The FAQ has addressed these issues.
I, personally, believe that Global Warming is a simple cycle of our planet. Since we only have accurate temperature records relatively recently, its very hasty in my opinion to be concluding that this is an unnatural problem. (*glares at The Day After Tommorow*)
I do, however, believe that air-quality is a problem. If the amount of carbon-dioxide increases in our air, there could be substantial problems to our health.