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Indicator Specification
Across the ocean, the pH of surface waters has been relatively stable for millions of years. Over the last million years, average surface water pH oscillated between 8.3 during cold periods (e.g. during the last glacial maximum, 20 000 years ago) and 8.2 during warm periods (e.g. just prior to the industrial revolution). Rapid increases in atmospheric CO2 concentration due to emissions from human activities are now threatening this stability, as the CO2 is subsequently partially absorbed in the ocean. Currently, the ocean takes up about one-quarter of the global CO2 emissions coming from human activities, e.g. combustion of fossil fuels. The uptake of CO2 in the sea causes ocean acidification, as the pH of sea water declines, even though ocean surface waters will remain alkaline.
When CO2 is absorbed by the ocean, it reacts with water, producing carbonic acid. Carbonic acid dissociates to form bicarbonate ions and protons, which further react with carbonate ions. The carbonate ions act as a buffer, helping to limit the decline in ocean pH; however, they are being used up as more and more anthropogenic CO2 is added to the ocean. As carbonate ion concentrations decline, so does the ocean’s capacity to take up more anthropogenic CO2. Hence, the ocean’s ability to moderate atmospheric CO2 and thus climate change comes at the cost of substantial changes in its fundamental chemistry.
Ocean acidification can have wide-ranging impacts on biological systems by reducing the availability of carbonate. Decreasing carbonate ion concentrations reduce the rate of calcification of marine calcifying organisms, such as reef-building corals, mussels and plankton. pH also affects biological molecules and processes, e.g. enzyme activities and photosynthesis. Thus, anthropogenic acidification could affect entire marine ecosystems. Organisms appear to be increasingly sensitive to acidification when they are concurrently exposed to elevated seawater temperature. Of equal importance is the effect of acidification on primary producers, as it changes the bioavailability of essential nutrients, such as iron and zinc. Primary producers are responsible for a significant part of global carbon fixation, thereby forming the basis of marine food webs.
In April 2013, the European Commission (EC) presented the EU Adaptation Strategy Package. This package consists of the EU Strategy on adaptation to climate change (COM/2013/216 final) and a number of supporting documents. The overall aim of the EU Adaptation Strategy is to contribute to a more climate-resilient Europe.
One of the objectives of the EU Adaptation Strategy is Better informed decision-making, which will be achieved by bridging the knowledge gap and further developing the European climate adaptation platform (Climate-ADAPT) as the ‘one-stop shop’ for adaptation information in Europe. Climate-ADAPT has been developed jointly by the EC and the EEA to share knowledge on (1) observed and projected climate change and its impacts on environmental and social systems and on human health, (2) relevant research, (3) EU, transnational, national and subnational adaptation strategies and plans, and (4) adaptation case studies.
Further objectives include Promoting adaptation in key vulnerablesectors through climate-proofing EU sector policies and Promoting action by Member States. Most EU Member States have already adopted national adaptation strategies and many have also prepared action plans on climate change adaptation. The EC also supports adaptation in cities through the Covenant of Mayors for Climate and Energy initiative.
In September 2016, the EC presented an indicative roadmap for the evaluation of the EU Adaptation Strategy by 2018.
In November 2013, the European Parliament and the European Council adopted the 7th EU Environment Action Programme (7th EAP) to 2020, ‘Living well, within the limits of our planet’. The 7th EAP is intended to help guide EU action on environment and climate change up to and beyond 2020. It highlights that ‘Action to mitigate and adapt to climate change will increase the resilience of the Union’s economy and society, while stimulating innovation and protecting the Union’s natural resources.’ Consequently, several priority objectives of the 7th EAP refer to climate change adaptation.
No targets have been specified.
The time series shows both direct measurement data from the Aloha station pH as well as calculations for gap filling (see methodology reference below).
A trend line has been added.
The methodology for gap filling is described in the methodology reference below.
Not applicable
In general, changes related to the physical and chemical marine environment are better documented than biological changes because links between cause and effect are better understood and often time series of observations are longer. Ocean acidification occurs as a consequence of well-defined chemical reactions, but its rate and biological consequences on a global scale is subject to research.
No uncertainty has been specified
Work specified here requires to be completed within 1 year from now.
Work specified here will require more than 1 year (from now) to be completed.
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/ocean-acidification-1 or scan the QR code.
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