Volcanic winter

A period of widespread cooling caused when volcanic eruptions inject aerosols into the atmosphere, reducing sunlight reaching Earth’s surface.

Volcanic sulfur dioxide: A gas released by volcanoes that can form reflective sulfate aerosols in the atmosphere. Its conversion to sulfate particles produces much of the sunlight-blocking haze behind volcanic cooling.
1815 eruption of Mount Tambora: A massive 1815 eruption in Indonesia that injected sulfur gases into the stratosphere and was followed by global cooling. Its aftermath included the unusually cold 1816, known as the Year Without a Summer.
Monsoon: A seasonal reversal of winds that produces marked wet and dry seasons in several regions. Reduced sunlight can weaken monsoon circulation and disrupt seasonal rainfall after eruptions.
Nuclear winter: A hypothesized global cooling caused by sunlight-blocking smoke from widespread fires after nuclear war. Both reduce surface sunlight, but volcanic winter begins with aerosols from eruptions rather than combustion smoke.
Volcanic explosivity index: A logarithmic scale that ranks explosive eruptions using criteria such as erupted volume and plume height. Eruption size alone does not determine how much climate-relevant sulfur reaches the stratosphere.
Stratospheric aerosol: A suspension of fine particles in the stratosphere, including sulfate droplets formed from volcanic sulfur dioxide. These long-lived particles scatter incoming sunlight and drive the cooling.
Year Without a Summer: The climatic and agricultural crisis of 1816, marked by abnormally cold and wet conditions across parts of the Northern Hemisphere. It is the best-known societal episode associated with Tambora's volcanic cooling.
Crop failure: A substantial loss of agricultural production caused by damaging conditions or disruptions. Shortened growing seasons and unusual frosts can turn volcanic cooling into food shortages.
Impact winter: A period of severe cooling hypothesized after a large asteroid or comet impact lofts dust and debris into the atmosphere. It resembles volcanic cooling in its sunlight-blocking effect but has an impact-driven source.
Paleoclimatology: The study of past climates using natural archives such as ice, sediments, corals, and tree rings. Its evidence helps test how often severe volcanic cooling occurred before instrumental records.

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