How chemical fossils help us understand past greenhouse climates... and future ones

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Organic matter preserved in ancient marine, lake, and peat deposits are vast repositories of information on Earth’s climate through time. Biomarkers - molecular fossils with structures that can be linked to specific biological sources - provide insight into the organisms living in the past, and by extension, the environmental conditions necessary for such organisms to thrive. 

Further information is provided by the isotopic compositions of such biomarkers, which can be used to reconstruct a variety of climatic and environmental conditions.  We use these geochemical signatures to explore the ancient Earth system, allowing us to better understand how changes in greenhouse gases affected temperature, rainfall, ecosystems or feedbacks; and from these insights, we can better constrain the impacts of future global warming.