No one knows what the effects of various emissions are. Scientists build computer models and run simulations based on various assumptions. Some of those computer models predict things like a 15 foot rise in oceans over the next 10 years and those scientists get truckloads of money delivered to them to continue their research. Some models show a negligable effect or even a positive effect in the form of preventing the next glaciation cycle (ice age, if you will - although we're still in one) and those scientists get tarred and feathered by their numerous detractors as tools of "big oil".
The money, by the way, comes primarily from various groups who use "climate change" or "global warming" or "environmentalism" as an excuse to promote their anti-globalization, anti-technology, anti-human socialist agenda. THEY get the money from well-meaning but ultimately foolish people who believe as gospel the pronouncements of the research that suits their agenda; what we might call "useful idiots". Just be sure to do everything they say and everything will be allright: sort your plastic, trade in your safe, comfortable car for a moped, live in a thach hut with no electricity, or if at all possible just kill yourself now, you vile parasite.
Al Gore goes on and on about this subject - I figure when he stops using more electricity in a month than most households use in a year and stop flying around in private jets to promote his agenda - when HE starts *acting* worried, then I'll consider worrying. Until then, based on the actual lifestyles of all of the big "environmentalism" boosters, I'm going to assume it's not an actual problem.
I'll just add that we all want our environment to be clean and free of toxic pollutants. The more wealthy a country is, the more it can focus its surplus energies and resources on such problems. So promoting free trade and the advancement of technology would be the best approach to increasing the resources available to make things ever cleaner. 99% of all species that have ever existed have gone extinct and yet various greenies would have us prevent the extiction of any life form from now on. Assuming that could even be accomplished by some advanced civilization, it wouldn't be "natural" at all - it would be a garden. But it seems like a lot of the leadership in the environmental movement ascribe to an agenda that would have an effect opposite their stated goals - making everyone (but them) poorer and more obedient to an enviro-priesthood (them, again). If you want a real example of a made-up hazard being used by modern-day facists to seize control of state apparatus, look no further than the environmental movement.