In brief

• The minister in charge of NIWA, Judith Collins, provided incorrect information to Centrist about how NIWA conducts climate analysis. 

• NIWA’s under fire after the Gabrielle Flood Review raised questions  about missing data on big historical floods and whether that could have saved lives.

• Collins denied historic records were missing, and also denied NIWA has to resort to  its Historic Weather Events catalogue for extreme weather analysis, since its main data base is complete.  The Review found contrary evidence on both counts. 

• The false statements raise critical questions over whether NIWA is ‘fit for purpose’ and whether systemic research failures are putting lives and property at risk

NOTE: You can read Part 1 of this investigation here

Minister Collins’ false assurances

The minister in charge of climate agency NIWA has given false information to Centrist whilst – ironically – trying to defend NIWA from allegations it had misled Parliament.

The one paragraph backstory is the Climate of Fear report that revealed dozens of historic mega storms were missing from NIWA’s Historic Weather Events (HWE) database, making NIWA’s extreme climate predictions worthless as they didn’t know the past. NIWA deflected, saying it didn’t use HWE, and that no records were missing from its main National Climate Database. Fast-forward to July this year, and NIWA’s claims collapsed when the Gabrielle flood review panel found 11 people had been killed, and NIWA’s missing historic storm data was a contributing factor.

We put all this to Science and Innovation Minister Judith Collins and asked if she still had confidence in NIWA and its board.

Collins tells Centrist that she’s been assured by NIWA that “no historical climate records have been lost”, and that NIWA doesn’t use its historical weather events catalogue because all the necessary data is contained in NIWA’s NZ National Climate Database:

“NIWA climate scientists, and other climate scientists nationally and internationally, use the New Zealand National Climate Database to identify and analyse weather events or trends in climate, including the frequency or severity of weather events. They do not use NIWA’s Historic Weather Events catalogue [Centrist emphasis].

“I accept these explanations. Accordingly I confirm that I continue to have confidence in NIWA and its board,” concluded Minister Collins.

NIWA’s use of (inaccurate) historic weather data revealed

However, a NIWA analysis of Cyclone Gabrielle flooding dated 23 February this year and released to Centrist by Hawke’s Bay Regional Council, shows NIWA’s assurances to Collins were false.

The document formed the core of NIWA’s evidence to the HBRC Independent Review of Cyclone Gabrielle’s flood response, and in its list of scientific references at the end of the NIWA report, the only NIWA database referenced is “NIWA 2018: NIWA’s Historic Weather Events Catalogue”.

The supposedly superior National Climate Database is not referenced, apparently because its records don’t go back far enough, which throws shade on Collins’ claim that “NIWA climate scientists… use the New Zealand National Climate Database [CliFlo] to identify and analyse weather events or trends in climate, including the frequency or severity of weather events. They do not use NIWA’s Historic Weather Events catalogue.”

In fact, in NIWA’s report to the independent review panel, under a “Historical Data” subheading, the climate agency explicitly states its main records are not reliable for analysing trends in extreme events like floods:

“Due to the systematic record being relatively short lived when considering climatic events such as large floods, information on historic events can increase the accuracy of estimated return intervals. This is because knowledge over a longer time frame can increase the rigour of flood frequency estimates.

A range of resources were used to collate historical flood information on rivers within the Hawke’s Bay region (Cowie 1957, Hawke’s Bay Rivers Board 1919, 1928, Hawke’s Bay Catchment Board & Regional Water Board 1985, Hawke’s Bay Regional Council 2004, Hawkins 1977, NIWA 2018 [Centrist emphasis], Williams 1985).

And of course, “NIWA 2018” is the reference in the study source list to the “NIWA Historical Weather Events catalogue” that Minister Judith Collins assured the public  that NIWA “do not use”.

Not only did NIWA “use” it in their main analysis for the inquiry in February this year (five months prior to the minister’s false statement) but, just to labour the point, it was the only NIWA database they could trawl for historical data on Hawke’s Bay floods.

[Editor’s note: If you need more evidence that NIWA does use the HWE and has therefore misled its minister and, through her, the public, read this)

NIWA’s misinforming of its own minister gets worse, however, when the claim that “no historical climate records have been lost” is put to the test.

The NIWA frequency and severity analysis looked at floods in Hawke’s Bay dating back to 1893, and they thought they would “capture” all major floods since then:

“In this analysis we are using 1893 as the start of the historical period. It is not going too far back to have less confidence that there were other large historical peaks that occurred but were not recorded in the literature (we assume we have captured all the exceedances over the perception threshold during the historical period)”, NIWA’s analysis records.

So, having recognised that its premium CliFlo database was pretty much useless on events before 1960, NIWA used its Historical Weather Events catalogue.

Unfortunately, it turns out that historical data was still missing.

The Independent Review set up by Hawke’s Bay Regional Council found that “flood risk had been underestimated in a number of locations, because large historic floods had not been included in the analysis of flood size, and there was limited detail and a wider understanding of trigger levels and likely areas of inundation.”

It noted NIWA “completed an initial summary report and subsequently a more detailed technical report assessing the flood flows that occurred during the cyclone. It is worth noting several key limitations in the analysis of issues that arose during the event.”

Among those issues, two big floods in 1941 and 1953:

“NIWA has assessed the return period of the 2023 flood as >1,000 years, but this does not include the 1941 and 1953 events so is possibly less than this. If 2023 were the second-largest flood since 1941, it would have a return period of approximately 50 years,” the independent report found.

Implications for government oversight and accountability

Given that Minister Collins stated that she continued to have confidence in NIWA and its board because she believed NIWA’s assurances that it didn’t use the HWE catalogue and that no historical records were missing from the main NZ National Climate Database, Collins still has some wriggle room.

With both of her claims in tatters because NIWA in July deceived her (NIWA knew it had relied on HWE for the Gabrielle inquiry), Collins is the third political victim of NIWA false statements after the agency last year misled its then minister Ayesha Verrall and subsequently Parliament when it assured Parliament the missing storm data claims in the Climate of Fear study were untrue, even though NIWA had not actually done any work to investigate and disprove the allegations.

We offered Collins the chance to comment on the false statements:

“I have sought and received assurances from the Chair of NIWA’s Board that the information provided was complete and accurate.”

Has Collins been duped? You be the judge.

Centrist, in the first part of this investigative series yesterday, called on the Government to hold NIWA accountable and urgently inquire into the systemic failures identified in the Gabrielle Flood Review which may affect extreme event planning in other regions and put lives and property at further risk.

Feature Image: Linkedin