Split from Aug FT meeting: Yet another Global Warming thread

[Hogeye]

Okay, I exaggerated in some earlier statements. My position is that the MWP was approximately as hot as the late 20th century (and possibly hotter.) The chart both of us have put up with the 9 reconstructions shows this clearly. The reconstructions have consensus support among climatologists, and can be found even on alarmist sites like RealClimate. How can you look at that chart and not admit that they are approximately the same?

Darrel, the quote you give is taken out of context. It says that, according to their current study "MWP temperatures were nearly 0.7C cooler than in the late twentieth century," but they admit that this is dubious: "However, we advise caution with this analysis. Although we conclude, as found elsewhere, that recent warming has been substantial relative to natural fluctuations of the past millennium, we also note that owing to the spatially heterogeneous nature of the MWP, and its different timing within different regions, present palaeoclimatic methodologies will likely "flatten out" estimates for this period relative to twentieth century warming..."

"Spatially heterogeneous" means that some places are warmer/cooler than others. But the global warming theory is about average global temperature, not regional or local anomalies, as you should know, and as both alarmists (like the folks at RealClimate) and skeptics (like Michael Crichton) emphasize.

[Dardedar]

The reconstructions have consensus support among climatologists,...

DAR
That's not the claim I am asking you to back up. This is:

"...the consensus is that the MWP was global..."

How can you look at that chart and not admit that they are approximately the same?

DAR
When are you going to follow the advice of your source and stop making such dubious comparisons? The "the spatially heterogeneous nature of the MWP, and its different timing within different regions" means it does not compare well with our current, precisely measured, human caused, global warming. And it has diddly to do with the actual concerns put forward regarding global warming.

"Spatially heterogeneous" means that some places are warmer/cooler than others. But the global warming theory is about average global temperature, not regional or local anomalies,...

DAR
Bingo. The MWP is a bunch of regional or local anomalies. This solves your mystery of why the oceans didn't rise then. As your source says:

"the spatially heterogeneous nature of the MWP, and its different timing within different regions"

Different timings, different regions, some places warmer, some places cooler. That's your regional MWP, as I have said all along. So apparently you have zero to back up the claim:

"...the consensus is that the MWP was global..."

D.

[Hogeye]

Hogeye> The reconstructions have consensus support among climatologists,...

Darrel> That's not the claim I am asking you to back up. This is: "...the consensus is that the MWP was global..."

The reconstructions are about global temperatures, and do show a clear MWP.

So now you refuse to make the obvious inference from the 9 reconstructions (that the MWP was approximately as warm as late 20th century), and give yet another out of context rendition of the quote from the abstract. The warning was about specific inferences ("available paleoclimatic reconstructions are inadequate for making specific inferences), not approximate comparisons. You appeal to the reconstructions quite selectively!

Hogeye> But the global warming theory is about average global temperature, not regional or local anomalies,...

Darrel> Bingo. The MWP is a bunch of regional or local anomalies.

The nine reconstructions say otherwise. Not even the abstract you selectively misquote denies that the MWP was global. You keep misunderstanding its claim that there were a lot of local anomolies ("the spatially heterogeneous nature of the MWP, and its different timing within different regions") erroneously to mean that the average global temperature was not hot. Just look at the global reconstructions!

[Dardedar]

DAR
Okay, as as I thought, you do not have a single reference supporting your claim that the scientific "...consensus is that the MWP was global...". If you find one let me know. As you know I have provided several citations supporting the position that it was not global and thus that the concensus is that it was not global. I thought perhaps you had discovered something new to share but you were just making things up.

D.
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"The Medieval Warm Period was a time of unusually warm weather around 800-1300 AD, during the European Medieval period. Initial research on the MWP and the following Little Ice Age (LIA) was largely done in Europe, where the phenomenon was most obvious and clearly documented.

It was initially believed that the temperature changes were global. However, this view has been questioned; the 2001 IPCC report summarises this research, saying "…current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of 'Little Ice Age' and 'Medieval Warm Period' appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries".[1]

Palaeoclimatologists developing regionally specific climate reconstructions of past centuries conventionally label their coldest interval as "LIA" and their warmest interval as the "MWP".[2][3] Others follow the convention and when a significant climate event is found in the "LIA" or "MWP" time frames, associate their events to the period. Some "MWP" events are thus wet events or cold events rather than strictly warm events, particularly in central Antarctica where climate patterns opposite to the North Atlantic area have been noticed.

The Medieval Warm Period partially coincides with the peak in solar activity named the Medieval Maximum (1100–1250)."

ALSO:

"2001 report (TAR)

The 2001 report used northern hemisphere warm-season and annual reconstructions from 1000 AD to present by Mann et al (1999), Jones et al (1999) and Briffa (2000) [2].

The IPCC TAR says of the MWP that the posited Medieval Warm Period appears to have been less distinct, more moderate in amplitude, and somewhat different in timing at the hemispheric scale than is typically inferred for the conventionally-defined European epoch. The Northern Hemisphere mean temperature estimates of Jones et al. (1998), Mann et al. (1999), and Crowley and Lowery (2000) show temperatures from the 11th to 14th centuries to be about 0.2°C warmer than those from the 15th to 19th centuries, but rather below mid-20th century temperatures [3].

The TAR discusses Was there a “Little Ice Age” and a “Medieval Warm Period”? and says Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe, and the conventional terms of “Little Ice Age” and “Medieval Warm Period” appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries. (ibid)"

link

etc.

[Barbara Fitzpatrick]

Darrel, that's pretty much what I had read, but couldn't remember where I'd read it. It's one of those biases you've first got to realize you have before you can do anything about it. It is normal for Americans and Europeans to extrapolate globally whatever data is found for America and/or Europe. It's something the peer-reviewed researcher has recognized (or been hit over the head with) and quit doing. Many others (non-peer reviewed researchers) don't even notice the bias. It's like gender bias or ethnic bias (or religion, of course). It comes with the society. Only education and critical thinking (whether or not you are a researcher, peer-reviewed or otherwise) allow you to expand outward and actually utilize all the data.

As best I remember, the areas the MWP covered were all coastal and within the effective range of the Gulf Stream. The rest of the planet was cooler enough to balance that North Atlantic warmth to within a few degrees C.

[Hogeye]

Isn't it interesting how the political Intergovernmental Panel on Climate Change ignores the data from these 9 global reconstructions.



No doubt they know where their research grants are buttered!

[Dardedar]

Troll.

Do you somehow find it useful in defending your nutty beliefs, to constantly misrepresent and distort the truth?

For those not interested enough to follow the link I just provided, it is the Intergovernmental Panel on Climate Change referencing the data from several if not most of those TEN global reconstructions. The references, once again (I have provided this chart and references several times), can be viewed here.

D.

[Savonarola]

Well, folks, if we've been reduced to calling each other names, repeating information already presented multiple times, and appealing to vast conspiracy theories, we're done here.

Thread closed.

Don't worry; I have the feeling we'll be doing this again soon.

--Sav, Science Moderator