Discussion > GHG Theory step by step
Golf Charlie
I don't think we see the MWP in the same way.
I see a short term warming from about 14.0C to 14.1C lasting about 150 years. When it started and ended is uncertain, but the cooling trend of the LIA clearly begins with the Salamos eruption. My MWP may have ended earlier, but the onset of the cooling sets a definate limiting end boundary.
I don't know for sure what your MWP looks like. You still haven't described it.When did it start, when did it end and what was the global average temperature?
Incidentally, be wary of getting too excited when a paleontologist says that something is warmer than the present. By convention the Present for paleontology is 1950 and the global temperature is 14.0C.
Entropic man
Schrodinger's cat
I notice that you used unadjusted HadCRUT3 in your graph. That underestimates the pre-WW2 warming because of the bucket and time-of-day systemic errors.
Using HadCRUT4 the effect of cherry picking the 1910-1940 dates is much less, but the slope of that graph is also reduced below the slope of the 1975-2000 line.
Entropic man
Michael Mann offers another explanation for the pause, preferring Speed Hump. Again, Arctic Sea Ice is his "proof" that the models are correct. This was syndicated, not just in Huffington Post.
02/09/2014 08:01 pm ET Updated Apr 11, 2014
Global Warming Speed Bump? The Answer May Be Blowing in the Wind!
By Michael E. Mann
"An interesting new paper by Matthew England and colleagues just published in the journal Nature Climate Change tosses another hat in the ring when it comes to explanations of the so-called “hiatus” or “pause” (I prefer “speed bump”) in global warming.
As I have discussed previously, the fact that global surface temperatures have not increased as much over the past decade as many climate models predict they should have, doesn’t necessarily contradict the model predictions at all. In reality, the speed bump may simply reflect the short-term natural fluctuations of climate (and keep in mind that, by some measures such as the melting of Arctic sea ice, climate change is actually proceeding faster than the models have predicted): "
I suppose the England paper was not up to the job, hence Karls approach was to discredit the data, to preserve the theory. Ironic that Entropic Man should now be trying to discredit the dates of the MWP, having denied its existence.
golf charlie
Nov 23, 2017 at 11:48 PM | Entropic man
What was wrong with Lamb's version of the MWP, that was accepted by the IPCC?
golf charlie
Another attempt at temperature records.
https://wattsupwiththat.com/2017/11/23/besting-the-best-surface-temperature-record/
golf charlie
By the way, EM, who has “denied” climate change? Unless you call questioning its extent, severity, projected extreme, adverse effects or cause “denial.” But, then, surely all science is riddled with those contentious issues? What to do, eh?
As a “scientist” (I do use that term in the loosest of possible ways), you do seem somewhat frightened of unknowns. As there were no contemporary meteorological records of the time, what evidence there is of the start or the end of the Mediæval Warm Period has to be by inference, either from proxies or from contemporaneous records. Neither will give you the complete data that you so desperately want; both will give evidence that it occurred – e.g. the Vikings farmed in Greenland for several years, and buried their dead; neither can be done now, using the equipment they had then; therefore it is considerably cooler now, than it was then. The exact dates of when this started and when it finished may never be known, but this cannot mean that it never happened. Let us just say that it began about half past Tuesday in the year of Olaf the Bald’s birth, and ended at about quarter to September in the year of his great-great-grandson’s death.
Radical Rodent
On the basis of my sample
Someone spelt biases wrong.
clipe
On the basis of my sample
Someone spelt biases wrong.
clipe
Twice!
Supertroll
Radical Rodent,
If the Vikings had timed their arrival in Greenland to "tea-time", it would really mess-up assumptions about the timing of world exploration.
There is no proof that the Vikings didn't circumnavigate via the North West Passage, therefore, by Entropic Man's logic, they did. Unless someone can prove they definitely didn't.
By the same logic, just because no one has found Trenberth's Missing Heat (the product of shonky Climate Science sums) doesn't mean it isn't hiding somewhere.
golf charlie
Another reason for the Vikings in Greenland dying out. Mentions the limited extent of their agriculture too. But does confirm there was a Medieval Warm Period. Mentions a different volcano and the Black Death.
The timing of the MWP remains vague, but Climate Scientists maintain it didn't happen because of a tree.
https://www.smithsonianmag.com/history/why-greenland-vikings-vanished-180962119/
golf charlie
Golf Charlie: you could be picked up there, as it was so cold in the MWP that there was too much ice for the Vikings. Perhaps they walked over ice to Greenland, to find that, by some divine miracle, that that little patch of Greenland was 2-3°C warmer than now, while the rest of the world shivered… well, except for that bit of Alaska, where it was warm enough for long enough for a forest to grow, before being subsumed by ice… oh, and those bits of Europe where retreating glaciers reveal plants that can only grow when it is ice-free. But, apart from those, everywhere else was decidedly chilly… except for… Well, you get the message. I do find it odd that, because we cannot specify a definite time of beginning and end, the event cannot have happened.
