How Land Carbon Dynamics Shape the Rise and Fall of Atmospheric CO2

PostPeak tackles the pressing questions surrounding Earth's transition into a post-peak CO2 era. The carbon cycle determines how much of the anthropogenic carbon stays in the atmosphere, and warms the planet. It will also shape the trajectory of atmospheric CO2 once emissions level off, with lingering legacy and hysteresis effects.I hypothesize the land carbon cycle is the key modulator in this transition, and accurately predicting its dynamics is essential for understanding how the entire climate system will respond to declining CO2 emissions. Despite decades of research, the myriad factors underlying land carbon dynamics remain poorly understood, and uncertainty prevails.To address this knowledge gap, the project PostPeak introduces a fundamentally new approach to global land carbon modeling, embedded in Earth system models. The approach capitalizes on the rapidly growing body of Earth observations and machine-learning algorithms, guided by process understanding. Using this hybrid model, we can explore the full range of plausible land dynamics, constrained by multi-stream observations, and provide a robust framework for addressing key questions about the post-peak era. Specifically, PostPeak's research aims to: (i) elucidate the spectrum of land dynamics adhering to global observational constraints; (ii) quantify the resulting spill-over effects into the post-peak emission era; (iii) determine how these dynamics modulate the timing and nature of falling CO2 levels; and (iv) identify where and how hysteresis effects impact ecosystems when CO2 is falling.The liaison of AI-powered land carbon dynamics and versatile Earth system modeling in PostPeak, promises a leap forward in climate-carbon system science and provides an unique opportunity to clarify the land carbon cycle's pivotal role in shaping the rise and fall of atmospheric CO2.