Climate scientists have identified several factors that influence the climate. Here is an explanation that I've posted for you before from the IPCC describing three basic ways to alter earth's radiation balance: (1) changes in solar inputs, (2) changes in reflection of solar radiation (i.e. albedo), and (3) changes in long-wave radiation coming from earth. And then they recognize feedback mechanisms play an additional role. The changes that you are asking about (e.g. volcanoes, sea ice extent, desertification, etc) must influence these factors to alter the radiation balance.