Terrestrial ecosystems play a crucial role in the global carbon cycle and climate feedbacks. Recent evidence suggests that these ecosystems may provide a positive feedback in a warming world, though the magnitude is uncertain. Terrestrial ecosystems influence the global carbon cycle by absorbing or releasing greenhouse gases like CO₂, methane, and nitrous oxide, and by controlling energy, water, and momentum exchanges between the atmosphere and land. These ecosystems are subject to climate feedbacks that can amplify or dampen climate change. The carbon cycle-climate feedback is particularly significant, as large amounts of carbon are stored in vegetation and soil. The carbon balance of an ecosystem is the difference between carbon gains and losses, primarily through photosynthesis and respiration. Quantifying these feedbacks is challenging due to limited understanding of carbon and nutrient processes in ecosystems. Empirical evidence shows that terrestrial ecosystems respond to climate variations, as seen in the interannual variations in atmospheric CO₂ growth rates linked to El Niño-Southern Oscillation. However, these short-term responses may not hold over longer timescales. Long-term correlations between atmospheric CO₂, methane, and nitrous oxide and global climate indicate that ecosystem-climate interactions operate on millennia timescales. However, empirical evidence for feedbacks on the timescale of current climate change (decades to centuries) is limited, necessitating the use of coupled carbon-cycle-climate models. These models show varied responses, with some indicating terrestrial CO₂ sequestration in the early industrial era but a decrease as the world warms. Some models even suggest terrestrial ecosystems becoming a source of CO₂, amplifying climate change. The fundamental assumption in these models is that photosynthesis and respiration can be analyzed separately, but recent evidence suggests these processes are interconnected, complicating predictions. Other factors, such as water availability, nitrogen, light, and air pollutants, also influence ecosystem carbon dynamics. Climate variability and extremes, such as the 2003 European heatwave, can significantly impact carbon balance. Nonlinear feedback loops, such as permafrost thaw and microbial priming, may enhance carbon release, potentially leading to stronger feedbacks than currently predicted. The interaction between carbon and nitrogen cycles also plays a role in ecosystem responses to climate change. Overall, the picture of a gradual increase in CO₂ and temperature needs to be replaced by a multifactor view, considering complex interactions and environmental variability. Current models may underestimate the potential for carbon sequestration and highlight the vulnerability of soil carbon. Future research should integrate long-term experiments with observations and models to better understand these complex interactions.Terrestrial ecosystems play a crucial role in the global carbon cycle and climate feedbacks. Recent evidence suggests that these ecosystems may provide a positive feedback in a warming world, though the magnitude is uncertain. Terrestrial ecosystems influence the global carbon cycle by absorbing or releasing greenhouse gases like CO₂, methane, and nitrous oxide, and by controlling energy, water, and momentum exchanges between the atmosphere and land. These ecosystems are subject to climate feedbacks that can amplify or dampen climate change. The carbon cycle-climate feedback is particularly significant, as large amounts of carbon are stored in vegetation and soil. The carbon balance of an ecosystem is the difference between carbon gains and losses, primarily through photosynthesis and respiration. Quantifying these feedbacks is challenging due to limited understanding of carbon and nutrient processes in ecosystems. Empirical evidence shows that terrestrial ecosystems respond to climate variations, as seen in the interannual variations in atmospheric CO₂ growth rates linked to El Niño-Southern Oscillation. However, these short-term responses may not hold over longer timescales. Long-term correlations between atmospheric CO₂, methane, and nitrous oxide and global climate indicate that ecosystem-climate interactions operate on millennia timescales. However, empirical evidence for feedbacks on the timescale of current climate change (decades to centuries) is limited, necessitating the use of coupled carbon-cycle-climate models. These models show varied responses, with some indicating terrestrial CO₂ sequestration in the early industrial era but a decrease as the world warms. Some models even suggest terrestrial ecosystems becoming a source of CO₂, amplifying climate change. The fundamental assumption in these models is that photosynthesis and respiration can be analyzed separately, but recent evidence suggests these processes are interconnected, complicating predictions. Other factors, such as water availability, nitrogen, light, and air pollutants, also influence ecosystem carbon dynamics. Climate variability and extremes, such as the 2003 European heatwave, can significantly impact carbon balance. Nonlinear feedback loops, such as permafrost thaw and microbial priming, may enhance carbon release, potentially leading to stronger feedbacks than currently predicted. The interaction between carbon and nitrogen cycles also plays a role in ecosystem responses to climate change. Overall, the picture of a gradual increase in CO₂ and temperature needs to be replaced by a multifactor view, considering complex interactions and environmental variability. Current models may underestimate the potential for carbon sequestration and highlight the vulnerability of soil carbon. Future research should integrate long-term experiments with observations and models to better understand these complex interactions.