Test for trends^*

It is important to note that in some cases, the early observations were recorded with fewer decimal points than at the present. Often, the early temperatures were measured to the accuracy of $0.1^\circ$C, which for climate series can lead to many values with the same value: for instance many measurements of 12.1$^\circ$C. It will be difficult to determine the exact rank of such series, as the measurements are not well resolved. A high number of equally ranked data points in the early part of the record may bias the trend analysis (Ø. Nordli, personal communications).