Thanks for the question...look at the entire graph...very little change from 1979 until a sudden

rise in the '97-'98 period (~20 yrs)...then relatively steady around the 0 deg.C line until 2014 (~15 yrs)...followed by (using mean pts) a 0.6 deg.C Increase from the 'Zero' line (~12 yrs).

Given the very rapid and unabated increase in atmospheric CO2 concentration (from the burning of Fossil Fuels...as explained to Mark H)...and no dedicated effort to stop such increases by the USA, or China in the near term...I would expect such an increase to continue at least on a linear path...reaching a total of 1.8 deg.C (on Dr. Spencer's plot) by 2050...never mind what it could be by 2100 w/o a decrease in FF usage. Ergo...a sudden Acceleration of Global temperatures...with IMO, massive impact on Humanity from sea level rise, natural disasters and changes in food production volumes in current locations.

Using a Flat Line assessment from 1979 doesn't do justice to what's been happening over the last 10+ years