Those who say Global Warming is nonsense is right in the sense that we will probably not see any significant threat to our civilization within a couple of decade, but global warming isn't something that you could stop overnight, even if the human civilization stop emitting all greenhouse gases right now, it would still take us around half a century to counteract what we have been emitting. By the time global warming becomes too obvious to ignore, it would be too late and we wouldn't be able to do anything about it.