Paper which challenged NZ temperature records gets its rebuttal

The credibility of New Zealand’s long-term temperature records is the subject of a new post at Sciblogs (HERE) by Gareth Renowden, a member of the committee of the NZ Meteorological Society.

recalls that back in the spring of 2014, a paper was published based on the authors’ recalculation of the country’s  long-term temperature record.

This work  was based on calculations made to support their court case against the National Institute of Water and Atmospheric Research (NIWA), which they emphatically lost.

It contended New Zealand’s long-term warming rate was only a third of the amount previously calculated.

Gareth Renowden now writes:

As I pointed out at the time, it was riddled with errors and bad scholarship, but it appeared in the peer-reviewed literature, and so required a peer-reviewed rebuttal.

It’s taken a while, but in the last few days Comment on “A Reanalysis of Long-Term Surface Air Temperature Trends in New Zealand” has been published in Environmental Modelling and Assessment3.

Led by NIWA principal climate scientist Brett Mullan, the authors are Jim Salinger, who first established the NZ long term temperature record4, Professor Jim Renwick from VUW, and David Wratt, now Emeritus Scientist (Climate), at NIWA, and an Adjunct Professor in the New Zealand Climate Change Research Institute at VUW. You could fairly describe them as experts – and their “comment” might better be called a demolition.

Here’s their conclusion:

In this paper, we identify what we consider to be several methodological flaws in the [de Freitas et al] paper. We conclude that, as a consequence, the temperature trend of an increase of 0.28 °C per century for the period 1909–2009 for New Zealand land surface temperatures derived in the dFDB paper is substantially too low, and that no need has been established for significant downward revision of the trend of around 0.9 °C per century found in previous studies.

They then provide a handy summary of the main flaws – which I’ve paraphrased below:

  • dFDB claimed their paper was the first to properly use a methodology developed by Jim Salinger and Rhoades, first published in 1993. It wasn’t – in two senses. It wasn’t the first, and they didn’t use it properly.
  • dFDB claimed NIWA’s long term temp record was based on calculations from Jim Salinger’s PhD thesis. It wasn’t.
  • dFDB’s interpretation of the Rhoades and Salinger technique was mistaken and flawed, using station overlaps that were too short and ignoring changes in maximum and minimum temperatures. The result was that they failed to make many adjustments that were required, and therefore underestimated the actual warming.
  • dFDB made a few arithmetical errors, dealt with missing data incorrectly, and mishandled trends in the Auckland and Wellington series.
  • dFDB ignored other lines of evidence that support warming of 0.7-1.0°C per century, such as temperature series derived by the Berkeley Earth project, the decline in NZ’s glaciers, and analyses of sea surface temperatures around NZ.

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In conclusion, Gareth Renowden  (MA Oxon) says the full paper is “an elegant and polite deconstruction of a shoddy, politically motivated piece of work that should never have passed peer review first time round”.

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New Zealand river water quality trends show cause for optimism

River water quality around New Zealand has improved significantly in the past decade, according to the latest National River Water Quality Trends (2007-2016) data released this week by Land, Air, Water Aotearoa.

For all river water quality parameters monitored over a 10 year period, more sites were improving than deteriorating.

This encouraging national picture has been welcomed by scientists and local government who say freshwater ecosystem management practices as likely contributing to the progress.

The data, recording the results from regular water quality monitoring carried out over the past 10 years, show the majority of the country’s rivers rate positively.

The information relates to nearly 1500 freshwater sites that are regularly monitored for water quality by regional or unitary councils.

Data are supplemented by the National Institute of Water and Atmospheric Research.

Trends analysis was led by Cawthron Institute Freshwater Group Manager and Ecologist, Dr Roger Young.

He described the overall picture as encouraging and said:

“Looking back from 2016 at a decade of data, for every monitored parameter, more sites showed evidence of improving water quality, than degrading.

“My hope is this could represent a turning point in New Zealand’s river health story.

“While this analysis gives us cause for optimism, water quality is just one indicator of river health and there is still more work to be done. While all parameters show there are more sites improving than degrading, there are still degrading sites for all parameters.

“In order to continue further improvements, we need to invest in freshwater ecosystem management, routine monitoring, and further research and innovation.”

The National River Water Quality Trends (2007\ – 2016) released by LAWA follows a similar 10 year analysis released in 2015 by National Institute of Water & Atmospheric Research (NIWA).

