Big Continental Area, Little Climate Change
For so large an area, Australia experiences a relatively small variation in climate. The land mass extends over only 33° of latitude, one third of which lies within the tropics. Its generally low, flat topography lacks the mountain ranges that diversify climatic regimes elsewhere. Summer temperatures hover around 29° C in the north and 18° C in the south, compared with winter temperatures of 24° C and 10° C. Cloncurry, Queensland, claims the highest temperature ever recorded, 52.7° C in 1889, but Marble Bar, Western Australia, set the heat wave record by surpassing 37.8° C on 170 consecutive days in 1923-24. The lowest temperature, -23° C was recorded at Charlotte Pass near Mount Kosciusko.
As an island continent, Australia displays major contrasts between its interior continental climates (with large temperature ranges and erratic rainfall) and its coastal maritime climates (with small temperature ranges and more reliable rainfall). Of all the continents, only Antarctica receives less precipitation than Australia an annual average of 42 centimetres. Periodic droughts, flooding, heat, and aridity are constant threats. Dry conditions create the potential for disastrous fires, such as those that charred thousands of acres and destroyed many homes in the vicinity of Sydney early in 1994. Almost all of northern Australia endures heat discomfort for over 150 days a year. The tropical seas along the coast offer little relief from the heat.
Very different wind belts cross northern, central, and southern Australia. Humid easterly blow off the Pacific Ocean across the tropical north, making the coastal rain forests of Tully, Queensland, the wettest place in Australia; they receive an average of 405 centimetres per year. These summer winds are augmented by monsoonal westerlies which blow out of Indonesia into Arnhem Land, Northern Territory, and the Kimberleys, Western Australia, and by destructive tropical cyclones (or hurricanes) off the Coral Sea and Gulf of Carpentaria. Northern Australians refer to summer as ''the wet'' and to winter as ''the dry".
Across the center of Australia move the subtropical anticyclones, from west to east. These cells of high pressure bring clear skies, summer heat, and almost no rain to the desert core of the continent. Southern Australia extends into the belt of westerlies that encircle the Earth around 40° S. latitude: the ''roaring forties.'' These bring cloudy cold fronts (cyclones) twice weekly to Tasmania and Victoria during the winter, when rainfall is concentrated. Perth enjoys a classic mild Mediterranean-like climate, with its cool, moist winter and warm, rainless summer. Australia's erratic weather has been attributed to the El Nino Southern Oscillation effect. Because of this effect, when unusually warm water gathers off the Pacific coast of South America, it disrupts the usual climatic rhythms of atmospheric pressure on the opposite side of the Pacific. Thus, every five years or so, rainfall due in Australia falls instead in the central Pacific, to be followed a few years later by an equally perturbing inundation of usually dry areas.
Climate does change. The last Ice Age ended only 10,000 years ago. Today, despite scientific skepticism, many Australians are concerned that rapid global warming caused by the 'greenhouse effect' may ruin agriculture and flood coastal cities.
A recurrent summer hazard is the bushfire a forest fire, or wildfire especially after seasons of intense heat which dry out plant litter. Fanned by hot winds, the leaves of oil-bearing eucalyptus trees burn explosively. Careless campers and arsonists are often responsible. Killer fires that damaged many towns occurred in 1851, in 1983, and during the January 1994 conflagration.
Conservationists advocate the reintroduction of trees and deep-rooted perennials, the preservation of bushland, the use of more native predators instead of pesticides (and biological control by fungi and insects rather than herbicides), the diversification and scaling down of the farming-forestry system, and a more self-sufficient, less urban population.