Climate change, ocean acidification and geo-engineering

Climate Change

In pockets of naturally high CO2 concentration (right), the ocean ecosystem looks very different from areas nearby (left). Global ocean acidification could bring similar changes in future (Image: Katharina Fabricius/AIMS)

Climate change and ocean acidification are, together, the biggest and least tractable threat facing the global ocean. The ocean is absorbing more than 90% of the heat trapped by our greenhouse gas emissions, and absorbing about a quarter of carbon dioxide emissions, which is causing acidification.

The scientific evidence that climate change and acidification of seawater will cause major damage to ecosystems across the globe is incontrovertible; they are also likely to compromise humanity’s food supply from the ocean. However, accurately projecting the extent, geography, timing, irreversibility and cost of impacts is, at present, difficult.

The only way to tackle these trends globally is to cut emissions of greenhouse gases and particularly carbon dioxide; however, the prospects of global agreement to do this within the timescales required appear slim. There is evidence from coastal waters that healthy ecosystems are more resilient to climate and acidification impacts; therefore conservation measures could also boost the resilience of high seas ecosystems.

A number of technologies that can either block sunlight or remove carbon dioxide from the atmosphere have been proposed, and are conventionally grouped under the heading of ‘geo-engineering’. Some would use the ocean; most would be likely to affect it in some way. There is no comprehensive global framework regulating these technologies.

For the Commission, this picture presents three overriding questions:

  • Given that long-term mitigation of climate change and ocean acidification can only be achieved through swift and substantial reductions in greenhouse gas (and particularly carbon dioxide) emissions, can the Commission recommend any measure(s) likely to facilitate progress in this area?
  • Can the Commission recommend any other measure(s) that will be of material use, in terms of (for example) local mitigation, adaptation or research, that are applicable in the high seas?
  • Can a comprehensive system of marine protected areas on the high seas be a response to these issues, given their contribution to resilience?

Download policy paper 2: Climate change, ocean acidification and geoengineering (in English only)