I added up the 2023 numbers from here: https://ourworldindata.org/grapher/cumulative-co-emissions?t...

You must have made a mistake in doing that. If you add “world” to the selection, Our World in Data adds them up for you, and you only have to divide 27253/181000. That gives you 0.1506, very close to 15%.

https://ourworldindata.org/grapher/cumulative-co-emissions?t...

Oops. You're very right. Math error on my part :( thank you for the correction.