The most obvious reason for a long continuous warming curve would be UHI at several stations. Hessell refers to an “urbanisation index”, which suggests that urban stations can be expected to warm in logarithmic proportion to population growth. As urban effects have been measured in towns with population as low as 2,000, virtually all of the 7SS stations have probably been affected. (Perhaps Lincoln could be classed as “rural” – although it is only 15km from a major metro area).

The other cause of warming trends (as opposed to step-changes) is growth of foliage which shelters the thermometer site. This issue is singled out for mention in metadata relating to Auckland, Wellington, Lincoln and Dunedin and obviously can’t be ignored.

Both of these factors are artifacts of the measuring system, and have nothing to do with any general NZ warming.

Andy, I’ll send you a copy.

Bob has moved on to Lincoln and Gary is looking at interpolation infill and cross-correlation issues.

The only truly slowly progressive change is for the Urban Heat Island Effect. And that should push modern readings down, with no effect or minimal on the oldest.

All this strangeness available to those with an Excel Spreadsheet.

Climatic Change, Volume 45, Number 2, 339-359, DOI: 10.1023/A:1005525903714

Behind a paywall here

http://www.springerlink.com/content/h90855kv473t75r3/

I don’t know the details of the peer review process at that journal.

There are other NZ tree ring studies but this is the only one I could find with a link to a dataset of the results that is available at NCDC NOAA here

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/newzealand/nztemp_data.txt

Note that the results are for Feb – Mar. I averaged the two to enable a simple plot to apply linear trends myself, so although it is a temperature reconstruction, it does NOT say anything about trends in the abstract, that is my compilation. A citation is also required for use.

Using my method to extract the 1910-1987 trend certainly contradicts NZT7 and 7SS but I think a better comparison is with a compilation of observed NZ temperatures from 1887 rather than 1910. I’m putting together a post for Richard Treadgold with more detail that everyone can address.

The IPCC cites NIWA 2005 and a 1 C rise which is actually obtained from Salinger 1995 “Southwest Pacific temperatures: trends in maximum and minimum temperatures” in which he compiles a 6SS 1861-1992 from observations but I can’t find the data for his plots. My solution is to use data from CliFlo to concatenate to the 7SS in order to obtain a 1887-2010 series which yields trends similar to the tree ring reconstruction. I will put the full story including the IPCC-NIWA citation in the post for Richard T.

Interesting that the IPCC cites values from Salinger 1995 but the only way I can think of to reproduce his 6SS plot is to estimate the data points from his plot.

The post will include 3 plots,

1st showing the juxtaposition of trends, my compilation of tree ring vs 7SS 1909-1987 (78 years)

2nd showing a comparison of trends, my compilation of tree ring vs my compilation of observed 1888-1987 (100 years)

3rd showing my compilation of the 1720-1987 tree ring plot.

Note the comment from Mike D at the end

Richard C

Is this a peer-reviewed journal-published paper obtainable from the NOAA website? And does it discuss a study of tree rings showing that the NZ warming trend 1910-87 was only 0.24°C/century?

If so, it would appear to contradict the NZT7 (and 7SS).

This is only 0.03 more than the Feb-Mar tree ring reconstruction for a similar period.

I extracted the EMD trend by extending the 7SS back with an average of Auckland Albert Park and Dunedin Leith Valley from CliFlo. The plot looks a little like Salingers but doesn’t have the pronounced cool period about 1900 and 1890 is generally warmer than 1910 by about 0.4 C.

I really do not think the downward adjustment to early 7SS data is warranted given the CliFlo data 1887-1910.

1910-1987, +0.24 C/century.

1888-1987, +0.23 C/century.

1788-1987, +0.02 C/century.