US Annual Mean Temperatures adjusted for urbanization (USHCN) show a cyclical behavior in the past 112 years. An analysis of a true trend is difficult for this entire data set since it began during a cold period and is ending at what may be a relative maximum. Trendlines from maximum to maximum and minimum are likely to be more accurate and this data is shown. There is a brief discussion of candidate causes for this cyclical behavior and the role of greenhouse gases in net trends.

It has been shown by Robock and many other researchers as early as 1913 that global cooling follows major eruptions especially in summer. The paper will also briefly show how the irregular pattern of major eruptions as depicted by NASA GISS AOT data has altered the global longer term temperature trends both up and down, countering or accentuating the changes during both warm and cold periods.