LONDON — From Mauritius to Manitoba, climate change is slowly moving from the headlines to the classroom. Schools around the world are beginning to tackle the difficult issue of global warming, teaching students how the planet is changing and encouraging them to think about what they can do to help slow that process.

Strapped school budgets, concerns about overburdening teachers and political opposition to what in some places is a contentious subject have complicated the spread of lessons on climate change. Nonetheless, many nations are adding or expanding such offerings, convinced that young people must learn about a phenomenon likely to have a big impact on their lives.

Schools, advocates say, can play an important role in fighting climate change by teaching young people greener habits and creating a generation of voters who will back measures to cut carbon dioxide pollution.

To slow dangerous warming, “we need an overall change of mind and a change of action that relates to everything that we think and do,” said Alexander Leicht, of Unesco, the agency overseeing the United Nations Decade of Education for Sustainable Development, which ends this year.