Was the Medieval Warm Period warmer than today?

The MWP was an accepted fact until recently. Even the IPCC accepted it in their 1996 report and included this graph of temperature (http://www.atmos.washington.edu/2001Q2/211/groupE/... ) showing it was clearly warmer than today. Since then it has become increasingly inconvenient to the Global Warming Alarmists. Thus there has been a concerted effort to try and delete it from history. Hence the famous David Deming quote where he reveals that a major person working in the area of climate change and global warming sent him an astonishing email that said: 'We have to get rid of the Medieval Warm Period.'

Since you “embrace the MWP” I trust you condemned the Mann, et al, “hockey-stick” graph that deleted it? I suspect, however, you did no such thing.

What do others think?

Nick c & jim z: Indeed. You cannot farm permafrost. So, if the Vikings farmed what is now permafrost (as archaeological evidence suggests) then it simply must have been warmer back then. Or are we missing something?

Monkey M: So, what’s your answer? I assume from your response that you think it was cooler than today, since you’re obviously trying to deny it was warmer by simply refusing to discuss it. Usually a tactic employed by those who know they’ve lost the argument.

Morbidmotion: My apologies for boring you. (see above).

Nickel Johann: How’s *that* for an ad hominem attack? The fact that nobody knows who they are (“they” being Craig Idso, Sherwood Idso, Keith Idso, etc.) is irrelevant. For the most part they are simply quoting the work of other scientists. Hundreds of them, in fact. Many companies, organisations & charities use mailboxes, are they all untrustworthy too?

JOHN WALKUP: Thank you for making an exception for me. Not that you made much of one, you say very little, just posted a few links really. For the record, I believe LHO killed JFK, all on his own. I always give the evidence an objective look before I decide which option I think is more likely to be correct. I’ve done exactly the same with global warming and have concluded that it is unlikely that we are heading for any hideous catastrophe.

Two of your links are to realclimate.org. Two of the authors of the debunked “hockey-stick” stick graph (that deleted the MWP completely) contribute to that site. Is it any wonder therefore, that they continue in their efforts to abolish the MWP?

Your other link is also somewhat dubious because that site dismisses the importance of the Mann, et al “hockey-stick” graph and is, therefore, biased.

Nathan T: I agree with you, but I think you’re missing the point. The Global Warming Alarmists would have us believe that we are heading towards a looming catastrophe due to global warming. However, the MWP suggests that warming is not a catastrophic even; quite the opposite, in fact. Thus, if the MWP was real and several degrees warmer than today, then we are not in as much trouble as we are being lead to believe.

dana: Oh dear, oh dear, oh dear. You first link is to two graphs, the second of which is the infamous Mann, et al, “hockey-stick” graph itself! I am absolutely staggered that you are still linking to it as a valid piece of science. Have you been living on a desert island for the past few years?

OK, on the remote possibility that you’ve genuinely not heard how bad it was, let’s go through the main problems, shall we?

1) They used a proxy (bristlecone pine tree ring data) that had been highlighted as a dubious temperature proxy, because it was actually more a proxy for CO2. Not only did they still use it, but they gave it 390 times more weight than any other dataset.

2) Proxy datasets that showed a pronounced MWP were left unused, in a folder marked “Censored Data”.

3) The computer model they used would produce a hockey-stick graph even if random data was used. Garbage in – hockey-stick out.

If you’d liked to have seen the studies, then you could have. They are all listed on the co2science website. They specify each study and give a summary of its conclusions.

And I suggest you look again at the bar graph. The bar that shows MWP warmer than Current Warm Period is the one on the right. I’m colour blind, but I think it’s red. Compare it to the scale on the left and it looks like 30+ to me, not 2-3.

Again, I said “anything up to 4°C”. Have a look at the quantitative graph here… http://www.co2science.org/scripts/CO2ScienceB2C/da... It shows 1 study estimates 3.75°C warmer, 3 estimate 3.25°C warmer, etc. If you want to read all about the whole WMP Project, hover your mouse over “Data” on the top menu.

As to your final paragraph, well, I’m sorry, but studies seem to show that it *was* that warm, so where does that leave your “runaway greenhouse effect” theory? Scaremongering?

