    2012.10.08 Tom Curtis asked McIntyre
    “Further, it is clear from blemishes and other alterations in the image you used in 2005 that the image you posted (and which can still be found above) was that posted by John Daley on his website in 2001. As John Daley corrected his attribution in 2004, a year before you misattributed the image, presumably you did not get the image directly from Daley or his website, but from some other person. Would you care to clarify who first brought the image to your attention, and in what context?
    I note that proper attribution involves attribution of secondary sources rather than primary sources when you use the secondary source rather than the primary source, as you clearly did not do in this case.”

    McIntyre answered:
    I don’t recall where I picked up the version used in the post. You say that Daly “corrected his attribution in 2004″ – do you have any evidence for this other than the fact that his attribution in 2004 (http://www.john-daly.com/hockey/hockey.htm) was correct? Why do you believe that Daly didn’t have a correct attribution all along? It looks to me like the incorrect attribution to IPCC 1995 in my March 2005 blogpost was my own slip, rather than something that I inherited from another commentary. Deming’s article, cited in my 2005 blogpost, got the 1990 attribution right for example. As I noted previously, I crosschecked the origin soon afterwards and all attributions after June 2005 were to IPCC 1990.

    So, a non-scientist advisor for a coal association gets misattributes a not-quite-right image to 1995, McIntyre propagates it, clearly proving that he did not have access to either IPCC 1990 or 1995. The WSJ uses the image, as do Wegman and Said … and many others, including Inhofe(2012) and his 2015 Senate talk. But McIntyre could not recall where this incredily-promoted image came from. How sad.

  97. Rick A (Jan 14 11.26pm):

    Doesn’t it take energy to melt ice (I hope I don’t have that backwards)? Are not ice sheets formed during ice ages storing energy which is release later when the ice sheets melt?

    It DOES take energy to melt ice (the latent heat of fusion), BUT ice sheets formed during the ice ages are NOT storing energy to release later. A large amount of energy has to be absorbed by ice to melt it, it doesn’t “release” energy as it melts. However, it does “release” energy as it freezes.

    Your inability to understand this shows a lack of basic thermodynamics.

  98. monicaswicked,
    Thanks, I’d missed that.

  99. appaling says:

    I find this whole issue quite confusing: There is a study that identifies the three warmest decades between 40N and 75N, one of them during the medieval warm period.

    Since the warm periods were localized and wandering around the globe it does not imply that the global temperature was high. (From Wikipedia, which though not a primary source tend to be mostly correct: “Temperatures in some regions matched or exceeded recent temperatures in these regions, but globally the Medieval Warm Period was cooler than recent global temperatures.”, quoted from Mann, M. E.; Zhang, Z.; Rutherford, S.; et al. (2009). “Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly”. Science 326 (5957): 1256–60).

    So we have some warm regions in the past due to natural variation, today we have the hottest decades *globally*!

    What is this discussion really about? Apples and oranges?

  100. appaling,
    I think your point is valid. Variability on decadal scales can be quite high, both regionally and globally. Not only is this reconstruction not global, that one of the warmest decades happened to be in the 1100s does not really indicate that anything other than decadal variability can be quite substantial – I think.

  101. JCH says:

    My hunch has always been that the MWP probably was, on a global basis, as warm as some point in the last decade of the 20th century.

  102. BBD says:

    Based on what, exactly?

  103. BBD says:

    Diaz et al. (2011):

    While there is evidence of medieval warmth, its spatial extent does not appear to be as geographically uniform as the warming seen during recent decades (Figs. 1 and 2). Based on the most recent MCA reconstruction (Fig. 2 in Mann et al. 2009), relative to a modern reference period (1961–90), the MCA was found to be warmer than the late twentieth century over ~1/3 of the equivalent global area in the reconstruction, but colder than the late twentieth century (post-1950s) over ~2/3 of the globe. Relative to an early twentieth-century 50-yr baseline (1900–49), the MCA was reconstructed to be warmer than that baseline for ~2/3 of the globe and colder than ~1/3. Therefore, the balance of evidence does not point to a high medieval period (A.D. ~1000–1300) in the Northern Hemisphere or the globe as a whole that was as warm as or warmer than the post-1970 period.

