Hi all,

There's been a lot of controversy on the net lately about Phil Jones' statement that global warming since 1995 has not been statistically significant. An awful lot of blog-pundits have interpreted this statement as saying that *no* warming has occurred. This interpretation is clearly false, but in considering the incident I've realised that I don't understand the exact nature of the null hypothesis when a researcher states that a global temperature trend is or isn't statistically significant. To be more specific, what is the 'population' in which a null hypothesis of a zero trend is specified? (I've had nearly no exposure to time series analysis, unfortunately )