A concrete fact

Usually it's a place like the Harper's Index where I find some oh-my-gosh statistic, but this gem came out of the recent issue of Architectural Record:

Concrete is the most widely manufactured material, with nearly three tons produced each year for each of the earth’s inhabitants. Architects value concrete for its durability, compressive strength, versatility, and expressive possibilities. However, production of cement, the fundamental ingredient in concrete, accounts for 5 percent of man-made carbon dioxide (CO2) emissions globally, according to the cement-sustainability initiative, a group of international manufacturers.

.... a hidden cost that may not show up in the plans or on the bill. The article goes on to outline industry initiatives to reduce the environmental footprint of the material's production.