Earth’s energy budget, climate feedbacks, and climate sensitivity

doi:10.12006/j.issn.1673-1719.2021.191

Abstract

Abstract:

This work extracts the chapter seven of the IPCC AR6 working group I on the Earth’s energy budget, climate feedback, and climate sensitivity, and gives a concise summary on the new findings and conclusions on the topic. AR6 suggests that the effective radiative forcing (ERF) from anthropogenic activity over the industrial era is 2.72 [1.96-3.48] W/m². Changes in well-mixed greenhouse gases and aerosols contribute to the total anthropogenic ERF with 3.32 [3.03-3.61] W/m² and -1.1 [-1.7--0.4] W/m², respectively. The net climate feedback parameter is assessed to be -1.16 [-1.81--0.51] W/(m²∙℃), and clouds remain the largest contribution to overall uncertainty in climate feedbacks. Equilibrium climate sensitivity (ECS) and transient climate response (TCR) are effective measures that can be used to assess the response of global mean surface air temperature to forcing factors. The best estimates of ECS and TCR are 3.0 [2.0-5.0]℃ and 1.8 [1.2-2.4]℃, respectively.

Key words: Effective radiative forcing (ERF), Climate feedback, Equilibrium climate sensitivity (ECS), Transient climate response (TCR)

ZHANG Hua, WANG Fei, ZHAO Shu-Yun, XIE Bing. Earth’s energy budget, climate feedbacks, and climate sensitivity[J]. Climate Change Research, 2021, 17(6): 691-698.

Figures/Tables 5

Fig. 1 Schematic representation of the global mean energy budget of the Earth under all-sky and clear-sky conditions at the beginning of the 21st century [5]. (Numbers indicate best estimates for the magnitudes of the globally averaged energy balance components together with their counterparts under clear-sky conditions)

Fig. 2 Change in effective radiative forcing for different factors from 1750 to 2019 [5](Uncertainty ranges of 5%-95% confidence range are also given)

Fig. 3 Contributions from different forcing factors to the global mean surface air temperature change from 1750 to 2019 [5]. (Uncertainties of 5%-95% confidence range are also given as shades)

Table 1 Synthesis assessment of climate feedbacks [5] W/(m2∙℃)

Table 2 Summary of equilibrium climate sensitivity (ECS) and transient climate response (TCR) assessment [5] ℃

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