Records show Dunedin floods not caused by climate change

A crowd-sourced rebuttal to the empty-headed Greens

Dunedin flood 2015

April 1923 – Flooding on Anzac Avenue, looking towards Harrow Street (DCC archives). Click to enlarge.

God bless our readers!

These two comments appeared under yesterday’s midnight post Greens blame “climate change” for Dunedin floods and provide all the proof we need that the Green Party is entirely wrong to blame the June 3 Dunedin flooding on climate change. Why? Because they show that the severe flooding two days ago is not new. Unusual, but not unique. A combination of rainfall data and photographs makes these comments as convincing as they were prompt.

First, from Ron

Hmm. A quick search came up with this fascinating site of extreme NZ rainfall data. It does make the obligatory incantation in the introduction (“As global warming brings more extreme and more frequent floods…”) but states:

22 Apr 1923 Dunedin 230mm in 24 hours
19-20 Mar 1929 Ross Creek (Dunedin outskirts) 279mm in 24 hours
[June 3] was 175mm in 24 hours

The Otago Daily Times said it was double the previous record for a full day since records began in 2006. [But 2006 was only the start of recording rainfall in the city centre rather than Musselburgh, 3 km away.]

Second, from Peter Yates

There are photos of the 1923 and 1927 floods here:
April 1923, Anzac Avenue, Central/North Dunedin.

13 May 1923, Leith over-flowing at HarbourTerrace, North Dunedin.

1927, South Dunedin.

In 1927 South Dunedin was mostly farmland. This is what the recent flooding would look like without the roads, buildings, and storm water pumps. I guess being in the 1920’s they were not caused by climate change, or global warming for that matter! 😉

Thanks for your excellent contributions, Ron and Peter. Looks like you were having a late night, too!

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13 Thoughts on “Records show Dunedin floods not caused by climate change

  1. Andy on 05/06/2015 at 11:49 am said:

    The flooding in Dunedin on Wednesday was not caused by climate change, a University of Otago climatologist says.

    ”I think this is just a weather event,” Dr Nicolas Cullen, of the department of geography, said.

  2. Richard Treadgold on 05/06/2015 at 11:53 am said:

    ”I think this is just a weather event,”

    Yay! A heavy, authoritative hammer for the head of the Greens.

  3. Andy on 05/06/2015 at 2:41 pm said:

    O/T but from the “weather is not climate dept”, in Norway

    ( I was in this area late April and it was very snowy then. I thought it would be gone now)

  4. Richard C (NZ) on 06/06/2015 at 3:56 pm said:

    After reading Muller et al (2013) in regard to surface solar radiation over time e.g. 10, 20, and 30 yrs (see link previous post thread), I went looking for the NZ equivalent. Didn’t find any at NIWA, any such information is on a commercial basis (user pays).

    Anyway, came across this:

    genesis ENERGY schoolgen

    Facilitator/Student Resource

    This resource guides students to download, process and present real-world numerical data from the Schoolgen online database of solar energy generation.

    Students will learn important cross-disciplinary skills in Microsoft Excel 2010 as well as emphasising the links between science and maths, and the usefulness of maths as a tool in science.

    Page 4,

    1.Go to the schoolgen website:
    2.Click on the NZ map to select your region/school:
    3.What is the Output Power of your schools PV panels right now?

    Searching the website returns Participating Schools

    For example, one I attended a long, long, time ago:

    Maeroa Intermediate School – Hamilton City 2 kw!

    Last 12 Months graph (that’s all unfortunately, no annual time series)
    2494 kWh electricity generated
    486 kg CO2 saved
    Peak solar radiation (SSR) January: 799.4 MJ/m2 = 25.7 MJ/m2 per day on average

    Last 7 Days graph data through to June 5, 2015
    Solar radiation (MJ/m2 per day)
    9.98 Sat
    5.01 Sun
    5.63 Mon
    4.52 Tue
    4.59 Wed
    5.65 Thu
    9.3 Fri

    Tuesday was 17.6% of a peak January days insolation, less than a fifth. I suspect fog and clouds have been a factor along with the lessor winter incidence.

