researchers concluded that elevated atmospheric CO2 actually reduces plant growth when combined with other likely consequences of climate change - namely, higher temperatures, increased precipitation or increased nitrogen deposits in the soil.

Notice that the increase in CO2 is "combined with...higher temperatures, increased precipitation, or increased nitrogen deposits in the soil..." Hardly proof of your delightful theory.

In fact, I, Dr. Science, am well aware that CO2 is created naturally, and is an important part of our atmosphere. People like you, who have an agenda, don't bother actually reading germane material to the discussion, you grab headlines (linked on your favorite socialist site), read the first sentence or two, and think that you have a case. You have nothing.

The dangerous gas that comes out of automobiles is Carbon MONOxide. It's what people use to commit suicide (when they start their car in the garage and fall asleep). It's dangerous in highly concentrated levels.

Carbon dioxide, on the other hand, is NECESSARY to life on planet earth. Take a look at this quote, Doonesbury:

Carbon dioxide is produced by all animals, plants, fungi and microorganisms during respiration and is used by plants during photosynthesis. This is to make sugars which may either be consumed again in respiration or used as the raw material for plant growth. It is, therefore, a major component of the carbon cycle. Carbon dioxide is generated as a byproduct of the combustion of fossil fuels or vegetable matter, among other chemical processes. Inorganic carbon dioxide is output by volcanoes and other geothermal processes such as hot springs.

Note the phrase "VEGETABLE MATTER." Sounds like a renewable energy source. Notice too that volcanoes and hot springs also create CO2, and usually at levels far higher than automobiles.