The grauniad has an article in the IT section about “A cracking alternative to cement”. They claim that cement is 10% of anthro CO2 (or 5-10% lower down; although that includes asphalt, which for some reason counts as cement based. Odd) is from cement. That didn’t fit with my memories.
So I dig out the trusty IPCC report and find maximum in 1997 of 6.6 PgC/yr (0.2 PgC/yr of this was from cement production) which is about 3%. Of course, being a newspaper the grauniad (all together now…) doesn’t bother cite a source for its data, so its hard to check up. Maybe things have changed dramatically since 1997? But I doubt it.
Anybody lese got any values? Couldn’t find them in the AR4 😦