For their study, the researchers from China, Europe and the US recorded the emissions from cement manufacturing and compared them to the amount of CO2 reabsorbed by the material over its complete life cycle, which includes normal use, disposal and recycling. They calculated that more than 76 billion tonnes of cement was produced around the world between 1930 and 2013, releasing a total of 38.2 gigatonnes of CO2 over that period.

At the same time, they discovered that 4.5 gigatonnes were gradually reabsorbed during that time frame through a process called carbonisation. This occurs when cement-based materials such as concrete and mortar absorb CO2, starting at the surface of the material – in buildings, roads and other infrastructure – and moving progressively inward, pulling in more and more carbon dioxide as years pass.

“It sounds counterintuitive, but it’s true,” said Steven Davis, associate professor of Earth system science at the University of California, Irvine, in a statement. “The cement poured around the world since 1930 has taken up a substantial portion of the CO2 released when it was initially produced.”

Although cement manufacturing is an especially carbon-intensive process and has received a lot of attention for its sizable contribution to global climate change, Davis and his colleagues argue that their research “reinforces that the leading culprit continues to be fossil fuel burning”.