I do believe the Earth has become warmer since exiting the mini Ice Age int he mid 1800s. I do think that human activity has some impact on that. I do think that we will never truly know the human impact on Global Warming (GW). I also think it is very arrogant to think we little humans cause so much damage to Earth. Earth is pretty resilient. It will get by without us if need be. My main concerns are deforestation, resource depletion, and clean oceans/water. Let's keep water/land clean and resources available.
CO2 is not a pollutant. It's a greenhouse gas just like methane & water vapor, except much milder in "damage". Carbon Monoxide (CO) used to be the big harmful greenhouse gas in enviros eyes as it destroyed the ozone layer. We made changes with exhaust systems to reduce CO output. Enviros changed focus. If one considers how the enviro cause started in the '60s and had amazing success with pollution, CO, forest and wetland protection, it is no surprise that they ran out of things to go after and now focus on an invisible gas that humans exhale involuntarily and plants love that might or might not make things warmer. They've run out of 1st world targets, and don't have the guts to face developing governments about deforestation anymore (like China).
That said, I also believe that big ball of gas in the sky, the Sun, has a pretty big impact on our warming and cooling. I think it's activity is far more critical with Earth entering and exiting ice ages and warm periods than CO2. Sunspot activity looks pretty important to me. This blog post with many links seems important as it was 5 years ago. In 2008 and so far in 2009, sunspot activity has been down. Could cooling and a mini or full blown ice age be coming? I hope not. An ice age would mean my home state (actually all of my former residences) would be under lots of ice. An Ice Age is much more dangerous than a 1 degree celsius rise in temps. When it was warmer, the Romans had vineyards in England. In Roman times, Britain was a bit WARMER than now, yet they enjoyed wine, hmmmmmmm. Slightly warmer than now and they survived. Let's do more research, let's get scientists working, and let's not just drown out and blacklist scientists who do not toe the GW line. More research is needed. More data is needed. A little less alarmism would be good.