A noted Australian climate scientist is warning that using forests to offset carbon dioxide emissions would be a huge task.
Scientists are agreed that only 1000 giga tonnes of carbon dioxide can be emitted into the atmosphere on top of what has already gone in, if the world is to stay below extra warming of two degrees Celcius.
Planting more trees alone will not halt climate change, the climate scientist, Tim Flannery, said.
He said to offset just 10 percent of what the world is now emitting, an area the size of New York state would need to be planted every year for 50 years.
Mr Flannery said other things could be done including seaweed farms and the use of cement and plastic that actually absorbs CO2.