Our climate is changing, largely due to the observed increases in human activities such as the burning of fossil fuels (coal, oil, and natural gas), agriculture and land clearing. Changes over the 20th century include increases in global average air and ocean temperature, widespread melting of snow and ice and rising global sea levels. The extra heat in the climate system has other impacts such as affecting atmospheric and ocean circulation, which influences rainfall and wind patterns (Department of the Environment).
World Meteorological Organization records show that the decade of 2001-10 was the world’s warmest decade on record, and that the 2000s were warmer than the 1990s which in turn were warmer than the 1980s. In Australia, average air temperatures have increased by around 0.9 degrees Celsius since 1910, and each decade has been warmer than the previous decade since the 1950s.
In 2014, the global average temperature was about 0.57°C (1.03°F) above the 1961-1990 average of 14.00 °C (57.2 °F). This made it nominally the warmest year on record, although the estimate uncertainties in the annual averages are larger than the differences between the warmest years.
In Europe, 19 countries reported record annual temperatures. Western North America including Alaska, eastern Eurasia, much of Africa, large areas of South America and southern and western Australia were also notably warm. Cooler-than-average conditions were recorded across large areas of the United States and Canada.
One of the largest drivers of year-to-year climate variability is the El Niño–Southern Oscillation (ENSO), which is typically associated with elevated global temperatures. It should be noted that 2014 was exceptionally warm despite not being an El Niño year (World Meteorological Organisation, 2015).
Global average precipitation in 2014 was close to the long-term average of 1033 mm. The southwest of the U.S.A, northeast China, eastern Brazil and some countries in Central America experienced drought in 2014.
Flooding in the Balkan Peninsula in May and June affected Serbia, Bosnia-Herzegovina and Croatia. Heavy rains led to flooding in Bangladesh, Pakistan and India in August and September and in Sri Lanka in December. In Africa, floods affected Morocco, Mozambique, South Africa, Kenya, Ethiopia, Somalia and Tanzania. Flooding in the Parana River basin affected Paraguay, Argentina and Brazil.
Natural climate variability creates such extremes every year, but the high incidence of flooding around the world is consistent with an accelerated hydrological cycle driven by the additional energy trapped in the atmosphere by greenhouse gases (WMO, 2015).
Slowing Ocean Currents
A report released by Nature Climate Change published some potentially dire evidence that the worlds ocean currents are slowing down because of Climate Change (Rahmstorf et al, 2015). The slowdown of an ocean circulation like that of the U.S. Gulf Stream could mean a dramatic and sudden rise in sea level. At the moment the sea level off the East coast of America is “anomalously low” because of the intricacies of the Gulf Stream. Firstly the water to the right of the Gulf Stream, towards Europe, is warmer than that on the left, towards the U.S.. Warm water expands and takes up more area than denser cold water, so sea level is also higher to the right side of the current, and lower to the left, off the US East Coast. If you weaken the Gulf Stream and hence the temperature contrast, sea level off the U.S. east coast will rise.
Secondly, another factor called the “geostrophic balance of forces” in the ocean means the sea surface slopes perpendicular to any current flow. So the Gulf Stream has a higher sea level on its right hand side, and a lower sea level on its left. So once again, if you weaken the flow, the balance of sea levels changes and the left hand side (U.S. east coast) will rise.
The World's oceans have warmed over the last 50 years, with the largest warming being found in the upper several hundred metres. Of the oceans and seas around Australia, the Tasman Sea has warmed the fastest. Marine species found in New South Wales have been identified in Tasmanian waters, carried by the southward flow of the East Australian Current. There is evidence of ocean change in the remotest parts of the planet. During research voyages in 2005, scientists working in the Southern Ocean found that at every measurement site in the deep basin adjacent to Antarctica, waters near the sea floor were cooler and less salty than they were a decade ago (CSIRO, 2015).
Most of the energy that accumulates in the climate system ends up in the oceans. Sea-surface temperatures (SSTs) were much warmer than average across the north and north-east Pacific as well as the polar and subtropical North Atlantic, southwest Pacific, parts of the South Atlantic and much of the Indian Ocean. They were particularly high in the Northern Hemisphere from June to October (World Meteorological Organisation, 2015).
