CO\(_2\) concentration in the Earth's atmosphere is increasing because 50% of the annual anthropogenic emissions are retained in the atmosphere. If nations agree to reduce annual CO\(_2\) emissions by one Giga ton every year starting from 2021, then in which year will the CO\(_2\) concentration in the atmosphere stop rising due to anthropogenic emissions?
Take the anthropogenic CO\(_2\) emissions in 2020 as 40 Giga tons.