Interestingly, I've also concluded that climate change skeptics are actually a boon to climate scientists. Their consistent questioning helps bring attention, interest, and even intrigue to discourse that might otherwise tend toward dry fact. And their analyses provide ready-made hypotheses to test for young graduate students. However, after considering their claims and scientist's responses, I can not doubt that the best available science indicates humans are modifying a continually changing climate at unprecedented rates. The climate is warming, and more and more of that change is attributable to humans.
However persuasive the evidence may be, it can also be overwhelmingly complex; the important point to remember is that we are having a significant effect on the environment. But you don't need 10,000+ dedicated and careful scientists to tell you that. Climate change skeptics start from a disbelief that humans could modify something as large as the entire Earth ecosystem. But look around you. Odds are, your entire environment is human-made. And it doesn't stop there. From airplane flights or Google maps we see human civilization spilling out over vast swathes of the landscape. Even in areas that are not paved over, the trained ecologist sees omnipresent invasive species, erosion, and pollution. In many parts of the world, natural areas have been completely transformed by human activity.
My favorite climate change objection raises the possibility of bias in temperature readings taken from areas that have recently urbanized. This "urban heat island" effect is a known source of bias and is corrected for in long-term temperature trends. However, it is becoming more difficult to find locations unaffected by urban heat islands effects as urban areas increase in size and coalesce into megacities. This, at least, is incontrovertible fact: we are seeing a complete transformation of the surface of the earth. Indeed, 2008 was the first year that more people lived in cities than in rural areas.
The good news is that although our impact on the environment is significant, and growing, it is largely based on cumulative effect: in any given year, we are not really that far from a sustainable society. Ending coal power and then using clean energy to power our transportation networks could do it. However, the first step is to stop building new coal power plants. If not for the critical build-up of heavy metals pollutants in the food chain, or the respiratory health of people who live near coal plants, or the massive ecological devastation of mountaintop removal and open-pit mines, than for the entire health and fate of the planet.
I have read the papers and considered the arguments and believe that we must act. Business-as-usual imposes an unacceptable risk of catastrophic consequences. There should always be time for doubt and discussion, but not while we and China continue to build coal power plants.
In-depth scientific information on climate change.