As part of the summit, hundreds of schools across the country are signing up to the Let's Go Zero activity, aiming to become carbon-zero by 2030.

Carbon-zero schools are ones that promise to stop emitting carbon in seven areas, including where they get their food and how they use water and recycle their waste.

They agreed to cut carbon emissions from shipping by 40 percent by 2030. And by 2050, they expect zero carbon shipping.