They cite their sources. I got paywalled by the Marcott paper, but that seems like it has data you’re looking for. I think most of the referenced links are as follows:

Shakun https://www.nature.com/articles/nature10915

Marcott https://www.science.org/doi/10.1126/science.1228026

Annan and Hargreaves https://cp.copernicus.org/articles/9/367/2013/cp-9-367-2013.html

Hadcrut4 https://psl.noaa.gov/data/gridded/data.hadcru4.html