Simulated CO2 level, starting at 421.08 ppmv in 2023, and zero emissions,
based on linear relation between CO2 level and removal rate (fossil only), per:
https://sealevel.info/Global_Carbon_Budget_2023v1.1_with_removal_rate.xlsx and
https://sealevel.info/Global_Carbon_Budget_2023v1.1_with_removal_rate_plot2.png

Equilibrium CO2 level is 285.00, half-way down to that is 353.04 ppmv.
Half-life is 37.84 years, e-folding lifetime (adjustment time) is 54.59 years.
YEAR  CO2
2023  421.1
2024  418.6
2025  416.1
2026  413.7
2027  411.4
2028  409.1
2029  406.8
2030  404.6
2031  402.4
2032  400.2
2033  398.1
2034  396.0
2035  394.0
2036  392.0
2037  390.0
2038  388.1
2039  386.2
2040  384.4
2041  382.6
2042  380.8
2043  379.0
2044  377.3
2045  375.6
2046  373.9
2047  372.3
2048  370.7
2049  369.1
2050  367.6
2051  366.1
2052  364.6
2053  363.1
2054  361.7
2055  360.3
2056  358.9
2057  357.6
2058  356.2
2059  354.9
2060  353.7
** date 2060.8: One half-life (37.8 years) reached **
2061  352.4
** 353.0 ppmv: half of the 136.1 ppmv CO2 above equilibrium is gone **
2062  351.2
2063  350.0
2064  348.8
2065  347.6
2066  346.4
2067  345.3
2068  344.2
2069  343.1
2070  342.1
2071  341.0
2072  340.0
2073  339.0
2074  338.0
2075  337.0
2076  336.1
2077  335.1
** date 2077.6: e-folding life (54.6 years) and level (335.06 ppmv) reached **
2078  334.2
2079  333.3
2080  332.4
2081  331.6
2082  330.7