Editing IPCC:AR6/WGI/Chapter-4 (section)

=== Climate Change Commitment and Change Beyond 2100 ===

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'''Earth system modelling experiments since AR5 confirm that the zero CO''' <sub>2</sub> '''emissions commitment (the additional rise in GSAT after all CO''' <sub>2</sub> '''emissions cease) is small''' ( ''likely'' '''less than 0.3°C in magnitude) on decadal time scales, but that it may be positive or negative.''' There is ''low'' ''confidence'' in the sign of the zero CO <sub>2</sub> emissions commitment. Consistent with SR1.5, the central estimate is taken as zero for assessments of remaining carbon budgets for global warming levels of 1.5°C or 2°C. {4.7.2, 5.5.2} .

'''Overshooting specific global warming levels such as 2°C has effects on the climate system that persist beyond 2100''' ( ''medium confidence'' ''').''' Under one scenario including a peak and decline in atmospheric CO <sub>2</sub> concentration (SSP5-3.4-OS), some climate metrics such as GSAT begin to decline but do not fully reverse by 2100 to levels prior to the CO <sub>2</sub> peak ( ''medium confidence'' ). GMSL continues to rise in all models up to 2100 despite a reduction in CO <sub>2</sub> to 2040 levels. {4.6.3, 4.7.1, 4.7.2}

'''Using extended scenarios beyond 2100, projections show''' ''likely'' '''warming by 2300, relative to 1850-1900, of 1.0°C-2.2°C for SSP1-2.6 and 6.6°C-14.1°C for SSP5-8.5.''' By 2300, warming under the SSP5-3.4-OS overshoot scenario decreases from a peak around year 2060 to a level very similar to SSP1-2.6. Precipitation over land continues to increase strongly under SSP5-8.5. GSAT projected for the end of the 23rd century under SSP2-4.5 ( ''likely'' 2.3°C–4.6°C higher than over the period 1850–1900) has not been experienced since the mid-Pliocene, about 3 million years ago. GSAT projected for the end of the 23rd century under SSP5-8.5 ( ''likely'' 6.6°C–14.1°C higher than over the period 1850–1900) overlaps with the range estimated for the Miocene Climatic Optimum (5°C–10°C higher) and Early Eocene Climatic Optimum (10°C–18°C higher), about 15 and 50 million years ago, respectively ( ''medium confidence'' ). {2.3.1.1, 4.7.1}

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