Widespread bushfires in Australia have been contributing to one of the largest increases in CO2 levels in the Earth's atmosphere since records began to be kept more than 60 years ago, Britain's Meteorological Office said on Friday.

"A forecast of the atmospheric concentration of carbon dioxide shows that 2020 will witness one of the largest annual rises in concentration since measurements began at Mauna Loa, in Hawaii, 1958," the office said in a statement.

The Met said levels of CO2 in the atmosphere were expected to surpass 417 parts per million in May, with the average for 2020 forecast to be 414.2 ± 0.6ppm. That expected average would exceed the 2019 average by 2.74 ± 0.57 ppm.

Similar concentrations of CO2 were last seen in the Earth's atmosphere between 3 million and 5 million years ago, scientists say. Back then, sea levels were 10 meters to 20 meters (33 feet to 65 feet) higher than today, with temperatures some 2 to 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit) warmer.

The rise in emissions of the greenhouse gas CO2 contributes to global warming, which is seen as a major factor driving the fires in Australia. Bushfires have burnt huge swathes of land in the country's southeast and killed at least 31 people since September.

Read more: Australian bushfires – a first-person experience

Fires have been nearing the Australian capital, Canberra

Search for killed US firefighters

Among the latest fatalities were three US firefighters killed on Thursday when their C-130 Hercules tanker plane went down in the southeastern state of NSW, shortly after dropping retardant on a blaze in the Snowy Monaro region.

A team is working to recover the victims' bodies, according to Australian Transport Safety Bureau Chief Commissioner Greg Hood.

More than 500 aircraft from various countries are fighting the fires, Hood said

Hood said it was difficult to secure evidence of the crash and to recover the remains of the three men as the fire was still burning at the crash site, with the presence of aviation fuel from the plane posing an additional hazard.

The premier of NSW, Gladys Berejiklian, said a memorial service would be held in the state capital of Sydney for the three men and three Australian volunteer firefighters who have been killed fighting the current spate of fires.

She said more than 1,700 volunteers and other personnel were currently combating the blazes, with five fires described as being at an "emergency warning" level in the state and near the national capital, Canberra.

Read more: Wildfires: Climate change and deforestation increase the global risk

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tj/sms (Reuters, AP)

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