A retired climate scientist says his analysis of rainfall and temperature records for the last 100 years shows climate change is not happening in Tauranga.
Dr John Maunder's records of Tauranga rain and temperature on a month by month basis show there is no significant trend in either set of climate data.

John Maunder says there is no evidence to suggest climate change is occurring for Tauranga.

"Although I am sure some people will see or think that they can see changes," says John.
"My main point is that though there are some changes, it goes up and down.
"Overall it's a good 100 year record - as good as you can get.
"From 1910 to 1920 there were some quite warm periods in there, but to take it from there to now and say there's been cooling would be wrong.
"There have been some warming periods and there have been some cooling periods."
The temperatures are average afternoon temperatures, but not night time temperatures.
"There really have been no significant changes that I think you should get concerned about," says John.
"People might get upset about similar changes if they live in the Maldives, but in Singapore or Helsinki they would get by without any problems, end of story."
Any long term climate trends are more likely to be signalled by farmers, says John.
"If farmers in the Bay of Plenty begin growing bananas instead of kiwifruit, or the Southland farmers switch from dairy to grapevines - the farming community is pretty astute."
John, who lives in Matua, is former President of the Commission for Climatology of the World Meteorological Organization from 1989 to 1997.
For the last 55 years he's been involved in the 'weather business' in various countries, including New Zealand, Australia, Canada, US, Ireland, Switzerland, and the UK.
His publications include four books: 'The Value of the Weather' (1970), 'The Uncertainty Business - Risks and Opportunities in Weather and Climate' (1986), 'The Human Impact of Climate Uncertainty - Weather Information, Economic Planning, and Business Management' (1989), and the 'Dictionary of Global Climate Change' (1994). The information is prepared so as to provide a 'need to know' background on climate change, and 'global warming' with the aim to promote a better understanding of this complex matter.  

The Maximum Temperatures for each day have been recorded at various sites in Tauranga since February 1913.
From February 1913 to February 1989 the observation site was 'Tauranga Aero', from January 1970 to January 1994 the observation site was 'Tauranga', and from June 1990 to the present day the observation site was the Tauranga Airport automatic weather station.
The data from all three sites is combined into one homogeneous temperature series using the current observation site as the base station. Although adjusting temperature observations from one site to another is not without its difficulties, it is considered that the homogeneous temperature series described in this web page is a fairly true record of what the temperature would have been if the current observation site had been used since 1913, with the understanding that although standard accepted methodologies are used, any adjustments are only estimates of what would have occurred if the location of the temperature records had always  been in the same place with the same surroundings, the same instruments, and the same recording screen.
 
The composite average maximum temperature data from February 1913 to June 2010 for Tauranga shows the following (last updated June 2010):

	Highest	Lowest	2008	2009	2010
JANUARY	28.4 degrees in 1935	22.6 in 1997	25.1	25.5	24.0
FEBRUARY	26.9 degrees in 1928	22.2 in 1934	24.0	25.2	24.9
MARCH	24.8 degrees in 1916	20.6 in 1960	23.0	22.7	24.1
APRIL	22.5 degrees in 1938	18.2 in 1992	20.3	20.1	21.0
MAY	19.6 degrees in 1916	14.8 in 1977	16.8	16.2	18.0
JUNE	16.6 degrees in 1916	12.9 in 1972	15.2	14.1	15.5
JULY	15.8 degrees in 1916	12.5 in 1939	14.5	14.5
AUGUST	16.2 degrees in 1915	11.6 in 1913	14.8	16.2
SEPTEMBER	18.4 degrees in 1915	14.8 in 1964	17.3	17.5
OCTOBER	20.3 degrees in 1915	16.0 in 1964	18.4	17.7
NOVEMBER	22.6 degrees in 1954	18.7 in 1995	20.5	21.3
DECEMBER	25.2 degrees in 1940	20.1 in 2004	23.3	23.2

