Pinatubo

An example of this is the 1991 eruption of Mount Pinatubo that cooled the planet down by up to 0.5C for two years.

Pinatubo, the resulting half a degree of global cooling was the result of about 15 million tonnes of sulphur dioxide injected into the stratosphere.

Normally huge volcanic eruptions, like 1991’s Mount Pinatubo, can cool Earth temporarily with sulfur and other particles reflecting sunlight.

In 1991, Mount Pinatubo north of Manila blew its top in one of the biggest volcanic eruptions of the 20th century, killing hundreds.

Nature does this already: After Mount Pinatubo in the Philippines erupted in 1991, sending 20 million tons of sulfur dioxide spewing into the atmosphere, global temperatures fell by about 1 degree Fahrenheit the following year.