Impact of Cumulated CO2 Emission on Air Temperature: Millennial-Scale Prediction

Abstract:

To comprehensively understand the impact of atmospheric CO₂ on air temperature, it is necessary to discuss about climate change by embracing attention to internal variability. However, the existing studies relevant to future prediction basically having century-scale analyses due to computational load problem, we remained in discussion about the transient change of earth system. This study demonstrated a comprehensive effect of CO₂ (including both external and internal variability), by a millennial-scale global warming prediction with the simplified-type earth system model. As a result, during initial 1000 years CO₂ emission had a positive influence in temperature in long-term, and in atmospheric CO₂ in short-term. The difference of response time was caused by latent heat (the delay of oceanic response to CO₂ emission). In the quasi-steady state, higher cumulated CO₂ emission encourages more independence of relationship between temperature and atmospheric CO₂. It revealed that there might be a definite limitation to effectiveness for global warming caused by the CO₂ emission in millennial scale. As future work of the global warming prediction, by collaborating with paleoclimatic studies, we need to figure out new mechanism leading to tipping point of earth system, especially an undescribed feedback system that provokes an irreversible change, while confirming a consistency of the model study with paleoenvironmental studies (e.g., paleoclimatic indicator, model, record) as clue for comprehending the high-priority process.