The stabilising influence that land and ocean carbon sinks have on rising carbon emissions is gradually weakening, say scientists attending last week's international Copenhagen Climate Change Conference.
"Forests, grasslands and oceans are absorbing carbon dioxide (CO2) from the atmosphere faster than ever but they are not keeping pace with rapidly rising emissions," says CSIRO scientist and co-chair of the Global Carbon Project, Dr Mike Raupach.
"While these natural CO2 sinks are a huge buffer against climate change, which would occur about twice as fast without them, they cannot be taken for granted."
Dr Raupach and Swiss scientist, Dr Nicolas Gruber, co-chaired one of 43 sessions at the conference – Climate Change, Vulnerability of Carbon Sinks.
Dr Raupach says concern about the vulnerability of carbon sinks is based on identifying several mechanisms that could cause the present stabilising role of oceans and land to be weakened or even reversed.
"Such a change would have drastic consequences for the predicted magnitude or speed of climate change occurring and scientists will meet in Copenhagen to review and question the latest research from which advice can ultimately be provided to decision-makers."
Discussions will focus on:
- Changes in the carbon sink on land through shifts in atmospheric composition, temperature and rainfall changes, deforestation, fire frequency and insect attacks, all of which can slow or reverse sinks or initiate sources of CO2 to the atmosphere.
- Release of carbon presently locked in frozen soil, as both CO2 and methane (a more potent greenhouse gas than CO2).
- Shifts in large-scale agricultural production of food and fibre, potentially speeding up land clearing and tropical deforestation. This process currently contributes 15-20 per cent of anthropogenic carbon emissions.
Findings on the exchange of heat and CO2 between the atmosphere and deep ocean, which suggest that climate change is effectively irreversible in less than 1000 years.
Australian science is represented at the conference in sessions on; sea ice, sea level rise, ocean circulation, atmosphere and ocean tipping points, carbon sequestration, carbon capture and storage, changing the way we live and adapting future agricultural production.