Australia's huge bushfires are forecast to help drive global atmospheric levels of carbon dioxide to one of the fastest annual increases on record.

Average carbon dioxide levels reached about 411.5 parts per million (ppm) in the atmosphere in 2019, adding to a steady climb propelled by human activities, according to a calculation of figures released by Britain's Met Office.

However, the pace could accelerate this year, in part because of the carbon being released by the Australian fires.

"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, in 1958," the Met Office said in a statement.