- Sydney has been blanketed in thick smoke on and off for the past few weeks due to severe bushfires surrounding the city.
- The current period of poor air quality in New South Wales is both the "longest" and "most widespread" on record.
- While climate change is playing a role in creating extreme bushfire conditions, a "perfect storm" of factors has led to Sydney's smoky state.
- In addition to the abnormal bushfire conditions, two atmospheric systems are driving winds through Australia's hot interior.
- Visit Business Insider Australia's homepage for more stories.
Hazy smoke choking the city, which works its way even into air-conditioned apartments, ash falling from the sky, shirts used as makeshift filters and a bright red sun – is this the new summer norm for Sydney?
As bushfires rage around the New South Wales, ensconcing Sydney from all sides, strong winds have blown a blanket of smoke over the city, bringing "hazardous" air quality and a general feeling that this is something largely unprecedented.
Climate change is on everybody's mind as Australia's bushfire seasons grow more intense, but the acrid haze over Sydney is not just thanks to a changing climate – it's also driven in part by a pair of atmospheric events which are also responsible for the drought.
A spokesperson for the NSW Department of Planning, Industry and Environment confirmed to Business Insider Australia the current period of poor air quality is the "longest" and "most widespread" in the state's history.
"NSW has experienced other periods of poor air quality that lasted several weeks, including the 1994 Sydney bushfires and the Black Christmas bushfires of Dec 2001 - Jan 2002. This event, however, is the longest and the most widespread in our records," the spokesperson said.
"During the bushfire emergency our network has recorded some of the highest air pollution ever seen in NSW, particularly for PM2.5, which are particles less than 2.5 micrometres in diameter."
Of course, there's a sense an inner-city bubble has been perforated here. Many Australians live in bushfire-prone regional areas and know all too well what it's like to deal with not only smoke but also the inclement threat of loss of life and property.
But for the significant chunk of the population who live in cities along Australia's coastline, the thought of smoky summers becoming the norm makes the looming reality of potentially catastrophic climate change much more palpable.
According to AirVisual, a service which provides a live ranking of air quality in the world's cities, Sydney had on Wednesday the 12th-worst air quality on the planet – worse than cities infamous for particulate pollution, like Shenzhen or Mumbai.
Speaking to Pedestrian.tv, meteorologist at the Bureau of Meteorology Helen Kirkup warned the conditions, which have led to NSW's worst bushfire season, will likely persist throughout the summer.
“We are looking at a below-average rainfall summer so that’s not going to help anything,” Kirkup said. “We are expecting, once it’s dry and it’s getting hot, we are going to have bad fire conditions persist through the summer.”
So, can we expect Sydney summers to be hazy, ashy nightmares, all thanks to the changing climate?
Climate change is a big factor – but there's more at play
Dale Dominey-Howes, a professor of hazard and disaster risk sciences at the University of Sydney, says the smoke lingering over Sydney has been caused by a "perfect storm" of factors, and – like the bushfires themselves – can constitute a significant hazard.
"Climate change is exacerbating every risk factor for more frequent and intense bushfires," Dr Dominey-Howes told Business Insider Australia. "Widespread drought conditions, higher than average temperatures – these are all made worse by climate change."
But Dr Dominey-Howes says the smoke over Sydney has been caused by a combination of these exacerbated bushfire conditions and two atmospheric systems which are "coming together and driving winds from the interior towards the east coast."
Firstly, is the Southern Annular Mode (SAM), which is a belt of westerly winds, which expands and contracts in a north-south movement between Antarctica and the equator. In its negative phase, the SAM brings strong westerly winds across Australia. The SAM can bring increased rains in southern Victoria and Tasmania, but also corresponds with dry patterns in much of eastern Australia – especially New South Wales.
The second system is the Indian Ocean Dipole (IOD) – also known as the Indian Niño – which refers to sustained changes in the surface temperature of the western and eastern Indian Ocean. The IOD is one of the key drivers of Australia's climate. It has been in a "rain-suppressing" negative phase since May.
"These systems drive wind from Australia's dry and hot interior, which – along with the unusually bad bushfire conditions – creates the conditions we're seeing with the smoke," Dr Dominey-Howes said.
"Although the unusual bushfire conditions are aggravated by climate change and playing their part, there are several other factors making the smoke and dust particularly bad."
Dr Dominey-Howes says it's possible this unfortunate overlap of factors could feasibly last "four to eight weeks," and suggested there could come a point where the government should consider supplying respirator masks – particularly for people who work outside.
Andrew Watkins, head of long-range forecasting Bureau of Meteorology, told the Sydney Morning Herald last month conditions would likely proceed through the first half of summer, with the arrival of a monsoon trough in the Southern Hemisphere providing likely respite.
In November, The Guardian reported scientists were concerned climate change was "supercharging" the Indian Ocean Dipole, with rising ocean surface temperatures creating more regular and intense events.
Though we can likely expect a worsening of Australian bushfire conditions in future thanks to the effects of human-caused climate change, the smoke blanketing Sydney for the past two weeks may not be the new normal – for now, at least.