The major drivers of climate:
Orbital, take thousands of years, what's happening now is occurring much faster. Orbital variations are out. Volcanism, if the explosion is large enough to fill the upper atmosphere with dust will cool the Earth for a few years, and then when the aerosols fall out of the atmosphere, the earth will warm rapidly, but only back to the pre-eruption conditions. That explanation can't hold water. Changes in the solar irradience, well solar irradience has been trending down for the last 40 or so years, while temperatures have gone in the opposite direction. Then there is the observations in the stratosphere. If this warming were due to increasing irradience from the sun or orbital changes, then the entire atmosphere would warm as more radiation passes through. Instead, we have observed a warming troposphere, and a cooling stratosphere. This is entirely consistent with what happens when you make the lower atmosphere more opaque to radiation. There is less radiation escaping to space, due to increasing concentrations of greenhouse gases. So the stratosphere will cool.
That much is unequivocal. The atmosphere shows a clear indication that the changing state is due to the radiative effects of increasing greenhouse gas concentrations. Skepticism of this fact is not supported, and there is no competing explanation to choose.
That's not to say that the science is settled, it's just that skepticism of the human DNA found on the crime scene are not justified by science.