A New 66 Million-Year History of Carbon Dioxide Offers Little Comfort for Today


The international study, reconstructing 66 million years of climatic history, suggests that global temperatures could be even more responsive to carbon dioxide levels than current models estimate. This analysis also highlights the enduring effects of greenhouse gases. The findings have the potential to shape future climate policies.

This study on the history of carbon dioxide (CO2) over 66 million years comes at a crucial time as the world faces an unprecedented climate crisis with more frequent extreme weather events. An international group of more than 80 scientists conducted this thorough study to shed new light on historical CO2 levels and their relationship with terrestrial temperatures.

By tracing the evolution of CO2 from the era of dinosaurs to the present day, it provides crucial insights not only into the Earth’s climatic history but also into the profound and potentially lasting impact of human activities on our climate. Published in the journal Science, the results indicate that the global climate may be more responsive to CO2 levels than current models suggest.

A Historical Perspective on CO2

Examining data dating back up to 66 million years, the reconstruction reveals that current CO2 levels, primarily attributed to human activity, are comparable to those observed 14 million years ago. This finding partially challenges previous assessments of CO2 evolution.

To reach these conclusions, researchers analyzed diverse and intricate data. They particularly scrutinized air bubbles trapped in ice cores, providing a direct record of the past atmosphere as well as the chemistry of ancient soils and oceanic sediments. These various data sources facilitated the construction of a detailed curve of CO2 levels over an exceptionally long period, unveiling trends and variations that were previously overlooked or poorly understood.

The implications of this study are profound and somewhat alarming. The results suggest that for each doubling of CO2 concentration in the atmosphere, the Earth’s average temperature may rise by 5 to 8 °C. This estimation significantly surpasses prior predictions, indicating a much higher climate sensitivity to greenhouse gases than current models suggest. This realization underscores the importance of the long-term effects of CO2 emissions, which could induce lasting and profound climate changes extending over millennia.

Consequences for the Ecosystem and Climate Policy

The study highlighted a direct link between historical increases in CO2 and the warmest periods on Earth. A striking example is approximately 50 million years ago, when CO2 levels soared to 1600 parts per million (ppm), well beyond current levels. Global temperatures during this time period, known as the Eocene, were 12 °C higher than they are today. This correlation underscores the significant influence of greenhouse gases on the Earth’s climate.

Importantly, these CO2 fluctuations not only impacted the climate but also had major repercussions on ecosystems. During these warm periods, the distribution of plants and animals underwent drastic changes, with the emergence of new species and the extinction of others. These ecological changes reflect how climate variations can profoundly reshape biodiversity and ecosystems.

The implications of this study go beyond a mere historical understanding of the climate and extend to contemporary climate policies. Although the study does not provide specific predictions for the temperatures of the year 2100, it enlightens policymakers on the potential long-term consequences of current CO2 levels.

Researchers hope that this study will serve as a solid foundation for future climate models. By incorporating these robust observations, scientists can better comprehend the processes operating at different temporal scales.

The authors emphasize the importance of considering the cascading effects of greenhouse gases, which could persist for millennia. This long-term perspective is crucial for developing effective climate strategies. It also underscores the need to act swiftly to reduce CO2 emissions to limit impacts on ecosystems. By highlighting the close relationship between CO2 levels and large-scale climate and ecological changes, this study reinforces the argument for ambitious and immediate climate action.