2010-11-26 12:44:40This is going to start a storm...
Robert Way

robert_way19@hotmail...
134.153.163.105
Here's some research that is going to cause some problems soon...

http://wattsupwiththat.files.wordpress.com/2010/11/a_regional_approach_to_the_medieval_warm_period_and_the_little_ice_age.pdf
2010-11-26 12:54:57Quotes
John Cook

john@skepticalscience...
124.185.20.155

Conclusion (emphasis mine):

The presently available palaeotemperature proxy data records do not support the
assumption that late 20th century temperatures exceeded those of the MWP in most regions
,
although it is clear that the temperatures of the last few decades exceed those of any multidecadal
period in the last 700–800 years. Previous conclusions (e.g., IPCC, 2007) in the
opposite direction have either been based on too few proxy records or been based on
instrumental temperatures spliced to the proxy reconstructions
. It is also clear that
temperature changes, on centennial time-scales, occurred rather coherently in all the
investigated regions – Scandinavia, Siberia, Greenland, Central Europe, China, and North
America – with data coverage to enable regional reconstructions. Large-scale patterns as the
MWP, the LIA and the 20th century warming occur quite coherently in all the regional
reconstructions presented here but both their relative and absolute amplitude are not always
the same. Exceptional warming in the 10th century is seen in all six regional reconstructions.
Assumptions that, in particular, the MWP was restricted to the North Atlantic region can be
rejected
. Generally, temperature changes during the past 12 centuries in the high latitudes
are larger than those in the lower latitudes and changes in annual temperatures also seem to
be larger than those of warm season temperatures. In order to truly assess the possible
global or hemispheric significance of the observed pattern, we need much more data. The
unevenly distributed palaeotemperature data coverage still seriously restricts our possibility
to set the observed 20th century warming in a global long-term perspective and investigate
the relative importance of natural and anthropogenic forcings behind the modern warming.

I find the WUWT response is rather subdued, considering how excited they get about knucklehead stuff like elderly physicist rants.

2010-11-26 13:47:41Comment
Robert Way

robert_way19@hotmail...
134.153.163.105
Just wait until Goddard gets ahold of this work... Yeah it is rather subdued but wait for it. This will be a graph they use for every single argument. Everytime greenland loses ice they'll throw up the greenland graph...
2010-11-26 15:19:54Greenland ice loss
John Cook

john@skepticalscience...
124.185.20.155

I have been thinking about this - sure, Greenland's land temperature in the past, even over the early 20th century, is comparable to recent decades. But the ice loss is nowhere near the scale of current levels. Is this because ice loss is primarily driven by ocean warming? And while atmospheric temperatures jump around due to internal variations, even on decadal time frames, ocean warming is more driven by the planet's energy imbalance - even in a regional case like Arctic ocean warming?

Robert, this would be a topic you'd be best equipped to tackle, having posted on the subject of what drives ice loss several times in the past. So if that graph of Greenland temperature is going to be milked by skeptics, it could serve as a teachable moment by explaining what drives ice loss which then can transition into an exposition of how the oceans has been accumulating heat at such a dramatic rate (eg - at a rate of 2.5 Hiroshima bombs per second).

2010-11-26 15:56:47comment
Robert Way

robert_way19@hotmail...
142.162.16.174
Problem is the MWP has been been assumed to have dynamic oceanic origins... I think that if all the North Atlantic sector was warmer than now during the MWP that implies that North Atlantic SSTs were the driving mechanism... Plus i've seen work showing a positive AMO during that period... that means warmer than average SSTs in the North Atlantic during that period... implying that Greenland would of lost ice extensively... It's complicated no doubt. My understanding is that the difference between now and the MWP in a lot of cases is tropical pacific cooling which is hypothesized to be due to a predominant La Nina during that period... I think this is one of those subjects that is going to be extremely difficult to address right now... ugh I prefer when things are straightforward...
2010-11-26 16:36:00
Ari Jokimäki

arijmaki@yahoo...
192.100.112.210

Apparently this is not a peer-reviewed study. At least I can't find any journal entry about it.

The problem with this study is its conclusion. A generalized conclusion is being made that MWP was warmer than the temperatures in last few decades and yet the proxies used in this study are almost all from the region known to have strong MWP. Only 6 regions are included to the study: Scandinavia, Siberia, Greenland, Central Europe, China, and North America. North-Atlantic region and North in general is currently known to show strongest MWP. Most of the used proxies are from this region. Only study region clearly outside of that is China. Curiously, China is also known to be a MWP hot spot:

http://www.skepticalscience.com/medieval-warm-period-intermediate.htm

This is like Loehle "study" all over again. The conclusions of this study are nonsense. Sorry for being so harsh. :)

2010-11-27 04:13:20conclusion
dana1981
Dana Nuccitelli
dana1981@yahoo...
71.137.148.215

It's the last line of the conclusion that bugs me.

"The unevenly distributed palaeotemperature data coverage still seriously restricts our possibility to set the observed 20th century warming in a global long-term perspective and investigate the relative importance of natural and anthropogenic forcings behind the modern warming."

WTF do these reconstructions have to do with the relative importance of natural and anthropogenic forcings behind the recent warming?

2010-11-27 05:57:15Comment
Robert Way

robert_way19@hotmail...
134.153.163.105
Dana,

They have a lot to do with modern warming. There's evidence to suggest that a portion of the recent warming is from similar processes as during the MWP and RWP. So we could potentially have an anthropogenic signal superimposed on the natural warming. The interesting thing is that it doesn't change our future regardless of the results and I think people don't realize that. Natural variations will only be able to mask AGW for so long even if we go into an extremely cold natural phase.
2010-11-27 06:12:25
Ari Jokimäki

arijmaki@yahoo...
91.154.99.160

Robert: "There's evidence to suggest that a portion of the recent warming is from similar processes as during the MWP and RWP."

What processes are those? And the evidence?

2010-11-27 08:31:00Comment
Robert Way

robert_way19@hotmail...
134.153.163.105
What processes? millennial scale climate variability (who knows, maybe solar/ocean?)

http://www.skepticalscience.com/pics/Viauetal.2006.png

This is north america only so consider the amplitude to be too large. The article still concludes that it is unprecedented warmth we are feeling now.

That all being said I think the evidence is pretty clearly out there that there are millennial scale changes in climate. The MWP was a global phenomena and it was warm. Not as warm as post 1975 current climate but still that in itself says something. I mean we have all even pointed to previous posts that say that most of the warming of the 1940s and such was natural... I just see an increasingly dominant greenhouse gas signature overpowering the other signals right now. That being said I dont think that GHGs are what took us out of the LIA but rather that there were natural processes at play there. My personal belief is oceans but that is unsupportable. I just know ive heard of predominantly positive AMO during the MWP and predominantly negative during the LIA which is essentially a proxy for the heat transport to the north atlantic... nevertheless... I think its been established anyways with that paper john showed us all on IMP (internal multidecadal something) that some of the recent warming has a natural component... I think that we have to consider that the 2000s are the years when natural factors (solar for example) have plunged and yet temperatures continued to rise. It is now we get to see how dominant GHGs are...