Ocean acidification may increase by 170 per cent this century

Owen Gaffney, International Geosphere-Biosphere Programme

Marine scientists launched a major new report on ocean acidification this week at COP 19 in Warsaw. The summary for policymakers concluded that if emissions continue on the current trajectory, the acidity of the world’s oceans may increase by around 170 per cent by the end of the century, bringing significant economic losses. People who rely on the ocean’s ecosystem services – often in developing countries – are especially vulnerable.

The authors of the report agreed on ‘levels of confidence’ in relation to ocean acidification statements summarising the state of knowledge. 

 Very high confidence

  • Ocean acidification is caused by carbon dioxide emissions from human activity to the atmosphere that end up in the ocean;
  • The capacity of the ocean to act as a carbon sink decreases as it acidifies;
  • Reducing carbon dioxide emissions will slow the progress of ocean acidification;
  • Anthropogenic ocean acidification is currently in progress and is measurable;
  • The legacy of historical fossil fuel emissions on ocean acidification will be felt for centuries.

 High confidence

  • If carbon dioxide emissions continue on the current trajectory, coral reef erosion is likely to outpace reef building sometime this century;
  • Cold-water coral communities are at risk and may be unsustainable;
  • Molluscs (such as mussels, oysters and pteropods) are one of the groups most sensitive to ocean acidification;
  • The varied responses of species to ocean acidification and other stressors are likely to lead to changes in marine ecosystems, but the extent of the impact is difficult to predict;
  • Multiple stressors compound the effects of ocean acidification.

Medium confidence

  • Negative socio-economic impacts on coral reefs are expected, but the scale of the costs is uncertain;
  • Declines in shellfisheries will lead to economic losses, but the extent of the losses is uncertain;
  • Ocean acidification may have some direct effects on fish behaviour and physiology;
  • The shells of marine snails known as pteropods, an important link in the marine food web, are already dissolving.

The new report includes infographics showing ocean pH in 2100 (high emissions scenario) and Aragonite saturation in 2100 (high emissions scenario) summarising some of the key conclusions. 

The summary for policy makers was led and published by the International Geosphere-Biosphere Programme and is the result of the world’s largest gathering of experts on ocean acidification ever convened. The Third Symposium on the Ocean in a High CO2 World was held in Monterey, California in September 2012 and was attended by 540 experts from 37 countries. The summary was launched at the UNFCCC climate negotiations in Warsaw on Monday 18 November, for the benefit of policymakers at an event organised by the Intergovernmental Oceanographic Commission.

More info

Access the summary for policy makers here: http://www.igbp.net/publications/summariesforpolicymakers/summariesforpolicymakers/oceanacidificationsummaryforpolicymakers2013.html