On the detection of greenhouse warming

Two facts that have been cited as evidence of the onset of greenhouse warming are the extent to which the most recent value in a global temperature series is unusually warm and the observation that the four warmest years on record occurred in the 1980's. We examine these results in more detail, and we address the question as to whether these facts constitute evidence in favor of the detection of greenhouse warming. We conclude that they do not support detection unless we are prepared to attribute all warming in the data to the greenhouse effect.