Since NOAA/ESRL Has No Monthly Updates Since February On Their Landing Page, CO2 Data Averaged From Weeklies

Disclaimer: This is going to be, of necessity, kind of crude, but it's better than nothing, I guess.

PPM Week Beginning March 1st 2026
429.62
PPM Week Beginning March 8 2026
429.91
PPM Week Beginning March 15 2026
429.46
PPM Week Beginning March 22 2026
430.93

March average PPM less data for March 29-31
429.98

PPM Week Beginning March 29 2026
431.73
PPM Week Beginning April 5 2026
431.88
PPM Week Beginning April 12 2026
429.80
PPM Week Beginning April 19 2026
431.15

April average including March 29-31, pending April 26-30
431.14

Weekly data: https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_weekly_mlo.txt
ESRL Global Monitoring trace GHG landing page: https://gml.noaa.gov/ccgg/trends/