69 Climate change 1 Why is it important? Earth’s surface is warming rapidly, and our global climate - biodiversity of higher temperatures, reduced is changing, with impacts already discernible to the and altered patterns of rainfall, and changes in present generation. Rising air temperatures, increasing the severity and frequency of extreme weather severity and frequency of heatwaves, changing rainfall and bushfire patterns with more extreme and frequent drought and - coastal settlements, infrastructure and coastal flood, altered ocean temperature and chemistry, and ecosystems of sea level rise and storm surge sea level rise all present potential significant risks to our - marine ecosystems, fisheries and aquaculture environment, economy, society and way of life. of warmer, more acidic oceans and altered South Australia is already seeing the effects of climate ocean currents change (Box 1). South Australia’s future climate challenges - human health and infrastructure of an increased include: number and severity of heatwaves, bushfires and • securing a reliable urban water supply extreme weather events. • coping with the effects on - agricultural productivity of higher temperatures, more frequent extreme weather events, reduced rainfall and greater variability of rainfall distribution Opposite page: The junction of the River Murray with the Southern Ocean, 1846 State Library of South Australia B15276/43 70 In summary Aspect and observation Assessment grade Confidence Very poor Poor Good Very good In grade In trend Climate change State greenhouse gas emissions Per capita emissions and emissions per unit of gross • state product have decreased. Per capita emissions are still one of the highest in the world. Atmospheric concentrations of greenhouse gases are increasing. State sources of greenhouse gases are increasing. Rainfall The reporting period includes the third and fifth wettest years on record. • The long-term trend is for a decline in rainfall. Temperature The reporting period includes the warmest year on record. • The long-term trend is for increases in average (air and sea surface) and extreme temperatures. Energy Energy production is still the dominant source of state emissions (74%). • Renewable energy has increased as a proportion of total installed capacity and of the proportion supplied and used. Sea level The global trend is for a rise in sea level, with variances based on local geomorphology, wind • direction/strength, etc. Oceans Sea temperature and acidity are increasing; salinity is changing. • 71 Climate change Aspect and observation Assessment grade Confidence Very poor Poor Good Very good In grade In trend Marine and terrestrial biodiversity Trends in biodiversity are negative to variable, with • changes in gene pools, species ranges, biological patterns and ecosystem dynamics. Human health, infrastructure, agriculture and forestry Reduced rainfall will affect water supplies • and agriculture. Climate variability has increased, leading to increased frequency and severity of some extreme weather events such as heatwaves. The increased frequency of extreme events will impact police, emergency services, infrastructure maintenance, volunteers, etc. Recent • Improving • Stable Level of Evidence and consensus too low to make an assessment trend • Deteriorating • Unclear confidence Limited evidence or limited consensus Adequate high-quality evidence and high level of consensus Grades Very poor Poor Good Very good 72 Box 1 The critical decade: extreme weather for South Australia Hot days and heatwaves • During the drought of 1997–2009, the inflows into the Murray–Darling system were the lowest • The summer of 2012–13 was the hottest on record. on record and included the highest sea Climate change surface temperatures on record for the • In 2006–07, it is estimated that drought Australian region. reduced national gross domestic product by almost 1%. • In Adelaide, from 1993 to 2006, an increase in total hospital admissions of 7% was recorded • For both south-west and south-east Australia, during heatwave periods compared with non- nearly all of the climate models used in a recent heatwave periods. analysis project a significant increase in drought by the end of the century. • The nature of heatwaves has already changed in many parts of Australia. Over 1971–2008, Bushfires the duration and frequency of heatwaves have increased, and the hottest days during a • The Forest Fire Danger Index, one of the heatwave have become even hotter. measures of bushfire threat, increased significantly at 16 of 38 weather stations across • In Adelaide, the long-term average (1961–1990) Australia between 1973 and 2010, with none of number of days per year above 35 °C was 17.5, the stations recording a significant decrease. but during 2000–09 the average number of such days rose to 