Everyday uses for the NZTR

1. Computer models that forecast the weather

Gareth Renowden at Hot Topic has finally lost whatever finger-nail grip he ever had on climate science.

He now claims (incredibly) that national temperature records “play no part in planning” since forecasts come from computer models, not carefully-kept historical records. It’s sad, really, that NIWA totally disagrees with him. And we shall prove it.

Our good friend Chris de Freitas wrote an excellent article for the NBR on 14 November reporting on the paper by him and his co-authors—a reanalysis of the NZ temperature record (NZTR), published last month in Environmental Modeling & Assessment. Renowden first quotes de Freitas:

National temperature trends are widely used for a large number of societal design and planning purposes and it is important that they should be as reliable as modern methods allow.

Renowden comments:

This is transparent nonsense. Historical temperature trends are interesting, but they play no useful part in future planning. To plan in the face of rapid climate change, we need good regional projections for temperature changes, sea level rise and increases in weather extremes. Those will come from climate models, not temperature records.

We do agree that New Zealand’s national and regional temperature projections will continue to come from NIWA’s uber-expensive super computer. But you have to feed it something. So the 64,000-dollar question is: Where does the mathematical model come from and what data goes into it?

In simple terms: what on earth does it start with? The answer is, of course, it starts with reality: with now.

So here’s what NIWA does. It takes twelve models from the 2007 IPCC CMIP3 suite, forced by the long-outdated A1B scenario for global emissions. Then, according to its web site:

Historical observations are used to develop regression equations that relate local climate fluctuations to changes at the larger scale. These historical observations are then replaced by the model changes in the regression equations to produce the fine-scale projections. [emphasis added]

So, historical observations of the New Zealand climate (for example, the 7SS temperatures) are the starting point for downscaling the global models. This is hardly surprising, as every projected trend is by definition an extension of past trends. You have to know accurately where you are to start with.

NIWA doesn’t say whether it uses the 7SS raw data or the homogenised series set out in Mullan10, but I’m betting it’s the latter. That means the downscaling project is fed with a temperature trend that’s 300% too high.

It has proved impossible to verify climate models. Their projections have a very poor record world-wide and virtually all the CMIP3 models have consistently over-stated global mean surface temperatures for the past 20 years. However, an effort is invariably made to improve performance by calibrating and tweaking the model until it is able to “hindcast” the observed temperature record for previous decades.

David Wratt and Brett Mullan say on the NIWA website:

If we are to have confidence in future projections of climate models, it is vital to first test them against observed climate to see whether they realistically simulate different climatic conditions which were observed during the earth’s past. [emphasis added]

So the downscaled NIWA model has been calibrated by reference to Mullan’s version of the 7SS, using exaggerated adjustments. If it is managing to hindcast the national temperature trend as warming at the rate of 0.91°C/century, its untestable future projections are completely useless.

An important example of misleading projections from the NIWA model is that of mean sea level rise (MSLR). We know from tide gauges that there has been no acceleration of MSLR around New Zealand during the past century. The NIWA model should therefore pick up the fact that the MSLR has not been compatible with the temperature data it has been fed from Mullan’s 7SS. But it doesn’t, because it uses a calculated history of global SLR drawn from satellite data, and ignores the actual painstaking readings that New Zealand scientists have recorded for decades, in some of the longest records in the Southern Hemisphere.

So, Gareth, what do you have to say now about the “transparent nonsense” you alleged of Chris de Freitas? What he said is a perfectly accurate reflection of what NIWA does. What you said is demonstrably wrong—you can check the references for yourself. I think the least you can do is to apologise.

Wratt and Mullan also say on the web site:

Confidence in the ability of climate models to estimate future climate changes comes from the fact that they are based on accepted physical laws such as conservation of mass, energy and momentum, as well as a wealth of observations for their more empirically-based components such as cloud reflectivities or infrared absorptive properties of greenhouse gases. [emphasis added]

Errors in any of these components render the computer model output useless and should be corrected as soon as possible.

Imagine that overseas scientists reported that NIWA was using an incorrectly stated law of physics: say, an incorrect constant value, or a wrongly formed equation. NIWA scientists would move so quickly to fix a mistake like that that they would be mere blurs in the corridors, their speed immense. They have put in an enormous amount of work to build up credibility with colleagues around the world and would spare no effort to correct such critical errors.

