(Glaciers, like those on Greenland, may experience rapid meltdown and cause sea levels to rise. Once gone glaciers won’t freeze up again. Droughts similar to that now being experienced in the southeast US may be more frequent and perhaps permanent. Populations without water to support them will have to move, never to return.)
Fortunately action could be taken immediately. Energy, of which most of it comes from carbon emitting sources, can be used more efficiently. Changing a light bulb does help.