This December, Paris will host the 21st United Nations Climate Change Conference of the Parties (COP). Set annually, the conference were set up in 1995 to bring countries together in an effort to tackle climate change. It resulted in the Kyoto Protocol, an international treaty that requires member States to reduce greenhouse gas emissions. The Protocol commitment period ended in 2012, famously failing to result in the reductions of emissions so badly needed. A second round of commitment is now in action, and member States are once again debating how to tackle climate change.
Alongside reducing carbon emissions, Kyoto also encourages man-made carbon sinks – ways to take carbon out of the atmosphere to offset carbon emissions. The carbon we emit does not stay in the atmosphere indefinitely, instead circulating through sources and sinks - ecosystems, the geosphere, the ocean, and the atmosphere. The ocean is a vast natural sink, with carbon entering the ocean through one of two pathways. Atmospheric carbon is dissolved through the surface layers of the ocean and converted to carbonate, whilst dissolved organic carbon can enter from terrestrial runoff – such as from rivers. Surface water carbon is transported to deep water via a physicochemical process known as the ‘solubility pump’, and can be returned to surface waters in upwelling zones.
In 2004 research lead by NOAA’s Pacific Marine Environmental Laboratory Director Christopher Sabine estimated that the ocean has taken in around 48% of fossil fuel and cement-manufacturing emissions between 1800 and 1994. Unfortunately work by geochemist Samar Khatiwala, Columbia University, suggests that the ocean’s carbon sink capacity is decreasing, likely as a result of ocean acidification, warming, and loss of algal and coastal habitats that sequester carbon. With fossil fuel emissions continuing unabated, relying purely on natural carbon sinks to temper our emissions may no longer be an option. For a number of years, researchers, policy makers, and commercial ventures have been looking to increase carbon storage options - including geoengineering of the oceans.
The full article was published in – and can be read in – The Marine Professional, a publication of the Institute of Marine Engineering, Science & Technology (IMarEST).
Image: Air - sea exchange of carbon dioxide. Credit Hannes Grobe (Alfred Wegener Institute for Polar and Marine Research), retouched by McSuch/WikiMedia (CC BY-SA 2.5)