Compared with the 2015 report, a change in the trend of nitrogen is particularly noteworthy, with significant progress in the number of improving sites compared with the number that are deteriorating.

The trends are based on analysis of the comprehensive data that’s freely available on the LAWA website. Regular water quality monitoring by New Zealand’s Regional and Unitary Councils, supplemented with NIWA data, means there’s water quality info for nearly 1,500 sites.

 

The LAWA website (HERE) provides more detailed information about the health of rivers in 16 regions around the country.

Source: Land Air Water Aotearoa

 

Climate model gets the measure of myrtle rust’s behaviour under NZ conditions

Plant & Food Research scientist Dr Rob Beresford spent the month of June poring through research articles, crunching data and creating mathematical formula to better gauge what myrtle rust may mean for New Zealand.

The end result was the Myrtle Rust Risk Model, specifically designed to understand and predict how myrtle rust will behave under New Zealand conditions.

The Ministry for Primary Industries is using it to help inform its responses, such as targeted surveillance for the disease.

“The model has three key attributes,” says Dr Beresford.

“It warns when the weather is suitable for any spores in the air to infect susceptible plants; it predicts the time from when infection occurs to when rust symptoms may appear; and it assess the suitability of conditions for spores to be produced from infected plants that are showing symptoms.”

With no history of myrtle rust in New Zealand until its arrival in May, developing the model was not easy because of a large number of unknowns.

Dr Beresford’s first step was to dig deep into scientific literature and record observations from countries where the disease is already established, such as Brazil, the US (Hawaii) and Australia.

“Although the overseas research is tremendously useful, you can’t assume that myrtle rust will behave in New Zealand in ways observed in other countries with similar climates,” says Dr Beresford.

“New Zealand has its own seasonal weather patterns. Moreover, the genetic differences between plant species in the myrtle family could influence susceptibility, just as there can be differences in the strains of the rust pathogen itself. So, it’s very complex.

“All these things have to be calculated and factored in to the model, with mathematical parameters set to represent things such as plant susceptibility, temperature range and humidity.

“Essential to doing this well is having a good understanding of the biology of the disease and host plant species.”

The risk model is distinctive in simulating the biology of the disease at a fine scale of time and space. Additionally, thanks to NIWA’s sophisticated weather analysis and prediction maps in combination with its climate-data mapping skills, the NIWA data can be factored into the model hourly, allowing for day-to-day measurability and reporting.

This model can work in conjunction with other climate models developed for myrtle rust that take a more general, broad-brush climate matching approach or rely on long-term weather data.

“The next step to further refine the model is to do more in-depth research into host plant susceptibility,” says Dr Beresford. “This means we can tweak the model from reporting relative risk to something even more definitive.”

Funding for the development of the model came from the Ministry for Primary Industries.

Plant & Food Research is currently collaborating with NIWA on mapping the risk of myrtle rust infection in different regions.

Hayward kiwifruit in Bay of Plenty at risk from climate change

The most commonly grown variety of kiwifruit around Te Puke will not be commercially viable in the area by the end of the century, scientists predict.

A study into how climate change will affect production of the Hayward cultivar in the Bay of Plenty – the common bright green kiwifruit – has just been published in the New Zealand Journal of Crop and Horticultural Science.

The lead author, NIWA scientist Dr Andrew Tait,says it is globally recognised that the effects of climate change is an emerging risk to the economic value of fruit crops, especially those grown in warm, temperate regions such as kiwifruit.

“Our study shows that kiwifruit production around Te Puke steadily decreases over coming decades. It will be marginal by 2050 and most likely not viable by 2100 under all but the most stringent of global greenhouse gas emission options.”

The good news is that other parts of New Zealand will become suitable for kiwifruit production as temperatures rise.

About 90 per cent of New Zealand’s kiwifruit industry is based in the Bay of Plenty and more than half of that around Te Puke. Production is mostly the Hayward variety which is suited to the climate and soils of the area, including warm springs, mild summers and autumns and high sunshine hours.

Kiwifruit need sufficient “winter chilling” between May and July to produce high flower numbers in spring that result in fruit. High winter chilling, or colder sustained temperatures over this period, generally results in more flowers and an earlier flowering period.

