The Central England (HadCET) Temperatures

I see many contrarians using the Hadley Central England Temperature record (HadCET) temperature record in an attempt to say that "modest warming" has been happening for 300 years, long before CO2 could be to blame, suggesting that continued warming in recent decades can't be attributable to CO2. Much of this rhetoric depends on dishonesty for at three reasons: 

  1. HadCET is a local temperature record for Central England. It's not a good indicator of global temperatures.
  2. There were no daily means available between 1659 and 1772, only monthly means. These means are not terribly reliable compared to modern temperature records, depending on estimates and historical diaries, instead of daily readings. From 1772 to 1878, HadCET only records daily means but lacks Tmax and Tmin data. HadCET is only directly comparable to modern temperature records in 1878. Most annalists consider HadCET to be moderately reliable following 1772, and we should treat the data prior to 1772 with a significant amount of skepticism.
  3. Contrarians frequently plot both CO2 and HadCET on scales that obscure the relationship between the two, as in the graph below.

Clearly whoever plotted this graph decided to choose a temperature scale of 14 C to make the warming trend look small. This person also chose carbon emission data to maximize the chart area. These scales are deliberately chosen to hide whatever correlation may exist between these two sets of data. If I plot CO2 and HadCET properly, you can see a much closer relationship. Here I show both from 1750, since that's as far back as I have CO2 data downloaded.

A better approach is to plot CO2 forcings on the x-axis and HadCET on the y-axis, since that will show the relationship between the two. This shows a slope for the relationship at 0.7 C/W/m^2 (with an r^2 of 0.4). That slope is actually a bit higher than the slope of GMST and CO2 forcings, though the r^2 for the relationship is lower for HadCET than for GMST.
The new GloSAT dataset has a reliable temperature record going back to 1785 (with a couple years missing between 1785 and 1790). This gives us GMST anomalies going nearly back to the first reliable year in HadCET (1772). So I plotted both GloSAT and HadCRUT5 with CO2. Here the log relationship is clear.

Finally, we have a smoothed reconstruction from Lamb (a version of which was published in the 1990 IPCC report) that shows that Central England temperatures have experienced a temperature profile that shows rapid warming since about 1970 that eclipses warmest years of the Medieval Warm Period.













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