Meteorology and climate science are two very different fields that have little to do with one another. Global dimming is a phenomenon that masks warming, it doesn't cancel it out. Climate change is not speculation, it is a fact confirmed by actual data and real world measurements. A theory, BTW is much more than idle speculation based on a few data points. The formal scientific definition of theory is a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. A theory can be used to predict events or phenomena that have not yet been observed.
There is no longer any debate among climate scientists that climate change is occurring, that it's happening much faster than in the past, and that human activity is driving it.