This seems to me a bait-and-switch question in that it relies on a muddling of terms. Global warming is different than anthropogenic global warming, and AGW can be either serious or trivial, so asking if I believe the “basic theory” is true is really an unanswerable question. I could answer yes or no depending on what I perceive that theory to be.
If the basic theory is that man, by producing CO2, is responsible for a significant amount of warming - and that warming is a threat to life on earth - then no, I do not accept it. If the theory, however, is nothing more than does the addition of CO2 to the atmosphere lead to some amount of warming then, yes, I accept it.