Planet’s innate ability to absorb CO₂ declining: CSIRO

A decline in carbon dioxide (CO₂) emissions absorbed by land and oceans is speeding up the growth of atmospheric CO₂, according to a paper published recently in the journal Proceedings of the National Academy of Science.

Lead author and executive director of the Global Carbon Project, CSIRO’s Dr Pep Canadell, says the acceleration is due to three factors: global economic growth, the world’s economy becoming more carbon intense and deterioration in the land and oceans’ ability to absorb carbon at the required rate.

“What we are seeing is a decrease in the planet’s ability to absorb carbon emissions due to human activity,” Canadell says.

“Fifty years ago, for every tonne of CO₂ emitted, 600 kg were removed by land and ocean sinks. However, in 2006, only 550 kg were removed per tonne and that amount is falling.”

“The carbon cycle is generating stronger-than-expected and sooner-than-expected climate ‘forcing’ — that is, mechanisms that ‘force’ the climate to change,” said CSIRO’s Dr Mike Raupach, a co-chair of the Global Carbon Project.

“In turn, climate change itself is feeding back to affect the carbon cycle, decreasing land and ocean sinks.

“The longer we delay reducing emissions, the more restorative capacity will be lost.”

Dr Canadell says the results have major implications for the current and future growth of atmospheric CO₂.

“The majority of current emission scenarios for modelling climate through the 21st century assume sustained decreases in the carbon intensity of the global economy, which have not occurred since 2000,” he said.

Most of the co-authors of the study are members of the UN Intergovernmental Panel on Climate Change which was awarded the Nobel Peace Prize for 2007 earlier this month.