I simply said I don’t think we’ll ever conclusively know whether the MWP was warmer globally or not, so the doubt goes both ways. There is plenty of evidence to suggest that the MWP existed and resulted in warmer global temps than those of today. IMHO, there is enough evidence to assume that it was warmer.

The MWP’s mere existence, regardless of whether or not it was warmer than today, can still be used to support the idea that a large portion (if not almost all) of the post 19th-century warming is natural variation.

Much of the local, historical evidence for the MWP indicates (on a regional basis) pretty consistently temperatures higher today. Of course there are always the occasional exceptions, as regional temperatures vary more greatly than global temperatures, but the balance of historical evidence suggests that the MWP was warmer than today (this evidence is easy enough to locate on the internet – check the “medieval” category for a handful of examples)

So my viewpoint would be that, on the balance of evidence available today, that the MWP was indeed a little warmer than today. The Holocene optimum was warmer still. However, this remains a “balance of evidence” rather than a clear cut proof, so will always remain a degree subjective and open to interpretation.

The multi-proxy studies were supposed to resolve this question, but in truth they have created more questions than answers.

The “pre-Mann” temperature curve produced by the IPCC back in 1995 (I think?) based on the subjective evidence shows the MWP warmer than today. The Mann curve resulted in a seed change in IPCC “opinion”.

Unfortunately the only real answer we will get is if the globe warms in the future. Until then, as you say, we do not really know. I really hope that you are right.

I agree, you can’t make the conclusion the MWP was warmer than today based on Fig 8. But it wasn’t meant to – it was simply done to show what Mann’s results would’ve looked like using proper computational methodology. Whether you should be able to draw any concrete conclusions from it due to its statistical nature is important to many scientific and mathematical people, but the vast majority of people just look at the hockey stick and don’t know/care about the statistics. When the hockey stick shows-up in a school book, Time magazine, an Earth Day pamphlet, a memo to a politician, etc, do you think there are any footnotes regarding statistical significance? Do you think the vast majority of readers know enough about statistics to even care?

IMHO, we’ll never come to a significant conclusion regarding the MWP. The proxy information is too scarce and likely too imprecisely correlated with temperature on a global scale. Much of what we have concerning the MWP is anecdotal information, and even this is sporadic. There can certainly be regional conclusions that the MWP was warmer than today, but on a global scale, it may be impossible to prove one way or the other.

Whether the MWP was actually warmer than today is also irrelevant, IMHO. But acknowledging it’s presence and approximating its magnitude goes a long way in determining how anamolous the 20th-century warming actually was and how much natural variability we’ve seen in the past 1000 yrs. The hockey stick implies the MWP basically didn’t exist (i.e., MWP evidence is simply regional variability), which makes the 20th century appear to be without question due solely to human GHG emissions and warming at an unprecedented and alarming rate. Most any layperson who looks at it and accepts the hockey stick to be true would easily be swayed. So I think you know why it appears in so many locations and has become the object of such fascination on both sides!

I don’t remember exactly what the data was zeroed to in Fig 8. It’s probably mentioned on this site somewhere or in Mann’s paper.

Re#11, there is no doubt humans affect weather on a local scale, and it’s possible there are climatic effects. But it’s difficult to tell how significant these climatic effects are.

Yes, the IPCC acknowledges half of the 20th century warming to be natural – the warming which occurred in the 1st part of the century. That leaves the other half, but the IPCC doesn’t say ALL of that other half is anthropogenic. I don’t remember their exact wording (which also may be different in the Working Group vs Summary for Policymakers), but I think the IPCC stated that it was either likely or certain that some of the 20th century temperature rise was due to human activity. I don’t think it was ever quanitified. It could be 0.3 deg, or it could be 0.003 deg. Nevertheless, if the warming of the 1st part of the century is entirely natural, and if it is equal in magnitude to the warming of the 2nd part of the century, then one could rationalize that a large part (or almost all) of the warming of the 2nd part of the century was also likely natural.

I don’t really get it – the data that you presented is solely so prove Mann et al wrong but you can’t draw any conclusions from it – sorry I must be really thick – I just dont see this part.

Also the 0.3 deg is with respect to a mean – what mean? – that was not clear on the graph.

I believe the figure you refer to is Fig 8 (the number and close paraenthesis in your post shows-up here as a smiley face), which starts out at 1400 AD. You also refer to the Medieval Warm Period and the temperature differentials on the figure, as if the time periods coincide.

I don’t think you’ll find many people claim the MWP lasted beyond 1400. Many accounts say it actually ended roughly 1200-1300 AD. So if the figure you’re referring to starts at 1400 AD, it doesn’t include the MWP at all (or, at the most, the very tail end of it), and temperatures were likely higher prior to that. If you believe the figure used by the IPCC in 1995 (Figure 3), the MWP temps peaked around 1200. Figure 4 implies that temps likely peak later than shown in Figure 3 but are still headed downward before 1400. So the 0.3 degrees you speak of is small than the peak of the MWP. How much smaller, we don’t know.

Also, that 0.3 degrees you speak of is a differential with respect to a mean. The 0.6 degree change of the 20th century is relative to the beginning point of the century, not a mean. The temperature at the beginning point, 1900, is well below the mean used to center the graph. So you’re comparing apples-to-oranges with your 0.3 vs 0.6. When compared to the same mean temperature in what you called “reconstructed without bias,” the temperatures in the early 1400s were higher than those of the late 20th century. And as stated earlier, the early 1400s were likely not the warmest period of the MWP.

Keep in mind also that Figure 8 is an attempt to correct flaws in the hockey-stick methodology interpretation of proxy information. It does not attempt to account for flaws in proxy data, the possibility of which has been raised elsewhere on climateaudit.

Lastly, and what is possibly most important of all, is that the reconstructions in Figure 8 lack statistical significance. Without statistical significance, drawing concrete conclusions from the data is next to impossible. In many cases, it’s actually not even publishable.

In it the reconstructed data without bias shows the max temperature rise at about 1450 is 0.3 degrees (Fig) Now to my mind even if you accept that the data analysis is flawed the degree of heating at this time is less that half the generally accepted warming of today (0.6deg).

Ender, if the study is flawed, the degree of heating in 1450 could have been 0.6, 0.9, or -0.3, or something else, so we cannot conclude it is less than half the “generally accepted” warming of today because we don’t know what it was.

As to your final question “how often do you think the reconstruction would also be hockey-stick shaped?”. My tentative answer would be “hardly ever”

You see, John, this is what scientists call “a hypothesis”. A theory, or conjecture, which is as yet unproven. I also had a hypothesis, which had rather more detailed and technical rationale behind it, outlined in Lost Cedars #2. It seems from Steve’s assessment that your hypothesis is not standing up to scrutiny, and whilst it wasn’t entirely clear before, the comments on this site that suggest the hockey stick imprint appears in the final “temperature” reconstruction can stand.

The Pacific Research website needs some tweaking but I don’t see this as strictly Steve’s responsibility, any more than I believe that Prof Mann is responsible for checking every website that uses his graph.

after much tedious prodding from me

Nice choice of words, very apt I would have worded it differently though; perhaps something along the lines of “wasting a lot of Steve’s time demonstrating something that the rest of us had already guessed”

As I said earlier, and I think from your comment you broadly agree, now this is settled we can move on. The hockey stick carries no weight as a temperature reconstruction. Now can we please move on to other studies!!!