Trouble is the natural order of things. And, despite what many want us to believe, mankind is not an enemy of nature, mankind is very much a part of nature.
This is very true. The problem is that our effect on nature has changed. For the vast majority of our time on Earth, humans were relatively rare, and as hunter-gatherers, we didn't impact climate any more then many other species.
However, even then we had some profound effects. A lot of people see evolution as what the environment imposes on organisms, which is true enough, but they don't understand that organisms also change environments. The "wolves change rivers" story is too simplified to be true; the increase in bears preying on elk also led to a reduction in the herds, and the beginning of recovery for many tree species, and climate change had a role. But we see all sorts of organism-caused climate changes.
The big deal is that we now do it on an industrial scale that dwarfs anything humans have ever done before. So where the Mesopotamians managed to mess up Iraq with careless irrigation that led to saline buildup and desertification, or where the Romans turned Israel into a desert with clear-cutting forests, we can now affect climate on a global scale.
And it's an experiment we've never done before. Some things are predictable, and some yet aren't. But it's generally not good, even if there are some areas that will actually get better for us; most will get worse.
It's not what we'd like to hear, but it's true.
