Multi-model experiments to support the revision of the CLRTAP Gothenburg Protocol
Tim Butler et al., to be submitted
Motivation
The 1999 Gothenburg Protocol (GP) of the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP), as amended in 2012, underwent a review completed in 2022. The review concluded that current air quality legislation in the UNECE region is insufficient to meet the long-term clean air objectives of CLRTAP and that global reductions in methane emissions will be required to meet these objectives.
The Task Force on Hemispheric Transport of Air Pollution (TF HTAP) was organized under the CLRTAP with the mandate to quantify the long-range (hemispheric to global) influence of remote sources of air pollution (including methane) in the UNECE region. To support the revisions of the GP, TF HTAP is currently organizing a new round of multi-model experiments (HTAP3-OPNS) to quantify the long-range contribution to ozone, PM, and the deposition of N and S in different world regions.
Previous HTAP assessments (HTAP1 and HTAP2) have shown that ground-level ozone is significantly influenced by long-range transport on intercontinental scales. While the primary policy audience of the HTAP assessments is CLRTAP and UNECE member states, the work organized here is of scientific and policy significance for other regions.
In this document, we describe the motivating science and policy questions, the design of the several different sets of experiments to be conducted to answer these questions, the input datasets to be used in carrying out the experiments, and the requested output fields necessary for the analysis of the experiments.