You keep acting like this is all decided though, and it's not on either side.
Some things are decided. It IS warming. I think most people agree with that, but some skeptics will argue as if it isn't one moment, and then say it is due exclusively to natural causes the next (see gsvol). Obviously, it can't be both and that is a contradictory position.
CO2 emissions by humans ARE unprecedented in geologic history. Nothing else on Earth ever pumped out fossil fuels and combusted them into the atmosphere on a global scale for hundreds of years (or even on a local scale for one day) before people.
CO2 IS a greenhouse gas. Always has been, always will be due to it's chemical structure.
CO2 IS at it's highest levels in human history, and in the last several million years. To put it into perspective, the Himalayas didn't exist yet, India was an island subcontinent, and the Red and Mediterranean Seas didn't exist either. This matters because the arrangement of continents and oceans/seas factors mightily into climate and climate patterns.
Man IS the reason why CO2 is elevated.
Now, all those known things combine to paint a picture. On top of that, we live in a fully settled and occupied world with by far the largest human population in history that is growing all the time. Disruptions to the development of food, the availability of water, and ecosystems that people depend on for these things will undoubtedly lead to human suffering and death. Natural disruptions already lead to this as it is. Also, the large amount of people on the Earth puts strain on natural environments and ecosystems.
as far as the natural world:
What was once unbroken rainforest (for example) for thousands of square miles in parts of the world are now fractured islands of trees only a few hundred square miles in size. Populations of animals and plants no longer pass freely from one area to another, and are isolated. This reduces the ability of populations to recover from natural events like disease, fire, too many predators, whatever. We've put all of nature's eggs in small baskets of preserves, parks, and marginal land areas that just weren't very good for human settlement (badlands), and now are pushing on the climate. Those species can't just move into new areas that have become more suitable, or are still suitable for them. They're stuck. Ecological collapse would then ensue.