How Reliable Are Global Temperature Reconstructions of the Common Era?

Short answer: Very unreliable!

More evidence that the climate models used for the Global Warming/Climate Change propaganda and demagoguery are junk! E.g. these climate models are not capable of reliable and correct backcast!

Global mean annual temperature increase of 1 °C is more like a measurement error than anything else! This is so absurd! E.g. coming out of the Little Ice Age, urban heat island effect etc. etc.
What a waste of time and resources!

From the abstract:

"Global mean annual temperature has increased by more than 1 °C during the past 150 years, as documented by thermometer measurements. Such observational data are, unfortunately, not available for the pre-industrial period of the Common Era (CE), for which the climate development is reconstructed using various types of palaeoclimatological proxies. In this analysis, we compared seven prominent hemispheric and global temperature reconstructions for the past 2000 years (T2k) which differed from each other in some segments by more than 0.5 °C. Whilst some T2k show negligible pre-industrial climate variability (“hockey sticks”), others suggest significant temperature fluctuations. We discuss possible sources of error and highlight three criteria that need to be considered to increase the quality and stability of future T2k reconstructions. Temperature proxy series are to be thoroughly validated with regards to (1) reproducibility, (2) seasonal stability, and (3) areal representativeness. The T2k represents key calibration data for climate models. The models need to first reproduce the reconstructed pre-industrial climate history before being validated and cleared for climate projections of the future. Precise attribution of modern warming to anthropogenic and natural causes will not be possible until T2k composites stabilize and are truly representative for a well-defined region and season. The discrepancies between the different T2k reconstructions directly translate into a major challenge with regards to the political interpretation of the climate change risk profile. As a rule of thumb, the larger/smaller the pre-industrial temperature changes, the higher/lower the natural contribution to the current warm period (CWP) will likely be, thus, reducing/increasing the CO2 climate sensitivity and the expected warming until 2100."

"... from the overall geometry, it can be inferred that the MWP [medieval warm period] may have reached temperature levels similar to the current warm period (CWP) today ..."

Earth | Free Full-Text | How Reliable Are Global Temperature Reconstructions of the Common Era? (open access)

Credits: See my blog post