Final answer:
Volcanic eruptions affect the global climate by releasing sulfur dioxide and particles that cause haze-effect cooling, reflecting sunlight, and decreasing Earth's temperatures for a short period.
Step-by-step explanation:
Volcanic eruptions can significantly affect global climate by releasing gases and particles into the atmosphere. These substances can remain there for years, and their presence influences climate patterns. One of the most impactful elements released is sulfur dioxide, which can lead to the formation of haze-effect cooling.
This phenomenon happens when volcanic ash, dust, and sulfur dioxide create a layer in the atmosphere that blocks sunlight, leading to a temporary decrease in global temperatures. A historical example of this effect is the eruption of volcanoes in Iceland in 1783, which led to significantly lower winter temperatures in Europe and North America for a couple of years
Furthermore, volcanic particles reach the upper atmosphere and have the ability to reflect sunlight back into space, cooling the Earth's surface. This cooling can last for several years, but it does not constitute a long-term climate change since these particles are relatively short-lived compared to greenhouse gases (GHGs) that remain for much longer in the atmosphere.
Additionally, eruptions emit carbon dioxide, a greenhouse gas, but usually not in quantities sufficient to offset the cooling effects of the aerosols and dust. It's these cooling effects that predominantly govern how volcanic eruptions change the climate in the short term.