There is no significant trend in global average temperature

Abstract

The HadCRUT4 time series of 166 annual values of global average temperature was analysed both deterministically and stochastically and the results compared. The deterministic model comprised the sum of a linear trend and a multi-decadal oscillation fitted by ordinary least squares regression. The stochastic model was an ARMA(1,2) model with a drift term included. The deterministic model showed a linear trend of 0.5℃ per century while the stochastic model showed no significant drift. In both cases, the residuals were tested for self-correlation using standard statistical tests. The residuals from the deterministic model were significantly self-correlated whereas those from the stochastic model were not. We conclude that the stochastic model was a much better fit to the data and that the apparent linear trend of the deterministic model was spurious and a consequence of performing a regression in which time was the explanatory variable.