Over hundreds of thousands of years, there HAVE been warm periods and periods of glaciers. Those who cite such an obvious fact as denial of the effect that billions of humans with coal & oil digging & burning and lumbering and burning and mechanized fishing...etc... can have are just wearing blinders to avoid what they don't like to think about.
   "Senator Snowball" of Oklahoma personified that attitude by his stupid confusion of "current weather where he was" to international climate.

It is complicated to prove one way or another that 'it is too late to do anything'............. but I will tell you that ANY progress in cutting back on fossil fuels and stopping the destruction of the world's rain forests and banning many pesticides and altering fishing habits....yes... and slowing population growth WILL be better than what we are doing now. IF we don't make the effort, it WILL one day be too late. I am old enough I will 'probably' not see the inevitable panic, but when Florida is half submerged and Mexico is like Saudi Arabia and penguins can barely find nesting places in Antarctica, I don't want decide how... or whether... to defend my house. My son may need to...