Eh hem....
From a biologists point of view (me) -
Sulfur dioxide increases cloud cover. Sulfur dioxide comes out of your car and various industrial processes. Cloud cover makes Earth reflective, temperatures drop. Carbon dioxide converts solar radiation to UV rays and traps it in the lower atmosphere, heating the surface. That's a chemical property of carbon dioxide.........not debatable. As for the carbon cycle, CO2 concentration (parts per million) has steadily increased since 1860 (measured in geological fossils), started increasing faster in 1958. It's increased about 300 ppm in the last 150 years. The atmosphere and biosphere are in equilibrium, same with the ocean and the atmosphere. This is called the carbon cycle. Old dead stuff makes it unbalanced, that's where greenhouse gas comes from. Greenhouse gas absorbs energy and radiates it back to the surface. In case you were wondering, old dead stuff would be fossil fuels.
Temperature fluctuates on this planet, it always will. This is why we don't consistently see warmer temperatures. However, since 1800 we can see evidence of ice melting easier and winter months getting shorter. As CO2 levels rise, oceanic chemistry changes (that's usually right about when a mass extinction occurs - and there's been millions of these extinctions - LINK - vertical axis = percentage extinction of genera, horizontal axis = millions of years ago). As ice caps melt -LINK - (don't argue, they've melted several times in the history of this planet), warm water moves along the oceanic conveyor to the north and cold water moves south. This trend leads to an ice age (happened 6 times in history). If present trends continue, Michigan will have the same climate as Florida in about 100 years.
So, logistical analysis - CO2 has chemical properties - more CO2 in atmosphere would warm planet due to it's chemical properties - Burning fossil fuels moves carbon out of geological sinks and into the atmosphere - A warming trend is evident - Temperature increases, air can hold more moisture, weather patterns change - Temperature alters the biomes - in history, biome change always lead to an extinction.
Will the world end soon? No, but everything I mentioned seems to always lead to the same place - extinction. That's why we should START concentrating on changing. We're just accelerating a series of natural cycles which will lead to extreme changes in our environment.