Tomcat: A very good point, well made. It often amuses me how the GWAs pronounce that any claim that disagrees with the GW doctrine, no matter how rigorous, is instantly and completely invalid. But anything that supports the doctrine, no matter how flawed, (e.g. the “hockey-stick”) is irrefutable. That simply isn’t how science is supposed to operate.

3DM: A calm and well-reasoned answer as ever. I agree with you and have nothing to add.

EnragedParrot: For the most part I tend to agree. Your statement that “probabilistically speaking, it's very likely that today's temperatures are warmer” is more your opinion rather than a verifiable fact and, naturally, my opinion is the opposite. (I’ll remind you that co2science quote 30+ studies that say it was warmer).

I would have to disagree with you about the hockey-stick not ignoring the MWP. It left data that showed it unused, in a folder marked “Censored Data”. What’s that, if it’s not ignoring the MWP?

Response to EnragedParrot’s edit: The MWP *is* important, because, if it was significantly warmer than today, it demonstrates that we are not in as much danger as the alarmists are suggesting.

If you don’t like = ^_^ =’s evidence of the MWP then I again draw your attention to the 30+ studies on co2science.

And your statement that “there was never a point when the global mean temperature [exceeded those of today]” is again your opinion – you have no proof of that.

And the debate over the Mann “hockey-stick” graph is not as technical and complicated as the alarmists would like us to believe. The computer model was tested with random data and it produced a hockey-stick graph very similar to the “real” one. How complicated is that? The alarmists claim it’s a complicated issue in an effort to avoid discussing it and “bury” the scandal.

Linlyons: So, co2science is corrupt, is it? Well, what about the 30+ studies that they cite regarding the MWP alone, are they all corrupt too? It amuses me that oil industry funding instantly invalidates everything the funded expert says. No attempt is made to refute them with a scientific debate, it’s just “they’ve received some funding from the oil companies, so you can’t use them.” Yeah, okay.

Your “7% - 10% of all humans that have ever lived on this earth, are alive today” statistic, if true, is quite amazing. I’d never heard that before. However, let’s not forget that the rate of rise of the world’s population is falling. In fact, in some of the developed world the population *is* falling. In the U.K. for example the indigenous population is dropping – the only reason the country’s population is remaining stable is due to immigration.

Also, advances in technology are increasing crop yields.

Thus, I doubt that we’re going to encounter and great problems with food supply.

Bob: A-ha! The man himself!

You say “2005 and 6 were even warmer.” Only if you cherry pick one particular temperature record; most others still have 1998 as the hottest year and as I’ve pointed out many times, satellite data shows that there’s been no warming since 2002.

Inflated estimates of sea level rise are a common GWA scaremongering tactic, but, even the IPCC have been lowering their estimates for their last 2 reports. Currently they’re predicting that a 4°C rise would cause less than 18 inches of sea level rise and even that may still be too high. How much of a difference would < 18 inches have made? Besides, 4°C is the top of the estimate of MWP temperature so the sea level rise may have been much less.

Temp record of the week. As ever, Bob, you’ve missed the point. The point is that they are highlighting out how unreliable the surface data record is, you know, the one you’ve used to claim that 2005 & 6 were the hottest years ever?

But Bob, CO2 *is* an aerial fertilizer. Plants grow better in a CO2 enriched environment. Are you claiming that’s not true?

The Mann graph was more than just “overly smoothed” as I’ve mentioned several times. The fact that GWAs such as you continue to try to defend it is one of the reasons I remain a sceptic. If the global warming community would admit the truth and publicly distance themselves, it might restore some of their credibility.

Bottom line, you offer no comment on the 30+ studies cited by co2science that suggest the MWP was warmer than today.

Trevor: Always a hard man to debate against! (That’s a compliment, BTW)

You quote the temperature of the MWP, but based on what? Clearly not on the studies cited by co2science. Since they cite 30+ studies that suggest it was warmer than today, I have to ask, were these studies included in the work that resulted in your figures? Or were they conveniently left out, perhaps left in a folder marked “Censored Data” as Mann did? Can you tell me, categorically that they were included?

Many of the studies use the methods that you cite.

Again, I don’t accept that co2science’s funding is relevant, they are not carrying out the research themselves, simply quoting others’ work.

