Final answer:
The 1991 eruption of Mt. Pinatubo led to a significant amount of volcanic ash and sulfur dioxide being released into the atmosphere, resulting in a reflection of solar radiation and a subsequent global cooling effect, lowering global temperatures by approximately 0.4 °C.
Step-by-step explanation:
After the eruption of Mt. Pinatubo in 1991, which spewed volcanic ash and sulfur dioxide into the atmosphere, these materials reflected incoming solar radiation. As a result, in the following years, there was global cooling caused by these particles and gases in the atmosphere. Observations show that after the Pinatubo eruption, the SO₂ aerosols that were released reduced the amount of sunlight reaching Earth's surface, leading to a decrease in global temperatures by about 0.4 °C. Additionally, this volcanic winter significantly affected weather patterns and had implications on agriculture and ecosystems due to the cooler climate.