It is generally accepted that declining carbon dioxide (CO2) levels were an important factor in the Eocene
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/atmospheric-carbon-dioxide-through-eoceneoligocene-climate-transition
[2] http://admin.indiaenvironmentportal.org.in/category/author/gavin-l-foster
[3] http://admin.indiaenvironmentportal.org.in/category/author/paul-n-pearson
[4] http://admin.indiaenvironmentportal.org.in/category/author/bridget-s-wade
[5] http://admin.indiaenvironmentportal.org.in/category/journal/nature
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/carbon-dioxide
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-change
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/climate-science
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/antarctica