Well, we don’t need to imagine anything, because this is reality: what has actually happened is that local scientists have reported that NIWA has been using an incorrectly stated national temperature record. Why are they not running to fix it? Do they disagree with the laws of physics?

We haven’t seen a reply yet to our rebuttals of your debating points, Gareth.

 

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Richard C (NZ)
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Richard C (NZ)

>”NIWA doesn’t say whether it uses the 7SS raw data or the homogenised series set out in Mullan10, but I’m betting it’s the latter. That means the downscaling project is fed with a temperature trend that’s 300% too high.” No, not the 7SS or any homogenised series. It’s their Virtual Climate Station Network (VCSN): https://www.niwa.co.nz/climate/our-services/virtual-climate-stations I very much doubt the trend in the VCSN is anything like the 7SS. The VCSN takes the raw CLiFlo data from all over NZ as a base, as I understand, and interpolates from that. NIWA are very quiet about this. It might be interesting to challenge them to graph the trend in the VCSN against the trend in the 7SS. The paper you need to refer to is: Regional climate modelling in New Zealand: Comparison to gridded and satellite observations D. Ackerley, S. Dean, A. Sood and A.B. Mullan (2012) http://www.metsoc.org.nz/publications/journals Page 4 pdf, 2.3 Observational data 2.3.1 Virtual Climate Station Network (VCSN) data. In this study, we use the gridded fields of the Virtual Climate Station Network (VCSN) at NIWA, which was produced from observed station data using the methods described in Tait et al. (2006)… Read more »

Richard C (NZ)
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Richard C (NZ)

Ackerley et al (2012), page 14 pdf:

Figure 5: The annual, New Zealand mean (a) Tmax (oC), (b) Tmin (oC) and (c) daily mean
precipitation (mm day-1) from VCSN (black lines), RCM1 (red lines) and RCM2 (yellow lines)
data between 1980 – 1999. The correlation values (given in the key for each graph) are between
the VCSN time series and each of the model time series separately. Statistically significant
correlations (p≤0.05 using a student t-test) are given an asterisk.

“RCM” is Regional Climate Model.

1980 – 1999 trend is irrelevant to the 7SS contention so it’s the VCSN trend prior to 1980 that needs to be published, and preferably graphed against the 7SS.

Shouldn’t be difficult.

Richard C (NZ)
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Richard C (NZ)

>”The VCSN takes the raw CLiFlo data from all over NZ as a base, as I understand, and interpolates from that.”

This product predates BEST but BEST made a song-and-dance about their revolutionary approach. It would also be interesting to see the VCSN trend against BEST’s NZ trend:

http://berkeleyearth.lbl.gov/regions/new-zealand

BEST NZ trend 1910 – 2013: 0.87 ± 0.26

Richard C (NZ)
Guest
Richard C (NZ)

>”I very much doubt the trend in the VCSN is anything like the 7SS”

I suspect it is more like GHCN from 1880, 0.2 °C / Century:

http://photos1.blogger.com/x/blogger/4986/984/1600/695397/GHCN_NZ_Temp_record.jpg

From the source of the graph, Not PC:

“And just for your interest, here’s a graph [above] from the Global Historical Climatology Network dataset for NZ’s latitude and longitude (unlike NIWA, GCHN has no political axe to grind) so you can see for yourself the “general warming trend in NZ” that Frogblog is talking about. Does 0.02 degrees/decade sound catastrophic to you?”

http://pc.blogspot.co.nz/2007/01/still-cold.html#links

GHCN NZ trend from 1880: 0.2 °C / Century
BEST NZ trend from 1860: 0.71 °C / Century

Given BEST is just below NIWA’s 7SS from 1910, 0.87 °C / Century vs 0.91 °C / Century, then I think the BEST vs GHCN difference is a good indication of what the 7SS vs VCSN difference would be from 1909.