  104. izen says:

    In the past those rejecting mainstream climate science would invoke the MWP and refer or link to a map at CO2science of all the (to date) studies that had detected and dated a local warming of the climate around a 1000 years ago. It now seems to have migrated to a site calling itself science-skeptical. Orwellian irony abounds in this field.

    It was always a bit of an own goal. You can ‘play’ it as a version of the mah-jong tile-matching game.
    Try to find two records where the peak temperature matches in time. This is especially difficult if they are in different hemispheres of the globe!

    http://pages.science-skeptical.de/MWP/MedievalWarmPeriod.html

  105. BBD says:

    There’s a rather good debunk of the CO2Science MWP con trick here. And let’s spare a thought for the fossil-fuel funded misinformers the Idso family, whose tireless efforts to confuse and mislead the public are showcased at CO2Science.

  106. Willard says:

    > What is this discussion really about?

    The word “unprecedented.”

    But it’s sooo 2005. For 2016, I just want to say one word to you. Just one word. Are you listening?

    “Satellites.”

  107. JCH says:

    Yes, well, skeptics are very adverse to calculating a GMST, so there’s nothing to worry about because they’ll sort of need one.

    But I have crayons.

  108. BBD

    ” Clearly not to me. So resolve my confusion by being more specific. If Andrew is correct and the issue in mind is data selection, then surely this implies that those dendro chaps don’t know nuffing?”

    Jesus are you dense?
    look at the table.

  109. BBD says:

    Answer the question, please, Steven.

  110. BBD says:

    Here, again, are the things I would like you to clarify:

    Clearly not to me. So resolve my confusion by being more specific. If Andrew is correct and the issue in mind is data selection, then surely this implies that those dendro chaps don’t know nuffing?

    Or is there a darker implication?

    that’s never been the chief dispute.

    What was the chief dispute?

  111. Yes, I’m quite keen to understand what Steven thinks the chief dispute was. Certainly seems to me that the chief dispute relates to whether or not a hockey-stick-like shape is a reasonable representation of our millenial temperature history.

  112. JCH says:

    He’s fond of saying it was not about the blade; it was about the handle.

  113. BBD says:

    That’s still an argument about the hockey stick, though, isn’t it?

  114. BBD says:

    I really would like to know what the problem with Wilson16 is supposed to be. Presumably it is about data selection since Steven urged me to look at ‘the table’ by which I assume he means W16 table 1, which is sitting in front of me.

    This may well relate to the handle of the stick, so I await Steven’s response with real interest.

  115. izen says:

    While SM is being coy…

    If the wiggles in the handle of the hockey stick could be shown to be comparable in rate or magnitude to the current warming it disproves the exceptional claim for recent warming.

    The selection of long tree ring series from a restricted region of the N hemisphere imports the detrending of any past natural variation because they were constructed by dendrochronologists with a uniformism bias.

    The problem with claiming past natural variations comparable with present trends, apart from the implications for climate sensitivity, is the total absence of any evidence sea levels have responded in the past to hypothetical warm periods as they are at present.

  116. izen,

    the total absence of any evidence sea levels have responded in the past to hypothetical warm periods as they are at present.

    That’s a good point. I hadn’t thought of that before.

  117. JCH says:

    is the total absence of any evidence sea levels have responded in the past to hypothetical warm periods as they are at present.

    But are sea level reconstructions of the past good enough to rule out a MWP roughly equivalent to the last decade of the 20th century?

  118. But are sea level reconstructions of the past good enough to rule out a MWP roughly equivalent to the last decade of the 20th century?

    I would have thought that the would suggest that it couldn’t have been globally as warm as the last decade of the 20th century. Maybe the uncertainties are large enough to include this as possible, though.

  119. BBD says:

    Is it possible that JCH is cracking a funny? I might have missed the first one, too…

  120. BBD,
    Indeed, I often miss the subtle jokes 🙂

  121. JCH says:

    1/4 open and 3/4s closed, which I think is impossible. There used to be a website about an effort that included Michael E. Mann, and lots of other scientists, to get together and try to constrain the MWP/MCA. They could not constrain it, and the other side seems uninterested in doing any work.

