While it is true that volcanoes emit water vapour and carbon dioxide, they contribute little to greenhouse gas concentrations. Large volcanic eruptions can blast huge amounts of sulphur dioxide into the upper atmosphere (stratosphere). There the sulphur dioxide transforms into tiny particles of sulphate aerosol. These particles reflect energy form the sun back into space preventing some of the sun’s rays from heating the earth. This conversion in the upper atmosphere takes some months, and so maximum cooling occurs up to a year after the eruption. It may take as long as seven years before the cooling influence of the volcanic aerosol disappears completely.
One degree
