摘要：How sensitive is our climate system to CO2? This is a key issue in a world of rising greenhouse gas concentrations. Estimating the temperature sensitivity of the Earth to changes in atmospheric CO2 has therefore been the subject of intensive research. Yet, uncertainty in our knowledge of this sensitivity is still large—as expressed by the broad 2-4.5°C range of climate sensitivity (ΔT2x) estimates (Meehl et al., 2007). Commonly ΔT2x is defined as the equilibrium global-mean temperature change for doubling the pre-industrial CO2 concentration. The direct radiative effect is a warming by 1°C but what makes the total warming uncertain is the strength of the fast climatic feedbacks—mainly ice-albedo, water vapor, lapse rate and cloud feedback. Here, we discuss how paleo-data can be used to reduce uncertainty in the range of ΔT2x.