    Just found this… had never seen it before:

  122. On p. 13 of our dynamic duo’s booklet, there’s a figure that looks like this one:

    The caption reads “Fig. 2: Traditional View of Global Temperatures for the Past 11,000 Years.” The acknowledged source is Reprinted with permission, David Archibald. The prefacing text reads:

    Here’s another view of the world — and it’s the way we looked at temperatures for close up to 40 years, before worries about global warming made the previous chart so popular.

    No citation has been provided to substantiate the claim that Archibald’s figure corresponds to how we “saw the world for close up to 40 years.” The “previous one” is traced “Steven Lawrence, after MBH 1998.” Perhaps John Mashey has more details on its provenance. In any case, the text that describes Fig. 2 reads:

    In the figure above we see rapid temperature rise for the first 1,000 years after the end of the last Ice Age and then fairly gentle fluctuations within a narrow band of temperatures after that, including the present day. According to this view of the world, what’s happening to us now has happened before — without our emitting vast quantities of CO2. If this view is accurate, then worries about global warming seem, at best, premature, and the use of the term “Optimums” to describe times when it was warmer than today may indicate that some warming is not that bad.

    It’s unclear if our dynamic duo considers this “view of the world” that seriously, since one of their “Two Big, Fat Disclaimers” on p. 8 contains:

    Both your others believe global warming exists, is a problem and needs to be addressed.

    Since the section title of our dynamic duo’s booklet is What’s at Stake, it might be important to reconcile our dynamic duo’s view with a “view of the world” resembling what the Auditor once or twice called the Geological Perspective.

    I’m not sure why “but it happened before” matters that much, but here we are.

  123. BBD says:

    JCH

    My hunch has always been that the MWP probably was, on a global basis, as warm as some point in the last decade of the 20th century.

    Perhaps September, 1992?

    🙂

  124. Andrew dodds says:

    BBD –

    Well, just by eyeballing, 1950s temperatures seem about the same as touted for the MWP and RWP. And late 1992 was close to the 1950s in temperature.

    So, errm, yes.

  125. BBD says:

    JCH

    1/4 open and 3/4s closed, which I think is impossible.

    Sorry, I don’t quite get this. What do you mean?

    The graph is AR5 WG1 6.10:

  126. BBD says:

    Andrew

    Well, just by eyeballing,

    Even by checking 🙂

    1992 0.45
    1992.08 0.42
    1992.17 0.46
    1992.25 0.23
    1992.33 0.32
    1992.42 0.24
    1992.5 0.13
    1992.58 0.09
    1992.67 -0.01
    1992.75 0.1
    1992.83 0.04
    1992.92 0.22

  127. BBD says:

    Willard

    From the geological perspective of the Auditor:

    Mostly, it seems to me that, when you step back and look at climate history from a geological perspective, the existence of change on all scales is really quite remarkable.

    I think ‘troubling’ rather than remarkable, if I was a lukewarmer.

  128. JCH says:

    On Google Scholar you can find a whole bunch of papers that find warming at a certain local during the MWP, but I’m not finding very many that found cooling in a certain local during the MWP.

    Abstract

    Global temperatures are known to have varied over the past 1500 years, but the spatial patterns have remained poorly defined. We used a global climate proxy network to reconstruct surface temperature patterns over this interval. The Medieval period is found to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally. This period is marked by a tendency for La Niña–like conditions in the tropical Pacific. The coldest temperatures of the Little Ice Age are observed over the interval 1400 to 1700 C.E., with greatest cooling over the extratropical Northern Hemisphere continents. The patterns of temperature change imply dynamical responses of climate to natural radiative forcing changes involving El Niño and the North Atlantic Oscillation–Arctic Oscillation.

  129. BBD says:

    Mann et al. (2009) is referenced in Diaz et al. (2011) quoted upthread. Mann was a co-author.

  130. BBD says:

    Lambeck et al. (2014):

    The record for the past 1,000 y is sparse compared with that from 1 to 6.7 ka BP, but there is no evidence in this data set to indicate that regional climate fluctuations, such as the Medieval warm period followed by the Little Ice Age, are associated with significant global sea-level oscillations.

  131. JCH says:

    are associated with significant global sea-level oscillations.

    I don’t see how izen can be wrong.

  132. BBD says:

    You are getting as gnomic as Steven, JCH. I’m no longer sure where my feet are.

  133. Pingback: Another hockey stick | …and Then There's Physics

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