25.1. This increase is more • The increase has been most prominent in rapid than climate model projections. south-east Australia, and has been manifest as a longer duration fire season, with fire weather • Research at the Natural Hazards Research extending into November and March. Centre has shown that heatwaves are the most significant natural hazard in Australia in terms Sea level rise of loss of life. • A sea level rise of 0.5 metres (compared Rainfall with 1990), which lies near the lower end of the estimates for 2100, leads to surprisingly • Over 2010–11, every state and territory had sites large impacts. that either set all-time rainfall records for a two- year period or were very much above average. • For coastal areas around Australia’s largest cities, a sea level rise of 0.5 metres would • Across Australia, it is more likely than not that lead to very large increases in the incidence of heavy rainfall events will become more frequent extreme events, typically by a factor of several as the temperature increases. hundred and, in some places, by as much as one thousand. Drought • A multiplying factor of 100 means that a so- • During 2002–03, drought is estimated to have called one-in-a-hundred-year event would occur reduced Australia’s agricultural output by 26%. on average every year. Source: Climate Commission (2013) 73 Climate change Hallett wind farm Department of Manufacturing, Innovation, Trade, Resources and Energy 74 Climate change 2 What do we know about it? Strong and clear evidence supporting climate change infrastructure and globally interdependent agricultural science has been derived from a range of sources, systems (CSIRO 2011). including our historic climate record (palaeoclimatic evidence from tree rings and lake sediments, etc.), climate measurements from the recent past and 2.2 Current climate change sophisticated climate models. A number of scientific Our current climate is changing far more rapidly than in disciplines contribute to our understanding of climate the geological past. Global average temperatures both on change, including atmospheric physics, chemistry, land and over the ocean rose by just over 0.7 °C in the biology, oceanography, hydrology and geology. 100 years from 1910 to 2009 (Figure 1). Average surface air temperature has increased by nearly 1 °C in Australia 2.1 Past climate change and South Australia, higher than the global average, and will continue to rise (Climate Commission 2011a, CSIRO Climate change refers to long-term change in the average 2011). The rate of global warming is increasing, with the pattern of weather over decades or longer. Earth’s climate past 50 years warming at nearly twice the rate as over has varied enormously many times since Earth formed the past 100 years (CSIRO 2011). South Australian average 4.5 billion years ago; it has been both warmer and cooler temperatures have been rising steadily since the 1970s, than today, driven by changes in the sun’s intensity, and temperatures for the past decade (2001 to 2010) Earth’s orbit around the sun, the changing configuration were the warmest since records began in 1900 (BoM of continents and oceans, and natural variations in the 2011). There has been a clear decline in average rainfall level of greenhouse gases in the atmosphere (Australian in southern Australia since 1970, which has been linked Academy of Science 2010, CSIRO 2011). to rising temperatures, and this drying trend is likely to persist. The geological records show us that past temperature changes have affected the world dramatically, altering Around the world, many changes have been observed atmospheric and oceanic circulation, rainfall patterns that are consistent with the increase in global average and water availability, ice cover, vegetation, ocean temperature: warming oceans, widespread retreat acidity and sea level. Past climate change also shows of mountain glaciers and ice caps, ice loss from the us that global climate is sensitive to small influences Greenland and Antarctic ice sheets, sea level rise, (Australian Academy of Science 2010). Processes similar continued decreases in the extent and volume of arctic to past climate change can act to amplify current sea ice, increasing water vapour in the atmosphere, human influences. decreasing ocean alkalinity, shifting weather systems, and changes to animal and plant behaviour (Australian Our evolutionary history can be, at least in part, linked Academy of Science 2010). to past climate change, with a growing body of work in palaeoanthropology showing a correlation between evolutionary events and times of natural climatic variability. Modern human civilisation has evolved and developed during a relatively
Details
-
File Typepdf
-
Upload Time-
-
Content LanguagesEnglish
-
Upload UserAnonymous/Not logged-in
-
File Pages35 Page
-
File Size-