A large underwater volcano recently erupted in the South Pacific. Volcanoes can send huge amounts of gases and ash into the atmosphere. Very large eruptions can affect the climate.
In 1815, one of the most powerful volcanic eruptions in the last several thousand years occurred in the South Pacific. The following year was known as the Year without a Summer in the fledgling nation of the United States. Snow events occurred on the east coast in mid-summer. Western Europe had a very cold summer as well.