[gwright]

I was just stating a mathematical fact. If you observe an increase in temperature over a 100 year time period but the last 20 years of that period there is no significant change then the 100 year average will continue to drop if the temperature continues to remain steady.

Note, I just picked 100 to illustrate the math. I'm not sure exactly what number would be right there but the point is that the slope of the line continues to drop as long as the there is no change in the observed value that you are measuring.