Issue: Climate and Greenhouse
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Water restrictions, bushfires and dust everywhere—these three have come to symbolise the impact of the latest drought.
The 2002–03 drought was one of the worst on record, not only because it was dry but also because it was very hot. It also affected more of Australia than usual (see box inside).
Canberrans saw more than hot, dry and windy weather during the reporting period (2000–03). There were also some heavy rains, with one storm in February 2003 washing enough soil and ash into Canberra’s dams to make the water undrinkable.
This variation is an extreme example of how much the weather can vary from one year to the next. This is typical of the ACT’s climate, and more examples are listed below.
- November 2000 had the highest number of rainy days on record; February 2002 was one of the wettest Februaries on record (see graph below).
- Some months were extremely dry, particularly in winter and spring 2002, and again in summer 2003.
- Temperatures were higher than usual during most of the reporting period, particularly in the dry months referred to above.
- Potential (or pan) evaporation was above average in the period from winter 2002 to summer 2003, as was the number of sunshine hours.
- Relative humidity was lower than normal. This is not surprising given the hot and dry conditions during that period.
- Several windy periods in October and November 2002 and March 2003 resulted in dust storms and fallen trees in Canberra.
Rainfall records from Hall show that there was much more rain than usual during February 2002
The ACT's climate appears to be changing slightly, with a possible shift towards warmer and, perhaps, more windy conditions as well as increasing variability.
At the official weather station at Canberra Airport, temperatures have increased approximately 0.2°C per decade since the 1970s. Evaporation is possibly decreasing slightly, but it is too soon to draw any firm conclusions.
While there is no obvious trend in annual rainfall, there have been significant fluctuations in rainfall seasonality over the last 100 years. Rainfall records have started to show a shift towards slightly more autumn and winter rainfall, and slightly less spring rainfall. There has been little change in summer rainfall.
Planning for water resources in the ACT region must allow for the larger and more frequent weather extremes that have been a feature of the climate since the 1980s.
This is likely to be exacerbated in coming decades by the combined effects of the Pacific Decadal Oscillation and El Nino–La Nina (see why was the 2003 drought so bad?).
Changes in the timing and amount of rain are likely, with slightly less rainfall overall and a decline in rainfall intensity. This could mean it will rain more often, but with less rain from each rainfall event.
Paradoxically, larger extremes are also likely, which could mean more floods, fewer cold spells, more hot spells, and windier conditions overall. It is essential that natural resource management and planning factor in these likely changes.
These climate changes are commonly called global warming, and it is believed that they are at least partly a result of the enhanced Greenhouse effect.
An 'average' Canberran was responsible for 12.8 tonnes of Greenhouse gases (measured as carbon dioxide equivalents) in the year 2000. This adds up to 3.980 million tonnes of Greenhouse gases for the ACT population as a whole, which is an increase of 12% since 1990 (see the table below).
|Table: Greenhouse gas emissions from the ACT|
|Emissions sources||Emission estimates (Mt carbon dioxide equivalents)|
Greenhouse gases are those gases that regulate the amount of heat trapped by the earth's atmosphere; increasing amounts of the gases have been predicted to cause global warming.
Because of its small population and the lack of heavy industry, the ACT contributes about 1% of A ustralia's total emissions. The Territory's Greenhouse emissions could be lower still if not for the climate, urban and building design, and lifestyle.
The main source of Greenhouse gases in the ACT is from activities that use energy generated by fossil fuels.
In the year 2000 alone, Canberrans used enough electricity from coal-fired power stations to be responsible for 2.363 million tonnes of Greenhouse gases. This is the single largest source of Greenhouse gas emissions from the ACT, representing 59% of the ACT's contribution to the Greenhouse effect.
Emissions from transport, the next largest source, were estimated to be 0.954 million tonnes during 2000, reflecting the ACT's dependence on the private motor vehicle for getting around.
* 2008 emissions estimated using a business-as-usual scenario. Values may not add due to rounding. Source: ACT Greenhouse Strategy: 2002 Review of performance and options for the future .
As the table shows, emissions from energy sources have increased and are expected to continue to increase in the ACT. This is partly because the population is increasing and partly because people and businesses (including government) use more energy.
The increases in emissions from gas are a result of increased used of natural gas as an energy source. Emissions from natural gas are lower than from electricity generation, so total emissions would be higher without this.
If present trends continue, the ACT's Greenhouse gas emissions are expected to increase to 4.605 million tonnes in 2008. This is well above the ACT Government's self-imposed target of reducing emissions to 3.557 million tonnes (the 1990 emissions amount) by 2008.
The Greenhouse contribution of an estimated 5.769 million tonnes from the January 2003 fires, although significant, will be seen only as a large peak in the calculations for 2003. As with all wildfires, it will not carry through to later years because trees store carbon as they regrow. Any change of landuse—from forest to suburbs or to a fire protection zone around the edge of the city—will result in a relatively small addition to estimates of Greenhouse emissions. It is the continued growth in emissions from energy sources that present the greatest challenge to the ACT. According to a recent review 1 of the ACT Greenhouse Strategy, the only way for the ACT to meet the 2008 target is to find some new ways of reducing emissions.
Even with all the programs now in place under the ACT Greenhouse Strategy only 75% of the necessar y reduction in emissions would be achieved.
The longer-term target, of a further 20% reduction by 2018, was not addressed by the review because there were too many uncertainties.
A suite of recommendations from the review may work some way towards improving the situation. They direct the ACT Government to find ways of reducing emissions that are cost-effective and that will have the greatest longterm impact, without neglecting long-term sustainability considerations.
The review recommends that new and existing options should be examined, particularly with regard to Greenhouse gas emissions from transport. Improved monitoring of the amounts of energy and fuel imported into the ACT was also recommended.
All six recommendations of the review are fully supported by the Commissioner for the Environment.
High quality, long-term records are crucial for sound planning and management. As the climate changes, and the evidence is starting to show real change, accurate data that show the new conditions will underpin a considered response.
But weather monitoring in the water supply catchments appears to be inadequate—particularly in the high relief areas in the Brindabellas and Namadgi National Park. Data sourced for this report revealed records that were too short and had many gaps. For climate variability and change, records need to be longer and of higher quality.
It is also important to encourage ongoing high-quality data collection at stations on rural properties, for example Hall (Lochleigh), Michelago (Soglio), Bungendore (Gidleigh) and Fairlight Station, amongst many others.
Crucial to accurate Greenhouse accounting is reliable annual information on the amounts of electricity, natural gas, and petroleum products imported into the ACT, as well as the total quantity and composition of green and putrescible waste sent to landfill in the ACT.
The review of the ACT Greenhouse Strategy made clear the urgency and importance of these data and recommended that this deficit be addressed. The current information is not adequate.
In consultation with the Commissioner for the Environment, the ACT Government should:
- adopt the six recommendations in the ACT Greenhouse Strategy: 2002 Review of performance and options for the future , released in March 2003
- put in place a reliable system for long-term uninterrupted weather monitoring in the ACT's water supply catchments.
- ACT Greenhouse Strategy: 2002 Review of performance and options for the future