On your latest point, it is interesting that the USA, being <2% of the world’s area, cannot be used as a proxy to throw doubt on the theory, yet <2% of <2% of the USA can be used as a proxy to provide conclusive evidence. What a curious world some people live in.
Radical Rodent
<I> I do find it odd that, because we cannot specify a definite time of beginning and end, the event cannot have happened.</I>
Well, if one is claiming a global warming event comparable or greater than current warming, it does not seem unreasonable to ask when this event happened, exactly.
The tactic seems to be to specify a timespan centuries long and then claim every evidence of unusually warm (or wet) conditions as evidence for the MWP even when they were centuries apart and there is evidence of colder conditions elsewhere at the same time.
The big takeaway is that at least this portion of North America was significantly colder than Europe was during the MWP and not really in a warm period of any kind at all. In fact, it was already cold when the Vikings arrived. “It’s becoming clearer that the Medieval Warm Period was patchy, not global,” remarked Young in a press release.
https://www.popsci.com/medieval-warm-period-may-not-have-been-so-warm-after-all
Phil Clarke
It is well known that so called global climate is actually quite patchy. During the recent warming phase, the Antarctic has shown no warming despite the peninsula geothermal and carbon dioxide effects.
Schrodinger's Cat
Golf Charlie
Lamb's analysis was made in the1980s and used in the 1990 IPCC report. It was based on archeological data and records, not temperatures.
The problem was that these do not give numbers, so it is difficult to dinfer actual temperature averages or compare one period with another.
For example, in Roman times there were vineyards in England. There were 40 vineyards recorded in the Domesday book after 1066 and 139 vineyards when Henry VIII became king in 1509. We now have vineyards in England and Scotland. Does that mean that the British Isles were warmer in Tudor England than in your MWP and are even warmer in the 21st century?
From the 1995 IPCC report numerical temperatures based on proxies were available, partly due to Lamb's work at CRU. His original qualitative work had been superceded.
Entropic man
Nov 24, 2017 at 12:23 PM | Phil Clarke
Phil Clarke now accepts there was a Medieval Warm Period, but wants to argue temperatures.
Entropic Man now accepts there was a Medieval Warm Period, but wants to argue dates.
Could you both argue with Mann and Connolley? They might accuse you of denying the veracity of the Hockey Stick.
golf charlie
Golf Charlie
Still waiting for your quantitative data on the major climate event you imagine the MWP to be.
If you can't measure it, it probably doesn't exist.
Entropic man
But there is no way to measure it – it is in the past! The best we can do is look at proxies and historical records of associated events. What we DO know is that trees cannot grow under ice and that graves cannot be dug in permafrost.
Having admitted that there was a MWP, are you now denying that there ever was? I am surprised you are not in more trouble, by the way, as you have already admitted that climate scientists have been wrong.
Radical Rodent
Phil Clarke now accepts there was a Medieval Warm Period, but wants to argue temperatures.
And dates. And distribution.
Phil Clarke
Radical rodent
The proxy studies, including Mann et al and the Marcott et al ensemble, show a rise of 0.1C from about 1000AD to 1150AD. If you want to call that the MWP, then I am quite happy to accept it.
What I do not accept is golf Charlie's major climate event. He has been very reluctant to describe it with numbers, but he implies a jump in temperature of 1C plus, lasting 400 years. If it existed, it would show very clearly in every proxy dataset. Since it does not appear in the data, golf Charlie's MWP probably did not happen.
Incidentally, before you use the old argument, remember past experience. In science, absence of evidence is not evidence of absence but that is the way to bet.
Entropic man
From the 1995 IPCC report numerical temperatures based on proxies were available, partly due to Lamb's work at CRU. His original qualitative work had been superceded.
Also note that the schematic showing a prominent MWP and LIA shown in the first IPCC report and sometimes credited to Lamb seems to have been based on Central England Temperatures. That's if you believe Steve McIntyre.
Phil Clarke
If you can't measure it, it probably doesn't exist.
Nov 24, 2017 at 1:57 PM | Entropic man
Is that how Global Warming Theory fails?
golf charlie
Nov 24, 2017 at 2:33 PM | Phil Clarke
If you read your own link, you will note that Steve McIntyre was simply solving a question posed by William M Connolley. If only more of the Hockey Team had sought some help with the tricky maths sooner, from people who understand it.
golf charlie
And dates. And distribution.
Nov 24, 2017 at 2:22 PM | Phil Clarke
When and where do you believe there was a Medieval Warm Period?
golf charlie
Nov 23, 2017 at 10:15 PM | Entropic man
You have stuck to Mann's Hockey Stick. You have denied the existence of the MWP. Now you accept that the MWP existed, but try to blame me for your confusion about when it happened.
You proposed Mt Salamos as the end date of the MWP. Was that just a diversion?