Dunedin descendants threatened with Blenheim lifestyle

• Guest post •

— by Barry Brill, Chairman of the NZ Climate Science Coalition

The Royal Society’s Human Health Impacts report forecasts that average air temperatures in New Zealand could rise by between 2.5°C and 5.0°C by the year 2100 – a mean of 3.75°C.

Let’s take an actual example. At present the maximum temperatures in Dunedin average 8.5°C in the winter months and 13.5°C in the summer, or a mean of 11°C year-round. That is just a smidgeon higher than  the average annual air temperature for the whole South Island, which is just 10.58°C.

The yearly mean for Dunedin is forecast by the report to rise to 14.75°C by the end of the century, an increase of 3.75°C.

Now, it needs to be emphasised that this increase is expected to be incredibly slow and gradual during the next 50 years. The IPCC predicts a global rise of about 1.4°C over that whole period, and that is less than one-third of a degree spread over each decade. That change is so small it is barely imaginable. The annual changes would be detectable only by extremely precise instruments as most daily temperatures are measured in whole degrees.

Not now, not later, but much later — much, much later …

Grandchildren of Dunedin residents now aged 20+ are unlikely to be aware of any material changes during their working lives. It would be the great-grandchildren and remoter issue of Dunedinites who might have to deal with the risks mentioned in Human Health. How are they likely to fare?

In the first place, we have to expect that these future citizens will be very much richer than we are today. The scenarios that produce high emissions (and therefore the high temperature changes assumed in the report) are based on very high increases in average income, compounded over many decades. If that doesn’t actually eventuate, then the increases in temperature won’t eventuate either.

Income levels are important because the report emphasises that vulnerability to future climate-related health hazards turns upon wealth, and related issues such as education, health systems, infrastructure and housing quality. So the good news is that, as the average household’s wealth is expected to be nine times higher than it is today, these future generations should have little trouble coping with the predicted increased risks.


The major predicted impact is “floods, storm tides and high intensity rainfall events”. This is because higher temperatures are associated with higher humidity and therefore more precipitation. In addition, the rate of sea level rise is forecast to accelerate to an average 85cm/century or nearly a centimetre per year.

The report makes specific reference to the June 2015 flooding that wreaked havoc in South Dunedin. This was caused  by a rain-burst of 142mm in 24 hours: a 1-in-100-year event. In consequence, the Dunedin City Council resolved to spend $90 million in a 30-year capital works programme, which will renew and upgrade the entire stormwater system. The “Three Waters Project” will also mitigate tidal influences on the system.

Before 2100, there will be ample time to complete at least one more 30-year upgrade programme and there will be perhaps five times as much funding available to ensure the area is fully flood-proofed. Even if the 2015 rain-burst were then to occur regularly, there should be no significant health consequences for Dunedin descendants.

Heat Waves

The next major impact is “hot days” above 25°. The report expects this to increase from less than 40 days to 80 days a year in various places throughout NZ, with heat-related deaths doubling or more. The annual number of such deaths in Auckland and Christchurch is now about 14. However, the number of cold-temperature-related deaths NZ-wide is apparently about 1600 each year. This is probably an over-estimate (as the report suspects) as an authoritative paper in The  Lancet puts the UK yearly ratio of ‘too-cold deaths’ to ‘too-hot deaths at 7:0.4, i.e., for every Briton who currently dies of heat there are 17.5 who die from the cold.  

Heat waves are most unlikely to be an issue for Dunedin descendants. However, we know that the  effects of global warming are greatest on winter nights and increase in higher latitudes, so Dunedin would receive a disproportionate benefit in the form of reduced cold-related deaths. Lives saved might be a hundred or more each year.

Food Availability

One concern raised by the Royal Society dominates all others – the availability of food. As early as 2050, they say 140 climate-related deaths per annum will occur “as a result of changes in fruit, vegetable and red meat consumption, and bodyweight-related risk factors”. New Zealanders will be starving to death! Quite soon!

This is an extraordinary claim. Food production has increased by 14% as a result of the increase in atmospheric CO2 from 0.03% to 0.04% during the past century – and the NIWA model assumes CO2 emissions will increase faster than ever up to 2050. Warmer weather brings longer growing seasons and fewer frosts. Increased rainfall and CO2 boost yields per hectare while reducing fertiliser and irrigation costs. To be sure, farmers will need to adapt to these more favourable conditions, but our farmers are famed for their adaptability.

The Royal Society worries about increased pollen from an expected step-up in grass and tree production, resulting from longer seasons and increased CO2 levels. Future pollen is an excellent proxy to quantify future fruit, vegetable, meat and dairy growth levels, and should be welcomed.