Richard C (NZ)
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Richard C (NZ)

>”NIWA doesn’t say whether it uses the 7SS raw data or the homogenised series set out in Mullan10, but I’m betting it’s the latter. That means the downscaling project is fed with a temperature trend that’s 300% too high.” The fact that NIWA calibrates their RCM against VCSN (as upthread) not 7SS was pointed out in ‘Paper adds interesting perspective on NZ temperature trend’ here: https://www.climateconversation.org.nz/2014/10/paper-adds-interesting-perspective-on-nz-temperature-trend/#comment-1205074 Your response RT, was: [RC – as I mentioned, this info is technical and I find it hard to absorb in one bite. That means others will struggle, too. Now that’s fine, it’s a technical topic, but you make the bite larger by increasing the number of lines. Would you kindly paste text that will flow in the normal way, please? I’ve put this slab through NoteTab to join the lines and show what I mean. You’re helping to create a quite unique research tool here, but I’d ask you to respect the prime purpose of this blog, which is to make the information accessible. Thanks for your help. – RT] Apparently your reformatting did not aid your understanding of the underlying information. Please take the time… Read more »

Richard C (NZ)
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Richard C (NZ)

Change to VCSN Data Access: From 13-Oct-2014 public access to VCSN (Virtual Climate Station Network) data has been discontinued. Please contact vcsn@niwa.co.nz if you wish to discuss data access. http://cliflo.niwa.co.nz/ de Freitas et al (2014) publication: Received: 29 December 2013 /Accepted: 7 October 2014 Published online: 26 October 2014 Pre-emptive strike by NIWA? I didn’t know there was any public access to VCSN, the blurb indicated that access was fee-based. Just wish I’d extracted T Max/Min/Mean when there was public access, if it were possible. Still, anyone can “discuss” data access apparently, but Climate-Smart Farmers aren’t happy: Virtual Climate Station Network Well from 13th October 2014 we have a problem. We no longer have access to the Virtual Climate Station network that drives the weekly climate updates. NIWA, the Crown-owned agency that holds this data has decided to terminate access and deny this information to landusers, unless you pay a fee to use their NIWA FarmMet subscription service. We think we had developed, in collaboration with NIWA, a pretty useful service that helped land users make better decisions using information that was local. And we had plans for working with NIWA to further… Read more »

Richard C (NZ)
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Richard C (NZ)

From Climate-Smart Farmers: >”1. Click on this Map browser and zoom into your location.” Works, gets you to the ESRI ArcGIS: http://www.arcgis.com/home/webmap/viewer.html?webmap=0aaa6f39e216467db95694eb7a07cb1d&extent=161.038,-48.6674,180,-32.0151 Go to Masterton. The 7SS reference station for Masterton is “Site 7 East Taratahi AWS (2612) 8 km southeast of Masterton” (see map link below) but is actually south and a little west of Hood Aerodrome according to the map. Oddly, the 7SS reference station East Taratahi AWS does not appear in VCSN. Masterton Aero, not 7SS but mentioned in pdf below, is VCSN Hood Aerodrome: https://www.niwa.co.nz/sites/niwa.co.nz/files/import/attachments/Masterton_CompositeTemperatureSeries_13Dec2010_FINAL.pdf The VCSN grid containing East Taratahi AWS appears to be the VCSN node (south of Hood Aero): AGENT_NO 29831 NETWORK P193132 LONGT 175.63 LAT -41.02 NAME Carterton District The P193132 Mean series should conform to the 7SS Masterton series in toto because all of the Masterton 7SS stations are homogenized to East Taratahi AWS and East Taratahi AWS is within P193132. But “No information available”. Climate-Smart Farmers old workaround no longer works. That was to take the above information to the default plot and enter it here: DEFAULT PLOT LINKS (will open in new windows) Air Temperature and Frost: http://wrenz.niwa.co.nz/vcsoper/P203148_air.png [NiWA] – “Important Notice:… Read more »

Richard C (NZ)
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Richard C (NZ)

Comparing VCSN to 7SS directly is just a matter of obtaining VCSN Max/Min data for the 7 VCSN nodes corresponding to each of the 7SS reference stations.

That negates the mission of obtaining the VCSN average Mean series for all of NZ (a mammoth task – probably expensive). But only useful if VCSN has data prior to 1980 back to 1909.