Productivity significantly increased between 1980 and 2010 due to technology changes and the introduction of a chemical sprayed on the vines in late winter to improve the effects of winter chilling. New Zealand kiwifruit exports were worth $1558 million in the year ending June 2016 – up from $930 million the previous year.

But the use of the chemical, hydrogen cyanamide, may be restricted or banned in future.

“As air temperatures in New Zealand continue to rise, the potential for more years with marginal or poor winter chilling conditions steadily increases. This could put significant stress on the kiwifruit industry in the Te Puke area, particularly if hydrogen cyanamide is banned,” Dr Tait says.

“If this happens soon then there is an urgent need to consider the viability of Hayward kiwifruit production in other areas of the country, alongside genetic improvement.”

NIWA temperature data and high resolution mapping abilities showed areas further inland in the Bay of Plenty as well as Canterbury and Central Otago had potential as Hayward kiwifruit growing regions.

Through good planning, the New Zealand kiwifruit industry is likely to remain viable for many decades to come, Dr Tait says.

Report explains the science of NZ’s freshwater estate

Sir Peter Gluckman, the Prime Minister’s Chief Science Advisor, has released a report designed to assist in understanding the complexity of issues surrounding the condition and stewardship of our freshwater.

With growing interest in the state of New Zealand’s freshwaters and the policy decisions needed to ensure stewardship of the estate, the report aims to provide common understandings of the scientific and technical knowledge on which freshwater ecosystem management should be based. In doing so, the paper acknowledges the many  values New Zealanders place on freshwater and the different diversity of stakeholders.

The report provides an overview of the issues and a technical analysis for those who wish to explore the science further.

“My office started working on this report nearly a year ago, recognising the complexity of decisions and trade-offs that New Zealand faces between conserving our ecosystems and mitigating our agricultural, industrial and urban impacts,” said Sir Peter.

“Because of the Government’s recent ‘Clean Water’ consultation package, which includes proposed new approaches to defining ‘swimmability’, I thought it would be useful to accelerate the release of our report before the end of that consultation phase.”

Sir Peter’s report was developed with the assistance of the Freshwater Group at NIWA. It was reviewed by New Zealand and international academics and by the Departmental Science Advisors from the Department of Conservation and the Ministry for Environment.

The intent was to ensure diverse scientific perspectives on the challenges presented by New Zealand’s varied river catchments, lakes, estuaries and wetlands could be fully explored.

The issues extend from understanding the influence of distinct landscapes and watersheds, climate, and the diversity of uses and values of freshwater systems, to the ecology of our native freshwater plants, fish, insects, and birds. The report explores the impacts of our pastoral agricultural system, urbanisation, industrialisation and climate change, and how these might be managed to maintain and restore New Zealand’s freshwater estate.

“Water is not a trivial issue for New Zealand and New Zealanders,” said Sir Peter.

“Our cultural and economic relationship to our land and water defines us, and I felt the importance of the issues merited a full explanation of all the freshwater science that informs them.”

The report is available on the PMCSA website HERE. 

 

NIWA team finds native forests are absorbing more carbon dioxide

New research led by NIWA atmospheric scientists Drs Kay Steinkamp and Sara Mikaloff-Fletcher indicates that New Zealand’s forests absorb much more carbon dioxide than previously thought, with much of the uptake occurring in the southwest of the South Island.

Carbon dioxide is a primary greenhouse gas and responsible for most of the human-induced warming in the atmosphere. Globally, carbon sinks, such as oceans and forests, have helped mitigate the effects of climate change by absorbing about half the carbon dioxide emitted by human activities over the past few decades.

New Zealand’s forest carbon uptake played a key role in meeting our commitments under the Kyoto Climate treaty and is expected to play an important role in meeting our COP21 commitments.

The results of the research have just been published in the scientific journal Atmospheric Chemistry and Physics.

Dr Mikaloff-Fletcher and her team used an “inverse” modelling approach to estimate the amount of carbon uptake. This is done by measuring the carbon dioxide present in the atmosphere at a network of sites, and then using high resolution weather models to determine what parts of New Zealand the air has passed over before reaching the site.

Simulations from a land model, run by partners at GNS Science, and ocean carbon data provide additional information. From there, the team calculates the best combinations of sources and sinks to match the data.

