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<p>Recent climate change mitigation strategies rely on the reduction of methane (CH<span class="inline-formula">₄</span>) emissions. Carbon and hydrogen isotope ratio (<span class="inline-formula"><i>δ</i>¹³</span>C<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="88378e1204e3d563d6a246890a4aa185"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00001.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><i>δ</i>²</span>H<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="dd3c9475b226171f6a2b3b617af53c34"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00002.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00002.png"/></svg:svg></span></span>) measurements can be used to distinguish sources and thus to understand the CH<span class="inline-formula">₄</span> budget better. The CH<span class="inline-formula">₄</span> emission estimates by models are sensitive to the isotopic signatures assigned to each source category, so it is important to provide representative estimates of the different CH<span class="inline-formula">₄</span> source isotopic signatures worldwide.</p> <p>We present new measurements of isotope signatures of various, mainly anthropogenic, CH<span class="inline-formula">₄</span> sources in Europe, which represent a substantial contribution to the global dataset of source isotopic measurements from the literature, especially for <span class="inline-formula"><i>δ</i>²</span>H<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="84fcb0f9a34ee9d79bf982a447f5f148"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00003.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00003.png"/></svg:svg></span></span>. They improve the definition of <span class="inline-formula"><i>δ</i>¹³</span>C<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="e2a2695324ac508109ef1a73806e4a16"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00004.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00004.png"/></svg:svg></span></span> from waste sources, and demonstrate the use of <span class="inline-formula"><i>δ</i>²</span>H<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="1f8fb3ffd735a682c8d52e77a126bcd4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00005.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00005.png"/></svg:svg></span></span> for fossil fuel source attribution.</p> <p>We combined our new measurements with the last published database of CH<span class="inline-formula">₄</span> isotopic signatures and with additional literature, and present a new global database. We found that microbial sources are generally well characterised. The large variability in fossil fuel isotopic compositions requires particular care in the choice of weighting criteria for the calculation of a representative global value. The global dataset could be further improved by measurements from African, South American, and Asian countries, and more measurements from pyrogenic sources.</p> <p>We improved the source characterisation of CH<span class="inline-formula">₄</span> emissions using stable isotopes and associated uncertainty, to be used in top-down studies. We emphasise that an appropriate use of the database requires the analysis of specific parameters in relation to source type and the region of interest.</p> <p>The final version of the European CH<span class="inline-formula">₄</span> isotope database coupled with a global inventory of fossil and non-fossil <span class="inline-formula"><i>δ</i>¹³</span>C<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="7df24eafe1d02fa963c1dc28bf3e1bfa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00006.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00006.png"/></svg:svg></span></span> and <span class="inline-formula"><i>δ</i>²</span>H<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><msub><mi/><mrow><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="4717a0ac9b66ca01002207df5cfec087"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-14-4365-2022-ie00007.svg" width="17pt" height="10pt" src="essd-14-4365-2022-ie00007.png"/></svg:svg></span></span> source signature measurements is available at <a href="https://doi.org/10.24416/UU01-YP43IN">https://doi.org/10.24416/UU01-YP43IN</a> <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx98">Menoud et al.</a>, <a href="#bib1.bibx98">2022</a><a href="#bib1.bibx98">a</a>)</span>.</p>