My understanding of climatology is that sulfur elements have a proven cooling effect while there is less certainty around particulate elements (which could have a cooling or warming effect). I'm wondering how changes in energy use since the 1970s might have impacted climate change, particularly with coal and petroleum. Coal plants at the time produced large amounts of sulfur and particulate pollution because suitable emissions control equipment was not yet developed. Flue gas desulfurization was not commonly used prior to the 1970s and even then it is not used at every facility, even in developed countries. Petroleum was used for transportation and also power stations due to the known effects of coal emissions, but petroleum produces even more particulate matter than coal and petroleum powered machinery of the time was very inefficient and produced massive quantities of smoke and smog. I'm wondering if cleaning up coal and petroleum emissions might have changed how energy use impacts the climate over time. While energy use was less efficient in the 1970s, might a "unit" of coal or petroleum energy produced then have had a lessened effect on the climate than a unit produced now? Would any trend like that not have mattered much in the longer term as the sulfur and particulates left the atmosphere (I think they have a lower lifespan than carbon dioxide)? Also, might there have been climatic effects from the installation of much taller smokestacks on power plants that caused emissions (I'm thinking sulfur and particulates would be most important) to enter higher parts of the atmosphere and disperse more easily than the more localized effects of shorter smokestacks?