    Today graph data download for 6/6/2015 (MJ/m2):
    0.02 8:00:00 AM
    0.22 9:00:00 AM
    0.62 10:00:00 AM
    1.34 11:00:00 AM
    1.56 12:00:00 AM
    1.07 1:00:00 PM

    So at 10am the reading is 620 J/m2. J/m2 is “radiant exposure”, NOT power equivalent to W.m2 (J/s/m2).

    Radiant exposure

    The time of exposure must be stipulated (see Mathematical definitions, T is the time of irradiation). I’m not sure what time of exposure this data is over. The data comes from the nearest NIWA station to the school so it’s a matter of looking up the NIWA solar field (wherever that is – CliFlo?).

    T = 60 secs then 620 J/m2 is 620/60 = 10.3 J/s/m2 = 10.3 W/m2 which seems too low.
    T = 1 sec is immediately 620 W/m2 which is way too much.
    T = 10 sec is 62 W/m3 and more realistic, maybe.

    Hamilton NZ Weather
    Currently (at 3:30 PM) Solar Radiation: 86 W/m²
    Currently (at 3:45 PM) Solar Radiation: 91W/m²

    So maybe 10 secs then. Obviously T is critical but schoolgen pdf says nothing about it. Just this on page 9:

    *The solar radiation energy measures the amount of energy from the sun that has hit the earth on every square metre (it is measured at the nearest NIWA weather station to your school).

    Nothing about T so it’s off to the NIWA solar information somewhere (maybe CliFlo?).

  5. Richard C (NZ) on 06/06/2015 at 4:37 pm said:

    I suppose rather than be bothered with NIWA’s MJ/m2 units I can be content with the Hamilton NZ Weather data in W/m².

    Currently (at 4:30 PM) Solar Radiation: 30W/m²

  6. Richard C (NZ) on 06/06/2015 at 5:06 pm said:

    Solar “Station Records” at Hamilton NZ Weather above (SSR).

    June to date: 650 wm2, 12:20 03 Jun 2015

    Year to date: 1429 wm2, 12:35 02 Feb 2015

    All time: 1750 wm2, 12:52 21 April 2007

    The 2007 record was 321 W.m2 higher than 2015 (conversely 2015 was 321 W.m2 less than 2007). This is a big number (think miniscule CO2 change), a time series would be instructive. The station was moved from Hamilton East to Horsham Downs on the Northeastern outskirts’ of Hamilton in mid-November 2008.

    Still, might be worth contacting these guys, Willoughby and Jaime, in the hope of getting a SSR time series of some sort for Hamilton: About/Contact

  7. Richard C (NZ) on 06/06/2015 at 7:44 pm said:

    NIWA has been very quiet about this:

    ‘Global dimming and brightening in New Zealand’

    Ben Liley, 2014

    See references, Liley (2009) is cited by the IPCC.

    Table 1, page 2.

    Auckland Airport (W.m2 per decade)
    -11.8, 1970 – 1990
    +3.7, 1990 – 2013

    Table 2, page 2.

    New Zealand (W.m2 per decade)
    -2.4, 1950 – 1990 (4 decade total -9.6)
    +4.85, 1991 – 2013 (2.2 decade total +10.67)

    In only 2.2 decades 1991 – 2013, SSR increased +10.67 W.m2. This is radiative energy that does work (a surface heating agent).

    For comparison, OLR – DLR (net longwave, Rnl) is a cooling effect at the surface (does no heating work). Nevertheless, Berkeley Lab found DLR and CO2 radiative change 2000 – 2010 for 2 sites in Alaska and Oklahoma:

    “Both series showed the same trend: atmospheric CO2 emitted an increasing amount of infrared energy, to the tune of 0.2 Watts per square meter per decade. This increase is about ten percent of the trend from all sources of infrared energy such as clouds and water vapor.”

