“ Then the mean date starts to get earlier, declining about linearly starting around 1900. One should note that it is generally accepted that CO2 didn't start t

“ Then the mean date starts to get earlier, declining about linearly starting around 1900. One should note that it is generally accepted that CO2 didn't start to have a substantial effect on climate until about 1950..” I think it’s because the trend line is smoothed out over +\-50 years data, or something like that. Or it might be hand drawn. I’m going to download the raw data and see what the trend line looks like using fewer data points.