Scientific research and observations provide evidence that climate change is already occurring in NSW.
The temperature is rising
As NSW has a very variable climate. When changes in the climate are charted, a cool or even exceptionally hot month or year is less important than a multi-decadal trend.
Reliable temperature records for the whole of the state, which began in 1910, show that the average temperature has risen steadily since the 1950s, with the rate of increase accelerating in more recent decades.
During the period from the 1950s to the 1980s, the annual average temperature rise was about 0.1°C per decade; since 1990 it has been about 0.5°C per decade.
|This graph showing historical anomalies in annual mean temperature takes 1961 to 1990 as the benchmark period. It is based on data from the Australian Climate Observations Reference Network – Surface Air Temperature (ACORN-SAT).|
For NSW as a whole, 2013 had the highest peak temperature and third-warmest mean temperature (See graph, ‘Annual Mean Temperature Anomaly’). The warmest year on record was 2009, with a mean temperature 1.37°C above average.
All years from 1997 to 2013 were warmer than the 1961 to 1990 average, and this was an unprecedented sequence of warm years. Since the turn of the century, every year has seen annual average temperatures of more than 0.5°C warmer than the 1961 to 1990 average.
Rainfall trends are unclear
Annual rainfall in NSW has varied between very dry years (such as 1940 and 2002) and very wet years (such as 1950, 1974 and, recently, 2010). The state experienced drier conditions during much of the first half of the last century. Greater variability in annual rainfall occurred during the 1950s to 1990s. The first decade of this century was characterised by below-average rainfall during the Millennium Drought period, which ended with two of the wettest years (2010 and 2011) in Australia on record.
|Historical annual rainfall anomalies since the start of the last century, as compared with the 1961 to 1990 base period.|
Report on observed changes in New South Wales climate 2010
The Office of Environment and Heritage report, Observed Changes in New South Wales climate 2010, presented the available research from peer-reviewed scientific papers, as well as from other respected sources such as the Bureau of Meteorology and CSIRO. It summarised the observed effects of changes as:
- annual increases in extreme-fire danger days
- prolonged and more severe droughts
- changes in wildlife behaviour
- decreases in mid-spring alpine snow depth
- rising sea levels
- increases in ocean-surface temperatures and acidity.