If definitive proof of climate change's severity was found, how should the world's leaders respond?

It already has been found, but the current goal should be to sever the ties of fossil fuel lobbyists from government, and work towards researching as many new technologies as possible to help fix it. We need to adopt an “all-green alternatives” approach to move away from fossil fuels, reduce fossil fuel use in the energy sector, work for alternatives in other industries, reduce emissions caused by deforestation, forest fires, or farmlands.