    Whoop-de-doo. CO2 change +0.4 W.m2 for 2 decades (NZ SSR change +9.7, 24.25 times greater)

    But CO2 is only 10% of DLR change according to Berkeley Lab, so total DLR change is +4 W.m2 for 2 decades at those 2 sites (assuming the decadal trend could be extrapolated back – not necessarily so). Even adding this extra 90% is still 2.4 times less than the NZ SSR change – and it does no heating work.

    No wonder NIWA is not shouting the Liley data from the rooftops.

  8. Richard C (NZ) on 06/06/2015 at 7:52 pm said:

    >”OLR – DLR (net longwave, Rnl) is a cooling effect at the surface (does no heating work).”

    Repeating from previous post thread:

    Surface solar radiation (SSR) – heating effect.

    Net longwave radiation (OLR – DLR = Rnl) – cooling effect

    Global Energy Flows:

    396 – 333 = 63 W.m-2 cooling of the earth’s surface (DLR includes CO2 component about 6 W.m-2).

    On a clear cool night enough cooling to freeze water:

    ‘Nocturnal ice making’

    In India before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common. The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by convection would be low enough to allow the water to freeze by dawn.[1]

    From Radiative cooling

  9. Ian Cooper on 08/06/2015 at 11:29 am said:

    Thanks to Ron for that excellent web site about extreme rainfall events in New Zealand’s past. When you have lived through a few of them this info is very relevant. The background research into the Multi-river floods that hit the lower North Island mid February 2004 is very interesting.

  10. Richard Treadgold on 08/06/2015 at 11:50 am said:

    “Thanks to Ron for that excellent web site about extreme rainfall events in New Zealand’s past.”

    Yes, I agree. He’s put a lot of work into that.

  11. Richard C (NZ) on 08/06/2015 at 7:08 pm said:

    New term (to me anyway): “Dramagreens”

    Credit, Bitter&Twisted in this comment thread:

  12. Richard C (NZ) on 14/06/2015 at 12:55 pm said:

    NZ should expect more droughts – climate change issues minister

    Groser – “…The science is very clear on this. The prevalence of these droughts will increase,”

    “Very clear” on what basis for knowing the future (crystal ball?), and Is that before or after the floods?

    Or are these droughtfloods?

  13. Richard C (NZ) on 15/06/2015 at 4:01 pm said:

    ‘Extreme weather linked to climate change’ [Re Northland and Dunedin floods]

    Dr Dean said New Zealand was exposed to conveyor belts, or atmospheric rivers, which brought moist air from the tropics.

    “Most of our extreme rainfall events are caused by subtropical air coming out of the tropics, very wet, and as climate change warms the tropics it causes more moisture to be held in that air. So as it comes down to New Zealand those air flows do carry more moisture. They can also actually potentially speed up, so it’s both the rate at which that moisture comes down as well as the [increased] moisture content that’s in the air.”

    OK, so what then is Groser on about with “The prevalence of these droughts will increase”? What is it: more rainfall (floods), or less rainfall (droughts)?

    An internally consistent and plausible message please.

    Except Dr Dean is telling porkies (either that or he doesn’t know what he’s talking about):

    ‘Precipitable Water in the Tropics’

    Precipitable Water (PW) data is available from the NOAA Earth System Research Laboratory from 1949 to 2014. The data is world-wide at 2.5 degree increments of latitude and longitude. A program was written to extract the yearly average PW for selected latitudes for the period of record. A graph of the results show that in the tropics from 5° N to 5° S the amount of PW decreased from about 1959 to 1997.

    [See graph]

    There was no such reduction in PW north of 5N or south of 5S [an increase would have been noted].

    # # #

    I think we can infer that Dr Dean’s statement “as climate change warms the tropics it causes more moisture to be held in that air” is, although fine in theory. not supported by the facts (i.e. observations).

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