Based on the graph, it appears that volcanic activity has a cooling effect on global temperature. The amount of solar radiation transmitted decreases after a large volcanic eruption, indicating that the volcanic particles in the atmosphere are blocking some of the solar radiation from reaching the Earth. This cooling effect can last for several years, as the volcanic particles take time to settle out of the atmosphere.
It is worth noting that the impact of volcanic activity on global temperature is complex and depends on a variety of factors, including the size and type of the eruption, the location of the volcano, and the prevailing weather patterns at the time of the eruption. Some studies have suggested that the overall net effect of volcanic activity on global temperature is relatively small compared to other factors, such as greenhouse gas emissions from human activities.