Since we are coming out of a below-average period in global temperature history, as well as a low in recent history (the Little Ice Age following the medieval warm period), I believe some component of current trends is natural. I also believe (sub)urbanization introduces some degree of measurement bias -- a location that was relatively rural 80 years ago now surrounded by suburban sprawl, shopping centers and parking lots will have a higher local temperature from local effects in addition to any possible regional change.
However, I cannot deny the likelihood that emissions, deforestation, and other man-made factors have an impact on climate. The big question that remains unresolved is how much of the current trend is natural, and how much is caused by man.