I too was confused as to why there were only 2-3 studies cited that suggest MWP<CWP, but I think I understand now. They’re not trying to state these are the *only* studies that exist. Rather they are listing the studies that suggest temperatures that are warmer than the consensus figures you quote. Thus, even the ones that show MWP<CWP are still warmer than what we are being lead to believe.

If we include both the Level 1 (quantitative) and Level 2 (qualitative) studies, we are looking at 66 independent studies (and growing) from all over the world that suggest a MWP temperature above what the mainstream scientific community is claiming. As co2science points out, this is very important because, given the current climate of attacking people who don’t tow the line, the people publishing these studies are really “sticking their necks out”.

You’re in a better position to answer these questions than me Trevor:

Are 66 studies enough to be relevant? And if not, how many would there need to be?

If you are correct about the figures, why were we so wrong about the MWP back in the 1990s? (with reference to the graph in my second link above.)

Finally, as a reasonable man, Trevor, do you not accept that the David Deming quote, Mann’s “Censored Data” folder and the sudden MWP U-turn are a little suspicious in the face of 66 studies that dispute the new consensus?

To EnragedParrot again: You comments about the range of uncertainty meaning that it’s possible that MWP>CWP, but unlikely, is moot if the graph itself is flawed. Another graph would suggest a virtual certainty that MWP>CWP. So again, the question is: can we trust that graph?

So, you’re saying that the MWP is not important because it simply wasn’t as warm as today? Well, ten years ago we thought it was, and we only stopped thinking it was after the flawed Mann hockey-stick graph appeared in 1998. And, suspiciously, after at least one GWA had said “We have to get rid of the MWP”. A complete U-turn in two years flat? I find that difficult to accept.

You can read about the McKitrick & McIntyre study into the Hockey-stick graph here… http://www.climatechangeissues.com/files/PDF/conf0... The part about the random red noise producing hockey-stick results begins in the penultimate paragraph on page 10.

Bob: Land surface record *again*. You say: “average thousands of those measurements and the data becomes vastly more reliable”. True, but what if hundreds, or even thousands, of stations are suspect? Past surveys have found that as many as one in eight are poorly sighted. And currently www.surfacestations.org is running a survey to assess all the surface stations in the US. A quick look at the results so far (http://www.surfacestations.org/USHCN_stationlist.h... ) shows an alarming number getting ratings of 4 or 5 (See the 5th column “CRN Rating”. Key to ratings at top right)

Currently they have rated 404 (of 1218) and fully 273 (68%) are rated 4 or 5 – which means they have an error >= 2°C .

And *this* you call reliable?

I think I’ll stick to the satellite data, thanks.

With reference to co2science’s MWP studies: They have a similar number of quantitative studies as you would have discovered for yourself had you taken but a few seconds to look.

To all those who have said that I should ignore co2science, because they have received funding from oil companies, are not climate scientists or bizarrely, because they had a mailbox for their address (so that’s Nickel Johann, linlyons, & Trevor)…

I noticed with interest that the bristlecone pine tree ring data that was so pivotal in the flawed Mann “hockey-stick” graph, was from a study by Graybill & Idso. The Idso in question was Sherwood B. Idso – one of the Idso family members who run co2science!

I had to laugh at that!

Thus, the Mann “hockey-stick” graph uses co2science too! So, does that mean we should dismiss it?

LOL

disgracedfish: I hold my hands up on this one, it would appear you are correct. Thus, I’m sorry, it appears my memory had failed me on this one and I’ve misrepresented the actual facts. Here’s what was actually found (see link above)…

“Of crucial importance here: the data for the bottom panel of Figure 6 is from a folder called CENSORED on Mann’s FTP site. He did this very experiment himself and discovered that the PCs lose their hockey stick shape when the Graybill-Idso series are removed. In so doing he discovered that the hockey stick is not a global pattern, it is driven by a flawed group of US proxies that experts do not consider valid as climate indicators. But he did not disclose this fatal weakness of his results, and it only came to light because of Stephen McIntyre’s laborious efforts.”

I’ll remind everyone that Steve McIntyre is the guy who recently discovered the error in the US surface temperature record. Incidentally, why did climate scientists not find this error?

EnragedParrot: Sorry, forgot to comment on your last point about realclimate.org. Given that two of the authors of the “hockey-stick” graph are regular contributors to realclimate (Mann himself & Bradley) would you accept the possibility that they might, just be slightly biased on the subject?