There's a game of Tetris happening on a global scale: The playing space is planet Earth, and all those pesky, stacking blocks represent carbon dioxide- a greenhouse gas that is piling up ever more rapidly as we burn the fossil fuels that run our cars, factories and power plants. Joss Fong outlines how this overload of CO2 leads to climate change and reminds us that, unlike Tetris, we won't get an opportunity to start over and try again.