The Paris Agreement calls for emissions reductions to limit climate change, but how will the carbon cycle change if it is successful? The land and oceans currently absorb roughly half of anthropogenic emissions, but this fraction will decline in the future. The amount of carbon that can be released before climate is mitigated depends on the amount of carbon the ocean and terrestrial ecosystems can absorb. Policy is based on model projections, but observations and theory suggest that climate effects emerging in today's climate will increase and carbon cycle tipping points may be crossed. Warming temperatures, drought, and a slowing growth rate of CO2 itself will reduce land and ocean sinks and create new sources, making carbon sequestration in forests, soils, and other land and aquatic vegetation more difficult. Observations, data-assimilative models, and prediction systems are needed for managing ongoing long-term changes to land and ocean systems after achieving net-zero emissions. ▪International agreements call for stabilizing climate at 1.5° above preindustrial, while the world is already seeing damaging extremes below that.▪If climate is stabilized near the 1.5° target, the driving force for most sinks will slow, while feedbacks from the warmer climate will continue to cause sources.▪Once emissions are reduced to net zero, carbon cycle-climate feedbacks will require observations to support ongoing active management to maintain storage.

中文翻译：

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碳循环——后巴黎世界的气候反馈


《巴黎协定》呼吁减少排放以限制气候变化，但如果成功，碳循环将如何变化？陆地和海洋目前吸收了大约一半的人为排放物，但这一比例在未来会下降。在气候缓解之前可以释放的碳量取决于海洋和陆地生态系统可以吸收的碳量。政策基于模型预测，但观察和理论表明，当今气候中出现的气候影响将会增加，可能会跨越碳循环临界点。气温变暖、干旱以及二氧化碳本身增长速度放缓将减少陆地和海洋汇并创造新的来源，使森林、土壤和其他陆地和水生植被的碳封存变得更加困难。在实现净零排放后，需要观测、数据同化模型和预测系统来管理陆地和海洋系统的持续长期变化。▪国际协议要求将气候稳定在比工业化前高 1.5 °C，而世界已经看到低于该水平的破坏性极端事件。▪如果气候稳定在 1.5 °C 目标附近，大多数汇的驱动力将减慢，而来自气候变暖的反馈将继续成为来源。▪一旦排放量减少到净零，碳循环-气候反馈将需要观测以支持持续的积极管理以维持储存。