Richard C (NZ)
Guest
Richard C (NZ)

VCSN nodes corresponding to each of the 7SS reference stations. Nodes are not all available i.e. VCSN has missing grids for 3 reference stations. The nearest and most appropriate nodes were chosen as representative of the 7SS reference station. Auckland North of Mangere Airport. not same node as Mangere EWS AGENT_NO 25397 NETWORK P176213 LONGT 174.78 LAT -36.98 NAME Manukau City Masterton South of Hood Aerodrome, same node as East Taratahi AWS AGENT_NO 29831 NETWORK P193132 LONGT 175.63 LAT -41.02 NAME Carterton District Wellington Wellington CBD altitude, not same as Kelburn altitude. Same node as Kelburn AWS AGENT_NO 28602 NETWORK P176127 LONGT 174.78 LAT -41.27 NAME Wellington City Karori altitude, same as Kelburn altitude. Not same node as Kelburn AWS AGENT_NO 24930 NETWORK P175127 LONGT 174.72 LAT -41.27 NAME Wellington City Nelson Stoke, south of Nelson Aero. Not same node as Nelson Aero. AGENT_NO 20596 NETWORK P145126 LONGT 173.22 LAT -41.33 NAME Nelson City Hokitika Hokitika Town, same node as Hokitika Aero AGENT_NO 19484 NETWORK P100098 LONGT 170.97 LAT -42.73 NAME Westland District Lincoln North of Lincoln, same node and location as Lincoln Broadfield EWS AGENT_NO 20993 NETWORK P130080 LONGT 172.47 LAT -43.63… Read more »

Richard C (NZ)
Guest
Richard C (NZ)

BEST looks nothing like VCSN either over 1990 – 1999. Resembles 7SS up-down-up but somehow they manage to introduce a ridiculous trend:

http://berkeleyearth.lbl.gov/auto/Regional/TAVG/Figures/new-zealand-TAVG-Trend.pdf

Data table:
http://berkeleyearth.lbl.gov/auto/Regional/TAVG/Text/new-zealand-TAVG-Trend.txt

Year, Month, Annual Anomaly
1980 6 -0.040
1985 11 0.557 (up 0.6)
1992 4 -0.848 (down 1.4)
1999 5 1.063 (up 1.9)

7SS
1980 12,0
1987 12.5 (up 0.5)
1995 11.8 (down 0.7)
1999 12.4 (up 0.6)

Except by their methodology, BEST should resemble VCSN.

It will be possible, but painstaking, to re-compile the VCSN Mean from Ackerley et al Figure 5 to plot against 7SS and BEST 1980 – 1999. Should be interesting.

Richard C (NZ)
Guest
Richard C (NZ)

>”BEST should resemble VCSN”

It does. Both VCSN and BEST are at altitude therefore cooler than 7SS. The 7SS is near sea level mostly.

Year NIWA-VCS NiWA-7SS BEST-NZT
1980 10.10 12.25 10.6
1981 10.75 12.86 11.05
1982 9.80 12.12 10.37
1983 9.85 12.03 10.30
1984 10.55 12.68 10.97
1985 10.60 12.85 11.03
1986 10.50 12.65 10.94
1987 10.55 12.77 11.03
1988 10.80 12.93 11.09
1989 10.80 12.97 11.28
1990 10.85 12.99 11.27
1991 10.00 12.16 10.53
1992 9.45 11.49 9.94
1993 9.80 11.84 10.24
1994 10.15 12.33 10.54
1995 10.45 12.59 10.82
1996 10.20 12.45 10.74
1997 10.10 12.27 10.54
1998 11.25 13.41 11.63
1999 11.15 13.35 11.613

Mean trends
NiWA-VCS: 0.147 C/decade
NIWA-7SS: 0.135 C/decade
BEST-NZT: 0.147 C/decade

Y intercepts
NiWA-VCS: 10.23
NIWA-7SS: 12.408
BEST-NZT: 10.673

VCS trends
VCS-Max: 0.25 C/decade
VCS-Min: 0.045 C/decade

In all 3 series it is only the 1998 and 1999 data that skews the trend:

Mean trends 1980 – 1997
NiWA-VCS: -0.133 C/decade
NIWA-7SS: -0.157 C/decade
BEST-NZT: -0.127 C/decade

VCS trends 1980 – 1997
VCS-Max: -0.042 C/decade
VCS-Min: -0.224 C/decade

Richard C (NZ)
Guest
Richard C (NZ)

