The fact is that our planet has had periods of cooling and warming over many many centuries obviously long before human activity could be blamed, so other factors must have been at play then, as they are now.
As we know this, obviously those same factors must play a huge part now. Solar activity is the obvious answer.
My big problem with all this is that some seem to insist that any change must be solely the fault of us when clearly this is not true.
Having said that of course it is up to all of us to do our bit, but I will not be joining the hypocrites who love to lecture the rest of us, yet still carry on driving their cars, going on holiday, heating their homes etc.