A few sources:
https://www.noaa.gov/news-release/carbon-dioxide-now-more-th...
https://www.nature.com/articles/s41586-019-1543-2?proof=t
https://www.science.org/doi/10.1126/science.1233137
https://royalsocietypublishing.org/doi/10.1098/rsta.2012.029...
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200...
EDIT: Fix words.