Ocean Acidification: Reducing CO2 levels is the only way to minimise risks

Compared with preindustrial levels shown here, the projected increase in ocean acidity is about 170% by 2100 if high CO2 emissions continue (RCP* 8.5).

Net CO2 absorption by the world’s oceans is known to benefit human-kind by reducing the concentration of this greenhouse gas in the atmosphere. But as CO2 dissolves in seawater carbonic acid is formed, causing the ocean to acidify at rates not seen for the last 55 million years. In a new report, summarizing the state of knowledge on ocean acidification for policy makers based on the latest research, experts conclude that ocean acidification may increase 170% this century with substantial costs expected from coral reef loss and declines in shellfisheries.

The report is report based on the research presented at the Third Symposium on the Ocean in a High-CO2 World (September 2012), organized by IOC-UNESCO, the Scientific Committee on Oceanic Research (SCOR) and the International Geosphere-Biosphere Programme (IGBP). It illustrates for policymakers what the implications could be of ocean acidification in the future – both with and without any action taken today.

Over the past two decades, researchers have shown that ocean acidification is increasing as humans have added more carbon dioxide (CO2) to the atmosphere. Historically, the ocean has absorbed approximately a quarter of all CO2 released into the atmosphere by humans since the start of the industrial revolution, resulting in a 26% increase in the acidity of the ocean. As ocean acidity increases, its capacity to absorb CO2 from the atmosphere decreases. This decreases the ocean’s role in moderating climate change. Ocean acidification can no longer remain on the periphery of international debates on climate or the environment.

Credit: Adapted from Bopp et al., 2013.
Ocean surface pH projections to 2100.

Ocean acidification also causes ecosystems and marine biodiversity to change. It has the potential to affect food security and it limits the capacity of the ocean to absorb CO2 from human emissions. The economic impact of ocean acidification could be substantial. According to the report, large parts of the polar oceans will become corrosive to the unprotected shells of calcareous marine organisms within decades. Reducing CO2 levels is the only way to minimise long-term, large-scale risks. Even if all carbon emissions were stopped today the acidification would continue for decades, jeopardizing the stability of marine ecosystems.

Predicting how whole ecosystems will change in response to the combined effect of rising CO2 levels and warming temperatures remains challenging. While we know enough to expect changes in marine ecosystems and biodiversity within our lifetimes, we are unable to make reliable, quantitative predictions of socio-economic impacts.

Several initiatives are underway to address the knowledge gap, foster new methods to examine the full ecosystem response to multiple environmental factors and develop policy options. They will be presented through a side event entitled “Ocean Acidification - the Other CO2 Problem”, organized during the United Nations Conference on Climate Change (COP19) on 18 November 2013 in Warsaw.

Coming together to address ocean acidification

The creation of the Ocean Acidification International Coordination Centre was announced in June 2012 at the UN’s Rio+20 summit. The centre, based at the International Atomic Energy Agency’s Marine Environmental Laboratories in Monaco, will facilitate, communicate and promote international activities in ocean acidification research and observation and link science with policy. It will be overseen by an Advisory Board consisting of leading scientists, economists and institutions, including IOC/UNESCO, NOAA, the Food and Agriculture Organization (FAO) and the Foundation Prince Albert II de Monaco.

A Global Ocean Acidification Observing Network was established in June 2012, working closely with the International Coordination Centre. The network will measure chemical and ecosystem variables needed to provide a baseline for the timely assessment of ocean acidification impacts. It will ensure data quality and comparability, and it will synthesise information for societal benefit.

Future Earth, a new 10-year international research initiative on global sustainability, will provide a mechanism for developing an internationally coordinated research agenda that will include issues like ocean acidification. Future Earth is sponsored by a Science and Technology Alliance for Global Sustainability comprising —among others— UNESCO, the International Council for Science (ICSU), the International Social Science Council (ISSC), the United Nations Environment Programme (UNEP), and the United Nations University (UNU).

IOC/UNESCO and SCOR sponsor the International Ocean Carbon Coordination Project (IOCCP), a monitoring and research programme. IOCCP focuses on the effect of increasing level CO2 emissions on ocean and studies the effect of ocean acidification on calcifying organisms and coral growth rates.

IOC/UNESCO is co-founder of the Ocean Acidification network, meant to provide a central source of information for ocean scientists on research activities in this area, and co-hosts the main international symposium on this issue, ‘The Ocean in a high CO2 World’. Its purpose is to provide an interdisciplinary forum to assess what is known about ocean acidification and priorities for future research every 4 years. This new publication is based on the research presented at the Third Symposium on the Ocean in a High-CO2 World, where 540 experts from 37 countries gathered in Monterey, California, in September 2012. The outcomes described here are informed by that discussion and the latest peer-reviewed research.

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