NZ unaffected by human-caused global warming
The New Zealand
Climate Science
Coalition
5 August 2011 FOR IMMEDIATE RELEASE
NZ unaffected by
human-caused global warming
No
temperature increase in the last hundred years
The current emissions trading scheme (ETS) has no
justification, because New Zealand has not been affected by
global warming, whether of natural origin or human causes,
in the last 100 years. When corrected with accepted
scientific techniques, the official New Zealand Temperature
Record (NZTR) shows that there has been no measurable change
in mean temperatures during 1909-2009.
The historical data shows a warming rate of 0.29°C per century, while the corrected figure is 0.26°C per century. But both amounts are within the margins of error, and are effectively zero.
These figures were announced today by the New Zealand Climate Science Coalition, in releasing a new detailed study of the temperature records held in the ‘CliFlo’ climate database.
“This study generally follows in the footsteps of NIWA’s NZTR Review, released last December, except in one vital aspect” said Coalition chairman, Barry Brill, “The difference is that we have scrupulously followed the statistical techniques described in the scientific literature, while NIWA did not.”
“The seminal peer-reviewed paper is Rhoades & Salinger (1993) ‘Adjustment of Temperature and Rainfall Records for Site Changes’. This is the authority NIWA’s Minister (Hon Wayne Mapp) has cited repeatedly in Parliament. It is on the NIWA website and permeates their Review report.
“The Rhoades paper describes the series of statistical steps which are required for a valid data adjustment, including measurement of margins of error. NIWA adopted two of those steps but ignored four others. In consequence, their calculations were just plain wrong as the technical notes below demonstrate”, said Mr Brill
Mr Brill said there was a second peer-reviewed paper which had been ignored by NIWA and which dealt with urbanisation and shelter problems at New Zealand weather stations: JWD Hessell (1980) “Apparent trends of mean temperature in New Zealand since 1930”.
NIWA, the Crown Research Institute (CRI) which advises Governments on climate science, is also responsible for maintaining temperature archives. In constructing its “New Zealand Temperature Record” (NZTR), NIWA has made a series of random adjustments which produce a cumulative warming trend of 0.92°C over the last 100 years.
“The scientific literature is quite clear that such random adjustments should balance out over time” says Mr Brill. “Detailed work undertaken by the Coalition’s statisticians and scientists show that is exactly what happens to the NZTR when internationally accepted techniques are applied.
“The historical weather data shows a trend of 0.3° ± 0.3° per century – effectively zero” says Mr Brill. “And that’s the same overall outcome as the adjustments produce when they conform to international standards.
“It is widely accepted that New Zealand is partly insulated from any global warming by our surrounding oceans, but the extent and duration of that insulation is unknown. NIWA has stated that it expects New Zealand will experience a ‘discount’ of about 33% from any future worldwide warming trends.
“The NZCSC finding that New Zealand has suffered no material warming during the past century shows a 100% ‘discount’ from the 0.7°C trend experienced globally. In the absence of any evidence of change, the null hypothesis is that New Zealand’s established immunity will continue into the future.
“This is good news for all New Zealanders” said Mr Brill. “Our isolation may be a cost in economic terms, but it seems to be a clear benefit in environmental terms”.
Technical Notes
The Rhoades & Salinger
(1993) technique involves the following steps:
1.
Determine the timing of any site change shown in the
metadata of a candidate station.
2. Confirm
that the candidate station data was not contaminated by
non-meteorogical effects, at the relevant time.
3.
Identify neighbouring stations unaffected by any change
points or known problems a year or two before and after the
site change time. These are the reference stations. These
reference stations should be as close as possible to the
candidate station and share the same local weather
conditions.
4. For all the stations, obtain
the monthly temperature data. Then, starting at the site
change point, calculate a temperature difference series by
subtracting the previous year’s monthly value from each
monthly value. This is the temperature difference series
termed k=1 (12-month offset). Repeat using k=2 (i.e.
subtract the value 24 months prior). This has the effect of
removing seasonal variations, as well as determining
differences year-on-year at each station.
5.
Determine the correlations between the candidate station and
each of the reference stations, using the k=1 series. Use a
4th power rule to calculate the weighting to be applied to
each reference station from these correlations.
6.
Find the difference between the weighted sum of all the
reference series and the candidate series. This is the
z-series. Do this using both k=1 and k=2 series.
7.
Calculate the mean of the z-series, and determine the 95%
confidence limits.
8. If the absolute mean
of the z-series is less than the 95% confidence limits (i.e.
the confidence interval contains zero) then do not make an
adjustment. Otherwise subtract the mean of the z-series
(from point 7) from all monthly values prior to the site
change.
NIWA, in their method, have made the following
omissions or changes:
1. Candidate station
data are not checked for gradual contamination (except
Auckland pre-1960);
2. Reference stations
seldom share local weather conditions with the candidate
station, and are usually in different climate zones.
3.
NIWA uses annual mean temperatures, not monthly. They do
not create the differenced series between monthly values at
all.
4. Instead of taking a short symmetric
period (i.e. 1-2 years) before and after the site change,
they accept a different z-series of assymetric periods of
approximately ten years before and after. Although similar
in concept to the R & S z-series, it is prone to
non-climatic influences - something the R&S method
specifically sets out to address.
5. NIWA
compounds this problem by not using weightings on their
distant reference stations. The whole point of weighting
each reference station is to exclude (or reduce the
influence of) those stations showing some abnormal
non-climatic behavior relative to the other stations.
6.
NIWA does not calculate the 95% confidence limits of the
monthly z-series in order to determine whether an adjustment
is warranted. NIWA always applies their calculated shift.
This means the NIWA method is 100% open to Type I errors
(false positives).
Ends (1039 words)