I presume you mean “since 1980″.

No, since about 1992 (since about 2000 for the composite). Bear in mind that I started the graph for the individual locations at 1913 when all 7 can be compared on like-for-like basis.

What is the linear trend of the NZT7 from 1979 to now?

+0.007x or +0.07C/decade or +0.7C/century

Or the polynomial for that matter?

Using the NZT7 composite, the trend was up from 1979, topped out at about 2000, now down. Using the 4 similar locations, the trend was starting to turn from up, topped out at about 1992, now down.

As this is a 30-year period, I guess it would be taken as sufficient to establish a trend.

Yes but what type of trend, linear or polynomial? The linear trend is up, the polynomial trend is down. The polynomial trend is a more valid and sensible representation I think.

Richard C – I presume you mean “since 1980″.

What is the linear trend of the NZT7 from 1979 to now? Or the polynomial for that matter? As this is a 30-year period, I guess it would be taken as sufficient to establish a trend.

Must’ve missed it. Sorry, will try to remember next year to hire a WWII Dad’s Army spotlight and siren for the event.

They should be educating – not misleading.

They should be axed, not parleyed with. But then you would have to have a democratic/capitalist infrastructure to effect. Not something we might enjoy these days.

Clarence, you are only seeing a warming trend because that is what NIWA want everyone to see by their placement of the linear trend on the plot. Plot the data yourself using a polynomial trend instead of a linear trend and a different picture emerges. If you have a Google account you can view the curves here:-

NZT7 Polynomial Trend

https://docs.google.com/leaf?id=0B4_i4MX8e3UaZDNlYzY2ZDUtYWVkZi00OGE2LTliZTUtZDVmZWUyNzFiZjVi&hl=en

Three phases: cooling, warming then cooling again.

NZT7 Location Polynomials

https://docs.google.com/leaf?id=0B4_i4MX8e3UaNGQ0NjZmYjAtMTc1NS00N2FjLWEzYzEtNWZiZTFiZjI3Mjdi&hl=en

Clearly, the main contributors to the +0.91 C/century linear trend are Auckland, Nelson and Hokitika. They show a continuous warming trend from start to approx 1980 (Nelson, the entire series) but the other 4 show a cooling phase for the first 15-25 years, then a warm phase, then a cool phase. Obvious too, is that Auckland is unrepresentative compared to the other 6 locations being approx 2.5C warmer than the next location.

It only takes 3 adjustments, 1 for each location in the early years of Auckland, Nelson and Hokitika to change what could be a cooling phase to a warming phase in those locations. Those 3 then influence a linear trend in a manner contrary to the predominant trend of the other 4 but the early cooling phase is still evident in the polynomial trend of the NZT7 composite series.

Using a polynomial trend, the warm phase was only between 1940-1980 approx. for Masterton, Wellington, Lincoln and Dunedin. The difference in absolute value between 1909 and 2010 for the composite series only being approx 0.7C but that difference is reducing. 5 of the 7 locations show a cooling phase at present. Of the other 2, Auckland has topped out and only Nelson shows a continued warm phase.

The same can be said for other global metrics. The focus is kept on the “long-term” linear trend but this is totally misleading. The trends are curves and the most recent trend in the curves is deceleration. A linear trend will immediately mislead anyone who cannot differentiate between deceleration, constant rise and acceleration. I suspect many people interpret constant or decelerating rise as acceleration in the case of sea levels for example. A situation that certain factions are quite happy with and that includes the NZ Royal Society (Manning, Hunter et al) much to their shame. They should be educating – not misleading.

Yes. Despite a plethora of different adjustments (based on different subjective choices) which produce different temperatures in 98 out of the last 100 years.

Like the old series, the random adjustments of the new 7SS don’t move in both directions and cancel out. Instead 90% of them contribute to a warming trend – and accumulate to reach approx 1°C/century.

How did this entirely different series end up with the same curve as the old series? One explanation is that the trend is so obvious it will emerge regardless of method. Another possibility is that the revised series was manipulated to ensure it looked similar to its predecessor.

Which explanation is closest to the truth?

All that work a moot point?

This seamless transition from monarch to monarch is a source of pride in British realms. But does anyone claim that the dead king carries on “updated”, even after the new king is handed the orb and sceptre?

Richard, can you provide a cross-link to your related piece on 7SS – RIP? (#8552 it seems).