 This project included data from NIWA’s clean air station at Baring Head, near Wellington, its atmospheric research station at Lauder in Central Otago, and measurements taken from a ship that collects observations on a line between Nelson and Osaka, Japan.

“The inverse approach integrates information about carbon dioxide sources and sinks from atmospheric data, ocean data and models,” Dr Steinkamp says.

“The story the atmosphere is telling us is that there’s a big carbon sink somewhere in the South Island, and the areas that seem to be responsible are those largely dominated by indigenous forests. However, we cannot rule out an important role for carbon uptake in the hill country or from pasture from our current data.”

Dr Mikaloff-Fletcher says this was a very surprising result mainly because strong carbon sinks are expected when there is a lot of forest regrowth.

“Carbon uptake this strong is usually associated with peak growth of recently planted forests and tends to slow as forests mature. This amount of uptake from relatively undisturbed forest land is remarkable and may be caused by processes unique to New Zealand or part of a wider global story.”

The National Inventory method reported by Ministry for the Environment reports annually on New Zealand’s carbon uptake. This internationally standardised methodology puts the amount of carbon being absorbed by all New Zealand forests at 82 teragrams (Tg) CO2 (A teragram is one millon metric tons) total over 2011-2013, the period studied by Dr. Mikaloff-Fletcher’s team.

Once accounting rule differences are corrected for, the new NIWA measurement approach finds that actual carbon uptake could be up to 60% higher.

The inventory-based method estimates carbon uptake using measurements of tree growth taken from about 100 sampling areas, and extrapolates this to the entire country using statistical techniques and modelling. There is still considerable work to be done in comparing the two independent approaches.

“We need to find out definitively what processes are controlling this unexpectedly large carbon uptake, in order to understand the implications for land management and climate treaties. We need additional measurments to tell us if this is unique to the southern half of the South Island or holds across a wider range of New Zealand.”

Dr Mikaloff-Fletcher says the ability of forests to absorb carbon is a powerful tool to help address the challenge of climate change.

Next steps include incorporating data from NIWA’s newest atmospheric CO2 observing site, Maunga Kākaramea/Rainbow Mountain in the central North Island, deploying two new atmospheric CO2 observing sites and a major improvement to model resolution. This will start to shed light on what’s happening in the North Island and the Canterbury plains.

Significant progress made towards eradication of Hydrilla weed

A recent annual flora and fauna survey conducted by the National Institute for Water and Atmospheric Research shows the Ministry for Primary Industries has made good progress in removing Hydrilla verticillata, a highly invasive aquatic weed from the Tutira, Waikōpiro and Opouahi lakes in the Hawke’s Bay.

For the first time in more than five decades the Hydrilla weed has not been found in the three Hawke’s Bay lakes where it was first found, says Dr Mike Taylor, the ministry’s Manager Biosecurity Response.

“After over seven years of dedicated work, we are well on our way to reaching our goal of eradicating this invasive weed,” he says.

Hydrilla is a submerged, rooted freshwater aquatic plant which grows up to 9 metres. As it grows it becomes very dense and crowds out native aquatic plants, restricts light, and depletes oxygen. It is considered one of the world’s most invasive water weeds.

Hydrilla is one of 9 species currently managed as part of the National Interest Pest Responses, which is an ministry programme focused on responding to organisms that present significant risks to New Zealand’s biodiversity.

In collaboration with the Hawkes bay Regional Council, Department of Conservation, Fish and Game, and local iwi, MPI has been actively working on removing Hydrilla from Hawke’s Bay’s lakes since 2008.

The programme started off with the use of an aquatic herbicide, which was then followed up with the introduction of Ctenopharyngodon idella, the herbivorous grass carp (a type of fish), into the affected lakes in December 2008 and again in 2014.

“This has been successful as Hydrilla is a preferred food plant by grass carp. The carp used will not breed in New Zealand waters, so we aren’t having to deal with an increase of carp numbers in the local waters,” says Dr Taylor.

“Being able to remove Hydrilla from these lakes will remove the likelihood that Hydrilla can be transported to other water bodies.”

Native fauna, such as freshwater mussels, are re-colonising their preferred habitat which was previously smothered by the dense Hydrilla weed beds.

The ministry will be contracting NIWA to conduct a further flora and fauna survey in autumn 2017 to monitor progress.

The 2016 flora and fauna survey report is available here.