State dependence of CO2 forcing and its implications for climate sensitivity

• 成果类型: Article
• 署名作者: He, Haozhe; Kramer, Ryan J.; Soden, Brian J.; Jeevanjee, Nadir
• 署名单位: University of Miami; University System of Maryland; University of Maryland Baltimore; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; National Oceanic Atmospheric Admin (NOAA) - USA; Princeton University; National Oceanic Atmospheric Admin (NOAA) - USA
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-13095
• DOI: 10.1126/science.abq6872
• 发表日期: 2023-12-01
• 页码: 1051-1056
• 关键词: model intercomparison project; experimental-design; uncertainties; cmip5

摘要

When evaluating the effect of carbon dioxide (CO2) changes on Earth's climate, it is widely assumed that instantaneous radiative forcing from a doubling of a given CO2 concentration (IRF2xCO2) is constant and that variances in climate sensitivity arise from differences in radiative feedbacks or dependence of these feedbacks on the climatological base state. Here, we show that the IRF2xCO2 is not constant, but rather depends on the climatological base state, increasing by about 25% for every doubling of CO2, and has increased by about 10% since the preindustrial era primarily due to the cooling within the upper stratosphere, implying a proportionate increase in climate sensitivity. This base-state dependence also explains about half of the intermodel spread in IRF2xCO2, a problem that has persisted among climate models for nearly three decades.