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CCE Status Report 2022

The status report 2022 describes main CCE activities since the Centre was transferred to the German Environment Agency (UBA) in 2018. These activities include the following major projects:

i) Coordination of a revision process of empirical Critical Load for nitrogen (CLempN) in Europe resulting in scientifically adjusted CLempN ranges (Bobbink et al., 2022);

ii) Call for national data on Critical Load which yielded updated national Critical Load maps representing a respective spatial coverage of 40% for eutrophication and 45% for acidification of the model domain;

iii) Update of the European background database for Critical Load calculation, which was necessary in order to ensure a frictionless transfer of data and knowledge from RIVM to UBA. A comparison of Critical Load data between old and new database revealed only minor quantitative differences related to changes in input parameters to the simple mass balance (SMB) model for calculating Critical Load (Reinds et al., 2021);

iv) Assessment of Critical Load exceedances, which were calculated from Critical Load values of national data, the updated European Critical Load background database and modelled historic and projected deposition values provided by the EMEP Meteorological Synthesizing Center (MSC) West depending on past emissions and emission scenarios for 2030 - 2050 respectively. Calculated exceedances of Critical Load in the investigated years 2000 - 2020 occurred in a relatively large area of around 74% - 61% (decreasing trend from 2000 - 2020) of the model domain for eutrophication and a smaller area of 14% - 4% for acidification. Projections of Critical Load exceedances for the years 2030 to 2050 as a function of multiple emission scenarios highlighted ecosystem risks for eutrophication even under low emission scenarios;

v) Estimation of exceedance of critical atmospheric nitrogen inputs to the Baltic sea as a first attempt to evaluate the risk of open sea eutrophication.

Review and revision of the empirical critical loads for Europe

After more than two years, the joint scientific activity coordinated by the Coordination Center for Effects (CCE) to review and revise the empirical critical loads has been completed. The report can be downloaded here [Review and Revision of Empirical Critical Loads].

The ICP Modeling and Mapping (ICP M&M) and its members agreed to the scientific content that resulted in the updated empirical critical load values for nitrogen at their May 2022 online meeting. The ICP M&M asked the WGE at its annual meeting (8th joint WGE/EMEP meeting, September 12-16, 2022) to take note of the report and the updated empirical critical load values for nitrogen. The WGE accepted this request and acknowledged the report and project results. Following this formal acknowledgement, the ICP M&M Task Force recommends the use of the report and updated values in the effects-oriented work.

The report describes the scientific background and results of the review and revision of the empirical critical loads of nitrogen established for Europe in 2011 under the umbrella of the UNECE Convention on Long-Range Transboundary Air Pollution (LRTAP Convention). In 2020, the CCE launched a project embedded in the framework of the LRTAP Convention to update the empirical critical loads. New relevant information from studies (2010 - summer 2021) on the effects of nitrogen on natural and semi-natural ecosystems was incorporated into the existing European database on empirical critical loads of N (CLempN). In the current review and revision, gradient studies were used for the first time to assess and determine CLempN. CLempN were structured according to the updated European Nature Information System (EUNIS) classification. Consensus on the results was reached in a UNECE Expert Workshop on Empirical Critical Nitrogen Loadings (26-28 October 2021, Bern, Switzerland) organized by the Swiss Federal Office for the Environment (FOEN), the CCE and the B-WARE Research Center. The findings, presented in Table 1 of the Executive Summary, show that in many cases the outer ranges of empirical critical loads have been reduced. The resulting European database for 2021 includes both revised and newly defined ranges of values for CLempN for each EUNIS class. The results of this report are of significant importance for the protection of N-sensitive natural and semi-natural ecosystems across Europe. This knowledge will be used to support European policies to reduce air pollution.



The CCE aims at establishing a more dynamic communication within the WGE, and especially with its NFCs. Togehter with the TF Modelling & Mapping and the Centre for Dynamic Modelling (CDM) we plan to publish a newsletter at least twice a year. Please, feel free to submit information relevant for the whole group so we can include it into our next newsletter.

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