The Earths environment has always been in a constant state of change, according to geographic theory the Earths modern atmosphere is probable the fourth general atmosphere of Earths history. However, there is absolutley NO question that human activity is forcing the pace of change to this Earths atmosphere at a rate that is unsustainable & irreversable. The Earth though will continue to exist long after we've gone, just not with life now as we know it.
The thing with Global Climate Change is that it causes such extreme & irratic weather patterns that are off the charts in terms of past trends. Remember too that we've only been recording temperature averages & extreme weather events since something like 1880, which is a little while after industrialisation processes began. You don't have 95% of the worlds exclusive scientists getting up & screaming for no reason. And likewise 162 industrialised countries signing up to ratify a protocol to reduce emissions. What we have isn't really a "sleeper" situation anymore. Since 1998 extreme weather events & rapid changes in weather cycles have increased exponentially. Not to mention the melting of millions of year old glaciers, permafrost & ice sheets, and the subsequent rise in sea level & sinking of Islands in the Pacific. Being the likely result of a 2.5degreC temperature increase in the peninsula region during the last 50years. Remember too that when the IPCC forecasts a conservative estimate that sea levels will rise at sometime like .50m over this century, it might not sound like much, but we're talking about here is mega mega tonnes of water, considering the Earths land mass is over 70% ocean. Add to all that noticeable migation of plant & animal species to higher altitudes and places they've never before been seen.
Think about the Earths atmosphere in tangible terms, the Earths resources are finite remember, and is one giant self-contained system. There's no where for excess water to go, or for that matter for the mega tonnes of carbons & pollutants that we pump into the atmosphere that are causing what scientists are calling a Greenhouse Effect. Pure logic alone in this regard must dictate that human activity is having a profound effect on earths living systems.
I suggest doing some extra reading around the subject might help: