I don't worry about global warming or any other threat whose most important effects are several decades out. Technology is going to change everything by then: either we'll kill ourselves in more immediate ways, or at least destroy most of civilization (which would do a lot to reduce carbon emissions!) --- or we'll make a lot more technological progress, probably developing brain uploading, strong AI, or other game-changing capabilities we can't forsee yet. Probably the former.
People who worry about what will happen when the sun burns out in five billion years are the worst.