The article explores the relationship between greenhouse warming and carbon-cycle dynamics through the lens of early Cenozoic history. It highlights that past episodes of greenhouse warming provide insights into how climate and the carbon cycle interact, which can help predict future consequences of continued carbon emissions. By 2400, if emissions continue unabated, humans could release about 5,000 Gt C into the atmosphere, leading to a significant increase in atmospheric CO₂ levels, which would have severe impacts on ocean pH and carbonate ion concentrations. The study emphasizes the importance of understanding feedback mechanisms that could amplify or moderate greenhouse gas concentrations, such as ocean overturning and weathering processes. The Cenozoic era, the last 65 million years, offers a valuable historical context for studying these interactions. During this time, greenhouse gas concentrations were much higher, leading to warmer global temperatures and little or no ice at the poles. The Early Eocene Climatic Optimum (EECO) is a notable example, where CO₂ levels were high and global temperatures reached a long-term maximum. The PETM, a significant hyperthermal event, saw a rapid increase in global temperature and massive carbon input, with evidence of ocean acidification and deep-sea carbonate dissolution. The sources of these carbon injections remain uncertain, but they could include deep-seated rocks, methane release from gas hydrates, or oxidation of organic matter. The hyperthermals occurred over short timescales, allowing researchers to study Earth-system dynamics. These events show characteristics of positive feedbacks that accelerated warming before negative feedbacks restored the carbon cycle to a steady state. The study also discusses the importance of understanding feedback mechanisms in predicting future climate responses. The ocean plays a crucial role in absorbing carbon, but warming and freshening of surface waters can slow this process. The PETM provides insights into the long-term fate of carbon emissions, showing that atmospheric CO₂ levels do not return to pre-industrial values but stabilize at higher levels. The study highlights the need for further research into these feedbacks to improve climate models and predictions.The article explores the relationship between greenhouse warming and carbon-cycle dynamics through the lens of early Cenozoic history. It highlights that past episodes of greenhouse warming provide insights into how climate and the carbon cycle interact, which can help predict future consequences of continued carbon emissions. By 2400, if emissions continue unabated, humans could release about 5,000 Gt C into the atmosphere, leading to a significant increase in atmospheric CO₂ levels, which would have severe impacts on ocean pH and carbonate ion concentrations. The study emphasizes the importance of understanding feedback mechanisms that could amplify or moderate greenhouse gas concentrations, such as ocean overturning and weathering processes. The Cenozoic era, the last 65 million years, offers a valuable historical context for studying these interactions. During this time, greenhouse gas concentrations were much higher, leading to warmer global temperatures and little or no ice at the poles. The Early Eocene Climatic Optimum (EECO) is a notable example, where CO₂ levels were high and global temperatures reached a long-term maximum. The PETM, a significant hyperthermal event, saw a rapid increase in global temperature and massive carbon input, with evidence of ocean acidification and deep-sea carbonate dissolution. The sources of these carbon injections remain uncertain, but they could include deep-seated rocks, methane release from gas hydrates, or oxidation of organic matter. The hyperthermals occurred over short timescales, allowing researchers to study Earth-system dynamics. These events show characteristics of positive feedbacks that accelerated warming before negative feedbacks restored the carbon cycle to a steady state. The study also discusses the importance of understanding feedback mechanisms in predicting future climate responses. The ocean plays a crucial role in absorbing carbon, but warming and freshening of surface waters can slow this process. The PETM provides insights into the long-term fate of carbon emissions, showing that atmospheric CO₂ levels do not return to pre-industrial values but stabilize at higher levels. The study highlights the need for further research into these feedbacks to improve climate models and predictions.