[A-CG35] Projection and detection of global environmental change

[ACG35-P03] Quantifying committed warming from individual climate forcers based on the Simple Climate Model for Optimization (SCM4OPT)

*Xuanming Su¹, Katsumasa Tanaka^2,3, Kaoru Tachiiri¹, Michio Watanabe¹, Michio Kawamiya¹ (1.Japan Agency for Marine-Earth Science and Technology, 2.Laboratoire des Sciences du Climat et de l’Environnement, 3.National Institute for Environmental Studies)

Keywords:Simple climate model, Climate change, Committed warming

We use a simple climate model SCM4OPT v3.0 newly calibrated based on 26 Atmosphere-Ocean General Circulation Models (AOGCMs) from CMIP6. We applied a normalized marginal method to the SCM4OPT v3.0, to quantify the allowable warmings for various sources for the 2 ℃ and 1.5 ℃ climate targets. Based on the most up-to-date emission datasets, we calculated 1) temperatures resulting from emissions of the historical period of 1850-2016 (committed warming) and 2) temperatures resulting from emissions of the full period of 1850-2100 (full warming). Then we subtracted the committed warming from the full warming, to obtain the allowable warming. We computed 1) scenario uncertainties by using 161 future pathways considering various socioeconomic development levels (SSP1-5) and radiative forcing targets, and 2) climate uncertainties by emulating the behaviors of 26 AOGCMs.

The preliminary results show that the warming in 2016 is 1.19±0.30 ℃. The committed warming in 2100 is 0.88±0.25 ℃, which is dominated by CO₂. Specifically, 0.58 ℃ is caused by historical fossil fuels emissions and 0.14 ℃ by historical land use change. Historical CH₄, N₂O and fluorinated gas (F-gas) and Montreal Gas emissions are also important contributors to the committed warming, accounting for 0.06 ℃, 0.05 ℃ and 0.09 ℃, respectively, due to the relatively large contribution from historical CH₄ emissions and the relative long lifetime for N₂O and F-gas and Montreal Gas emissions. Significant cooling effects also remain, like those from sulfate aerosols and OC emissions, which contribute about -0.03 ℃ and -0.02 ℃, respectively. We will highlight the importance of the committed warming caused by various forcing sources.