As at 2016 Ref Celsius Fahrenheit
Global mean surface temperature for twentieth century as per NOAA (Jan 2015) a 13.90 57.02
1997 global mean surface temperature anomaly from C20 b 0.51 0.92
Global mean surface temperature for 1997 a+b= 14.41 57.94
Re-basing global mean surface temperature to Jones99      
1997 anomaly from 1961-1990 as reported at NOAA in 1998 c 0.42 0.76
Global mean surface temperature for 1961-1990 as reported by Jones99 d 14.08 57.34
Global mean surface temperature for 1997 per Jones99 c+d= 14.50 58.10
As at 1998      
1997 global mean surface temperature per NOAA 1998 e 16.92 62.45
Less anomaly from 1961-1990 reported for 1997 c 0.42 0.76
Global mean surface temperature for 1961-1990 mean per NOAA 1998 f=e-c= 16.50 61.69
Global mean surface temperature for 1961-1990 mean per Jones99 d 14.08 57.34
Difference in estimated global mean temperature: NOAA 1997 less Jones99 d-f= 2.42 4.35