Australia's bushfires are believed to have spewed as much as two-thirds of the nation's annual carbon dioxide emissions in just the past three months, with experts warning forests may take more than 100 years to absorb what's been released so far this season.

Until recently, Australia's forests were thought to reabsorb all the carbon released in bushfires, meaning they achieved net zero emissions, but scientists say climate change is making bushfires burn more intensely and frequently.

Experts warn Australian forests may take more than 100 years to recover all the carbon spewed out from bushfires this summer. Credit:Kate Geraghty

Dr Pep Canadell, a senior research scientist for CSIRO and the executive director of the Global Carbon Project, said that meant slower regrowth rates in Australian forests between bushfires.

"We used to see hundreds of thousands of hectares burned in bushfires, but now we are seeing millions on fire," he said. "It is drying in south-east Australia, that prompts the question if these trees will be able to bring all that carbon back [into regrowth].