What is the short-term climatic effect of dust and ash from volcanic eruptions?

• A. Short-term cooling of the planet
• B. Long-term warming of the planet
• C. No effect on climate
• D. Severe warming of the planet

Answer: (A)

Dust and ash from volcanic eruptions cause a cooling of the planet in the short term. The key driver is sulfur dioxide released into the stratosphere, which forms sulfate aerosols that reflect and scatter sunlight, increasing the Earth's overall reflectivity (albedo). With less solar energy reaching the surface, global temperatures drop for months to a couple of years after a large eruption. This cooling is temporary because the aerosols settle out and fade over time, and any warming effect from volcano-derived CO2 plays out on longer timescales and cannot counteract the immediate cooling. So the best description of the short-term climatic effect is cooling, not warming or no effect.