Because everything affects everything else humans may be responsible for global warming, even if only in small part.
However, it may be useful to allow ourselves to apply Common Sense in understanding what is going on and our part in that. We humans may not be so guilty of affecting our weather as some would have us think.
Let us leave on one side for now why the planet Mars which once enjoyed an environment similar to ours lost its pleasant environment. It was, self-evidently not a result of automobiles, coal fire burners or any animal activities. We will return to Mars in another report.
Meanwhile, the Icelandic volcano above is releasing all sorts of so-called greenhouse gases into the atmosphere. These emissions are measurable.
Those measurements provide an interesting insight into the proposition that humans affect the weather and global warming due to their production of greenhouse gases. For instance, one volcanic eruption on just one day emits into our atmosphere the equivalent in greenhouses gases and other pollutants to all of the human activity from industry and other activities. There is more than one volcano in the world. In the American state of Alaska, presently there are 81 listed volcanoes. Around the world are many more famous ones. Beneath the oceans thousands of them bubble away, their gases taking almost an hour to reach the surface into the atmosphere.
That is not to suggest that we humans have no effect on our atmosphere nor that volcanic eruptions are the sole cause. Instead, common sense would indicate that global warming may have other causes and that by blaming ourselves or allowing ourselves to be blamed by people have a non-common sense agenda risks our sinking Mankind into mindless and avoidable poverty.