Bishop Hill Abraham on the MWP
Jul 14, 2011 Climate: HSI Climate: MWP John Abraham, the US academic who keeps falling out with Lord Monckton, has written an article about the MWP. It's a bit of a mixed bag, but there is much of interest.
For example, there's this rather naughty bit of quoting out of context:
the National Academy of Sciences thoroughly investigated [the MWP] and concluded, “the late 20th century warmth in the northern hemisphere was unprecedented during at least the last 1000 years."
Unfortunately, examination of the NAS report shows that they actually said:
The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years
So they did not conclude that 20th century temperatures were unprecedented, they made an opening observation that Mann had claimed this. As I'm sure readers here know, they concluded that Mann's claims were "plausible", which is not the same as concluding that they were correct.
Abrahams also gets comments from a number of paleo people in reference to two questions:
- Was the MWP global in extent and warmer than today?
- Does the presence of the MWP call into question human-caused global warming?
The responses are very interesting, because several of the respondents don't seem to have addressed question 1. I'd love to know what they said - my guess is it's something along the lines of "we don't know". Such a response is certainly suggested by Abraham's conclusions:
...the existence of the MWP is not in serious doubt; but whether it was global in extent or warmer than today is. In addition, the presence of a MWP does not call into question whether humans are now causing the Earth to warm.
These two points are both fair I think. The first point is particularly interesting: it's a reasonable interpretation of the science but it's a long way removed from the IPCC's conclusion that temperatures are "likely" the highest in 1300 years.
Reader Comments (71)
I still waiting for some "climate scientist" to claim that the MWP was caused by the burning and other plundering by the Huns, etc. that occurred at the fall of the Roman Empire.
The null hypothesis is this: natural variations (which we do not adequately understand) caused both the MWP and the far-from-unprecedented warming we have seen since 1980.
It is up to climate alarmists to provide a robust alternative to that simple picture, and despite 20 years of trying (by fair means and foul) and the expenditure of tens of billions of dollars, they have failed to do so.
Hengist writes:
"I find your statement that we do not know what makes up the natural variation which caused the MWP disingenuous..."
Hengist, I did not say that. Your problem is that you are using the word 'cause' when there is not occasion to use it. You are trying to force it into no hole, so to speak.
I said that the MWP is an example of natural variation. There is no arguing with that, unless you believe in flying saucers, witches, or such, right?
Nature does not have a cause. Nature just is. Unless you want to raise religious questions, but they exceed the scope of this blog.
So, if the MWP is an example of natural variation then nature has the capacity to cause it and, therefore, nature might be causing it now. So, the existence of "today's warming," even warming matching that of the MWP, does not show that it is unnatural or unprecedented. "Today's warming" might be natural and the burden of proof is on those people, the Warmista, who claim that it is manmade.
As regards the question of what it is in nature that caused the MWP, the answer is that no one knows. Someday we will find out. Before that can happen, our so-called climate scientists have to get up from their Gaia Models, go outside, and do some actual research in the actual environment. Or surrender their funding to some actual physical scientists.
Hengist writes:
"So to sum up the causes of the MWP : natural variability. Causes of the natural variability in Mediaval times: we don't know. As Theo explains "the MWP was a natural event then "today's warming," which is of the same order, has a ready explanation in nature. In other words, what we experience now has occurred before and was caused by nature alone" Not much of an enquiry in that quarter is it."
You remind me of a middle teen who is learning that his parents do not have all the answers and is learning in addition that all of the money in the world could not buy an answer to the question that he wants answered. You insist that there must be an answer to these questions:
1. Why is Earth warming today?
2. Why did Earth warm during the MWP?
3. Is the cause of the MWP the same as the cause of "today's warming?"
4. Why are you not giving me the cause of "today's warming?"
What we agree on is that the MWP was natural. I just explained that the MWP was an example of natural variation. From the MWP, we learned something about what Nature is capable of. From that, I concluded that there is no need for a human cause of "today's warming" because it is very likely natural.
With regard to questions 1, 2, and 3, I have explained that no one knows the answers. In doing so, I am not setting aside or in any way avoiding my duty as scientist; to the contrary, I am explaining the limits of our scientific knowledge at this time. That is the primary duty of the scientist, to explain the limits of science at the moment.
As regards question 4, I am not giving you a cause for "today's warming" because I would have to tell lies to do so. Anyone who tells you that they know the cause is lying or deluded. That is the reality. It is up to you to develop the maturity to accept it.
Caleb,
(This is reposted from Josh's cartoon forum) Above, I wrote:
"If Abraham wants to redo his "study," he can use the following question:"
"As a scientist, do you believe that temperatures in the MWP were higher than today, lower than today, roughly comparable to today, or do you believe that there is too little evidence to justify a comparison?"
Notice that the only choice that favors Mann and The Team is "lower than today." However, if you make that choice you also have to affirm that there is adequate evidence to justify the comparison. Yet the only source of such evidence is Mann and his sycophants. And that evidence has been totally and rightly debunked. What percentage of scientists would actually choose the "lower than today" option. I say a tiny percentage, certainly in the single digits. The Warmista are in bad shape indeed. Essays such as the one by Abraham only emphasize that fact.
Hengist asks:
"At the risk of being called a troll with a red herring can I ask how can that explanation [natural variability] be said to be falsifiable?"
All that is needed to falsify it is for some genuine scientist to provide genuine evidence that "today's warming" is outside natural variation or that manmade CO2 or some other manmade substance is causing "today's warming" apart from any contribution by natural variation. Efforts to show something along the lines have been pathetic. Mann's pathetic Hockey Stick might be the best of the bunch.
geronimo;
In your fine post, you do a double typo: "drop form -40C to -36C,"
Jul 15, 2011 at 3:48 PM |
That would be "rise from -40°C to -36°C". (BTW, the degree trick ° is Alt-248).
