By Bart M. Kellett and Wayne Meyer
The River Murray
Over the coming days we are going to present three key messages from the Lower Murray Landscape Futures Project, which preceded the Climate Change, Communities and Environment Project that is currently underway. This project performed an in-depth quantitative analysis of regional plans under a series of climate change scenarios. Today we will focus on the first key message.
Business as usual is not an option
A business as usual approach, based on what has worked in the past, is not likely to work in the future. There is significant evidence that we are moving further and further away from past climate conditions. The headings below summarise the compelling measures of changing climate in Australia.
The implications of these changes for landscapes in southern Australia are far reaching. Yields and economic returns from traditional cropping and grazing systems are likely to become more variable and generally decrease without significant adaptation. Surface runoff and groundwater discharge to rivers will decrease, leading to lower water allocations for irrigated agriculture. On the plus side, there is likely to be less deep drainage and hence, less risk of dryland salinity. The rate of ecological decline is likely to quicken, and the risk of wind erosion and dust storms is likely to increase.
In essence, the most likely outcome from the measured trends is that southern Australia will generally become a little more arid in its climate features. Managing for the inevitable ups and downs of seasonal weather variability will need to be done in the expectation that it will be warmer and slightly drier with more frequent ‘arid’ like conditions (longer and deeper dry periods, longer and hotter heat waves, more frequent storms, slightly lower humidity). This will increasingly be different to that which we have experienced in our recent history.
Below is a summary of evidence of changing climatic conditions in Australia. This information was sourced from a short publication by CSIRO and Bureau of Meteorology released this year. You can access it at http://www.bom.gov.au/climate
Concentrations of greenhouse gases in the atmosphere are increasing
Concentrations of greenhouse gases in the atmosphere have increased significantly over the last 100 years. For the past 800,000 years and possibly the past 20 million years, levels of just one greenhouse gas, carbon dioxide, have been between 180 and 300 parts per million (ppm). The level in 2009 of 386 ppm is much higher than the natural average.
Australia is getting hotter
All of Australia has experienced warming over the last five decades and some areas have experienced an increase in average temperature by 1.5 – 2°C. Also, the number of record hot days per annum has been increasing each decade since the 1960’s and the number of record cold days per annum has been decreasing over the same time period.
There is less rainfall where most Australians live
Over the last five decades, rainfall has increased in northern and central Australia and decreased in eastern and southern Australia. The decrease varies between 5 and 50 mm/year.
Sea surface temperatures are rising
Sea surface temperatures in the Australasian region have increased by about 0.4°C over the last 50 years.
The sea level is rising
The global mean sea level has risen by about 200mm since 1870. Since 1993, sea level rise, mostly resulting from thermal expansion has been 1.5 to 3 mm/year in southern and eastern Australia and 7 to 10 mm/year in northern and western Australia.