Outdoor Lighting and Crime - Amper

2000). Regardless, there are often inexplicably large differences between countries in specific
crime rates, eg homicide (Graycar 2001).
The following sections present within-country comparisons of available lighting and crime
growth data.
2.3 GROWTH IN LIGHTING AND CRIME IN INDIVIDUAL
COUNTRIES
2.3.1 Australia
Despite substantial effort, the writer did not find suitable records of energy use for outdoor
lighting in Australia and the proportions of various lamp types installed. The same applies to
records of illumination levels or total light output, so recourse has been had to astronomical
observations.
For the period 1880 to 2001, artificial skyglow values shown in Figure 1 (all of the figures are
grouped at the end of this document) have been inferred from limiting unaided visual stellar
magnitudes assembled by the writer from observations in recent decades from Melbourne
suburbs plus a few more as far back as the mid-1950s (reported in Dudley 2000).
Fluctuations must have taken place during social upheavals such as the Great Depression and
the two World Wars, especially WW2 because a blackout was enforced, 13 but they are not
shown because of the absence of specific data for the years in question. The skyglow changes
caused by population changes at those times were small in the USA (Garstang 2000), but
social, economic and technological effects on skyglow could well be larger than the
population effects. The sky reference area chosen for skyglow observations and calculations
is at 45 degrees altitude, due south of an observing site about 11 km northeast of the
Melbourne central business district. The zenith might have been a better reference position,
but this is relatively unimportant for the present purpose.
The pre-electric-lighting ordinate of the skyglow curve in Figure 1 is 0.27 mcd/m 2 , typical of
the luminance of the natural clear moonless night sky. For the luminance of the Melbourne
sky to start at that value and to be where it is now and where it has been in recent decades is
most readily explained if the growth rate of the artificial component is taken as exponential.
The observed increase is close to doubling in each decade. 14 To sufficient accuracy for the
present purpose, the skyglow luminance S mcd/m 2 is given by
S = 0.27 + 0.00189*2^((year-1880)/10).
13 The writer recalls the household stress of this as a child.
14 The writer’s original analysis of Melbourne skyglow observations was done in 1999
because skyglow was interfering with measurements of astronomical performance of image
intensifiers. At that time, the writer was unaware that prior results elsewhere showed
exponential growth; yet another case of ‘reinventing the wheel’. Regardless, this finding does
add a little more weight to the realisation that growth in light pollution represents a global
problem in sustainability.
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