Supplementary Information – Hokitika

Are we feeling warmer yet?

NZ Climate Science Coalition & Climate Conversation Group
30 Nov 2009

A number of people have now asked us for the raw data we used to create the unadjusted versus adjusted temperature graphs in our study Are we feeling warmer yet? We will shortly post a list of station names from the NIWA CliFlo database. While we could post the data directly, it would be fairly pointless, as you would need to know in detail the weather stations and the methods we used to combine them. Each station required some experimentation and detective work, assumptions had to be made and we may well have made errors. We make no claim to be infallible, so we publish these notes to let the reader judge whether our study has merit.

We will shortly be making the Salinger adjusted dataset available. We would like to thank Warwick Hughes for providing us with that data.

In this document we want to work through an example weather station—Hokitika—to illustrate our approach and methods. We also want to address NIWA’s response, currently on their website, that the Wellington adjustments are justified by altitude differences between stations where no time series overlap is available (Thorndon, Kelburn and Airport). The assumption is made by NIWA that stations can be adjusted together in such cases (even though they have no common overlap period and are also separated both spatially and temporally) as long as they share a common height above sea level.

By giving examples of stations with both altitude separation and an overlap period, we show that the lapse rate can differ and even the sign of the temperature difference can be reversed. Some higher stations record warmer temperatures than nearby lower stations. Therefore, it is invalid to move two station records together simply because they share a station height.

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