The notion that we are incapable of impacting the environment is psychosis. It is a very well established fact that all organisms impact the environment they reside.
Humans live in the global environment now, so we impact them all, even our much needed oceans. Changes to the environment do impact the climate of said environment as well, this is another undeniable fact.
Now, let's go back many millions of years ago to the last species to alter the global environment as much as we do. The reason I say it like that is because it's not the changes that pose a threat, it's the amount of change without a counter balance.
The dinosaurs are a large collection of species which altered the global environment in one way so drastically that their dietary system became imbalanced. We are causing more change than they did, our technology has slowed the impact on ourselves but we have done nothing to stop it.
Their ecosystem became so imbalanced that most of their species were extinct long before the cataclysm that wiped out all but a handful. We can expect the same result, if we do nothing then a single cataclysmic event will wipe us out simply because we will have no stable ecosystems to rely on for food.
To complicate matters, our impact is causing the climate to destabilize, returning the Earth to a state in which modern life cannot survive. When the planet first formed, the climate was very chaotic, and nothing today evolved until after it had been stabilizing for billions of years.
This is why climate change is really important, if we do not change our ways, the changes we cause to the environment will cause our extinction. This is undeniable, observable, and repeated fact.