The fast-growing research area of event attribution has been developing new scientific tools to determine the influence of man-made Climate Change on extreme events by estimating the change in the likelihood of extremes relative to a climate that would not have been influenced by human activity. The UK’s Met Office applied a new event attribution technique to the global and UK mean record temperature of 2014. “It is estimated that human influence has increased the likelihood of the observed record-breaking temperatures in the UK by a factor of ten,” according to its analysis (Christidis, Stott and Zwiers in WMO, 2015).
Climate Change in Western Australia
Over the past 100 years extreme heat has caused more deaths in Australia than any other natural hazard. In Perth, the number of heatwave days has increased 50% since 1950. Hot weather is increasing in Western Australia, with the state recording its highest annual average maximum temperature in 2014 (Steffen, Hughes & Pearce, 2015).
In March 2015 a report titled 'titled ‘The Heat is on: Climate Change, Extreme heat and Bushfires in Western Australia’, was released by the Climate Council Australia with some damning evidence.
Some Key findings were:
- Climate change is increasing the intensity and frequency of heatwaves in Western Australia and driving up the likelihood of very high fire danger weather
- Recent fires in Western Australia have been influenced by record hot dry conditions
- By 2030, the number of professional firefighters in WA will need to more than double to meet the increasing risk of bushfires
- In Perth, from 1994-2006, there were over 20 heat attributable deaths per year. If average maximum temperatures were 2°C warmer, this number would almost double to 40 deaths
Faced with the unprecedented temperatures in Central Australia in 2013 the Australian Bureau of Meteorology had to add new colours, deep purple and pink, to its weather map covering temperatures between 50 and 54 degrees.
Western Australia has the longest coastline of any Australian state or territory. Climate Change will lead to sea level rise and potentially greater storm surges which will impact on coastal settlements, infrastructure and ecosystems.
Between 20,000 and 30,000 residential buildings, with a current value of between $5 billion and $8 billion may be at risk of inundation from a sea level rise of 1.1 metres. A 1.1 metre sea level rise will also put up to 9000 kilometres of WA’s roads, up to 114 kilometres of WA’s railways and up to 2100 commercial buildings at risk. These assets have an estimated value of up to $11.3 billion, $500 million and $17 billion respectively.
Global sea levels increased by 1.7 millimetres per year over the 20th century. Over the past 15 years, this trend has increased to approximately 3.2 millimetres per year. This rate varies significantly around Australia. Since the early 1990s the southern coast of WA has experienced increases of up to 4.6 millimetres per year, while the western coast has experienced increases of up to 7.4 millimetres per year (Department of the Environment).
Australian Department of the Environment reports:
- ‘Climate change risks to Australia's coasts: a first pass national assessment’, Department of Climate Change, 2009.
- ‘Climate change risks to coastal buildings and infrastructure - A supplement to the first pass national assessment’, Department of Climate Change and Energy Efficiency, 2011.
- Maps dictating the potential rise in sea level along Australia’s coasts can be found here.
Rainfall in south-west WA has already reduced by around 15 per cent since the mid-1970s. From 1911 to 1974 the average stream flow into Perth Dams was 338 gigalitres. From 1975 to 2000 average stream flow was almost half this value at 177 gigalitres. From 2001 to 2010 inflows again halved to approximately 75 gigalitres. There is evidence that greenhouse gases emitted by human activities are responsible for half the decline in rainfall in south-west WA.
Modelling suggests a decrease in mean annual rainfall of 7 per cent and a 14 per cent reduction in surface water runoff in the period 2021 to 2050 relative to the period 1961 to 1990. If current climate trends continue, south-west WA will potentially experience 80 per cent more drought-months by 2070.
A hotter, drier climate would inflict a high economic impact on water supply infrastructure across the country, with Perth likely to be the most severely impacted city in Australia through Climate Change induced water scarcity (Department of the Environment).
In WA the Government is increasing the threat to our already stressed ecosystems and the environment in general through numerous measures. These include changes to the licensing requirement for land clearings, fast-tracking mining and industry development applications, opposition to renewable energy expansion and support for energy generation through coal, proposed changes to the federal-state relationships under the EPBC Act, and the substantial reduction of limited third party appeal rights.
The Greens will continue to speak up for the WA environment and continue to raise issues about Climate Change in Parliament.
To view the WA Greens policies concerning Climate change visit here.