The science of causality is an art of probability. For example, there are few scientists who will say "Smoking will kill you," but it's widely known that smoking will increase your probability of getting cancer or myriad other cardio-respiratory disorders. You might smoke 3 packs a day and live to be 100, but it's far less likely than if you quit smoking, ate right, and excercised.
Anthropogenic (people-caused) climate change is no different. We can't predict fully what the effects of dumping gigatons of carbon into our atmosphere will ultimately be because we don't yet fully understand how the climate functions. But just like you can't predict in your twenties whether those two packs a day will kill in your 50s or in your 90s, the correlation between smoking and illness, or the greenhouse gases we release and climate change, is strong enough to suggest that the most prudent option for our health would be to quit. Similarly, if people produce pollution, the prudent option is to stabilize population in the U.S. an in the world at large.
But consider that most of these fossil fuels are from ancient life. We know that the world was significantly warmer in the past, based on evidence of fossil fuels at the polar regions, suggesting that life was once abundant in these frigid extremes. We also know, based on geological evidence, that the atmosphere was much richer in carbon dioxide in those ages, as much as 6 times more carbon, suggesting a correlation between temperature and atmospheric carbon dioxide concentrations. It stands to reason, then, that if the fossil fuels we are burning now are essentially composed of that ancient atmospheric carbon, coverted to organic matter by photosynthesis before being trapped in sediment and fossilized into fossil fuels, then we are basically taking all that stored carbon and putting it back in our atmosphere.
The fact is, we don't really know exactly what this will do to our planet. But we do know, from the fossil evidence, that there is a definite link between carbon dioxide concentration and climate: historically, the more CO2, the higher the average global temperature.
Is this a hypothesis we really want to test?
Working for logical immigation reform based on a stable population, a recognition of the finite nature of our natural resources and the adverse impact of continued growth on our quality of life, standard of living, national interest, character, language, sovereignty and the rule of law. Pushing back and countering the disloyal elements in American society and the anti-American rhetoric of the leftwing illegal alien lobbies. In a debate, when your opponents turn to name calling, it's a good sign you've already won.