Final answer:
Sulfur-based aerosols have a longer effect on climate changes than pyroclastic material due to their ability to reflect sunlight and cause global cooling, as demonstrated by historic volcanic eruptions.
Step-by-step explanation:
The substances that have longer-term effects on climate changes between pyroclastic material and sulfur-based aerosols would be the sulfur-based aerosols. This is because sulfur-based aerosols, specifically sulfur dioxide (SO2) and the resulting sulfate aerosols, can reflect sunlight (a process known as albedo), leading to a cooling effect on the Earth's climate. Pyroclastic material, on the other hand, does not have as great an impact on albedo. In historical events such as the 1783 Icelandic volcanic eruptions, large amounts of sulfur dioxide were released, causing haze-effect cooling, which is a significant decrease in temperature due to particles blocking sunlight. Although both types of emissions can affect the climate after a volcanic eruption, sulfur-based aerosols tend to remain in the atmosphere longer and can even lead to global cooling, as was the case in 1783 and 1784 following the eruptions in Iceland.