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Everyone should note that Hengist is doing the Trenberth Shuffle, trying to make the "null" AGW. Hengist, a "null" hypothesis is the one that an honest scientist tries to SUPPORT, and only if he fails will he fall back on the "alternative(s)", like AGW. Natural Variation is the Null Hypothesis (H0). Only if a thorough and relevant and competent attempt to support it fails (convincingly, with a probability of at least 100:1 that the evidence is incompatible with it), can AGW (H1) be considered not to have been disproven.
I know it sounds all weird and backwards, but the net effect is to put the (heavy) onus of proof on the proposers of a new hypothesis. It is how science tries to avoid the dangers of confirmation bias, group think, data snooping, and so on.
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Mike;
your litany of endorsements by seriously compromised Professional Society administrators of AGW theses is the sort of offensive bilge that the late Hal Lewis and others have excoriated. But for the bureau-brained, I guess it all looks veddy Offishul and Scientifical.
RE: Jul 16, 2011 at 3:45 AM | Theo Goodwin
Yes, that is exactly the sort of question (or follow-up question) that should be asked.
A true scientist is not afraid to answer, "We honestly don't know." However a scientist hungry for funding might reply, "The is some evidence which suggests (insert disaster) might possibly happen in certain situations, but further research is needed." A scientist who depends on politics for funding will reply like a politician: When you look carefully at his 300 word answer, you will see it contains absolutely nothing solid, and is all fluff and innuendo.
It's a little bit of a rube's game to even be accepting implicitly, as much of the discussion upstream does, that current warming must be something close to 100% "either/or" natural vs C02. Why?
The thing is, this is a much greater problem for the IPCC than for skeptics. Most skeptics would be willing to assign *some* significant portion of current warming to increased C02. IPCC has been sitting on insisting that nearly none of it is natural variability.
Brain,
The claim was made the 100% of geologists refute AGW. I showed this claim was false. I cannot help that you and simpleminded like being lied to.
geo;
The problem is in part that the range of possible net sensitivities actually should include negative numbers, both in formal terms and on the weight of evidence. The IPCC won't even sniff at that possibility.
So 0% seems like a good compromise. ;)
The phrase “the late 20th century warmth in the northern hemisphere was unprecedented during at least the last 1000 years" has virtually the same force as evidence as "the 1998 warmth in the northern hemisphere was unprecedented during at least the whole of 1997," seen in the light of the period of the earth's existence. Moreover, to limit a period of a "unprecedentness" is tantamount to discrediting the very term itself, since it implies admitting that precedents might have occurred before that given time limit.
Are the causes of the MWP discussed in The Hockey Stick Illusion , anyone? I've been trying to find a discussion of it but with no luck, I find that odd.
So far the only thing I've got to go on is an assumption that the MWP's causes are the same as 20th C warming's causes. There's been rhetoric but no evidence. On the AGW side there's Goosse et al 2006 which discusses causes of the MWP and it's in the peer reviewed literature.
This Abrahams chap, for all his claims to be a scientist, is just behaving like a cherrypicker extraordinaire.
Re causes of the MWP, etc., have a look at Erl Happ's new posting:
http://www.happs.com.au/images/stories/PDFarticles/TheCommonSenseOfClimateChange.pdf
He's inviting critiques and quibbles, so have at it.
Short version: incoming UV modifies upper level ozone, which is very efficient at absorbing upwelling longwave (IR) and thus heating the stratosphere, driving cloud patterns (albedo changes).
Thanks Brian H ,
but Erl Happ's work isn't peer reviewed, Goosse et al 2006 is, so Goosse trumps Erl. Sorry. Any peer reviewed work to rebut the warmist Goosse et al 2006 ?
Hengist --
I think you're misreading Goosse et al. (2006) if you think it presents the cause of MWP. From it:
"Our modelling results suggest that the warm summer conditions during the early second millennium compared to the climate background state of the 13th–18th century are due to a large extent to the long term cooling induced by changes in land-use in Europe."
and
"For the last 6000 years, however, a reduction of northern hemispheric summer insolation leads to a summer cooling for Europe of more than 1.5 C..."
In other words, despite its title "The origin of the European “MedievalWarm Period", Goosse et al. claims to explain the *cooling* since MWP. If you believe them, the MWP extended back considerably in time, at least in Europe.
...and please, get over the assumption that peer-reviewed=true, not-peer-reviewed=false. Peer-reviewed means not completely groundless, but little more. Not-peer-reviewed means, well, pretty much nothing --some is utter garbage, some is very sensible stuff. I'm not convinced that the distributions of accuracy or worth are a lot different, except for a fatter tail of the not-peer-reviewed matter in the "completely off one's rocker" category.
@HaroldW
I'm not suggesting peer reviewed = true at all. But it's the top table of the debate and should inform us lesser mortals.
Hengist,
Sorry to but-in.
"I'm not suggesting peer reviewed = true at all."
You are in agreement with most of the posters here (if I may be so bold). So why keep insisting that it is necessary? Peer reviewed does not = scientific fact automatically but is part of scientific discourse. Many peer reviewed papers have been overtaken by further studies - that's what science does. Even Einstein doesn't get a free-pass on Relativity.
@simpleseekeraftertruth
So has Goosse been overtaken? I don't know that's why i'm asking. Or do you seriously expect the warmists to accept Erl's blogpost ?
Hengist,
Well trolled! The format almost exactly right but I think the second sentence was perhaps superfluous..