"Oscillation" refers to a repetitive back and forth movement or change between two points or states. It is like a pendulum swinging or a wave moving up and down. Full definition
His speech, titled «Influence of the Southern Oscillation of Global Temperature» can be viewed below. (desmogblog.com)
Motizuki, T., M. Ishii, M. Kimoto, Y. Chikamoto, M. Watanabe, T. Nozawa, T. Sakamoto, H. Shiogama, T. Awaji, N. Sugiura, T. Toyoda, S. Yasunaka, H. Tatebe, and M. Mori, 2008: Hindcasting the Pacific Decadal Oscillation in relevance to a near - term climate prediction. (usclivar.org)
Bamzai, A.S., 2003: Relationship between snow cover variability and Arctic Oscillation Index on a hierarchy of time scales. (ipcc.ch)