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<front>
<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub"></issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/egusphere-2025-4899</article-id>
<title-group>
<article-title>Emergent constraints on climate sensitivity and recent record-breaking warm years</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Boardman</surname>
<given-names>Patric J. L.</given-names>
<ext-link>https://orcid.org/0009-0004-4964-2909</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Clarke</surname>
<given-names>Joseph</given-names>
<ext-link>https://orcid.org/0000-0002-6250-1543</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Cox</surname>
<given-names>Peter M.</given-names>
<ext-link>https://orcid.org/0000-0002-0679-2219</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Huntingford</surname>
<given-names>Chris</given-names>
<ext-link>https://orcid.org/0000-0002-5941-7770</ext-link>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Jones</surname>
<given-names>Christopher D.</given-names>
<ext-link>https://orcid.org/0000-0002-7141-9285</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Williamson</surname>
<given-names>Mark S.</given-names>
<ext-link>https://orcid.org/0000-0002-4548-8922</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>University of Exeter, Mathematics and Statistics, Exeter, Devon, UK, EX4 4QE</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>UK Centre for Ecology and Hydrology, Wallingford, Oxfordshire, UK, OX10 8BB</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Met Office, Exeter, Devon, UK, EX1 3PB</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>School of Geographical Sciences, University of Bristol, UK</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Global Systems Institute, University of Exeter, Devon, Exeter, EX4 4QE, UK</addr-line>
</aff>
<pub-date pub-type="epub">
<day>15</day>
<month>10</month>
<year>2025</year>
</pub-date>
<volume>2025</volume>
<fpage>1</fpage>
<lpage>19</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2025 Patric J. L. Boardman et al.</copyright-statement>
<copyright-year>2025</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4899/">This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4899/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4899/egusphere-2025-4899.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4899/egusphere-2025-4899.pdf</self-uri>
<abstract>
<p>The Earth&amp;rsquo;s climate sensitivity remains a significant source of uncertainty in climate projections. A key metric is the Transient Climate Response (TCR), which incorporates aspects of both the Equilibrium Climate Sensitivity (ECS) and ocean heat uptake, and correlates well with historical global warming simulated by Earth System Models (ESMs). CMIP6 ESMs display a wider range of TCR values compared to earlier phases, with many exceeding the IPCC AR6 &lt;em&gt;very likely&lt;/em&gt; (90 % confidence) range of 1.2&amp;ndash;2.4 K. These high-sensitivity models also predict that warming will exceed the 2 &amp;deg;C Paris climate agreement limit, even under the relatively low emissions SSP1-2.6 scenario. Record global temperatures in 2023 and 2024 highlight how close the world already is to 1.5 &amp;deg;C of warming, raising doubts about whether the 2 &amp;deg;C limit remains within reach. Here, we use the latest observational data to update emergent constraints on TCR and projected warming. We estimate a TCR of 1.81 K with a&lt;em&gt; very likely&lt;/em&gt; range of 1.28 K to 2.33 K, which represents a small increase compared to estimates that use observational data through to 2019. Furthermore, we find that warming projections constrained by data through to 2024 fall within the low to mid-range of CMIP6 ESM projections for both the mid- and late-21st century, indicating that limiting global warming to below 2 &amp;deg;C remains feasible.</p>
</abstract>
<counts><page-count count="19"/></counts>
<funding-group>
<award-group id="gs1">
<funding-source>Natural Environment Research Council</funding-source>
<award-id>NE/S007504/1</award-id>
</award-group>
</funding-group>
</article-meta>
</front>
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