English: Temperatures with respect to the 1850-1900 mean as per IPCC definition of pre-industrial temperatures over the last 2 millennia and observational values ranging from 1880 to 2020. All data is smoothed using a 5 year moving average.

The 2000 year record is computed in https://www.nature.com/articles/s41561-019-0400-0 using a wide set of proxies that have been vetted by the Pages2k Consortium ^[1]. They include tree ring data, data from corals and ice core data. A direct link to data is at https://figshare.com/articles/Reconstruction_ensemble_median_and_95_range/8143094

The observational data set is pulled from NASA: https://climate.nasa.gov/vital-signs/global-temperature/

NASA data is adjusted up by 0.188 degrees C since the IPCC says 2006 to 2015 is 0.87 degrees warmer than 1850 to 1900 and NASA averages 0.682 in that time frame.

The 2000 year temperature is adjusted up by 0.287667, which is the NASA adjustment from above plus 0.099667 for the NASA average from 1961 to 1990 (the baseline for the 2000 year data set).