progressiveslol wrote on Jul 29^th, 2012 at 3:01pm:


How do you know, progs?

Gotta love those 'proxy' calculations.
That's the Church of Global Warming language equivalent for 'guess'.
And a guess is what it is.
Let me know when Godzilla comes back will you.

1) Was the Medieval Warm Period global? 2) Was it warmer than today? 3) And what does this all mean anyway?

Holocene
Holocene carbon emissions as a result of anthropogenic land cover change - Kaplan et al. (2010)

Disentangling seasonal signals in Holocene climate trends by satellite-model-proxy integration - Schneider et al. (2010)

Post-glacial regional climate variability along the East Antarctic coastal margin—Evidence from shallow marine and coastal terrestrial records - Verleyen et al. (2010)

Land surface temperature changes in Northern Iberia since 4000 yr BP, based on δ13C of speleothems - Martín-Chivelet et al. (2011)

Climate change and human impact at Sacrower See (NE Germany) during the past 13,000 years: a geochemical record - Enters et al. (2011)

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia - Fisher et al. (2011)

Relative sea-level fall since the last interglacial stage: Are coasts uplifting worldwide? - Pedoja et al. (2011)

The early Holocene sea level rise - Smith et al. (2011)

Patterns of local and regional grain size distribution and their application to Holocene climate reconstruction in semi-arid Inner Mongolia, China - Yin et al. (2011)

Response of a marine-terminating Greenland outlet glacier to abrupt cooling 8200 and 9300 years ago - Young et al. (2011)

Abrupt cooling repeatedly punctuated early-Holocene climate in eastern North America - Hou et al. (2011)

High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core - Kobashi et al. (2011)

Structure and origin of Holocene cold events - Wanner et al. (2011)

Polar amplification in the mid-Holocene derived from dynamical vegetation change with a GCM - O'ishi & Abe-Ouchi (2011)

Observational constraints on the causes of Holocene CO2 change - Goodwin et al. (2011)

Climate changes during the last c. 7500 years as recorded by the degree of peat humification in the Lofoten region, Norway - Vorren et al. (2011)

Evidence for Younger Dryas Global Climate Oscillation and Human Response in the American Southwest - Ballenger et al. (2011)

Pleistocene
The Younger Dryas impact hypothesis: A requiem - Pinter et al. (2011)

Timing and duration of North American glacial lake discharges and the Younger Dryas climate reversal - Rayburn et al. (2011)

The Mysterious Onset Of The Younger Dryas - Fiedel (2011)

A benthic δ13C-based proxy for atmospheric pCO2 over the last 1.5 Myr - Lisiecki (2010)

High carbon sequestration in Siberian permafrost loess-paleosols during glacials - Zech et al. (2011)

Interglacial and glacial variability from the last 800 ka in marine, ice and terrestrial archives - Lang & Wolff (2011)

Late Pliocene to Pleistocene sensitivity of the Greenland Ice Sheet in response to external forcing and internal feedbacks - Koenig et al. (2011)

Pre-glacial and interglacial pollen records over the last 3 Ma from northwest Canada: Why do Holocene forests differ from those of previous interglaciations? - Schweger et al. (2011)

Individual contribution of insolation and CO2 to the interglacial climates of the past 800,000 years - Yin & Berger (2011)

Do blue-ice moraines in the Heritage Range show the West Antarctic ice sheet survived the last interglacial? - Fogwill et al. (2011)

Last Glacial Maximum CO2 and δ13C successfully reconciled - Bouttes et al. (2011)

Annual layering in the NGRIP ice core during the Eemian - Svensson et al. (2011)

Heinrich event 1: an example of dynamical ice-sheet reaction to oceanic changes - Álvarez-Solas et al. (2011)

NALPS: a precisely dated European climate record 120–60 ka - Boch et al. (2011)

Sea surface and high-latitude temperature sensitivity to radiative forcing of climate over several glacial cycles - Rohling et al. (2011)

High-resolution 14C dating of a 25,000-year lake-sediment record from equatorial East Africa - Blaauw et al. (2011)

Was the Middle Würmian in the High Alps warmer than today? - Döppes et al. (2011)

The role of ocean thermal expansion in Last Interglacial sea level rise - McKay et al. (2011)

MWP fact. Just cause some Uptony loon can type with no links, and does not even type about MWP, does not make the MWP go away.

http://wattsupwiththat.com/2009/12/04/jo-nova-finds-the-medieval-warm-period/


http://www.co2science.org/data/mwp/mwpp.php

So who's right?  Does Ljungqvist confirm the results of Mann (2008) and Moberg (2005)?  Or do his results agree with Loehle and McCulloch (2008)?  Figure 2 provides a comparison of them all, starting in AD 500 (the earliest date in Mann 2008's global reconstruction), with the northern hemisphere instrumental record shown for comparison.


http://www.skepticalscience.com/images/recon_lj_with_others.png
Figure 2.  Comparison of northern hemisphere and global temperature reconstructions.  Northern hemisphere instrumental temperature records shown for comparison (CRUTEM land only, and HADCRUT land/ocean).

It's worth noting that all the reconstructions show the Medieval Warm Period, the Little Ice Age, and 20th-century warming (though Loehle 2008 only runs through 1935). 

Loehle's Medieval Warm Period is both warmer and earlier than the rest (and, as noted above, Loehle recognizes that his early peak circa AD 850 is probably incorrect).  Loehle also shows a much colder Little Ice Age.  All of the reconstructions diverge more in the period before AD 800, with Moberg being the coolest, Loehle the warmest, and Mann and Ljungqvist being in the middle of the pack.

When comparing Ljungqvist 2010 to Loehle 2008, it's important to remember that Ljungqvist's reconstruction is for the mid- and high-latitude Northern Hemisphere only, while Loehle's was supposed to be global.  In this light, the presence of relatively extreme temperatures in Loehle's reconstruction during both the Medieval Warm Period and the Little Ice Age ought to be viewed somewhat skeptically.  Whether or not these episodes were truly "global", they were certainly strongest in the Northern Hemisphere, particularly in the North Atlantic region. Ljungqvist 2010 suggests that his own reconstruction may have underestimated the magnitude of Northern Hemisphere cooling during the Little Ice Age, but Loehle's still appears to be an outlier if it is considered as a global reconstruction.

Finally, it's worth noting that comparison to the instrumental record suggests that modern temperatures are significantly warmer than those during the height of the Medieval Warm Period.  Additional projected 21st Century warming will produce a climate unlike anything experienced in the history of human civilization.

http://www.skepticalscience.com/print.php?n=394

Sure. Why not? Much easier to deny science than to attempt to understand it.