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U.S.A."],"published-print":{"date-parts":[[2025,6,24]]},"abstract":"<jats:p>\n                    The physics of the heat-trapping properties of CO\n                    <jats:inline-formula>\n                      <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" display=\"inline\" id=\"i1\" overflow=\"scroll\">\n                        <mml:msub>\n                          <mml:mrow\/>\n                          <mml:mn>2<\/mml:mn>\n                        <\/mml:msub>\n                      <\/mml:math>\n                    <\/jats:inline-formula>\n                    were established in the mid-19th century, as fossil fuel burning rapidly increased atmospheric CO\n                    <jats:inline-formula>\n                      <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" display=\"inline\" id=\"i2\" overflow=\"scroll\">\n                        <mml:msub>\n                          <mml:mrow\/>\n                          <mml:mn>2<\/mml:mn>\n                        <\/mml:msub>\n                      <\/mml:math>\n                    <\/jats:inline-formula>\n                    levels. To date, however, research has not probed when climate change could have been detected if scientists in the 19th century had the current models and observing network. We consider this question in a thought experiment with state-of-the-art climate models. We assume that the capability to make accurate measurements of atmospheric temperature changes existed in 1860, and then apply a standard \u201cfingerprint\u201d method to determine the time at which a human-caused climate change signal was first detectable. Pronounced cooling of the mid- to upper stratosphere, mainly driven by anthropogenic increases in carbon dioxide, would have been identifiable with high confidence by approximately 1885, before the advent of gas-powered cars. These results arise from the favorable signal-to-noise characteristics of the mid- to upper stratosphere, where the signal of human-caused cooling is large and the pattern of this cooling differs markedly from patterns of intrinsic variability. Even if our monitoring capability in 1860 had not been global, and high-quality stratospheric temperature measurements existed for Northern Hemisphere mid-latitudes only, it still would have been feasible to detect human-caused stratospheric cooling by 1894, only 34 y after the assumed start of climate monitoring. Our study provides strong evidence that a discernible human influence on atmospheric temperature has likely existed for over 130 y.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2500829122","type":"journal-article","created":{"date-parts":[[2025,6,16]],"date-time":"2025-06-16T15:50:21Z","timestamp":1750089021000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":14,"title":["Human influence on climate detectable in the late 19th century"],"prefix":"10.1073","volume":"122","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9717-460X","authenticated-orcid":false,"given":"Benjamin D.","family":"Santer","sequence":"first","affiliation":[{"name":"Physical Oceanography Department","place":["Woods Hole"]},{"name":"Woods Hole Oceanographic Institution","place":["Woods Hole"]},{"name":"Joint Institute for Regional Earth System Science and Engineering","place":["Los Angeles"]},{"name":"University of California at Los Angeles","place":["Los Angeles"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2020-7581","authenticated-orcid":false,"given":"Susan","family":"Solomon","sequence":"additional","affiliation":[{"name":"Earth, Atmospheric, and Planetary Sciences","place":["Cambridge"]},{"name":"Massachusetts Institute of Technology","place":["Cambridge"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David W. J.","family":"Thompson","sequence":"additional","affiliation":[{"name":"Department of Atmospheric Sciences","place":["Fort Collins"]},{"name":"Colorado State University","place":["Fort Collins"]},{"name":"School of Environmental Sciences","place":["Norwich, United Kingdom"]},{"name":"University of East Anglia","place":["Norwich, United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5371-8460","authenticated-orcid":false,"given":"Qiang","family":"Fu","sequence":"additional","affiliation":[{"name":"Department of Atmospheric Sciences","place":["Seattle"]},{"name":"University of Washington","place":["Seattle"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0725-6108","authenticated-orcid":false,"given":"Yaowei","family":"Li","sequence":"additional","affiliation":[{"name":"Earth, Atmospheric, and Planetary Sciences","place":["Cambridge"]},{"name":"Massachusetts Institute of Technology","place":["Cambridge"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2025,6,16]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1098\/rsnr.2018.0066"},{"key":"e_1_3_4_2_2","first-page":"6","article-title":"Arrhenius\u2019 1896 model of the greenhouse effect in context","volume":"26","author":"Crawford E.","year":"1997","unstructured":"E. 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