Why would the Otago/Southland region, which is currently a huge exporter of fruit and meat, be facing starvation at home within 33 years?  New Zealand’s major fruit-producing areas, such as Nelson, Blenheim and Hawkes Bay, are much warmer than Dunedin but have not experienced the dystopia predicted to accompany average temperatures of 14.35°C.

Pestilence & Disease

The only remaining concern relates to indirect effects caused by possible toxic algal blooms, microbial contamination and carriers of new diseases. The report does not offer any probability estimates or any other way of quantifying these theoretical risks. The obvious solution is to examine NZ regions that already have average annual air temperatures of 14.35° or more and see what happened there.

Blenheim has a mean annual temperature of 15.2°C, so it is a warmer place now than Dunedin is forecast to be at century’s end. It does not suffer from malaria or dengue fever, (or from Zika, Chikungunya, etc.)  and public health authorities do not even regard such epidemics as a significant risk. Existing threats from bacteria, viruses and protozoa have been successfully contained.


Future generations of Dunedinites can expect to spend money on flood protection but need not have any great worries about dengue fever or heat waves. They will be much richer in general, partly as a result of booming agricultural production. Each generation will need to adapt to a barely detectable improvement in (winter) temperatures, with an eventual adjustment to Blenheim-type lifestyles.


5 Thoughts on “Dunedin descendants threatened with Blenheim lifestyle

  1. A temperature increase of 1.4°C over 50 years is hardly slow and gradual. Such a rise is almost unprecedented in paleoclimatic history. Whether this future actually occurs will depend on how quickly we move off the the high emission pathways. The signs are promising and technology is improving rapidly.

  2. Richard Treadgold on November 7, 2017 at 1:39 pm said:

    Hi Simon, you’re first out of the blocks again — very vigilant!

    Unprecedented? Pull the other one. Anyway, as far as our human experience goes, and not just the book knowledge of would-be climate scientists, one third of a Celsius degree per decade is certainly undetectable without an extremely accurate thermometer, and your body would never notice it. With Barry, I’ll always call that slow and gradual.

    Are you saying it is unprecedented? A reference would be most helpful there, thanks. Remember that NIWA found 0.9°C of warming in the last 100 years, which they frequently refer to as “almost”, “about” or “nearly” one degree. Not far from there to 1.4°C, I suggest. Of course, that ignores the fact that the peer-reviewed science unequivocally agrees that the average NZ temperature as measured by the 7SS shows a trend of only 0.28±0.29 °C/century after adjustment by the RS93 method.

    But I’ve had a look at the HadCRUT3 record. From the Little Ice Age in about 1893 to 1940, 47 years, the monthly global surface temperature anomaly rose from -0.98°C to 0.39°C (say -1.0°C to 0.40°C). Factoring in error margins of at least 1­°C per observation, that easily becomes a rise of at least 1.4°C in under 50 years.

    What were you saying about paleoclimate history? But, please produce confirmation of your assertion and I’ll happily take another look.

    I should have added that the predicted rise had better get a move on, or it’ll be late for its own forecast.

  3. Marcott et al. A Reconstruction of Regional and Global Temperature for the Past 11,300 Years. Science 339, 1198 (2013)

  4. Barry Brill on November 13, 2017 at 12:24 pm said:

    Simon, the first point to note is that 1.4°C in 50 years is the second-worst-case prediction of WG1 in 5AR. The IPCC itself notes that all 32 of its model groups were “running hot” and could not be reconciled with observations.

    If this very serious warming were to occur, however unlikely that may be, the MSM would have us believe that it poses an existential threat – the end of civilisation (if not humanity) as we know it! Yet the Royal Society report offers no backing at all for such a view. It mentions some possible unquantified risks, most of which would be little more than an minor inconvenience. On the other hand, many lives will be saved in the winters and there will be other obvious benefits that the report avoids mentioning.

    Where is armageddon?

  5. Your Dunedin example is a poor one as the water table below South Dunedin continues to rise and the city’s antiquated wastewater system can not cope with extreme rain events.
    It is incredibly selfish to ignore the issue just because NZ will be less affected by climate change than other countries. Changes to precipitation patterns will affect many. Flora and fauna (e.g coral reefs) may not adapt fast enough to the rate of change.
    There was some evidence that the CMIP5 ensemble were running a bit hot but observations are back in the middle of the distribution now. CMIP3 has proven to be pretty accurate. Hansen’s original 1981 model has proven to be conservative, probably because emissions have increased faster than he forecast.

Leave a Reply

Your email address will not be published. Required fields are marked *

Post Navigation