I am pleased to see that the attempt to promote a New Zealand version of “climategate” has more or less foundered. Sure the ACT party and some more extreme opponents of the findings of climate scientists are still campaigning (see for example Auckland Public Meeting: Climategate, NIWA and the ETS). And well know local climate change denier Ian Wishart managed to get international reporting of his slanderous press release (BREAKING: NZ’s NIWA accused of CRU-style temperature faking) in several more conservative and extreme international blogs and papers (for example BREAKING: NZ’s NIWA Accused of CRU-Style Temperature Faking, Climategate Scandal Spreads to New Zealand as MSM Continues Ostrich Act, Oops! Now New Zealand NIWA Accused Of Faking Data, New Zealand’s NIWA Gets Busted “Tricking” Their Climate Data and New Zealand Climate Data Shows Clear Evidence Of Fraud). But the New Zealand media has, in general, been more balanced in its reporting. The information from climate scientists at NIWA has been getting through.

Temperature trends for raw data

For example, NIWA’s information on the temperature trends shown by raw data from 11 local  met stations (Temperature trends from raw data) has been picked up (Niwa publishes climate data to answer critics). NIWA released this because of the distorted information distributed by the NZ Climate Science Coalition, the Climate Conversation Group and Ian Wishart (Climate change deniers live in glass buildings ).

Some local bloggers picked up and reproduced this misinformation. In the process they have been slandering our local climate scientists and other bloggers who have attempted to correct the misinformation. My personal concern in this is not so much the facts of climate change, but the willingenss of some ideologically driven people to unjustly attack the integrity of honest scientists. And their willingness to distort information with this end in mind.

So it’s worth reproducing some of the latest information released by NIWA.  This uses publicly -accessible information (from the National Climate Database). The data used is from the period after 1930 when there were no significant site changes. Consequently the raw data could be used without adjustments to determine temperatures at the individual sites. (You will recall that the climate change denier’s report and press release claimed that NIWA’s adjustment of data to accommodate met station site changes was fraudulent. And that they (the deniers) went ahead to combine data without adjustments and produced a misleading graphic suggesting temperature was unchanged over time. The current data should avoid all issues of adjustments).

NIWA’s information says in part:

We have analysed raw data from these sites directly, with absolutely no adjustments to the numbers from the NIWA climate database. Taking all sites together and averaging the annual mean temperatures (difference from 1961–90 mean at each site) results in Figure 1 below.

Figure 1: Temperature departures from the 1961–90 normal, averaged over the eleven sites listed in Table 1. For years where not all sites are available, the average is over those that do have records.

Note that not all stations have annual mean temperature values for all years in 1931–2008. It is common practice to in-fill isolated missing months, but we have deliberately not in-filled missing data here to keep this analysis as non-contentious as possible. For each year, the available station values have been averaged. In the title of the Figure, the “p-value” comes from a statistical test, and indicates the probability that the indicated trend could have arisen by chance.

If the two outlying Island records (Raoul and Campbell Islands) are left out, and the remaining nine records averaged, the result is as shown in Figure 2. In either case, the trend over the 78 year period is close to 1°C.

Figure 2: Temperature departures from the 1961–90 normal, averaged over the nine sites listed in Table 1 that are located on the main islands of New Zealand (i.e., all but Raoul and Campbell Islands). For years where not all sites are available, the average is over those that do have records.