Carbon-Climate Coupling Dynamics Revealed by Decadal-Resolution Middle Miocene Records

Contemporary global warming is known to lag behind the rapid increase in atmospheric CO₂ levels. This delay, largely due to heat uptake and storage in the vast ocean interior, remains one of the key uncertainties in projecting climate change in future decades. Here, we present decadal-resolution paleoclimate reconstructions of atmospheric CO₂ and temperature to evaluate the carbon-climate coupling dynamics over an approximately 700-year time window of the middle Miocene, 16 million years ago. The middle Miocene is characterized by perturbations in the global carbon cycle caused by volcanic degassing, and global warming of about 6ºC relative to today. By analyzing fossil leaves and lipid biomarkers from the annually-varved Clarkia Lake deposit in Idaho, USA, we establish concurrent and continuous CO₂ and temperature records that capture short-term fluctuations superimposed on long-term warming and CO₂ increasing trends. Statistical analysis shows that CO₂ consistently lead temperature variation on a multi-decadal scale. Climate model emulators further confirm the role of ocean heat storage in shaping this delayed transient response. High temporal resolution reconstructions can provide constraints on Earth’s climate changes from a distant greenhouse world yet on societally relevant time scales, offering critical insights to improve our understanding of carbon-climate coupling dynamics. Such paleoclimate constraints are crucial for reducing uncertainties in projecting the near-term climate change under increasing CO₂ levels.