Actually, there is no set routine on when the earth warms or cools. And they can and do determine this through analysis of soils, setiments and glacial ice around the globe.
Valcanos have heated the earth in the past and have caused mass extinctions.
They can also determine with reasonable accuracy how long it took the earth to warm or cool when it has. This is the reason as you put it, that theories as to why the globe is warming right now that are not linked to man kind get vilified. The reason for that is the speed at which we are releasing CO2 into the atmosphere and the speed in which the globe appears to be warming.
try floating up to the ionosphere when they play with their weather weapons and see how much you fry. they have even poked holes in the ionosphere . you think the hole in the ozone layer came from freon chemicals like you were told?
One belch might be pushing it a bit. Even IF fossil fuels are not the main cause of global warming I think using them is not a good Idea. They are a major source of pollution and cause other ecological devastation which is provable.
Opposite of many people who say we dont know, I think the fact that we dont know is most of the tim a good reason not to use technology. Wait until we do know. Of course that takes out a lot of the profit and the guys making the big profit could care less how the general public is harmed by unintended effects.
I find the Volcanoe argument interesting because the government and oil companies could have used it to blame for global warming. Yet they did not. WHY? My guess is that the myth that we have "tamed" nature with technology is more important to justify using unproven technology. That is of course just a guess.