Final answer:
The local effects of Mount Pinatubo's 1991 eruption were catastrophic, with environmental destruction exacerbated by a coinciding typhoon, massive economic implications, and significant global climatic impacts, including a drop in the Northern Hemisphere's temperature by about 1 °C.
Step-by-step explanation:
In the aftermath of Mount Pinatubo's eruption in 1991, local effects were devastating, largely because of the massive volume of magma, ash, sulfur dioxide, minerals, and particulates expelled into the atmosphere. The subsequent ash fall blocked out sunlight, compelling temperatures to drop, and layered nearby areas in ash, leading to significant damage to infrastructure like roofs and roadways, and was detrimental to agriculture.
The eruption coincided with a typhoon that brought heavy rainfall and winds, exacerbating the environmental havoc through the creation of ash-laden mudflows, which further amplified the economic impact on the Philippines.
Not only was civilian infrastructure adversely affected, but key U.S. military bases, such as the Subic Bay Naval Base and Clark Air Base, were severely damaged, leading to the evacuation of military personnel.
Globally, the eruption caused a decrease in global temperatures by around 1 °C in the Northern Hemisphere, echoing the significant climatic impacts that large volcanic eruptions can have, similar to historical eruptions such as Krakatoa in 1883, which influenced global weather patterns for years.