One of the worst dust storms on record brought Sydney, Australia's largest city, to a standstill in September 2009. The storm was drought-related—and there may be more such storms to come, as global warming is expected to increase the frequency and severity of drought in southeastern Australia in coming decades.1
Climate change is expected to increase the intensity and frequency of drought in Australia.6,18 Sydney, the country's largest city, may face more storms like the one that occurred in 2009, which carried millions of tons of dust from the interior of the world's driest inhabited continent.2,10
Australia is already the driest inhabited continent on Earth2—and scientists expect it to become drier.3 With rising temperatures, decreasing rainfall and inflow, and declining soil moisture comes greater risk of drought.3,4
A drought is a prolonged, abnormally dry period during which there is not enough water to meet the needs of people, animals, and plants.5 Drought is not simply the absence of rainfall—it also includes a lack of surface moisture and irrigation water at critical points in the growing season for crops. These factors can even reduce groundwater supplies, and extended drought can undermine the economy and society.3
Australia has experienced several major droughts in recent decades, such as from 1982 to 1983, 1991 to1995, and 2002 to 2003. Together these droughts caused $13.7 billion in economic losses, and each drought cost the country more than the previous one.5,4,6,7
The most recent drought from 2006 to 2007 reduced Australia's economic growth by about 0.75 percent.2 It curtailed agriculture, killing sheep and drastically cutting grain yields.2 Restrictions on water use in urban areas cost around $815 million each year, and affected more than 80 percent of Australian households.2
Another drought in the Australian interior was linked to a dust storm that blanketed Sydney, the country's largest city, in 2009.8,9 The storm—which turned skies an eerie shade of red—reportedly carried as much as 17 million tons (16 million metric tonnes) of dust.10 The dust cloud extended from South Australia east to Victoria and New South Wales, and north to Queensland.11
The dust storm was one of the worst on record. Wind gusts of more than 37 miles (60 kilometers) per hour, which swept the dust into Sidney, joined with high temperatures and low humidity to increase the risk of fire in the city and its surroundings.11
These recent Australian droughts have been linked to higher temperatures.3,12 Australia's temperature has risen by an average of 1.6° F (.90° C) since 1910, with most of the warming occurring since 1950.3 The country's second-hottest year on record was 2009,13 when, on a day now known as Black Saturday (7 February) because of deadly brushfires, Melbourne's temperature reached 115° F (46.4° C).
During that same period, average annual rainfall in New South Wales declined by 3.6 inches (92 millimeters).3 Scientists think the decline in autumn rainfall in southeast Australia since the late 1950s may be partly due to increases in heat-trapping gases in Earth's atmosphere.3,14 Major bushfires over southeast Australia are linked to the positive phase of an ocean cycle called the "Indian Ocean Dipole"—when sea surface temperatures are warmer than average in the western Indian Ocean, likely in response to global warming.15,16
What the Future Holds
If our heat-trapping emissions continue to rise at their current rate, the proportion of Earth's surface in extreme drought is projected to expand by 30 percent toward the latter part of this century.6,17,19
Australia's climate is expected to become warmer and drier overall.3 In a medium-emissions scenario,19 temperatures are projected to rise about 1.8° F (1° C) in the next few decades.3 Rainfall is expected to decline 3-5 percent, and evaporation to increase 2-4 percent3—creating conditions conducive to an environment for increasing frequency of bushfires.
Drought is expected to occur 20-40 percent more often in most of Australia over the coming decades.6,18 If our heat-trapping emissions continue to rise at high rates,19 more severe droughts are projected for eastern Australia in the first half of this century.6,17 And droughts may occur up to 40 percent more often in southeast Australia by 2070.2 Unless we act now to curb global warming emissions, most regions of the country are expected to suffer exceptionally low soil moisture at almost double the frequency that they do now.3 Studies suggest that climate change is helping to weaken the trade winds over the Pacific Ocean, with the potential to change rainfall patterns in the region, including Australia.20,21,16,22
More frequent and intense droughts are likely to bring more dust storms like the one that wreaked havoc on Sydney in September 2009. New South Wales is Australia's most populous state—home to one-third of the country's population.23 Drought and dust storms associated with climate change could disrupt everything from travel and tourism to farming and electricity generation, with significant consequences for Australia's economy.23