Left graph: Decline in ocean pH measured at the Aloha station (University of Hawaii) and yearly mean surface seawater pH reported on a global scale (Copernicus Marine Service); Right graph: Decadal average sea surface temperature anomaly in different Euro

Figure Created 07 Nov 2023 Published 14 Dec 2023 Last modified 14 Dec 2023
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Left graph: A decline in pH corresponds to an increase in the acidity of ocean water. Data originate from the Aloha station pH time series (adapted from Dore, J.E., et al., 2009, 'Physical and biogeochemical modulation of ocean acidification in the central North Pacific', Proceedings of the National Academy of Sciences of the United States of America 106:12235-12240). Changes here are similar to those that are observed over a shorter time frame in Europe (see here: In figure, "In situ measurement (Aloha station)" corresponds to data based on in-situ measurements, while "Calculated (Aloha station)" corresponds to calculated data. Global annual average of surface ocean pH from the Copernicus Marine Service, based on a reconstruction method using in situ data and remote sensing data, as well as empirical relationships. Indicator is available at annual resolution, and from the year 1985 onwards. The error on each yearly value varies, and is added to the data file sheet. The estimated yearly uncertainty envelope shown in the figure is defined as the annual mean of pH ± 2 standard deviations, which corresponds to a 95% confidence interval of the mean estimate. Right graph: Time series (1870-2022) of decadal average observed sea surface temperature anomalies (°C), with respect to the period 1991-2020, for each of the European basins, for the European seas as a whole, and for the global ocean. Data sources: HadSST4.0.1.0 (1850-2022), ERSSTTv5 (1880-2022), HadISST1 (1870-2022) and satellite-based ESA CCI/C3S SST Climate Data Record v2.1 (1991-2022).

European data


Additional information

Left graph:
See HOT_surface_CO2_readme.pdf for explanatory material, metadata, and notes

Temporal coverage:

Left graph: 1985-2021; Right graph: 1853-2022


Geographic coverage

Temporal coverage


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