Australia is grappling with massive bushfires fuelled by record-breaking temperatures and months of severe drought.

In the worst-affected state, New South Wales, fires have burned more than 4 million hectares (9.9m acres) destroying more than 900 houses.

Across the country, 12 people have died – including three volunteer firefighters – with most of the casualties in New South Wales.

Science What’s the situation in New South Wales?

Hot, dry weather combined with prolonged drought and strong winds have created perfect conditions for fire to spread rapidly.

Around 100 fires are burning across the state, with up to half as yet uncontained by firefighters and continuing to threaten lives.

The fires have been exacerbated by 40C temperatures and strong winds, creating difficult conditions for the 2,500 firefighters deployed in the field.

The small town of Balmoral, south-west of Sydney, was largely destroyed and scores of homes were razed amid catastrophic conditions on 22 December.

In northern NSW large fires are burning in the region between Port Macquarie and Byron Bay.

In the countryside to the west of Sydney, there are fears that the vast Gospers Mountain fire, which originated in the Wollemi National Park, may merge with the Green Wattle Creek blaze in the lower Blue Mountains.

The fire in the Blue Mountains, a world heritage area and popular tourist destination, has burnt over 64,000 hectares, though much of it is now being controlled, according to the NSW Rural Fire Service.

Fire crews in the region took advantage of cooler conditions last week to perform ‘back burning’, where small areas are deliberately burned to create breaks to stop or slow the main fire.

Smoke from bushfires has periodically blown south-eastwards to reach Sydney, causing severe air pollution in Australia’s largest city.

Further south of Sydney major roads have been closed major roads have been closed at several times during the last week with emergency-level fires spanning a 500km (310 miles) area across New South Wales and the neighbouring state of Victoria.

To put the fire damage in New South Wales in perspective, 1.8 million hectares burned in the 2018 California wildfires and some 900,000 hectares were lost in the 2019 Amazon fires.

Flames up to 70m (230ft) in height have been reported.

Science What is the situation in other states?

In Victoria, the state’s Country Fire Authority issued emergency warnings across the region of East Gippsland telling 30,000 people to leave the area before roads became too dangerous.

Fires have been burning in the area since late November but the latest warnings for East Gippsland are of bushfire-driven thunderstorms, which would increase the risk of the fires spreading further out of control.

In the small town of Mallacoota residents fled to the beach following a warning siren, with only a change in the wind direction keeping the fire from reaching them on the shore.

In the state of South Australia, the Cudlee Creek fire is reported to have destroyed more than 80 homes in the Adelaide Hills region.

The fires are also thought to have destroyed up to a third of the vines that provide grapes for the Adelaide Hills wine industry.

So are bushfires getting worse?

Many Australians are asking that very question and whether these fires are linked to climate change – but the science is complicated.

Scientists have long warned that a hotter, drier climate will contribute to fires becoming more frequent and more intense.

Australia’s deadliest bushfire disaster was “Black Saturday” in February 2009, when some 180 people died in Victoria.

Data shows that Australia has warmed overall by slightly more than one degree Celsius since 1910, with most of the heating occurring since 1950, the Bureau of Meteorology says.

Science Hottest day on record

Australia broke its all-time temperature record twice in December.

An average maximum of 40.9C was recorded on 17 December, broken a day later by 41.9C, both beating 2013’s record of 40.3C.

By the end of the month every state had measured temperatures above 40C – including Tasmania.

The main climate driver behind the heat has been a positive Indian Ocean Dipole (IOD) – an event where sea surface temperatures are warmer in the western half of the ocean, cooler in the east.

The difference between the two temperatures is currently the strongest in 60 years.