Welcome to Week 2 of Climate Change: Challenges and Solutions! This week, Tim introduced us to Ancient Past Climate Change and we began to look at the story of the Earth over the past 4.5 billion years. One of the most interesting parts of this was that we learned about how the Earth has become a giant snowball three times in its history – completely frozen to the equators in some theories. But, as you can see, we are not frozen over now! It was the build up of carbon dioxide from the regular eruption of volcanoes around the planet that melted the snowball. So what role do volcanoes play in the Earth’s Climate?
First though, let’s see what is emitted from a volcano. This varies considerably between volcanoes due to the different types of magma that a volcano may produce. Similarly, the amount of gas that is ejected varies between volcanoes. Typically, water vapour comprises around 60% of the gas, with carbon dioxide comprising 10-40% [Source]. Sulfur Dioxide is also emitted, and if the explosivity is high enough, can be injected 10s of kilometres into the stratosphere [Source]. A summary of gases can be found below:
Water vapour and carbon dioxide will provide a warming effect on the climate, as both are greenhouse gases. However, water vapour has a typical residence time in the atmosphere of 9 days, so excess from volcanoes will likely result in extra precipitation a few days later. Carbon dioxide though, has a residence time of 5-200 years [IPCC, wg1], so volcanoes have a long-term warming effect.
Sulfur dioxide, when in the stratosphere, converts to aerosols that offer a cooling effect, but these stay in the atmosphere for a couple of weeks at most [Source], unless they are injected high into the stratosphere, where they can stay for up to a year. Dust particles also emitted can reflect solar radiation, but again, these only remain for a few weeks depending on the explosivity of the volcano in question [Source]. The cooling effect that is offered from the dust particles and sulfate aerosols can offset the warming effect from extra water vapour and carbon dioxide over short timescales.
Key message: Volcanoes provide long-term warming, short-term cooling 🙂