For the year as a whole the highest average daily maximum temperature of 20.3 degrees was in 1916, and the next highest 'warmest years' are 1915 (20.1 degrees), 1928 (20.0 degrees), and 1998 (20.0 degrees).
The lowest average daily maximum temperature was 18.1 degrees was in 1992, and the next 'coldest years' 1923 (18.6 degrees), 1977 (18.6 degrees), 1918 (18.7 degrees), 1980 (18.7 degrees), 1993 (18.7 degrees), and 2004 (18.7 degrees).
The average daily maximum temperatures for each year since the last 'very warm' year in 1998 (which itself was the fourth warmest year on record are: 1998 20.0, 1999 19.7, 2000 19.5, 2001 19.3, 2002 19.3, 2003 19.2, 2004 18.7, 2005 19.6, 2006 19.3, 2007 19.3, 2008 19.4, and 2009 19.5 degrees.

Rainfall
From January 1898 to December 1904, the observation site was the Tauranga Harbour, from November 1904 to April 1907 the site was 'Tauranga', from January 1910 to December 1923 the sites was Waikareao in Otumoetai, from January 1924 to September 1940 the site was at 148 Waihi Road in Judea, from October 1940 to January 1941 the site was at Te Puna, and from February 1941 to the present, the site is the Tauranga Airport.
 
C.S Thompson of the former New Zealand Meteorological Service computed a homogeneous rainfall series for Tauranga and some other stations in New Zealand, appropriate to the recording sites, and the methodology use is published in the NZ Meteorological Service Miscellaneous Publication No 180 in 1984.
 
Although adjusting rainfall observations from one site to another is not without its difficulties, it is considered that the homogeneous rainfall series described in this web page is a fairly true record of what the rainfall would have been if the current observation site had been used since 1898, with the understanding that although standard accepted methodologies are used, any adjustments are only estimates of what would have occurred If the location of the rainfall records had always  been in the same place with the same surroundings, and the recording gauge.
 
(Last updated July 2010)
Tauranga:
The 10 wettest YEARS on record are:
1962   156 % of the long term average
1916   147 %
1917   143 %
1938   138 %
1920   136 %
1956   135 %
1971   133 %
1979   131 %
2005   128 %
1935   127 %
(In chronological order these wettest years occurred in 1916,1917,1920,1935,1938, 1956,1962,1971,1979, 2005, and 1935)

The 10 driest years on record are:
2002   57 % of the long term average
1915   59 %
1982   64 %
1993   66 %
1906   72 %  
1919   73 %
1997   74 %
1973   75 %
1986   75 %  
1999   76 %
(In chronological order these driest years occurred in 1906, 1915, 1919, 1973, 1982, 1986, 1993, 1997, 1999, and 2002)

The 10 wettest months on record:
634 mm in May 2005 (511% of long term average for May)
504 mm in March 1979 (462% of long term average for March)
447 mm in December 1962 (447% of long term average for December)
383 mm in April 1911 ( 319% of long term average for April)
381 mm in June 1925 (293% of long-term average for June)
357 mm in October 1916 319% of long term average for October)
348 mm in July 1951 ( 270% of long term average for July)
343 mm in Feb 1936 (376% of long-term average for February)
331 mm in April 1948 (276% of long-term average for April)
319 mm in March 1972 (290% of lon-term average in March)
(In chronological order these wettest months occurred in 1911, 1916, 1925, 1936, 1948, 1951, 1962, 1972, 1979, and 2005)
 
The 10 driest months on record:
1 mm in January 1928
2 mm in July 1902
4 mm in December 1930
5 mm in March 1943
7 mm in February 1973
7 mm in October 1984
8 mm in January 1900
8 mm in February 1973
10 mm in April 1958
11 mm in February 2010
(In chronological order these driest months occurred in 1900, 1902, 1909, 1928, 1930, 1943, 1958, 1973, 1984, and 2010.)

Official archivist of New Zealand's climate records is the National Institute of Water and Atmospheric Research NIWA.
Niwa's 147-year-old national mean temperature series, the 'NIWA Seven-station Series' or NSS shows New Zealand experienced a twentieth-century warming trend of 0.92°C.
This is challenged by climate scientists who say the raw data correctly shows New Zealand average temperatures remained steady at 12.6°C +/- 0.5°C for a century and a half.