NIWA:

“Warming, over New Zealand through the past century, is unequivocal”

NIWA, corroborated by BEST:

“Cooling, over New Zealand through 1980 to 1997, is unequivocal”

Richard C (NZ)
Guest
Richard C (NZ)

Correction:

“Cooling, over New Zealand through [1972] to 1997, is unequivocal” (2.6 decades)

1972 is when NIWA’s VCSN begins but I’ve no access to data 1972 – 1980 and 1999 – Present. But BEST serves as a VCS proxy from 1972 because the methodologies are similar i.e. we can consider a “BEST-VCS” series instead of VCSN. And VCS, 7SS, and BEST profiles are identical (near enough) from 1972, just the altitudes (therefore absolute temperatures) and sensitivities differ (7SS most sensitive).

There was cooling from 1972 to 1997 then an abrupt climate shift at the time of the 1998/99 El Nino. In other words, the only warming that has occurred in New Zealand over the last 4 decades has been natural variation. Numbers and trends another time.

Richard C (NZ)
Guest
Richard C (NZ)

BEST-NZT 1972-1987 (2.6 decades) trend: -0.002 C/decade
NIWA-7SS 1972-1987 (2.6 decades) trend: -0.024 C/decade

El Nino
BEST-NZT 1988/89 shift: +0.40
NIWA-7SS 1988/89 shift: +0.39

BEST-NZT 1987-2013.25 (1.625 decades) trend: -0.156 C/decade
NIWA-7SS 1987-2013 (1.7 decades) trend: -0.017 C/decade

BEST is moving annual mean on monthly data. NiWA data is annual mean.

Richard C (NZ)
Guest
Richard C (NZ)

The Regional Climate Model (RCM1), forced with ERA-40 re-analysis, conforms to 7SS, VCS, and BEST-NZ over 1980-1999 (including the 1998/99 El Nino) because ERA-40 is essentially the same data (see Ackerley et al, 2011). So RCM1 is reasonably reliable as long as it is constrained by the observations.

But if Gareth Renowden thinks RCM1 projections past the observations are anything to go by for policy, he is deluded.

Richard C (NZ)
Guest
Richard C (NZ)

The UKMO’s “decadal” forecast is now down to 5 years and they renew each year to give the impression they’re doing Ok. But one look at the current forecast (see Figure 3) shows just how unrealistic their model forecast is:

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/decadal-fc

Each update will just get more embarrassing every year from now on.

Richard C (NZ)
Guest
Richard C (NZ)

Corrections (hopefully got this right now):

BEST-NZT 1972 y intercept: 10.776
NIWA-7SS 1972 y intercept: 12.469

BEST-NZT 1972-1997 (2.6 decades) trend: -0.024 C/decade
NIWA-7SS 1972-1997 (2.6 decades) trend: -0.024 C/decade

BEST-NZT 1997 y value: 10.7136
NIWA-7SS 1997 y value: 12.4066

BEST-NZT 1998/99 El Nino shift from 1997: +0.46
NIWA-7SS 1998/99 El Nino shift from 1997: +0.39

BEST-NZT 1997 y intercept: 11.174
NIWA-7SS 1997 y intercept: 12.798

BEST-NZT 1997-2013.25 (1.625 decades) trend: -0.156 C/decade
NIWA-7SS 1997-2013 (1.7 decades) trend: -0.017 C/decade

BEST is moving annual mean on monthly data and approximates NIWA-VCS but 0.44 C warmer, both at altitude. NIWA-7SS is annual mean at near-sea level.

Richard C (NZ)
Guest
Richard C (NZ)

‘Climate change scenarios for New Zealand’ [NIWA]

The New Zealand downscaled projections follow the IPCC Fourth Assessment approach. That is, changes are relative to 1980-1999, which we abbreviate as “1990” for convenience.

Mean Temperature:

Downscaled projections of mean temperature changes over New Zealand are shown in Figure 3 (annual-average changes).

Averaging over all models and all 6 illustrative emissions scenarios gives a New Zealand-average warming of 0.2–2.0°C by 2040…..[….]. For just the A1B scenario alone, the projected warming is 0.3–1.4°C by 2040 ……[…], with a 12-model average (or “best estimate”) of 0.9°C …[…] for 2040

https://www.niwa.co.nz/our-science/climate/information-and-resources/clivar/scenarios

# # #

So how are they going?

