Robot wrote on Jul 1
st, 2019 at 12:34am:
Quote:
Since AD 1990, though, average temperatures in the extra-tropical Northern Hemisphere exceed those of any other warm decades the last two millennia, even the peak of the Medieval Warm Period, if we look at the instrumental temperature data spliced to the proxy reconstruction.
So you have proxy data with the attendant error bars and thermometer reconstructions?
"The decadal mean temperatures in the extratropical Northern Hemisphere seem to have equalled or exceeded the AD 1961–1990 mean temperature level during much of the Roman Warm Period and the Medieval Warm Period. The temperature since AD 1990 is, however,
possibly higher than during any previous time in the past two millennia if we look at the CRUTEM3+HadSST2 90–30°N instrumental temperature data (Brohan et al. 2006; Rayner et al. 2006) spliced to the proxy reconstruction. "
Hardly definitive.
Robot wrote on Jul 1
st, 2019 at 12:34am:
Basically, the Medieval Warm Period was warmer than the Cold War Era, but the 21st century is warmer than the MWP.
PERHAPS.

"Despite significant improvement in our understanding of the temperature variability during the past one or two millennia, especially for the Northern Hemisphere, the controversial question whether Medieval Warm Period peak temperatures exceeded present temperatures remains unanswered. IPCC (2007) and NRC (2006) concluded that the data coverage still is too limited and unevenly distributed around the globe to say anything with reasonable certainty about temperatures on a global or hemispheric scale prior to c. AD 1600. The amplitude of the multi-decadal to centennial preindustrial temperature variability constitutes a major uncertainty. The estimate of this variability ranges from c. 0.2 to 1°C in the different reconstructions. "
Robot wrote on Jul 1
st, 2019 at 12:34am:
Ljunqgvist only looks at 90–30°N latitude, so this isn't exactly an apples-to-apples comparison, but as Ljunqgvist points out, his reconstruction agrees pretty well with others that include all Northern latitudes.
" The amplitude of the temperature variability between the warmest and coldest century
(prior to the twentieth century) in our reconstruction is
0.62°C. As a comparison, this amplitude is
0.22°C in Mann and Jones (2003), 0.58°C in Moberg et al. (2005), and 0.51°C in the ‘error-invariables’ "
Yep really close.