Hi, it's Force Whitaker, sitting in the host seat today. Countdown is Ted's new global

initiative to accelerate solutions to the climate crisis. Countdown is about sharing new ideas

that too few of us know about and encouraging everyone to participate in initiatives that can make a difference

by taking action. We all have a stake in the future of the climate.

Now, here's the talk from the Countdown Global Launch event

given by Cement Researcher, Karen Scrivener.

Karen is a cutting-edge scientist who specializes in concrete.

She has great ideas about how to make this indispensable material

work for both the planet and for those who live on it.

You can get involved at countdown. ted.com

and hear more of these ideas by subscribing to the countdown podcast,

wherever you're listening to this.

Concrete is the second most used substance on Earth after water.

And for this reason, it has a significant environmental impact. If it were a country,

it would rank third for emissions after China and USA. But in fact, concrete is an intrinsically

low-impact material with much lower emissions of CO2 and energy per ton than other materials

like iron and steel, even things like bricks.

But because of the enormous volumes we use, overall, it contributes to about 8% of man-made CO2 emissions.

Concrete is an essential material. We need it to house people to build roads, bridges and dams,

so we can't do without it, but we can significantly reduce its carbon footprint.

Concrete is held together by cement.

And cement we use today, called Portland Cement,

...