1990 – 2040 is 5 decades. Their mid-range “best estimate” projection is 0.9°C or 0.164 C/decade. BEST-NZT is similar to NIWA-VCS methodology and tracks NIWA-VCS but 0.44 C warmer:

NIWA-7SS 1980-1999 mean: 12.550
BEST-NZT 1980-1999 mean: 10.827

NIWA-7SS 1989/90-2008/9 is 1.9 decades
BEST-NZT 1989/90-2008.25 is 1.825 decades

NIWA-7SS 2004-2013 mean: 12.729 actual (12.862 projection)
BEST-NZT 2003.33-2013.25 mean: 10.960 actual (11.126 projection)

Already by 2013, NIWA’s mid-range temperature projections are warmer than observations:

NIWA-projection vs NIWA-7SS to end of 2013: +0.133
NIWA-projection vs BEST-NZT to 2013.25: +0.166

HemiMck
Guest
HemiMck

For those of us not keeping up with the detail, could we have an occasional summary or editors overview of the significance of the above.

Richard Treadgold
Guest

Excellent idea! How about it, RC?

Richard C (NZ)
Guest
Richard C (NZ)

Curiously, although BEST-NZT and NIWA-7SS exhibit almost identical profiles and trends 1980-1997, that is not the case 2004-2013. BEST is very much flatter and the trend is half that of the 7SS (0.3 C/decade vs 0.6 C/decade)). There is no significance in the trends because the start year was relatively cool and the end year relatively warm in each case. It’s just the difference that is significant. So why is BEST-NZ considerably different to the 7SS now after being identical 16 – 33 years ago? I think because there’s a totally different set of stations contributing. BEST states on the NZ page that there are currently 33 “active” stations but I think there are 37 as follows:: Station Name Months Distance (km) Earliest Most Recent AUCKLAND, ALBERT PARK 1904 Inside Jun 1853 Oct 2013 CHRISTCHURCH AP/HAREWOOD N Z 1789 Inside Jan 1864 Oct 2013 INVERCARGILL AERODROME 1423 Inside Jan 1865 Oct 2013 NAPIER AERODROM AWS 1417 Inside Jan 1870 Oct 2013 GISBORNE AERODROME AWS 1049 Inside Feb 1905 Oct 2013 KAITAIA OBSERVATORY 849 Inside Oct 1942 Oct 2013 TARA HILLS AWS 713 Inside Nov 1949 Sep 2013 DUNEDIN AERODROME A 463 Inside Dec… Read more »

Richard C (NZ)
Guest
Richard C (NZ)

[HemiMck] >”For those of us not keeping up with the detail, could we have an occasional summary or editors overview of the significance of the above.” [Richard Treadgold] >”Excellent idea! How about it, RC?” Yes, needed. It’s taken me a bit of work to get to this. In terms of RT’s original post, and Renowden’s assertions, we get to NIWA’s ‘Climate change scenarios for New Zealand’ which is my last thread header just upthread here: https://www.climateconversation.org.nz/2014/11/everyday-uses-for-the-nztr/#comment-1252516 That deals with how NIWA’s down-scaled Climate Model temperature projections are tracking warmer than observations at end of 2013 and the following comment deals with how their model projection divergence is different depending on whether observations are by 7SS or by BEST 37SS. The 37SS exhibits a much flatter current decadal trend than the 7SS which makes NIWA;s projections worse by that measure. Given BEST’s 37SS is similar methodology to NIWA’s VCS then those are the major observational benchmarks that must be considered i.e. the 7SS is a minor benchmark because of the much lower diversity of observations. We don’t have access to VCS, unless we pay for it, but BEST’s 37SS is a good proxy going… Read more »

Richard C (NZ)
Guest
Richard C (NZ)

