It is widely accepted that, on global average, major components of the earth's climate system (lower atmosphere, upper ocean, and cryosphere) have warmed during the past half century, and that the global stratosphere has cooled. These temperature changes are often quantified in terms of linear trends, although it is well recognized they have not been linear, or even monotonic, during this period. Simple statistical tools will be applied to several global temperature datasets to explore whether alternate models (in particular, step-like, decadal-scale changes) might better describe the nature of the observed changes.