>”BEST is very much flatter and the trend is half that of the 7SS” [2004 to 2013] Presumably VCS is similar. Except NIWA publishes annual means each year that correspond to 7SS temperatures (appears to be preliminary) not VCS, although they don’t state this explicitly. Preliminary it seems because they don’t update the 7SS immediately, for example the last available datapoint tp download is 2011 and the value differs from the published figure given for that year. NIWA has published a 2013 figure of 13.4 which is a marked increase from 12.5 in 2012 (+0.9 C) i.e. an apparently exceptional year-to-year change. This jump makes a big difference to the trend obviously. BEST does not yet have Oct, Nov, and Dec for 2013 but given the “damped” nature of their 37SS, those 3 months will not make much difference from that of the 12 months to Sept. BEST annual data is a centred average i.e. last datapoint 2013.25 is the centred mean of the 12 months Oct 2012 to Sept 2013. So looking at what BEST does have, there is quite a difference to the 7SS 2010 to 2013 (nominal means): NIWA-7SS 2010:… Read more »

Richard C (NZ)
Guest
Richard C (NZ)

Excel Workbook NIWA-VCS vs NIWA-7SS vs BEST-NZT.xls with graphs in Dropbox here:

https://www.dropbox.com/s/m5xqlqn4h2svrge/NiWA-VCS%20vs%20NIWA-7SS%20vs%20BEST-NZT.xls?dl=0

Caveat emptor.

Richard C (NZ)
Guest
Richard C (NZ)

A fun thing to do is to plot BEST’s moving centred annual mean 2004-2013 against NIWA’s forecast by adding 0.166 to the observations.

I’ve graphed that here:
https://www.dropbox.com/s/emv972u2sb8xg0j/NiWA%20projection%20vs%20observations.xls?dl=0

Richard C (NZ)
Guest
Richard C (NZ)

Once the end of 2013 data and 2014 data comes in, the projection-observation discrepancy will not be as pronounced because the cool 2004 year drops out. And the recent temperatures have been relatively high.

NIWA’s forecast may even match observations for a year or so but the fluctuation will swing back cool again eventually as it has all decade. That will leave NIWA high again. And if the regime can shift up +0.45 C abruptly as it did 1998/9 then it can shift down too. Temperatures are still trending down from the 1998/9 El Nino even with the recent warmth and 2010/11 El Nino.

Richard C (NZ)
Guest
Richard C (NZ)

>”Prior to 1972 is when the observation quality goes downhill and the trends become contentious. So the question arises: was there any ERA-40 initialization in the RCM prior to 1972? There may have been, I don’t know, I’m doubtful there was, but if so it would only be from Sept 1957.” Oooo, nasty: ‘Can Climate Trends be Calculated from Re-Analysis Data?’ [ERA-40] Lennart Bengtsson, Stefan Hagemann and Kevin I. Hodges, MPI Report, January 2004 https://www.mpimet.mpg.de/fileadmin/publikationen/Reports/max_scirep_351.pdf 3. Temperature Trends [page 3 pdf] For the 1979-2001 period the MSU and ERA40 TLT (temperature of the lower troposphere) are shown in Figure 1. The equivalent TLT has been calculated from the ERA40 data following the method used by Stendel and Bengtsson (1997). The ERA40 data show a slightly stronger warming trend in the lower troposphere than the MSU data. The calculated anomaly trend for the TLT in ERA40 is +0.11 K per decade versus +0.06 K per decade forMSU. The larger trend in ERA40 is still within the estimated error range as given by Christy et al. (2003) but likely overestimated. We will be discuss this further in section 6. For the longer period 1958-2001 results… Read more »

Richard C (NZ)
Guest
Richard C (NZ)

>”This is VERY wrong. it is 60% less in Figure 2″

Actually 65.5% less i.e. the corrected trend is only 34.5% of the actual ERA-40 trend.

Richard C (NZ)
Guest
Richard C (NZ)

Correction:

>”NIWA’s RCMs, when initialized by ERA-40 (e.g. RCM1 Ackerley et al, 2011), are being forced by observations that have a trend [????] % too high by the above assessment if ERA-40 is used from 1958.

In terms of ERA-40:

1.45/0.5 = 2.9 x 100 = 290%

Just as Richard Treadgold asserts but not in terms of NIWA’s 7SS, which is also warming too much in terms of corrected ERA-40 so in those terms:

1.08/0.5 = 2.16 x 100 = 216%

HemiMck
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HemiMck

Thanks RC RT for the summary up thread. I can at least follow the tread of the conversation now.

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